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37-419: Content is available for free 1 year after publication, except review content, which is available immediately. The journal also publishes special and virtual issues focusing on a specific theme. Since 2021, the journal has given an annual award, "The FEBS Journal Richard Perham Prize", for an outstanding research paper published in the journal. The winners receive a €5,000 cash prize (to be divided equally between

74-436: A change of electronic spin, which is forbidden by spin selection rules, making phosphorescence (from T 1 to S 0 ) much slower than fluorescence (from S 1 to S 0 ). Thus, triplet states generally have longer lifetimes than singlet states. These transitions are usually summarized in a state energy diagram or Jablonski diagram , the paradigm of molecular photochemistry. These excited species, either S 1 or T 1 , have

111-460: A chemical substance in order for a photochemical reaction to take place. According to the second law of photochemistry, known as the Stark–Einstein law (for physicists Johannes Stark and Albert Einstein ), for each photon of light absorbed by a chemical system, no more than one molecule is activated for a photochemical reaction, as defined by the quantum yield . When a molecule or atom in

148-399: A component of the machinery of vision . The dimerization of alkenes is relevant to the photodamage of DNA , where thymine dimers are observed upon illuminating DNA with UV radiation. Such dimers interfere with transcription . The beneficial effects of sunlight are associated with the photochemically-induced retro-cyclization (decyclization) reaction of ergosterol to give vitamin D . In

185-413: A half-empty low-energy orbital, and are consequently more oxidizing than the ground state. But at the same time, they have an electron in a high-energy orbital, and are thus more reducing . In general, excited species are prone to participate in electron transfer processes. Photochemical reactions require a light source that emits wavelengths corresponding to an electronic transition in the reactant. In

222-464: A photon-induced π to π* transition. The first electronic excited state of an alkene lacks the π-bond , so that rotation about the C–C bond is rapid and the molecule engages in reactions not observed thermally. These reactions include cis-trans isomerization and cycloaddition to other (ground state) alkene to give cyclobutane derivatives. The cis-trans isomerization of a (poly)alkene is involved in retinal ,

259-470: A prolonged illness. Neuberg began his professional career working as an assistant in the physiological chemistry department of Charité in 1898 while he was still working on his doctoral thesis. He gained his PhD in 1900 working on the chemistry of glyceraldehyde under the supervision of Alfred Wohl at the University of Berlin. In 1903, Neuberg became a privatdozent , and in 1906 a professor at

296-430: A relatively narrow band that can be efficiently used, as well as Rayonet lamps, to get approximately monochromatic beams. The emitted light must reach the targeted functional group without being blocked by the reactor, medium, or other functional groups present. For many applications, quartz is used for the reactors as well as to contain the lamp. Pyrex absorbs at wavelengths shorter than 275 nm. The solvent

333-555: A short period of time, and allowing reactions otherwise inaccessible by thermal processes. Photochemistry can also be destructive, as illustrated by the photodegradation of plastics. Photoexcitation is the first step in a photochemical process where the reactant is elevated to a state of higher energy, an excited state . The first law of photochemistry, known as the Grotthuss–Draper law (for chemists Theodor Grotthuss and John W. Draper ), states that light must be absorbed by

370-486: A solubilization process where the addition of large amounts of a second solute causes an increase in the aqueous solubility of a different solute. He also worked on catalase and the oxidation of fatty acids and amino acids, studied the structure of biochemicals, discovered other enzymes, and synthesized phosphorylated intermediates of carbohydrate metabolism. He is considered one of the founders and leaders of modern dynamic biochemistry. Due to his Jewish origin, Neuberg

407-712: Is an important experimental parameter. Solvents are potential reactants, and for this reason, chlorinated solvents are avoided because the C–Cl bond can lead to chlorination of the substrate. Strongly-absorbing solvents prevent photons from reaching the substrate. Hydrocarbon solvents absorb only at short wavelengths and are thus preferred for photochemical experiments requiring high-energy photons. Solvents containing unsaturation absorb at longer wavelengths and can usefully filter out short wavelengths. For example, cyclohexane and acetone "cut off" (absorb strongly) at wavelengths shorter than 215 and 330 nm, respectively. Typically,

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444-646: Is used to describe a chemical reaction caused by absorption of ultraviolet ( wavelength from 100 to 400  nm ), visible (400–750 nm), or infrared radiation (750–2500 nm). In nature, photochemistry is of immense importance as it is the basis of photosynthesis, vision, and the formation of vitamin D with sunlight. It is also responsible for the appearance of DNA mutations leading to skin cancers. Photochemical reactions proceed differently than temperature-driven reactions. Photochemical paths access high-energy intermediates that cannot be generated thermally, thereby overcoming large activation barriers in

481-426: Is usually, but not always, the only relevant singlet excited state. This excited state S 1 can further relax to S 0 by IC, but also by an allowed radiative transition from S 1 to S 0 that emits a photon; this process is called fluorescence . Alternatively, it is possible for the excited state S 1 to undergo spin inversion and to generate a triplet excited state T 1 having two unpaired electrons with

