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Action of Mercaptan and Disulfide in Hydrogen Atom Exchange Reactions; Action des Thioalcools et des Disulfures dans les Reactions d'Echange d'Atomes d'Hydrogene; Vozdejstvie merkaptanov i disul'fidov v reaktsiyakh obmena atoma vodoroda; Accion de los Mercaptanos y Disulfuros en las Reacciones de Intercambio del Hidrogeno Atomico

Conference:

Abstract

Free- radical, photochemical, and high-energy radiation-induced reactions may be catalysed or inhibited by rapid hydrogen atom exchange reactions of mercaptans and disulfides. The radical-induced, light-initiated, and benzophenone-sensitized decarbonylations of aldehydes are catalysed by mercaptans. The chain-propagating hydrogen transfer reaction, R' + RCH = O -> RH + RC = O , is made more rapid by a similar sequence of hydrogen atom transfers involving the sulfur compound: R' + C{sub 6}H{sub 5}CH{sub 2}SH -> RH + C{sub 6}H{sub 5}CH{sub 2}S'; C{sub 6}H{sub 5}CH{sub 2}S + RCH = 0 -> C{sub 6}H{sub 5}CH{sub 2}SH + RC = 0. The photoreduction of benzophenone in 2-propanol leads to benzpinacol by a non-chain reaction via the radicals (C{sub 6}H{sub 5}){sub 2}C-OH and (CH{sub 3}){sub 2}COH. The reaction is retarded and inhibited by mercaptan and disulfide, which reconvert the radicals to the starting materials by rapid hydrogen transfer reactions and are themselves regenerated in their alternate valence states, each molecule of sulfur compound negating the chemical consequences of many quanta: (C{sub 6}H{sub 5}){sub 2}C-OH + AS' -> (C{sub 6}H{sub 5}){sub 2}C = O + ASH; (CH{sub 3}){sub 2}C-OH + ASH -> (CH{sub 3}){sub 2}C = 0 + AS'. Proof of the mechanism is found in:  More>>
Authors:
Cohen, S. G. [1] 
  1. Brandeis University Waltham, MA (United States)
Publication Date:
Oct 15, 1965
Product Type:
Conference
Report Number:
IAEA-SM-64/30
Resource Relation:
Conference: Symposium on Exchange Reactions, Upton, NY (United States), 31 May - 4 Jun 1965; Other Information: 30 refs., 2 tabs., 4 figs.; Related Information: In: Exchange Reactions. Proceedings of the Symposium on Exchange Reactions| 430 p.
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; 38 RADIATION CHEMISTRY, RADIOCHEMISTRY AND NUCLEAR CHEMISTRY; ACETOPHENONE; ALDEHYDES; BENZHYDROL; BENZOPHENONE; BENZYL ALCOHOL; CHAIN REACTIONS; CHEMICAL REACTIONS; COBALT 60; DISULFIDES; HYDROGEN; HYDROGEN TRANSFER; ION EXCHANGE; PROPANOLS; RADIATION EFFECTS; SULFUR COMPOUNDS; THIOLS; TRANSFER REACTIONS
OSTI ID:
22127272
Research Organizations:
International Atomic Energy Agency, Vienna (Austria)
Country of Origin:
IAEA
Language:
English
Other Identifying Numbers:
Other: ISSN 0074-1884; TRN: XA13M2453082351
Submitting Site:
INIS
Size:
page(s) 279-298
Announcement Date:
Sep 12, 2013

Conference:

Citation Formats

Cohen, S. G. Action of Mercaptan and Disulfide in Hydrogen Atom Exchange Reactions; Action des Thioalcools et des Disulfures dans les Reactions d'Echange d'Atomes d'Hydrogene; Vozdejstvie merkaptanov i disul'fidov v reaktsiyakh obmena atoma vodoroda; Accion de los Mercaptanos y Disulfuros en las Reacciones de Intercambio del Hidrogeno Atomico. IAEA: N. p., 1965. Web.
Cohen, S. G. Action of Mercaptan and Disulfide in Hydrogen Atom Exchange Reactions; Action des Thioalcools et des Disulfures dans les Reactions d'Echange d'Atomes d'Hydrogene; Vozdejstvie merkaptanov i disul'fidov v reaktsiyakh obmena atoma vodoroda; Accion de los Mercaptanos y Disulfuros en las Reacciones de Intercambio del Hidrogeno Atomico. IAEA.
