Misplaced Pages

#350649

117-397: Ozone's odor is reminiscent of chlorine , and detectable by many people at concentrations of as little as 0.1  ppm in air. Ozone's O 3 structure was determined in 1865. The molecule was later proven to have a bent structure and to be weakly diamagnetic . In standard conditions , ozone is a pale blue gas that condenses at cryogenic temperatures to a dark blue liquid and finally

234-522: A Lewis acidic catalyst is used, such as ferric chloride . Many detailed procedures are available. Because fluorine is so reactive , other methods, such as the Balz–Schiemann reaction , are used to prepare fluorinated aromatic compounds. In the Hunsdiecker reaction , carboxylic acids are converted to organic halide , whose carbon chain is shortened by one carbon atom with respect to

351-427: A 1:1 mixture of HCl and H 2 O, the system separates completely into two separate liquid phases. Hydrochloric acid forms an azeotrope with boiling point 108.58 °C at 20.22 g HCl per 100 g solution; thus hydrochloric acid cannot be concentrated beyond this point by distillation. Unlike hydrogen fluoride, anhydrous liquid hydrogen chloride is difficult to work with as a solvent, because its boiling point

468-430: A chlorine derivative of perchloric acid (HOClO 3 ), similar to the thermally unstable chlorine derivatives of other oxoacids: examples include chlorine nitrate (ClONO 2 , vigorously reactive and explosive), and chlorine fluorosulfate (ClOSO 2 F, more stable but still moisture-sensitive and highly reactive). Dichlorine hexoxide is a dark-red liquid that freezes to form a solid which turns yellow at −180 °C: it

585-414: A chlorofluorinating agent, adding chlorine and fluorine across a multiple bond or by oxidation: for example, it will attack carbon monoxide to form carbonyl chlorofluoride, COFCl. It will react analogously with hexafluoroacetone , (CF 3 ) 2 CO, with a potassium fluoride catalyst to produce heptafluoroisopropyl hypochlorite, (CF 3 ) 2 CFOCl; with nitriles RCN to produce RCF 2 NCl 2 ; and with

702-747: A dangerously powerful and unstable oxidizer. Near the end of the nineteenth century, E. S. Smith patented a method of sodium hypochlorite production involving electrolysis of brine to produce sodium hydroxide and chlorine gas, which then mixed to form sodium hypochlorite. This is known as the chloralkali process , first introduced on an industrial scale in 1892, and now the source of most elemental chlorine and sodium hydroxide. In 1884 Chemischen Fabrik Griesheim of Germany developed another chloralkali process which entered commercial production in 1888. Elemental chlorine solutions dissolved in chemically basic water (sodium and calcium hypochlorite ) were first used as anti- putrefaction agents and disinfectants in

819-498: A dark blue liquid . It is dangerous to allow this liquid to warm to its boiling point, because both concentrated gaseous ozone and liquid ozone can detonate. At temperatures below 80 K (−193.2 °C; −315.7 °F), it forms a violet-black solid . Most people can detect about 0.01 μmol/mol of ozone in air where it has a very specific sharp odour somewhat resembling chlorine bleach . Exposure of 0.1 to 1 μmol/mol produces headaches, burning eyes and causing irritation to

936-731: A destructive action". Schönbein himself reported that chest pains, irritation of the mucous membranes and difficulty breathing occurred as a result of inhaling ozone, and small mammals died. In 1911, Leonard Hill and Martin Flack stated in the Proceedings of the Royal Society B that ozone's healthful effects "have, by mere iteration, become part and parcel of common belief; and yet exact physiological evidence in favour of its good effects has been hitherto almost entirely wanting ... The only thoroughly well-ascertained knowledge concerning

1053-445: A fluoride ion donor or acceptor (Lewis base or acid), although it does not dissociate appreciably into ClF 2 and ClF 4 ions. Chlorine pentafluoride (ClF 5 ) is made on a large scale by direct fluorination of chlorine with excess fluorine gas at 350 °C and 250 atm, and on a small scale by reacting metal chlorides with fluorine gas at 100–300 °C. It melts at −103 °C and boils at −13.1 °C. It

1170-468: A higher oxidation state than bromination with Br 2 when multiple oxidation states are available, such as in MoCl 5 and MoBr 3 . Chlorides can be made by reaction of an element or its oxide, hydroxide, or carbonate with hydrochloric acid, and then dehydrated by mildly high temperatures combined with either low pressure or anhydrous hydrogen chloride gas. These methods work best when the chloride product

1287-784: A low-pressure discharge tube. The yellow [Cl 3 ] cation is more stable and may be produced as follows: This reaction is conducted in the oxidising solvent arsenic pentafluoride . The trichloride anion, [Cl 3 ] , has also been characterised; it is analogous to triiodide . The three fluorides of chlorine form a subset of the interhalogen compounds, all of which are diamagnetic . Some cationic and anionic derivatives are known, such as ClF 2 , ClF 4 , ClF 2 , and Cl 2 F . Some pseudohalides of chlorine are also known, such as cyanogen chloride (ClCN, linear), chlorine cyanate (ClNCO), chlorine thiocyanate (ClSCN, unlike its oxygen counterpart), and chlorine azide (ClN 3 ). Chlorine monofluoride (ClF)

SECTION 10

#1732780055351

1404-454: A potent respiratory hazard and pollutant near ground level , a higher concentration in the ozone layer (from two to eight ppm) is beneficial, preventing damaging UV light from reaching the Earth's surface. The trivial name ozone is the most commonly used and preferred IUPAC name . The systematic names 2λ-trioxidiene and catena-trioxygen , valid IUPAC names, are constructed according to

1521-403: A process called ozonolysis , giving alcohols, aldehydes, ketones, and carboxylic acids, depending on the second step of the workup. Ozone can also cleave alkynes to form an acid anhydride or diketone product. If the reaction is performed in the presence of water, the anhydride hydrolyzes to give two carboxylic acids . Usually ozonolysis is carried out in a solution of dichloromethane , at

1638-519: A reduction in oxidation state , which can also be achieved by reducing a higher chloride using hydrogen or a metal as a reducing agent. This may also be achieved by thermal decomposition or disproportionation as follows: Most metal chlorides with the metal in low oxidation states (+1 to +3) are ionic. Nonmetals tend to form covalent molecular chlorides, as do metals in high oxidation states from +3 and above. Both ionic and covalent chlorides are known for metals in oxidation state +3 (e.g. scandium chloride

