Misplaced Pages

#60939

47-722: Camphor ( / ˈ k æ m f ər / ) is a waxy, colorless solid with a strong aroma. It is classified as a terpenoid and a cyclic ketone . It is found in the wood of the camphor laurel ( Cinnamomum camphora ), a large evergreen tree found in East Asia; and in the kapur tree ( Dryobalanops sp. ), a tall timber tree from South East Asia. It also occurs in some other related trees in the laurel family , notably Ocotea usambarensis . Rosemary leaves ( Rosmarinus officinalis ) contain 0.05 to 0.5% camphor, while camphorweed ( Heterotheca ) contains some 5%. A major source of camphor in Asia

94-605: A decongestant . Camphor was used in ancient Sumatra to treat sprains , swellings, and inflammation . Camphor also was used for centuries in traditional Chinese medicine for various purposes. In Europe, camphor was used after the Black Death era. In the 20th century, camphor was used as an analeptic by injection, and to induce seizures in schizophrenic people in an attempt to treat psychosis . Camphor has limited use in veterinary medicine by intramuscular injection to treat breathing difficulties in horses. Camphor

141-509: A British naval force sailed into Anping harbor and the local British representative demanded the end of the Chinese camphor monopoly. After the local imperial representative refused, the British bombarded the town and took the harbor. The "camphor regulations" negotiated between the two sides subsequently saw a brief end to the camphor monopoly. Camphor is produced from alpha-pinene , which

188-503: A distance. Trees put the "blue" in Blue Ridge, from their terpenoids released into the atmosphere. Sodium borohydride Sodium borohydride , also known as sodium tetrahydridoborate and sodium tetrahydroborate , is an inorganic compound with the formula Na B H 4 (sometimes written as Na[BH 4 ] ). It is a white crystalline solid, usually encountered as an aqueous basic solution . Sodium borohydride

235-501: A role in traditional herbal remedies. Terpenoids contribute to the scent of eucalyptus , the flavors of cinnamon , cloves , and ginger , the yellow color in sunflowers , and the red color in tomatoes . Well-known terpenoids include citral , menthol , camphor , salvinorin A in the plant Salvia divinorum , ginkgolide and bilobalide found in Ginkgo biloba and the cannabinoids found in cannabis. The provitamin beta carotene

282-576: A route to synthesize camphene in 1902, found out that borneol or isoborneol could easily be oxidized with permanganate in benzene solution with unprecedentedly high yields of 95+%, and patented it in 1903. The process was efficient enough to compete with natural camphor, and Japan was forced to lower prices in 1907, but the German company still increased its production, reaching 623 tons in 1913, only to be interrupted by WWI. Terpenoid Plant terpenoids are used for their aromatic qualities and play

329-459: A six-membered transition state that includes only a single alcohol molecule. It was suggested that the simultaneous activation of the carbonyl compound and borohydride occurs, via interaction with the alcohol and alkoxide ion, respectively, and that the reaction proceeds through an open transition state. α,β-Unsaturated ketones tend to be reduced by NaBH 4 in a 1,4-sense, although mixtures are often formed. Addition of cerium chloride improves

376-419: A slight local analgesia . Camphor is also used via an aerosol , typically by steam inhalation, sometimes in the form of branded nasal inhaler sticks, to inhibit coughing and relieve upper airway congestion due to the common cold. However, the clinical efficacy of these remedies is challenged. Camphor is used by marksmen to blacken the front and rear sights of rifles to prevent the sights from reflecting. This

423-469: A variety of compounds. Many additives for modifying the reactivity of sodium borohydride have been developed as indicated by the following incomplete listing. Oxidation with iodine in tetrahydrofuran gives borane–tetrahydrofuran , which can reduce carboxylic acids to alcohols. Partial oxidation of borohydride with iodine gives octahydrotriborate : [BH 4 ] is a ligand for metal ions. Such borohydride complexes are often prepared by