518-468: The DeMayo reaction , an alkene reacts with a 1,3-diketone reacts via its enol to yield a 1,5-diketone. Still another common photochemical reaction is Howard Zimmerman 's di-π-methane rearrangement . In an industrial application, about 100,000 tonnes of benzyl chloride are prepared annually by the gas-phase photochemical reaction of toluene with chlorine . The light is absorbed by chlorine molecules,

555-614: The European Journal of Biochemistry in 1967, with Claude Liébecq as editor-in-chief, succeeded by Richard Perham , during whose tenure the name became the FEBS Journal , in 2005. During the early years the Biochemisches Zeitschrift published numerous papers important in the history of biochemistry, including that of Michaelis and Menten . The two name changes make it difficult to compare all

592-504: The Woodward–Hoffmann selection rules . A [2+2] cycloaddition reaction is one example of a pericyclic reaction that can be analyzed using these rules or by the related frontier molecular orbital theory. Some photochemical reactions are several orders of magnitude faster than thermal reactions; reactions as fast as 10 seconds and associated processes as fast as 10 seconds are often observed. The photon can be absorbed directly by

629-588: The ground state (S 0 ) absorbs light, one electron is excited to a higher orbital level. This electron maintains its spin according to the spin selection rule; other transitions would violate the law of conservation of angular momentum . The excitation to a higher singlet state can be from HOMO to LUMO or to a higher orbital, so that singlet excitation states S 1 , S 2 , S 3 ... at different energies are possible. Kasha's rule stipulates that higher singlet states would quickly relax by radiationless decay or internal conversion (IC) to S 1 . Thus, S 1

666-438: The inner or outer coordination sphere of the metal. Here are some different types of photochemical reactions - Although bleaching has long been practiced, the first photochemical reaction was described by Trommsdorff in 1834. He observed that crystals of the compound α-santonin when exposed to sunlight turned yellow and burst. In a 2007 study the reaction was described as a succession of three steps taking place within

703-625: The University of Berlin. Neuberg was the first editor of the journal Biochemische Zeitschrift that he founded in 1906, which became the European Journal of Biochemistry in 1967, and is now (since 2005) the FEBS Journal . In his early work in Germany, he worked on solubility and transport in cells, the chemistry of carbohydrates , photochemistry , as well as investigating and classifying different types of fermentation . He

740-424: The activation energy required for many reactions. If laser light is employed, it is possible to selectively excite a molecule so as to produce a desired electronic and vibrational state. Equally, the emission from a particular state may be selectively monitored, providing a measure of the population of that state. If the chemical system is at low pressure, this enables scientists to observe the energy distribution of

777-714: The age of 45. Neuberg was forced out of his job in 1934 under pressure from the Nazis. Just before the outbreak of the Second World War , he left Germany to work for a while at the University of Amsterdam , then travelled to Palestine via France during the war, eventually leaving in 1940 to move to the United States to join his daughters who had already settled there. He died on 30 May 1956 in New York after

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814-717: The classical language gymnasium Lyceum I of the Ratsgymnasium until he was 15. In 1892 he moved with his parents to Berlin where he attended Friedrich-Werdersches Gymnasium. After graduating school in 1896, he studied astronomy, but soon switched to chemistry to comply with his father's wishes for him to become a master of brewery. He studied at the University of Würzburg and University of Berlin as well as Technischen Hochschule Charlottenburg. On 21 May 1907, Neuberg married Franziska Helene (Hela) Lewinski, with whom he had two daughters, Irene Stephanie in 1908 and Marianne in 1911. His wife died from leukemia on 24 March 1929 at

851-454: The discovery of the carboxylase and the elucidation of alcoholic fermentation which he showed to be a process of successive enzymatic steps, an understanding that became crucial as to how metabolic pathways would be investigated by later researchers. Carl Sandel Neuberg was born on 29 July 1877 to a Jewish family in Hanover as the first child of Julius and Alma Neuberg. He was educated in

888-447: The early experiments (and in everyday life), sunlight was the light source, although it is polychromatic. Mercury-vapor lamps are more common in the laboratory. Low-pressure mercury-vapor lamps mainly emit at 254 nm. For polychromatic sources, wavelength ranges can be selected using filters. Alternatively, laser beams are usually monochromatic (although two or more wavelengths can be obtained using nonlinear optics ), and LEDs have

925-471: The first and last authors) and the senior author of the study is invited to give a talk at the FEBS Annual Congress. The journal also gives more frequent poster prize awards to early-career scientists presenting at conferences. The journal was established in 1906 by Carl Neuberg , who also served as the first editor-in-chief. Its original name was Biochemische Zeitschrift . It was renamed to