1755-408: A result of the increasing molecular weight of the halogens down the group, the density and heats of fusion and vaporisation of chlorine are again intermediate between those of bromine and fluorine, although all their heats of vaporisation are fairly low (leading to high volatility) thanks to their diatomic molecular structure. The halogens darken in colour as the group is descended: thus, while fluorine

1872-488: A separate gaseous substance was recognised by the Brabantian chemist and physician Jan Baptist van Helmont . The element was first studied in detail in 1774 by Swedish chemist Carl Wilhelm Scheele , and he is credited with the discovery. Scheele produced chlorine by reacting MnO 2 (as the mineral pyrolusite ) with HCl: Scheele observed several of the properties of chlorine: the bleaching effect on litmus ,

1989-625: A solution of sodium carbonate. The resulting liquid, known as " Eau de Javel " (" Javel water "), was a weak solution of sodium hypochlorite . This process was not very efficient, and alternative production methods were sought. Scottish chemist and industrialist Charles Tennant first produced a solution of calcium hypochlorite ("chlorinated lime"), then solid calcium hypochlorite (bleaching powder). These compounds produced low levels of elemental chlorine and could be more efficiently transported than sodium hypochlorite, which remained as dilute solutions because when purified to eliminate water, it became

2106-479: A spark and can occur in ozone concentrations of 10 wt% or higher. Ozone can also be produced from oxygen at the anode of an electrochemical cell. This reaction can create smaller quantities of ozone for research purposes. This can be observed as an unwanted reaction in a Hoffman gas apparatus during the electrolysis of water when the voltage is set above the necessary voltage. Ozone will oxidize most metals (except gold , platinum , and iridium ) to oxides of

2223-575: A special category with respect to halogenation. Most organic compounds, saturated or otherwise, burn upon contact with F 2 , ultimately yielding carbon tetrafluoride . By contrast, the heavier halogens are far less reactive toward saturated hydrocarbons. Highly specialised conditions and apparatus are required for fluorinations with elemental fluorine . Commonly, fluorination reagents are employed instead of F 2 . Such reagents include cobalt trifluoride , chlorine trifluoride , and iodine pentafluoride . The method electrochemical fluorination

2340-851: A temperature of −78 °C. After a sequence of cleavage and rearrangement, an organic ozonide is formed. With reductive workup (e.g. zinc in acetic acid or dimethyl sulfide ), ketones and aldehydes will be formed, with oxidative workup (e.g. aqueous or alcoholic hydrogen peroxide ), carboxylic acids will be formed. All three atoms of ozone may also react, as in the reaction of tin(II) chloride with hydrochloric acid and ozone: Iodine perchlorate can be made by treating iodine dissolved in cold anhydrous perchloric acid with ozone: Ozone could also react with potassium iodide to give oxygen and iodine gas that can be titrated for quantitative determination: Ozone can be used for combustion reactions and combustible gases; ozone provides higher temperatures than burning in dioxygen ( O 2 ). The following

2457-639: A violet-black solid . Ozone's instability with regard to more common dioxygen is such that both concentrated gas and liquid ozone may decompose explosively at elevated temperatures, physical shock, or fast warming to the boiling point. It is therefore used commercially only in low concentrations. Ozone is a powerful oxidant (far more so than dioxygen) and has many industrial and consumer applications related to oxidation. This same high oxidizing potential, however, causes ozone to damage mucous and respiratory tissues in animals, and also tissues in plants, above concentrations of about 0.1 ppm . While this makes ozone

SECTION 20

#1732780055351

2574-416: Is hydrogen chloride , HCl, a major chemical in industry as well as in the laboratory, both as a gas and dissolved in water as hydrochloric acid . It is often produced by burning hydrogen gas in chlorine gas, or as a byproduct of chlorinating hydrocarbons . Another approach is to treat sodium chloride with concentrated sulfuric acid to produce hydrochloric acid, also known as the "salt-cake" process: In

2691-441: Is sodium chlorate , mostly used to make chlorine dioxide to bleach paper pulp. The decomposition of chlorate to chloride and oxygen is a common way to produce oxygen in the laboratory on a small scale. Chloride and chlorate may comproportionate to form chlorine as follows: Perchlorates and perchloric acid (HOClO 3 ) are the most stable oxo-compounds of chlorine, in keeping with the fact that chlorine compounds are most stable when

2808-554: Is 116.78°. The central atom is sp ² hybridized with one lone pair. Ozone is a polar molecule with a dipole moment of 0.53  D . The molecule can be represented as a resonance hybrid with two contributing structures, each with a single bond on one side and double bond on the other. The arrangement possesses an overall bond order of 1.5 for both sides. It is isoelectronic with the nitrite anion . Naturally occurring ozone can be composed of substituted isotopes (O, O, O). A cyclic form has been predicted but not observed. Ozone

2925-414: Is a chemical element ; it has symbol Cl and atomic number 17. The second-lightest of the halogens , it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate between them. Chlorine is a yellow-green gas at room temperature. It is an extremely reactive element and a strong oxidising agent : among the elements, it has the highest electron affinity and

3042-490: Is a chemical reaction which introduces one or more halogens into a chemical compound . Halide -containing compounds are pervasive, making this type of transformation important, e.g. in the production of polymers , drugs . This kind of conversion is in fact so common that a comprehensive overview is challenging. This article mainly deals with halogenation using elemental halogens ( F 2 , Cl 2 , Br 2 , I 2 ). Halides are also commonly introduced using salts of

3159-536: Is a substitution reaction . The reaction typically involves free radical pathways. The regiochemistry of the halogenation of alkanes is largely determined by the relative weakness of the C–H bonds . This trend is reflected by the faster reaction at tertiary and secondary positions. Free radical chlorination is used for the industrial production of some solvents : Naturally-occurring organobromine compounds are usually produced by free radical pathway catalyzed by

3276-474: Is a pale yellow gas, chlorine is distinctly yellow-green. This trend occurs because the wavelengths of visible light absorbed by the halogens increase down the group. Specifically, the colour of a halogen, such as chlorine, results from the electron transition between the highest occupied antibonding π g molecular orbital and the lowest vacant antibonding σ u molecular orbital. The colour fades at low temperatures, so that solid chlorine at −195 °C