Cohen, S. G. 1965. "Action of Mercaptan and Disulfide in Hydrogen Atom Exchange Reactions; Action des Thioalcools et des Disulfures dans les Reactions d'Echange d'Atomes d'Hydrogene; Vozdejstvie merkaptanov i disul'fidov v reaktsiyakh obmena atoma vodoroda; Accion de los Mercaptanos y Disulfuros en las Reacciones de Intercambio del Hidrogeno Atomico." IAEA.
@misc{etde_22127272,
title = {Action of Mercaptan and Disulfide in Hydrogen Atom Exchange Reactions; Action des Thioalcools et des Disulfures dans les Reactions d'Echange d'Atomes d'Hydrogene; Vozdejstvie merkaptanov i disul'fidov v reaktsiyakh obmena atoma vodoroda; Accion de los Mercaptanos y Disulfuros en las Reacciones de Intercambio del Hidrogeno Atomico}
author = {Cohen, S. G.}
abstractNote = {Free- radical, photochemical, and high-energy radiation-induced reactions may be catalysed or inhibited by rapid hydrogen atom exchange reactions of mercaptans and disulfides. The radical-induced, light-initiated, and benzophenone-sensitized decarbonylations of aldehydes are catalysed by mercaptans. The chain-propagating hydrogen transfer reaction, R' + RCH = O -> RH + RC = O , is made more rapid by a similar sequence of hydrogen atom transfers involving the sulfur compound: R' + C{sub 6}H{sub 5}CH{sub 2}SH -> RH + C{sub 6}H{sub 5}CH{sub 2}S'; C{sub 6}H{sub 5}CH{sub 2}S + RCH = 0 -> C{sub 6}H{sub 5}CH{sub 2}SH + RC = 0. The photoreduction of benzophenone in 2-propanol leads to benzpinacol by a non-chain reaction via the radicals (C{sub 6}H{sub 5}){sub 2}C-OH and (CH{sub 3}){sub 2}COH. The reaction is retarded and inhibited by mercaptan and disulfide, which reconvert the radicals to the starting materials by rapid hydrogen transfer reactions and are themselves regenerated in their alternate valence states, each molecule of sulfur compound negating the chemical consequences of many quanta: (C{sub 6}H{sub 5}){sub 2}C-OH + AS' -> (C{sub 6}H{sub 5}){sub 2}C = O + ASH; (CH{sub 3}){sub 2}C-OH + ASH -> (CH{sub 3}){sub 2}C = 0 + AS'. Proof of the mechanism is found in: equilibration of initially present mercaptan or disulfide during inhibition; in racemization of optically active alcohol during inhibition; in deuterium exchange during inhibition. Similar inhibition is seen when only one intermediate radical is formed, as in the benzophenone- benzhydrol and acetophenone-{alpha}-methyl-benzyl alcohol systems. Inhibition by sulfur compounds, by the same mechanism, is found in the {sup 60}Co {gamma}-ray induced conversion of benzophenone to benzpinacol; naphthalene has no protecting effect on benzophenone in the {sup 60}Co system, while quenching the photochemical reaction. The protection by sulfur compounds of solutes against radiation damage thus results from hydrogen atom transfer reactions. The photoreduction of benzophenone in an ether is also inhibited by the sulfur compounds, by hydrogen atom transfer reactions. A mechanism exists in this system (unlike the ketone-alcohol systems) by which the sulfur compounds may be consumed irreversibly. This leads to an induction period, instead of to permanent retardation, about 15 quanta being negated by each molecule of sulfur compound. (author) [French] Des reactions induites par des radicaux libres, par photochimie et par des rayonnements de haute energie, peuvent etre catalysees ou inhibees par des reactions rapides d'echange d'atomes d'hydrogene des thioalcools et des disulfures. Les decarbonylations d'aldehydes, induites par des radicaux libres, amorcees par la lumiere et sensibilisees par la benzophenone,sont catalysees par les thioalcools. La reaction en chaftie de transfert d'atomes d'hydrogene, R' + RCH = O -> RH + RC = O est acceleree par une suite analogue de transferts d'atomes d'hydrogene mettant en jeu le compose soufre: R' + C{sub 6}H{sub 5}CH{sub 2}SH -> RH + C{sub 6}H{sub 5}CH{sub 2}S'; C{sub 6}H{sub 