470-424: A way to store hydrogen for hydrogen-fueled vehicles, as it is safer (being stable in dry air) and more efficient on a weight basis than most other alternatives. The hydrogen can be released by simple hydrolysis of the borohydride. However, such a usage would need a cheap, relatively simple, and energy-efficient process to recycle the hydrolysis product, sodium metaborate , back to the borohydride. No such process

517-436: Is camphor basil (the parent of African blue basil ). Camphor can also be synthetically produced from oil of turpentine . The compound is chiral , existing in two possible enantiomers as shown in the structural diagrams. The structure on the left is the naturally occurring (+)-camphor ((1 R ,4 R )-bornan-2-one), while its mirror image shown on the right is the (−)-camphor ((1 S ,4 S )-bornan-2-one). Camphor has few uses but

SECTION 10

#1732772854061

564-450: Is a reducing agent that finds application in papermaking and dye industries. It is also used as a reagent in organic synthesis. The compound was discovered in the 1940s by H. I. Schlesinger , who led a team seeking volatile uranium compounds. Results of this wartime research were declassified and published in 1953. The compound is soluble in alcohols , certain ethers , and water, although it slowly hydrolyzes. Sodium borohydride

611-538: Is a terpene derivative called a carotenoid . The steroids and sterols in animals are biologically produced from terpenoid precursors. Sometimes terpenoids are added to proteins , e.g., to enhance their attachment to the cell membrane ; this is known as isoprenylation . Terpenoids play a role in plant defense as prophylaxis against pathogens and attractants for the predators of herbivores. Terpenoids are modified terpenes , wherein methyl groups have been moved or removed, or oxygen atoms added. Some authors use

658-403: Is abundant in the oils of coniferous trees and can be distilled from turpentine produced as a side product of chemical pulping . With acetic anhydride as the solvent and with catalysis by a strong acid, alpha-pinene is converted to isobornyl acetate . Hydrolysis of this ester gives isoborneol which can be oxidized to give racemic camphor. By contrast, camphor occurs naturally as D -camphor,

705-548: Is also used as an antimicrobial substance. In embalming , camphor oil was one of the ingredients used by ancient Egyptians for mummification . Solid camphor releases fumes that form a rust-preventative coating and is therefore stored in tool chests to protect tools against rust. In the ancient Arab world, camphor was a common perfume ingredient. The Chinese referred to the best camphor as "dragon's brain perfume", due to its "pungent and portentous aroma" and "centuries of uncertainty over its provenance and mode of origin". One of

752-501: Is an odorless white to gray-white microcrystalline powder that often forms lumps. It can be purified by recrystallization from warm (50 °C) diglyme . Sodium borohydride is soluble in protic solvents such as water and lower alcohols. It also reacts with these protic solvents to produce H 2 ; however, these reactions are fairly slow. Complete decomposition of a methanol solution requires nearly 90 min at 20 °C. It decomposes in neutral or acidic aqueous solutions, but

799-435: Is commonly applied as a topical medication as a skin cream or ointment to relieve itching from insect bites, minor skin irritation, or joint pain. It is absorbed in the skin epidermis , where it stimulates nerve endings sensitive to heat and cold, producing a warm sensation when vigorously applied, or a cool sensation when applied gently, indicating its properties as a counterirritant . The action on nerve endings also induces

846-516: Is done by setting light to a small amount of camphor, which burns at a relatively low temperature, and using the soot rising from the flame to deposit a coating on a surface held above it. Historically, this soot blackening was also used to coat barograph record charts. Camphor is believed to be toxic to insects and is thus sometimes used as a repellent. Camphor is used as an alternative to mothballs . Camphor crystals are sometimes used to prevent damage to insect collections by other small insects. It

893-453: Is kept in clothes used on special occasions and festivals, and also in cupboard corners as a cockroach repellent. The smoke of camphor crystal or camphor incense sticks can be used as an environmentally-friendly mosquito repellent. Recent studies have indicated that camphor essential oil can be used as an effective fumigant against red fire ants , as it affects the attacking, climbing, and feeding behavior of major and minor workers. Camphor