3393-399: Is a poor solvent, only able to dissolve small molecular compounds such as nitrosyl chloride and phenol , or salts with very low lattice energies such as tetraalkylammonium halides. It readily protonates electrophiles containing lone-pairs or π bonds. Solvolysis , ligand replacement reactions, and oxidations are well-characterised in hydrogen chloride solution: Nearly all elements in

3510-483: Is a reaction for the combustion of carbon subnitride which can also cause higher temperatures: Ozone can react at cryogenic temperatures. At 77 K (−196.2 °C; −321.1 °F), atomic hydrogen reacts with liquid ozone to form a hydrogen superoxide radical , which dimerizes : Ozone is a toxic substance, commonly found or generated in human environments (aircraft cabins, offices with photocopiers, laser printers, sterilizers...) and its catalytic decomposition

3627-486: Is a very poor conductor of electricity, and indeed its conductivity is so low as to be practically unmeasurable. Chlorine has two stable isotopes, Cl and Cl. These are its only two natural isotopes occurring in quantity, with Cl making up 76% of natural chlorine and Cl making up the remaining 24%. Both are synthesised in stars in the oxygen-burning and silicon-burning processes . Both have nuclear spin 3/2+ and thus may be used for nuclear magnetic resonance , although

Ozone - Misplaced Pages Continue

3744-432: Is a very strong fluorinating agent, although it is still not as effective as chlorine trifluoride. Only a few specific stoichiometric reactions have been characterised. Arsenic pentafluoride and antimony pentafluoride form ionic adducts of the form [ClF 4 ] [MF 6 ] (M = As, Sb) and water reacts vigorously as follows: The product, chloryl fluoride , is one of the five known chlorine oxide fluorides. These range from

3861-442: Is a weak ligand, weaker than water, a few compounds involving coordinated ClO 4 are known. The Table below presents typical oxidation states for chlorine element as given in the secondary schools or colleges. There are more complex chemical compounds, the structure of which can only be explained using modern quantum chemical methods, for example, cluster technetium chloride [(CH 3 ) 4 N] 3 [Tc 6 Cl 14 ], in which 6 of

3978-506: Is almost colourless. Like solid bromine and iodine, solid chlorine crystallises in the orthorhombic crystal system , in a layered lattice of Cl 2 molecules. The Cl–Cl distance is 198 pm (close to the gaseous Cl–Cl distance of 199 pm) and the Cl···Cl distance between molecules is 332 pm within a layer and 382 pm between layers (compare the van der Waals radius of chlorine, 180 pm). This structure means that chlorine

4095-472: Is also produced when photolysing the solid at −78 °C: it is a dark brown solid that explodes below 0 °C. The ClO radical leads to the depletion of atmospheric ozone and is thus environmentally important as follows: Chlorine perchlorate (ClOClO 3 ) is a pale yellow liquid that is less stable than ClO 2 and decomposes at room temperature to form chlorine, oxygen, and dichlorine hexoxide (Cl 2 O 6 ). Chlorine perchlorate may also be considered

4212-550: Is among the most powerful oxidizing agents known, far stronger than O 2 . It is also unstable at high concentrations, decaying into ordinary diatomic oxygen. Its half-life varies with atmospheric conditions such as temperature, humidity, and air movement. Under laboratory conditions, the half-life will average ~1500 minutes (25 hours) in still air at room temperature (24 °C), zero humidity with zero air changes per hour. This reaction proceeds more rapidly with increasing temperature. Deflagration of ozone can be triggered by

4329-658: Is even more unstable and cannot be isolated or concentrated without decomposition: it is known from the decomposition of aqueous chlorine dioxide. However, sodium chlorite is a stable salt and is useful for bleaching and stripping textiles, as an oxidising agent, and as a source of chlorine dioxide. Chloric acid (HOClO 2 ) is a strong acid that is quite stable in cold water up to 30% concentration, but on warming gives chlorine and chlorine dioxide. Evaporation under reduced pressure allows it to be concentrated further to about 40%, but then it decomposes to perchloric acid, chlorine, oxygen, water, and chlorine dioxide. Its most important salt

4446-894: Is extremely dangerous, and poisonous to most living organisms. As a chemical warfare agent, chlorine was first used in World War ;I as a poison gas weapon. In the form of chloride ions , chlorine is necessary to all known species of life. Other types of chlorine compounds are rare in living organisms, and artificially produced chlorinated organics range from inert to toxic. In the upper atmosphere , chlorine-containing organic molecules such as chlorofluorocarbons have been implicated in ozone depletion . Small quantities of elemental chlorine are generated by oxidation of chloride ions in neutrophils as part of an immune system response against bacteria. The most common compound of chlorine, sodium chloride, has been known since ancient times; archaeologists have found evidence that rock salt

4563-551: Is extremely thermally stable, and is sold commercially in 500-gram steel lecture bottles. It is a colourless gas that melts at −155.6 °C and boils at −100.1 °C. It may be produced by the reaction of its elements at 225 °C, though it must then be separated and purified from chlorine trifluoride and its reactants. Its properties are mostly intermediate between those of chlorine and fluorine. It will react with many metals and nonmetals from room temperature and above, fluorinating them and liberating chlorine. It will also act as

4680-460: Is influenced by the halogen. Fluorine and chlorine are more electrophilic and are more aggressive halogenating agents. Bromine is a weaker halogenating agent than both fluorine and chlorine, while iodine is the least reactive of them all. The facility of dehydrohalogenation follows the reverse trend: iodine is most easily removed from organic compounds, and organofluorine compounds are highly stable. Halogenation of saturated hydrocarbons

4797-515: Is less reactive than fluorine and more reactive than bromine. It is also a weaker oxidising agent than fluorine, but a stronger one than bromine. Conversely, the chloride ion is a weaker reducing agent than bromide, but a stronger one than fluoride. It is intermediate in atomic radius between fluorine and bromine, and this leads to many of its atomic properties similarly continuing the trend from iodine to bromine upward, such as first ionisation energy , electron affinity , enthalpy of dissociation of

Ozone - Misplaced Pages Continue

4914-442: Is less than +1.395 V, it would be expected that chlorine should be able to oxidise water to oxygen and hydrochloric acid. However, the kinetics of this reaction are unfavorable, and there is also a bubble overpotential effect to consider, so that electrolysis of aqueous chloride solutions evolves chlorine gas and not oxygen gas, a fact that is very useful for the industrial production of chlorine. The simplest chlorine compound