5}CH{sub 2}S + RCH = 0 -> C{sub 6}H{sub 5}CH{sub 2}SH + RC = 0. La photoreduction de la benzophenone en propanol-2 aboutit a un benzopinacol par une reaction qui n'est pas en chaine et se fait par l'intermediaire des radicaux (C{sub 6}H{sub 5}){sub 2}C-OH and (CH{sub 3}){sub 2}COH. . La reaction est retardee et inhibee par les thioalcools et les disulfures qui retransforment les radicaux en produits de depart par reactions rapides de transfert d'atomes d'hydrogene et retrouvent eux-memes leurs etats de valence primitifs, chaque molecule du compose soufre annulant les effets chimiques de nombreux quanta: (C{sub 6}H{sub 5}){sub 2}C-OH + AS' -> (C{sub 6}H{sub 5}){sub 2}C = O + ASH; (CH{sub 3}){sub 2}C-OH + ASH -> (CH{sub 3}){sub 2}C = 0 + AS'. On trouve la preuve de ce mecanisme dans l'equilibrage du thioalcool ou disulfure initialement present, dans la racemisation de l'alcool optiquement actif et dans l'echange de deuterium, pendant l'inhibition. On constate une inhibition analogue lorsqu'un seul radical intermediaire se forme comme dans les systemes benzophenone-benzhydrol et acetophenone-alcool {alpha}-methylbenzyliquee. On constate une inhibition due aux composes soufres, par le meme mecanisme, dans la transformation de la benzophenone en benzopinacole, induite par les rayons gamma de {sup 60}Co; le naphtalene n'a aucun effet de protection sur la benzophenone dans ce systeme, alors qu'il arrete brusquement la reaction photochimique. La protection de solutes contre les effets des rayonnements au moyen de composes soufres resulte donc de reactions de transfert d'atomes d'hydrogene. La photoreduction de la benzophenone dans un ether est aussi inhibee par des reactions de transfert d'atomes d'hydrogene. Dans ce systeme (et non dans les systemes cetone-alcool), il existe un mecanisme par lequel les composes soufres peuvent etre consommes d'une maniere irreversible, ce qui entraftie une periode d'induction et non de retardement permanent, les effets d'environ 15 quanta etant annules par chaque molecule de compose soufre. (author) [Spanish] Es posible catalizar inhibir las reacciones inducidas por radicales libres, por accion fotoquimica y por radiaciones de alta energia aprovechando los rapidos intercambios de atomos de hidrogeno en mercaptanos y disulfuros. Los mercaptanos catalizan la descarbonilacion de aldehidos inducida por radicales, iniciada por la luz y sensibilizada por la benzofenona. La reaccion en cadena de transferencia de atomos de hidrogeno, R' + RCH = O -> RH + RC = O , se acelera mediante una secuencia similar de transferencias de atomos de hidrogeno donde interviene el compuesto sulfurado: R' + C{sub 6}H{sub 5}CH{sub 2}SH -> RH + C{sub 6}H{sub 5}CH{sub 2}S'; C{sub 6}H{sub 5}CH{sub 2}S + RCH = 0 -> C{sub 6}H{sub 5}CH{sub 2}SH + RC = 0. La fotorreduccion de la benzofenona a 2-propanol conduce al benzopinacol en virtud de una reaccion que no es en cadena y que pasa por los radicales (C{sub 6}H{sub 5}){sub 2}C-OH and (CH{sub 3}){sub 2}COH. La reaccion se retarda y se inhibe mediante mercaptanos y disulfuros, que reconvierten los radicales en los productos iniciales por medio de reacciones rapidas de transferencia de hidrogeno y que recobran sus estados de valencia primitivos; en ese proceso, cada molecula de compuesto sulfurado anula los efectos qufmicos de numerosos cuantos: (C{sub 6}H{sub 5}){sub 2}C-OH + AS' -> (C{sub 6}H{sub 5}){sub 2}C = O + ASH; (CH{sub 3}){sub 2}C-OH + ASH -> (CH{sub 3}){sub 2}C = 0 + AS'. La prueba de este mecanismo se halla en los siguientes procesos que se observan durante la inhibicion: equili- bratniento del mecaptano o disulfuro inicialmente presentes, racemizacion del alcohol opticamente activo e intercambio de deuterio. Se observa una inhibicion analoga cuando solo se forma un radical intermedio, como en los sistemas benzofenona-benzhidrol y