940-411: Is more efficient at reduction, but the reductant eventually decomposes spontaneously to produce hydrogen gas and borates. The same reaction can also occur intramolecularly: an α-ketoester converts into a diol, since the alcohol produced attacks the borohydride to produce an ester of the borohydride, which then reduces the neighboring ester. The reactivity of NaBH 4 can be enhanced or augmented by

987-491: Is of historic significance as a compound that is readily purified from natural sources. The word camphor derived in the 14th century from Old French: camphre , itself from Medieval Latin : camfora , from Arabic : كافور , romanized :  kāfūr , perhaps through Sanskrit : कर्पूर , romanized :  karpūra , from Tamil : கற்பூரம் , romanized:  karpooram apparently from Austronesian Malay : kapur 'lime' (chalk). In Old Malay , camphor

SECTION 20

#1732772854061

1034-649: Is performed after placing it on a stand and setting fire to it usually as the last step of puja or devotional worship ritual to one or more deities. Camphor is mentioned in the Quran as being the fragrance of wine given to believers in heaven. Applied on skin, camphor may cause allergic reactions in some people; when ingested by mouth, camphor cream or ointment is poisonous. In high ingested doses, camphor produces symptoms of irritability, disorientation, lethargy, muscle spasms , vomiting, abdominal cramps, convulsions , and seizures . Lethal doses by ingestion in adults are in

1081-502: Is stable at pH 14. NaBH 4 is a salt, consisting of the tetrahedral [BH 4 ] anion. The solid is known to exist as three polymorphs : α , β and γ . The stable phase at room temperature and pressure is α - NaBH 4 , which is cubic and adopts an NaCl -type structure, in the Fm 3 m space group . At a pressure of 6.3 GPa, the structure changes to the tetragonal β - NaBH 4 (space group P42 1 c ) and at 8.9 GPa,

1128-613: Is the production of sodium dithionite from sulfur dioxide: Sodium dithionite is used as a bleaching agent for wood pulp and in the dyeing industry. It has been tested as pretreatment for pulping of wood, but is too costly to be commercialized. Sodium borohydride reduces aldehydes and ketones to give the related alcohols . This reaction is used in the production of various antibiotics including chloramphenicol , dihydrostreptomycin , and thiophenicol . Various steroids and vitamin A are prepared using sodium borohydride in at least one step. Sodium borohydride has been considered as

1175-531: The hydroxyl radical ) and to a lesser extent by ozone . These new species can dissolve into water droplets and contribute to aerosol and haze formation. Secondary organic aerosols formed from this pathway may have atmospheric impacts. As an example the Blue Ridge Mountains in the U.S. and Blue Mountains of New South Wales in Australia are noted for having a bluish color when seen from

1222-424: The selectivity for 1,2-reduction of unsaturated ketones ( Luche reduction ). α,β-Unsaturated esters also undergo 1,4-reduction in the presence of NaBH 4 . The NaBH 4 -MeOH system, formed by the addition of methanol to sodium borohydride in refluxing THF, reduces esters to the corresponding alcohols. Mixing water or an alcohol with the borohydride converts some of it into unstable hydride ester, which

1269-524: The ( R )- enantiomer . The reactions of camphor have been extensively examined. Some representative transformations include Camphor can also be reduced to isoborneol using sodium borohydride . In biosynthesis , camphor is produced from geranyl pyrophosphate , via cyclisation of linaloyl pyrophosphate to bornyl pyrophosphate, followed by hydrolysis to borneol and oxidation to camphor. The first significant manmade plastics were low-nitrogen (or "soluble") nitrocellulose (pyroxylin) plastics. In

1316-496: The 10th century. It also was used in sweet and savory dishes in the Ni'matnama , according to a book written in the late 15th century for the sultans of Mandu . It is a main constituent of a spice known as "edible camphor" (or kapur ), which may be used in traditional South Indian desserts like Payasam and Chakkarai Pongal . Camphor is widely used in Hindu religious ceremonies. Aarti