5031-479: Is low, it has a small liquid range, its dielectric constant is low and it does not dissociate appreciably into H 2 Cl and HCl 2 ions – the latter, in any case, are much less stable than the bifluoride ions ( HF 2 ) due to the very weak hydrogen bonding between hydrogen and chlorine, though its salts with very large and weakly polarising cations such as Cs and NR 4 (R = Me , Et , Bu ) may still be isolated. Anhydrous hydrogen chloride

5148-437: Is made by reacting anhydrous sodium perchlorate or barium perchlorate with concentrated hydrochloric acid, filtering away the chloride precipitated and distilling the filtrate to concentrate it. Anhydrous perchloric acid is a colourless mobile liquid that is sensitive to shock that explodes on contact with most organic compounds, sets hydrogen iodide and thionyl chloride on fire and even oxidises silver and gold. Although it

5265-427: Is mostly ionic, but aluminium chloride is not). Silver chloride is very insoluble in water and is thus often used as a qualitative test for chlorine. Although dichlorine is a strong oxidising agent with a high first ionisation energy, it may be oxidised under extreme conditions to form the [Cl 2 ] cation. This is very unstable and has only been characterised by its electronic band spectrum when produced in

5382-415: Is one of the most reactive elements. Chlorine is a weaker oxidising agent than fluorine but a stronger one than bromine or iodine. This can be seen from the standard electrode potentials of the X 2 /X couples (F, +2.866  V; Cl, +1.395 V; Br, +1.087  V; I, +0.615 V; At , approximately +0.3  V). However, this trend is not shown in the bond energies because fluorine

5499-420: Is oxidized to lead(II) sulfate : Sulfuric acid can be produced from ozone, water and either elemental sulfur or sulfur dioxide : In the gas phase , ozone reacts with hydrogen sulfide to form sulfur dioxide: In an aqueous solution, however, two competing simultaneous reactions occur, one to produce elemental sulfur, and one to produce sulfuric acid : Alkenes can be oxidatively cleaved by ozone, in

5616-400: Is present in solid crystalline hydrogen chloride at low temperatures, similar to the hydrogen fluoride structure, before disorder begins to prevail as the temperature is raised. Hydrochloric acid is a strong acid (p K a = −7) because the hydrogen bonds to chlorine are too weak to inhibit dissociation. The HCl/H 2 O system has many hydrates HCl· n H 2 O for n = 1, 2, 3, 4, and 6. Beyond

5733-419: Is produced in the atmosphere by spallation of Ar by interactions with cosmic ray protons . In the top meter of the lithosphere , Cl is generated primarily by thermal neutron activation of Cl and spallation of K and Ca . In the subsurface environment, muon capture by Ca becomes more important as a way to generate Cl. Chlorine is intermediate in reactivity between fluorine and bromine, and

5850-401: Is quite slow at temperatures below 70 °C in spite of the very favourable equilibrium constant of 10 . The chlorate ions may themselves disproportionate to form chloride and perchlorate (4 ClO 3 ⇌ Cl + 3 ClO 4 ) but this is still very slow even at 100 °C despite the very favourable equilibrium constant of 10 . The rates of reaction for the chlorine oxyanions increases as

5967-510: Is singular due to its small size, low polarisability, and inability to show hypervalence . As another difference, chlorine has a significant chemistry in positive oxidation states while fluorine does not. Chlorination often leads to higher oxidation states than bromination or iodination but lower oxidation states than fluorination. Chlorine tends to react with compounds including M–M, M–H, or M–C bonds to form M–Cl bonds. Given that E°( ⁠ 1 / 2 ⁠ O 2 /H 2 O) = +1.229 V, which

SECTION 50

#1732780055351

6084-567: Is stable to hydrolysis; otherwise, the possibilities include high-temperature oxidative chlorination of the element with chlorine or hydrogen chloride, high-temperature chlorination of a metal oxide or other halide by chlorine, a volatile metal chloride, carbon tetrachloride , or an organic chloride. For instance, zirconium dioxide reacts with chlorine at standard conditions to produce zirconium tetrachloride , and uranium trioxide reacts with hexachloropropene when heated under reflux to give uranium tetrachloride . The second example also involves

6201-553: Is the anhydride of perchloric acid (HClO 4 ) and can readily be obtained from it by dehydrating it with phosphoric acid at −10 °C and then distilling the product at −35 °C and 1 mmHg. It is a shock-sensitive, colourless oily liquid. It is the least reactive of the chlorine oxides, being the only one to not set organic materials on fire at room temperature. It may be dissolved in water to regenerate perchloric acid or in aqueous alkalis to regenerate perchlorates. However, it thermally decomposes explosively by breaking one of

6318-430: Is the anhydride. It is thus an effective bleach and is mostly used to make hypochlorites . It explodes on heating or sparking or in the presence of ammonia gas. Chlorine dioxide (ClO 2 ) was the first chlorine oxide to be discovered in 1811 by Humphry Davy . It is a yellow paramagnetic gas (deep-red as a solid or liquid), as expected from its having an odd number of electrons: it is stable towards dimerisation due to

6435-587: Is the route to the anesthetic halothane from trichloroethylene : Iodination and bromination can be effected by the addition of iodine and bromine to alkenes. The reaction, which conveniently proceeds with the discharge of the color of I 2 and Br 2 , is the basis of the analytical method . The iodine number and bromine number are measures of the degree of unsaturation for fats and other organic compounds. Aromatic compounds are subject to electrophilic halogenation : This kind of reaction typically works well for chlorine and bromine . Often

6552-402: Is used commercially for the production of perfluorinated compounds . It generates small amounts of elemental fluorine in situ from hydrogen fluoride . The method avoids the hazards of handling fluorine gas. Many commercially important organic compounds are fluorinated using this technology. Unsaturated compounds , especially alkenes and alkynes , add halogens: In oxychlorination ,

6669-472: Is usually made by reaction of chlorine dioxide with oxygen. Despite attempts to rationalise it as the dimer of ClO 3 , it reacts more as though it were chloryl perchlorate, [ClO 2 ] [ClO 4 ] , which has been confirmed to be the correct structure of the solid. It hydrolyses in water to give a mixture of chloric and perchloric acids: the analogous reaction with anhydrous hydrogen fluoride does not proceed to completion. Dichlorine heptoxide (Cl 2 O 7 )