962-575: The low energy of this transition being indicated by the yellowish color of the gas. The photon induces homolysis of the Cl-Cl bond, and the resulting chlorine radical converts toluene to the benzyl radical: Mercaptans can be produced by photochemical addition of hydrogen sulfide (H 2 S) to alpha olefins . Coordination complexes and organometallic compounds are also photoreactive. These reactions can entail cis-trans isomerization. More commonly, photoreactions result in dissociation of ligands, since

999-541: The most notable papers published in the journal, but some are the following: The journal is abstracted and indexed in: According to the Journal Citation Reports , the journal has a 2019 impact factor of 4.392. Carl Neuberg Carl Alexander Neuberg (29 July 1877 – 30 May 1956) was an early pioneer in biochemistry , and he has sometimes been referred to as the "father of modern biochemistry". His notable contribution to science includes

1036-404: The number of photons that are able to activate molecules causing the desired reaction. The large surface-area-to-volume ratio of a microreactor maximizes the illumination, and at the same time allows for efficient cooling, which decreases the thermal side products. In the case of photochemical reactions, light provides the activation energy . Simplistically, light is one mechanism for providing

1073-652: The photon excites an electron on the metal to an orbital that is antibonding with respect to the ligands. Thus, metal carbonyls that resist thermal substitution undergo decarbonylation upon irradiation with UV light. UV-irradiation of a THF solution of molybdenum hexacarbonyl gives the THF complex, which is synthetically useful: In a related reaction, photolysis of iron pentacarbonyl affords diiron nonacarbonyl (see figure): Select photoreactive coordination complexes can undergo oxidation-reduction processes via single electron transfer. This electron transfer can occur within

1110-431: The products of a chemical reaction before the differences in energy have been smeared out and averaged by repeated collisions. The absorption of a photon by a reactant molecule may also permit a reaction to occur not just by bringing the molecule to the necessary activation energy, but also by changing the symmetry of the molecule's electronic configuration, enabling an otherwise-inaccessible reaction path, as described by

1147-620: The reactant or by a photosensitizer , which absorbs the photon and transfers the energy to the reactant. The opposite process, when a photoexcited state is deactivated by a chemical reagent, is called quenching . Most photochemical transformations occur through a series of simple steps known as primary photochemical processes. One common example of these processes is the excited state proton transfer. Examples of photochemical organic reactions are electrocyclic reactions , radical reactions , photoisomerization , and Norrish reactions . Alkenes undergo many important reactions that proceed via

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1184-428: The same spin. This violation of the spin selection rule is possible by intersystem crossing (ISC) of the vibrational and electronic levels of S 1 and T 1 . According to Hund's rule of maximum multiplicity , this T 1 state would be somewhat more stable than S 1 . This triplet state can relax to the ground state S 0 by radiationless ISC or by a radiation pathway called phosphorescence . This process implies

1221-534: The steps and mechanisms of reactions, and formulate a theory for the alcoholic fermentation of glucose . Support for his theory was bolstered when he helped develop an industrial process that contributed materially to the German war effort in World War I , manufacturing glycerol —for the production of explosives —by the fermentation of sugar. Neuberg made a particularly important discovery in 1916: hydrotropy ,

1258-656: The wavelength employed to induce a photochemical process is selected based on the absorption spectrum of the reactive species, most often the absorption maximum. Over the last years , however, it has been demonstrated that, in the majority of bond-forming reactions, the absorption spectrum does not allow selecting the optimum wavelength to achieve the highest reaction yield based on absorptivity. This fundamental mismatch between absorptivity and reactivity has been elucidated with so-called photochemical action plots . Continuous-flow photochemistry offers multiple advantages over batch photochemistry. Photochemical reactions are driven by

1295-618: Was also a pioneer in the study of the chemistry of amino acids and enzymes . In 1913, Neuberg was invited to head the biochemistry section of the Kaiser Wilhelm Institute for Experimental Therapy, the director of which was August von Wasserman . In 1911 he discovered the enzyme pyruvate decarboxylase (EC 4.1.1.1, then called just "carboxylase") which catalyzes the decarboxylation of pyruvate to produce acetate . He also introduced methods for trapping of intermediate metabolites which allowed him to correctly interpret

1332-566: Was associated with a number of universities, and continued to work on enzymes and cell transport processes. On 5 Nov 1947, he received a medal from the American Society of European Chemists and Pharmacists. He served as a professor at the Brooklyn Polytechnic Institute . Photochemistry Photochemistry is the branch of chemistry concerned with the chemical effects of light. Generally, this term

1369-463: Was forced by the Nazis to end his work at the Kaiser Wilhelm Institute for Biochemistry in 1936 and he left Germany in 1937. The successor for his position at the Kaiser Wilhelm Institute for Biochemistry was Adolf Butenandt . Neuberg moved to the United States in 1940, however due to his age, he was unable to find a paid academic position, and he worked as a consultant for industry. Nevertheless, he

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