acetofenona-alcohol-{alpha}-metilbencflico. La accion inhibidora de los compuestos sulfurados que obedece al mismo mecanismo, se observa en la transformacion de la benzofenona en benzopinacol, inducida por los rayos gamma del {sup 60}Co; si bien el naftaleno interrumpe la reaccion fotoquimica, no ejerce efecto protector alguno sobre la benzofenona en ese sistema. Asi, pues, la proteccion de los solutos contra las dafios radioinducidos mediante compuestos de azufre se debe a reacciones de transferencia de atomos de hidrogeno. Los compuestos sulfurados tambien inhiben en virtud de reacciones de transferencia de atomos de hidrogeno, la fotorreduccion de la benzofenona en eteres. Se observa en este sistema (a diferencia de los sistemas cetona- alcohol) un mecanismo por el cual los compuestos sulfurados pueden consumirse de manera irreversible. Esto conduce a un periodo de induccion en lugar de un retardo permanente; cada molecula de compuesto de azufre anula los efectos de unos 15 cuantos. (author) [Russian] Reakcii so svobodnymi radikalami, a takzhe fotohimicheskie i navedennye radiaciej bol'shoj jenergii reakcii mogut byt' katalizirovany ili zatormozheny bystrymi reakcijami obmena atoma vodoroda merkaptanov i disul'fidov. Navedennye pod vlijaniem sveta radikaly i senzitivirovannye benzofenonom reakcii dekarbonizacii aldegidov katalizirujutsja merkaptanami. Cepnaja reakcija posledovatel'nogo perenosa vodoroda R' + RCH = O -> RH + RC = O uskorjaetsja analogichnoj posledovatel'nost'ju perenosov atoma vodoroda s uchastiem slozhnyh soedinenij sery: R' + C{sub 6}H{sub 5}CH{sub 2}SH -> RH + C{sub 6}H{sub 5}CH{sub 2}S'; C{sub 6}H{sub 5}CH{sub 2}S + RCH = 0 -> C{sub 6}H{sub 5}CH{sub 2}SH + RC = 0. Fotovosstanovlenie benzofenona v 2-propanole vedet k obrazovaniju benzpinakola cherez necepnuju reakciju posredstvom radikalov (C{sub 6}H{sub 5}){sub 2}C-OH and (CH{sub 3}){sub 2}COH. Jeta reakcija zamedljaetsja i tormozitsja merkaptanom i disul'fidom, kotorye vnov' prevrashhajut radikaly v ishodnye materialy bystrymi reakcijami perenosa vodoroda, a sami reagenty regenerirujutsja v svoi sostojanija drugoj valentnosti, prichem kazhdaja molekula slozhnogo soedinenija sery prohodit bez himicheskih posledstvij cherez mnogie kvanty: (C{sub 6}H{sub 5}){sub 2}C-OH + AS' -> (C{sub 6}H{sub 5}){sub 2}C = O + ASH; (CH{sub 3}){sub 2}C-OH + ASH -> (CH{sub 3}){sub 2}C = 0 + AS'. Dokazatel'stvami takogo mehanizma mogut sluzhit': privedenie v sostojanie ravnovesija pervonachal'no prisutstvovavshego merkaptana ili disul'fida vo vremja tormozhenija; grozdevanie opticheski aktivnogo spirta vo vremja tormozhenija; obmen dejterija vo vremja tormozhenija. Analogichnoe tormozhenie nabljudaetsja pri obrazovanii odnogo tol'ko promezhutochnogo radikala, kak jeto proishodit v spirtovyh sostavah benzofenona - benzgidrola i acetofenona - {alpha} - metilbenzila. Tormozhenie slozhnymi soedinenijami sery putem takogo zhe mehanizma nabljudaetsja v navedennom gamma-luchami kobal'ta-60 prevrashhenii benzofenona v benzpinakol; naftalin ne proizvodit zashhitnogo vozdejstvija na benzofenon v sisteme s kobal'tom-60, no on zaglushaet fotohimicheskuju reakciju. Takim obrazom zashhita rastvorennyh veshhestv ot radiacionnogo porazhenija slozhnymi soedinenijami sery javljaetsja rezul'tatom reakcij perenosa atoma vodoroda. Fotovosstanovlenie benzofenona v jefire takzhe tormozitsja slozhnymi soedinenijami sery, opjat'-taki reakcijami perenosa atoma vodoroda. V takih soedinenijah sushhestvuet mehanizm (v protivopolozhnost' spirtovo -ketonovym soedinenijam), blagodarja kotoromu slozhnye soedinenija sery mogut byt' pogloshheny neobratimym obrazom. Jeto privodit k periodu indukcii, vmesto postojannogo zamedlenija, prichem kazhdaja molekula slozhnogo soedinenija sery mozhet projti bez posledstvij priblizitel'no cherez 15 kvant. (author)}
place = {IAEA}
year = {1965}
month = {Oct}
}