6786-407: Is very important to reduce pollution. This type of decomposition is the most widely used, especially with solid catalysts, and it has many advantages such as a higher conversion with a lower temperature. Furthermore, the product and the catalyst can be instantaneously separated, and this way the catalyst can be easily recovered without using any separation operation. Moreover, the most used materials in

6903-413: The enzyme bromoperoxidase . The reaction requires bromide in combination with oxygen as an oxidant . The oceans are estimated to release 1–2 million tons of bromoform and 56,000 tons of bromomethane annually. The iodoform reaction , which involves degradation of methyl ketones , proceeds by the free radical iodination. Because of its extreme reactivity, fluorine ( F 2 ) represents

7020-473: The neutron activation of natural chlorine. The most stable chlorine radioisotope is Cl. The primary decay mode of isotopes lighter than Cl is electron capture to isotopes of sulfur ; that of isotopes heavier than Cl is beta decay to isotopes of argon ; and Cl may decay by either mode to stable S or Ar. Cl occurs in trace quantities in nature as a cosmogenic nuclide in a ratio of about (7–10) × 10 to 1 with stable chlorine isotopes: it

7137-483: The noble gases xenon and radon do not escape fluorination. An impermeable fluoride layer is formed by sodium , magnesium , aluminium , zinc , tin , and silver , which may be removed by heating. Nickel , copper, and steel containers are usually used due to their great resistance to attack by chlorine trifluoride, stemming from the formation of an unreactive layer of metal fluoride. Its reaction with hydrazine to form hydrogen fluoride, nitrogen, and chlorine gases

SECTION 60

#1732780055351

7254-492: The substitutive and additive nomenclatures , respectively. The name ozone derives from ozein (ὄζειν), the Greek neuter present participle for smell, referring to ozone's distinctive smell. In appropriate contexts, ozone can be viewed as trioxidane with two hydrogen atoms removed, and as such, trioxidanylidene may be used as a systematic name, according to substitutive nomenclature. By default, these names pay no regard to

7371-414: The 14 chlorine atoms are formally divalent, and oxidation states are fractional. In addition, all the above chemical regularities are valid for "normal" or close to normal conditions, while at ultra-high pressures (for example, in the cores of large planets), chlorine can exhibit an oxidation state of -3, forming a Na3Cl compound with sodium, which does not fit into traditional concepts of chemistry. Like

7488-545: The 1820s, in France, long before the establishment of the germ theory of disease . This practice was pioneered by Antoine-Germain Labarraque , who adapted Berthollet's "Javel water" bleach and other chlorine preparations. Elemental chlorine has since served a continuous function in topical antisepsis (wound irrigation solutions and the like) and public sanitation, particularly in swimming and drinking water. Chlorine gas

7605-419: The 1920s, it was not certain whether small amounts of oxozone , O 4 , were also present in ozone samples due to the difficulty of applying analytical chemistry techniques to the explosive concentrated chemical. In 1923, Georg-Maria Schwab (working for his doctoral thesis under Ernst Hermann Riesenfeld ) was the first to successfully solidify ozone and perform accurate analysis which conclusively refuted

7722-473: The Earth's crust is in the form of ionic chloride compounds, which includes table salt. It is the second-most abundant halogen (after fluorine) and 20th most abundant element in Earth's crust. These crystal deposits are nevertheless dwarfed by the huge reserves of chloride in seawater. Elemental chlorine is commercially produced from brine by electrolysis , predominantly in the chloralkali process . The high oxidising potential of elemental chlorine led to

7839-541: The German and Dutch names of oxygen : sauerstoff or zuurstof , both translating into English as acid substance ), so a number of chemists, including Claude Berthollet , suggested that Scheele's dephlogisticated muriatic acid air must be a combination of oxygen and the yet undiscovered element, muriaticum . In 1809, Joseph Louis Gay-Lussac and Louis-Jacques Thénard tried to decompose dephlogisticated muriatic acid air by reacting it with charcoal to release

7956-528: The Greek word ozein ( ὄζειν ) meaning "to smell". For this reason, Schönbein is generally credited with the discovery of ozone. He also noted the similarity of ozone smell to the smell of phosphorus, and in 1844 proved that the product of reaction of white phosphorus with air is identical. A subsequent effort to call ozone "electrified oxygen" he ridiculed by proposing to call the ozone from white phosphorus "phosphorized oxygen". The formula for ozone, O 3 ,

8073-439: The Greek word χλωρος ( chlōros , "green-yellow"), in reference to its colour. The name " halogen ", meaning "salt producer", was originally used for chlorine in 1811 by Johann Salomo Christoph Schweigger . This term was later used as a generic term to describe all the elements in the chlorine family (fluorine, bromine, iodine), after a suggestion by Jöns Jakob Berzelius in 1826. In 1823, Michael Faraday liquefied chlorine for

8190-496: The X 2 molecule (X = Cl, Br, I), ionic radius, and X–X bond length. (Fluorine is anomalous due to its small size.) All four stable halogens experience intermolecular van der Waals forces of attraction, and their strength increases together with the number of electrons among all homonuclear diatomic halogen molecules. Thus, the melting and boiling points of chlorine are intermediate between those of fluorine and bromine: chlorine melts at −101.0 °C and boils at −34.0 °C. As

8307-454: The carbon chain of the particular carboxylic acid. The carboxylic acid is first converted to its silver salt, which is then oxidized with halogen : Many organometallic compounds react with halogens to give the organic halide: All elements aside from argon , neon , and helium form fluorides by direct reaction with fluorine . Chlorine is slightly more selective, but still reacts with most metals and heavier nonmetals . Following

8424-436: The catalytic decomposition of ozone in the gas phase are noble metals like Pt, Rh or Pd and transition metals such as Mn, Co, Cu, Fe, Ni or Ag. There are two other possibilities for the ozone decomposition in gas phase: The first one is a thermal decomposition where the ozone can be decomposed using only the action of heat. The problem is that this type of decomposition is very slow with temperatures below 250 °C. However,

8541-606: The central Cl–O bonds, producing the radicals ClO 3 and ClO 4 which immediately decompose to the elements through intermediate oxides. Chlorine forms four oxoacids: hypochlorous acid (HOCl), chlorous acid (HOClO), chloric acid (HOClO 2 ), and perchloric acid (HOClO 3 ). As can be seen from the redox potentials given in the adjacent table, chlorine is much more stable towards disproportionation in acidic solutions than in alkaline solutions: The hypochlorite ions also disproportionate further to produce chloride and chlorate (3 ClO ⇌ 2 Cl + ClO 3 ) but this reaction