1363-515: The action of NaBH 4 (or the LiBH 4 ) on the corresponding metal halide. One example is the titanocene derivative: NaBH 4 reacts with water and alcohols, with evolution of hydrogen gas and formation of the corresponding borate, the reaction being especially fast at low pH. Exploiting this reactivity, sodium borohydride has been studied as a prototypes of the direct borohydride fuel cell . The dominant application of sodium borohydride

1410-616: The alkoxide followed by hydrolysis: It also efficiently reduces acyl chlorides , anhydrides , α-hydroxy lactones , thioesters , and imines at room temperature or below. It reduces esters slowly and inefficiently with excess reagent and/or elevated temperatures, while carboxylic acids and amides are not reduced at all. Nevertheless, an alcohol, often methanol or ethanol, is generally the solvent of choice for sodium borohydride reductions of ketones and aldehydes. The mechanism of ketone and aldehyde reduction has been scrutinized by kinetic studies, and contrary to popular depictions in textbooks,

1457-456: The earliest known recipes for ice cream dating to the Tang dynasty includes camphor as an ingredient. It was used to flavor leavened bread in ancient Egypt. In ancient and medieval Europe, camphor was used as an ingredient in sweets . It was used in a wide variety of both savory and sweet dishes in medieval Arabic language cookbooks, such as al-Kitab al-Ṭabikh compiled by ibn Sayyār al-Warrāq in

Camphor - Misplaced Pages Continue

1504-445: The early decades of the plastics industry , camphor was used in immense quantities as the plasticizer that creates celluloid from nitrocellulose, in nitrocellulose lacquers and other plastics and lacquers. Camphor has been used for its scent, as an embalming fluid , as topical medication , as a manufacturing chemical, and in religious ceremonies. Camphor has been used as a folk medicine over centuries, probably most commonly as

1551-518: The fate of the Japanese monopoly ... For no sooner was it accomplished than it excited the attention of a new army of investigators—the industrial chemists. The patent offices of the world were soon crowded with alleged commercial syntheses of camphor, and of the favored processes companies were formed to exploit them, factories resulted, and in the incredibly short time of two years after its academic synthesis artificial camphor, every whit as good as

1598-473: The laboratory as a proof of concept , but camphor was a scarce natural product with a worldwide demand. Komppa realized this, and began industrial production of camphor in Tainionkoski , Finland, in 1907 (with plenty of competition, as Kennedy Duncan reported). A different way of synthesis was developed at the same time by Dr. Karl Stephan from Chemische Fabrik auf Actien . This chemist, who had patented

1645-431: The mechanism does not involve a 4-membered transition state like alkene hydroboration, or a six-membered transition state involving a molecule of the alcohol solvent. Hydrogen-bonding activation is required, as no reduction occurs in an aprotic solvent like diglyme . However, the rate order in alcohol is 1.5, while carbonyl compound and borohydride are both first order, suggesting a mechanism more complex than one involving

1692-403: The natural product, entered the markets of the world ... And yet artificial camphor does not—and cannot—displace the natural product to an extent sufficient to ruin the camphor-growing industry. Its sole present and probable future function is to act as a permanent check to monopolization, to act as a balance-wheel to regulate prices within reasonable limits." This ongoing check on price growth

1739-572: The orthorhombic γ - NaBH 4 (space group Pnma ) becomes the most stable. For commercial NaBH 4 production, the Brown-Schlesinger process and the Bayer process are the most popular methods. In the Brown-Schlesinger process sodium borohydride is industrially prepared from sodium hydride (produced by reacting Na and H 2 ) and trimethyl borate at 250–270 °C: Millions of kilograms are produced annually, far exceeding

1786-553: The presence of terpenoids. Terpenoids, at least those containing an alcohol functional group, often arise by hydrolysis of carbocationic intermediates produced from geranyl pyrophosphate . Analogously hydrolysis of intermediates from farnesyl pyrophosphate gives sesquiterpenoids , and hydrolysis of intermediates from geranylgeranyl pyrophosphate gives diterpenoids , etc. In air, terpenoids are converted into various species, such as aldehydes , hydroperoxides , organic nitrates, and epoxides by short-lived free radicals (like