8658-424: The chlorine atom is in its lowest (−1) or highest (+7) possible oxidation states. Perchloric acid and aqueous perchlorates are vigorous and sometimes violent oxidising agents when heated, in stark contrast to their mostly inactive nature at room temperature due to the high activation energies for these reactions for kinetic reasons. Perchlorates are made by electrolytically oxidising sodium chlorate, and perchloric acid

8775-426: The combination of hydrogen chloride and oxygen serves as the equivalent of chlorine , as illustrated by this route to 1,2-dichloroethane : The addition of halogens to alkenes proceeds via intermediate halonium ions . In special cases, such intermediates have been isolated. Bromination is more selective than chlorination because the reaction is less exothermic . Illustrative of the bromination of an alkene

8892-429: The dark. Crystalline clathrate hydrates ClO 2 · n H 2 O ( n ≈ 6–10) separate out at low temperatures. However, in the presence of light, these solutions rapidly photodecompose to form a mixture of chloric and hydrochloric acids. Photolysis of individual ClO 2 molecules result in the radicals ClO and ClOO, while at room temperature mostly chlorine, oxygen, and some ClO 3 and Cl 2 O 6 are produced. Cl 2 O 3

9009-424: The deadly effect on insects, the yellow-green colour, and the smell similar to aqua regia . He called it " dephlogisticated muriatic acid air " since it is a gas (then called "airs") and it came from hydrochloric acid (then known as "muriatic acid"). He failed to establish chlorine as an element. Common chemical theory at that time held that an acid is a compound that contains oxygen (remnants of this survive in

9126-435: The decomposition rate can be increased working with higher temperatures but this would involve a high energy cost. The second one is a photochemical decomposition, which consists of radiating ozone with ultraviolet radiation (UV) and it gives rise to oxygen and radical peroxide. The process of ozone decomposition is a complex reaction involving two elementary reactions that finally lead to molecular oxygen, and this means that

9243-576: The delocalisation of the unpaired electron. It explodes above −40 °C as a liquid and under pressure as a gas and therefore must be made at low concentrations for wood-pulp bleaching and water treatment. It is usually prepared by reducing a chlorate as follows: Its production is thus intimately linked to the redox reactions of the chlorine oxoacids. It is a strong oxidising agent, reacting with sulfur , phosphorus , phosphorus halides, and potassium borohydride . It dissolves exothermically in water to form dark-green solutions that very slowly decompose in

9360-574: The development of commercial bleaches and disinfectants , and a reagent for many processes in the chemical industry. Chlorine is used in the manufacture of a wide range of consumer products, about two-thirds of them organic chemicals such as polyvinyl chloride (PVC), many intermediates for the production of plastics , and other end products which do not contain the element. As a common disinfectant, elemental chlorine and chlorine-generating compounds are used more directly in swimming pools to keep them sanitary . Elemental chlorine at high concentration

9477-447: The first time, and demonstrated that what was then known as "solid chlorine" had a structure of chlorine hydrate (Cl 2 ·H 2 O). Chlorine gas was first used by French chemist Claude Berthollet to bleach textiles in 1785. Modern bleaches resulted from further work by Berthollet, who first produced sodium hypochlorite in 1789 in his laboratory in the town of Javel (now part of Paris , France), by passing chlorine gas through

9594-482: The first two. Chlorine has the electron configuration [Ne]3s 3p , with the seven electrons in the third and outermost shell acting as its valence electrons . Like all halogens, it is thus one electron short of a full octet, and is hence a strong oxidising agent, reacting with many elements in order to complete its outer shell. Corresponding to periodic trends , it is intermediate in electronegativity between fluorine and bromine (F: 3.98, Cl: 3.16, Br: 2.96, I: 2.66), and

9711-482: The free element muriaticum (and carbon dioxide). They did not succeed and published a report in which they considered the possibility that dephlogisticated muriatic acid air is an element, but were not convinced. In 1810, Sir Humphry Davy tried the same experiment again, and concluded that the substance was an element, and not a compound. He announced his results to the Royal Society on 15 November that year. At that time, he named this new element "chlorine", from

9828-609: The gaseous products were discarded, and hydrogen chloride may have been produced many times before it was discovered that it can be put to chemical use. One of the first such uses was the synthesis of mercury(II) chloride (corrosive sublimate), whose production from the heating of mercury either with alum and ammonium chloride or with vitriol and sodium chloride was first described in the De aluminibus et salibus ("On Alums and Salts", an eleventh- or twelfth century Arabic text falsely attributed to Abu Bakr al-Razi and translated into Latin in

9945-422: The halides and halogen acids. Many specialized reagents exist for and introducing halogens into diverse substrates , e.g. thionyl chloride . Several pathways exist for the halogenation of organic compounds, including free radical halogenation , ketone halogenation , electrophilic halogenation , and halogen addition reaction . The nature of the substrate determines the pathway. The facility of halogenation

10062-456: The heaviest elements beyond bismuth ); and having an electronegativity higher than chlorine's ( oxygen and fluorine ) so that the resultant binary compounds are formally not chlorides but rather oxides or fluorides of chlorine. Even though nitrogen in NCl 3 is bearing a negative charge, the compound is usually called nitrogen trichloride . Chlorination of metals with Cl 2 usually leads to

10179-511: The high temperature environment of forest fires, and dioxins have been found in the preserved ashes of lightning-ignited fires that predate synthetic dioxins. In addition, a variety of simple chlorinated hydrocarbons including dichloromethane, chloroform, and carbon tetrachloride have been isolated from marine algae. A majority of the chloromethane in the environment is produced naturally by biological decomposition, forest fires, and volcanoes. Halogenation In chemistry , halogenation

10296-865: The higher elevations beneficial because of their ozone content. "There is quite a different atmosphere [at higher elevation] with enough ozone to sustain the necessary energy [to work]", wrote naturalist Henry Henshaw , working in Hawaii. Seaside air was considered to be healthy because of its believed ozone content. The smell giving rise to this belief is in fact that of halogenated seaweed metabolites and dimethyl sulfide . Much of ozone's appeal seems to have resulted from its "fresh" smell, which evoked associations with purifying properties. Scientists noted its harmful effects. In 1873 James Dewar and John Gray McKendrick documented that frogs grew sluggish, birds gasped for breath, and rabbits' blood showed decreased levels of oxygen after exposure to "ozonized air", which "exercised

10413-455: The laboratory, hydrogen chloride gas may be made by drying the acid with concentrated sulfuric acid. Deuterium chloride, DCl, may be produced by reacting benzoyl chloride with heavy water (D 2 O). At room temperature, hydrogen chloride is a colourless gas, like all the hydrogen halides apart from hydrogen fluoride , since hydrogen cannot form strong hydrogen bonds to the larger electronegative chlorine atom; however, weak hydrogen bonding

10530-683: The metals in their highest oxidation state . For example: Ozone also oxidizes nitric oxide to nitrogen dioxide : This reaction is accompanied by chemiluminescence . The NO 2 can be further oxidized to nitrate radical : The NO 3 formed can react with NO 2 to form dinitrogen pentoxide ( N 2 O 5 ). Solid nitronium perchlorate can be made from NO 2 , ClO 2 , and O 3 gases: Ozone does not react with ammonium salts , but it oxidizes ammonia to ammonium nitrate : Ozone reacts with carbon to form carbon dioxide , even at room temperature: Ozone oxidizes sulfides to sulfates . For example, lead(II) sulfide

10647-563: The most reactive chemical compounds known, the list of elements it sets on fire is diverse, containing hydrogen , potassium , phosphorus , arsenic , antimony , sulfur , selenium , tellurium , bromine , iodine , and powdered molybdenum , tungsten , rhodium , iridium , and iron . It will also ignite water, along with many substances which in ordinary circumstances would be considered chemically inert such as asbestos , concrete, glass, and sand. When heated, it will even corrode noble metals as palladium , platinum , and gold , and even

10764-794: The multiple bonds on alkenes and alkynes as well, giving di- or tetrachloro compounds. However, due to the expense and reactivity of chlorine, organochlorine compounds are more commonly produced by using hydrogen chloride, or with chlorinating agents such as phosphorus pentachloride (PCl 5 ) or thionyl chloride (SOCl 2 ). The last is very convenient in the laboratory because all side products are gaseous and do not have to be distilled out. Many organochlorine compounds have been isolated from natural sources ranging from bacteria to humans. Chlorinated organic compounds are found in nearly every class of biomolecules including alkaloids , terpenes , amino acids , flavonoids , steroids , and fatty acids . Organochlorides, including dioxins , are produced in

10881-567: The nature of free chlorine gas as a separate substance was only recognised around 1630 by Jan Baptist van Helmont . Carl Wilhelm Scheele wrote a description of chlorine gas in 1774, supposing it to be an oxide of a new element. In 1809, chemists suggested that the gas might be a pure element, and this was confirmed by Sir Humphry Davy in 1810, who named it after the Ancient Greek χλωρός ( khlōrós , "pale green") because of its colour. Because of its great reactivity, all chlorine in

10998-458: The other carbon–halogen bonds, the C–Cl bond is a common functional group that forms part of core organic chemistry . Formally, compounds with this functional group may be considered organic derivatives of the chloride anion. Due to the difference of electronegativity between chlorine (3.16) and carbon (2.55), the carbon in a C–Cl bond is electron-deficient and thus electrophilic . Chlorination modifies

11115-605: The oxidation state of chlorine decreases. The strengths of the chlorine oxyacids increase very quickly as the oxidation state of chlorine increases due to the increasing delocalisation of charge over more and more oxygen atoms in their conjugate bases. Most of the chlorine oxoacids may be produced by exploiting these disproportionation reactions. Hypochlorous acid (HOCl) is highly reactive and quite unstable; its salts are mostly used for their bleaching and sterilising abilities. They are very strong oxidising agents, transferring an oxygen atom to most inorganic species. Chlorous acid (HOClO)

11232-478: The oxozone hypothesis. Further hitherto unmeasured physical properties of pure concentrated ozone were determined by the Riesenfeld group in the 1920s. Ozone is a colourless or pale blue gas, slightly soluble in water and much more soluble in inert non-polar solvents such as carbon tetrachloride or fluorocarbons, in which it forms a blue solution. At 161 K (−112 °C; −170 °F), it condenses to form

11349-695: The oxygen from the first step is an intermediate because it participates as a reactant in the second step, which is a bimolecular reaction because there are two different reactants (ozone and oxygen) that give rise to one product, that corresponds to molecular oxygen in the gas phase. Step 1: Unimolecular reaction     O 3 ⟶ O 2 + O {\displaystyle {\ce {O3 -> O2 + O}}} Step 2: Bimolecular reaction     O 3 + O ⟶ 2 O 2 {\displaystyle {\ce {O3 + O -> 2 O2}}} Chlorine Chlorine

11466-444: The ozone decomposition follows a first order kinetics, and from the rate law above it can be determined that the partial order respect to molecular oxygen is -1 and respect to ozone is 2, therefore the global reaction order is 1. The ozone decomposition consists of two elementary steps: The first one corresponds to a unimolecular reaction because one only molecule of ozone decomposes into two products (molecular oxygen and oxygen). Then,

11583-406: The periodic table form binary chlorides. The exceptions are decidedly in the minority and stem in each case from one of three causes: extreme inertness and reluctance to participate in chemical reactions (the noble gases , with the exception of xenon in the highly unstable XeCl 2 and XeCl 4 ); extreme nuclear instability hampering chemical investigation before decay and transmutation (many of

11700-418: The physical properties of hydrocarbons in several ways: chlorocarbons are typically denser than water due to the higher atomic weight of chlorine versus hydrogen, and aliphatic organochlorides are alkylating agents because chloride is a leaving group . Alkanes and aryl alkanes may be chlorinated under free-radical conditions, with UV light. However, the extent of chlorination is difficult to control:

11817-590: The physiological effect of ozone, so far attained, is that it causes irritation and œdema of the lungs, and death if inhaled in relatively strong concentration for any time." During World War I , ozone was tested at Queen Alexandra Military Hospital in London as a possible disinfectant for wounds. The gas was applied directly to wounds for as long as 15 minutes. This resulted in damage to both bacterial cells and human tissue. Other sanitizing techniques, such as irrigation with antiseptics , were found preferable. Until

11934-453: The radicality of the ozone molecule. In an even more specific context, this can also name the non-radical singlet ground state, whereas the diradical state is named trioxidanediyl . Trioxidanediyl (or ozonide ) is used, non-systematically, to refer to the substituent group (-OOO-). Care should be taken to avoid confusing the name of the group for the context-specific name for the ozone given above. In 1785, Dutch chemist Martinus van Marum