1833-511: The production levels of any other hydride reducing agent. In the Bayer process, it is produced from inorganic borates, including borosilicate glass and borax ( Na 2 B 4 O 7 ): Magnesium is a less expensive reductant, and could in principle be used instead: and NaBH 4 reduces many organic carbonyls , depending on the conditions. Most typically, it is used in the laboratory for converting ketones and aldehydes to alcohols. These reductions proceed in two stages, formation of

1880-490: The pulverized wood and condensing the vapors. By the early 19th century most camphor tree reserves had been depleted with the remaining large stands in Japan and Taiwan , with Taiwanese production greatly exceeding Japanese. Camphor was one of the primary resources extracted by Taiwan's colonial powers as well as one of the most lucrative. First the Chinese and then the Japanese established monopolies on Taiwanese camphor. In 1868,

1927-463: The range 50–500 mg/kg (orally). Generally, ingestion of two grams causes serious toxicity and four grams is potentially lethal. Airborne camphor may be toxic if respired by humans. The Permissible Exposure Limit ( PEL ) for camphor in ambient air is 2 mg/m at exposure time ( TWA ) not more than 8 hours. 200 mg/m is considered a very dangerous concentration ( IDLH ). When its use in the nascent chemical industries ( discussed below ) greatly increased

Camphor - Misplaced Pages Continue

1974-432: The term "terpene" more broadly, to include the terpenoids. Just like terpenes, the terpenoids can be classified according to the number of isoprene units that comprise the parent terpene: Terpenoids can also be classified according to the type and number of cyclic structures they contain: linear, acyclic, monocyclic, bicyclic, tricyclic, tetracyclic, pentacyclic, or macrocyclic. The Salkowski test can be used to identify

2021-526: The turpentine of southern US pine stumps, with the result that the price of industrial camphor sold in carload lots in 1939 was between 32 cents and 35 cents a pound." The background of Gustaf Komppa 's synthesis was as follows. In the 19th century, it was known that nitric acid oxidizes camphor into camphoric acid . Haller and Blanc published a semisynthesis of camphor from camphoric acid. Although they demonstrated its structure, they were unable to prove it. The first complete total synthesis of camphoric acid

2068-610: The volume of demand in the late 19th century, potential for changes in supply and in price followed. In 1911 Robert Kennedy Duncan, an industrial chemist and educator, related that the Imperial Japanese government had recently (1907–1908) tried to monopolize the production of natural camphor as a forest product in Asia but that the monopoly was prevented by the development of the total synthesis alternatives, which began in "purely academic and wholly uncommercial" form with Gustav Komppa's first report : " ... but it sealed

2115-535: Was called kapur barus , meaning "the chalk of Barus", referring to Barus, an ancient port near modern Sibolga on the western coast of Sumatra . This port traded in camphor extracted from the Borneo camphor trees ( Dryobalanops aromatica ) that were abundant in the region. Camphor has been produced as a forest product for centuries, condensed from the vapor given off by the roasting of wood chips cut from Camphora officinarum , and later by passing steam through

2162-431: Was confirmed in 1942 in a monograph on DuPont 's history, where William S. Dutton said, "Indispensable in the manufacture of pyroxylin plastics, natural camphor imported from Formosa and selling normally for about 50 cents a pound, reached the high price of $ 3.75 in 1918 [amid the global trade disruption and high explosives demand that World War I created]. The organic chemists at DuPont replied by synthesizing camphor from

2209-408: Was published by Komppa in 1903. Its inputs were diethyl oxalate and 3,3-dimethylpentanoic acid , which reacted by Claisen condensation to yield diketocamphoric acid. Methylation with methyl iodide and a complicated reduction procedure produced camphoric acid. William Perkin published another synthesis a short time later. Previously, some organic compounds (such as urea ) had been synthesized in

#60939