12051-536: The reaction is not regioselective and often results in a mixture of various isomers with different degrees of chlorination, though this may be permissible if the products are easily separated. Aryl chlorides may be prepared by the Friedel-Crafts halogenation , using chlorine and a Lewis acid catalyst. The haloform reaction , using chlorine and sodium hydroxide , is also able to generate alkyl halides from methyl ketones, and related compounds. Chlorine adds to

12168-540: The reaction order and the rate law cannot be determined by the stoichiometry of the fitted equation. Overall reaction: 2 O 3 ⟶ 3 O 2 {\displaystyle {\ce {2 O3 -> 3 O2}}} Rate law (observed): V = K ⋅ [ O 3 ] 2 [ O 2 ] {\displaystyle V={\frac {K\cdot [{\ce {O3}}]^{2}}{[{\ce {O2}}]}}} It has been determined that

12285-417: The respiratory passages. Even low concentrations of ozone in air are very destructive to organic materials such as latex, plastics and animal lung tissue. The ozone molecule is diamagnetic. According to experimental evidence from microwave spectroscopy , ozone is a bent molecule, with C 2v symmetry (similar to the water molecule). The O–O distances are 127.2  pm (1.272  Å ). The O–O–O angle

12402-615: The second half of the twelfth century by Gerard of Cremona , 1144–1187). Another important development was the discovery by pseudo-Geber (in the De inventione veritatis , "On the Discovery of Truth", after c. 1300) that by adding ammonium chloride to nitric acid , a strong solvent capable of dissolving gold (i.e., aqua regia ) could be produced. Although aqua regia is an unstable mixture that continually gives off fumes containing free chlorine gas, this chlorine gas appears to have been ignored until c. 1630, when its nature as

12519-481: The spin magnitude being greater than 1/2 results in non-spherical nuclear charge distribution and thus resonance broadening as a result of a nonzero nuclear quadrupole moment and resultant quadrupolar relaxation. The other chlorine isotopes are all radioactive, with half-lives too short to occur in nature primordially . Of these, the most commonly used in the laboratory are Cl ( t 1/2 = 3.0×10  y) and Cl ( t 1/2 = 37.2 min), which may be produced from

12636-437: The sulfur oxides SO 2 and SO 3 to produce ClSO 2 F and ClOSO 2 F respectively. It will also react exothermically with compounds containing –OH and –NH groups, such as water: Chlorine trifluoride (ClF 3 ) is a volatile colourless molecular liquid which melts at −76.3 °C and boils at 11.8  °C. It may be formed by directly fluorinating gaseous chlorine or chlorine monofluoride at 200–300 °C. One of

12753-586: The thermally unstable FClO to the chemically unreactive perchloryl fluoride (FClO 3 ), the other three being FClO 2 , F 3 ClO, and F 3 ClO 2 . All five behave similarly to the chlorine fluorides, both structurally and chemically, and may act as Lewis acids or bases by gaining or losing fluoride ions respectively or as very strong oxidising and fluorinating agents. The chlorine oxides are well-studied in spite of their instability (all of them are endothermic compounds). They are important because they are produced when chlorofluorocarbons undergo photolysis in

12870-497: The third-highest electronegativity on the revised Pauling scale , behind only oxygen and fluorine. Chlorine played an important role in the experiments conducted by medieval alchemists , which commonly involved the heating of chloride salts like ammonium chloride ( sal ammoniac ) and sodium chloride ( common salt ), producing various chemical substances containing chlorine such as hydrogen chloride , mercury(II) chloride (corrosive sublimate), and aqua regia . However,

12987-406: The upper atmosphere and cause the destruction of the ozone layer. None of them can be made from directly reacting the elements. Dichlorine monoxide (Cl 2 O) is a brownish-yellow gas (red-brown when solid or liquid) which may be obtained by reacting chlorine gas with yellow mercury(II) oxide . It is very soluble in water, in which it is in equilibrium with hypochlorous acid (HOCl), of which it

13104-405: The usual trend, bromine is less reactive and iodine least of all. Of the many reactions possible, illustrative is the formation of gold(III) chloride by the chlorination of gold . The chlorination of metals is usually not very important industrially since the chlorides are more easily made from the oxides and hydrogen chloride . Where chlorination of inorganic compounds is practiced on

13221-445: Was conducting experiments involving electrical sparking above water when he noticed an unusual smell, which he attributed to the electrical reactions, failing to realize that he had in fact created ozone. A half century later, Christian Friedrich Schönbein noticed the same pungent odour and recognized it as the smell often following a bolt of lightning . In 1839, he succeeded in isolating the gaseous chemical and named it "ozone", from

13338-569: Was first used as a weapon on April 22, 1915, at the Second Battle of Ypres by the German Army . The effect on the allies was devastating because the existing gas masks were difficult to deploy and had not been broadly distributed. Chlorine is the second halogen , being a nonmetal in group 17 of the periodic table. Its properties are thus similar to fluorine , bromine , and iodine , and are largely intermediate between those of

13455-445: Was not determined until 1865 by Jacques-Louis Soret and confirmed by Schönbein in 1867. For much of the second half of the 19th century and well into the 20th, ozone was considered a healthy component of the environment by naturalists and health-seekers. Beaumont, California , had as its official slogan "Beaumont: Zone of Ozone", as evidenced on postcards and Chamber of Commerce letterhead. Naturalists working outdoors often considered

13572-628: Was used as early as 3000 BC and brine as early as 6000 BC. Around 900, the authors of the Arabic writings attributed to Jabir ibn Hayyan (Latin: Geber) and the Persian physician and alchemist Abu Bakr al-Razi ( c. 865–925, Latin: Rhazes) were experimenting with sal ammoniac ( ammonium chloride ), which when it was distilled together with vitriol (hydrated sulfates of various metals) produced hydrogen chloride . However, it appears that in these early experiments with chloride salts ,

13689-434: Was used in experimental rocket engine, but has problems largely stemming from its extreme hypergolicity resulting in ignition without any measurable delay. Today, it is mostly used in nuclear fuel processing, to oxidise uranium to uranium hexafluoride for its enriching and to separate it from plutonium , as well as in the semiconductor industry, where it is used to clean chemical vapor deposition chambers. It can act as

#350649