Published March 1962
| Version v1
Book
Evaluation of deuterium isotope effects in photochemical reactions of formic-d acid by use of C14
Creators
- 1. Chemistry Division, Oak Ridge National Laboratory, Oak Ridge, TN (United States)
Description
The usefulness of measured values of primary and secondary deuterium kinetic-isotope-effect ratios in the study of organic reactions is well known. However, measurement of such ratios by direct methods is sometimes difficult. An indirect method which can be used to circumvent difficulties in some cases is illustrated by the determination of the primary deuterium isotope effects in the vapour-phase reactions between HCOOH + Cl2 and HCOOH + Br2 which under the influence of visible light give CO2 and respectively 2 HCl and 2 HBr. For the evaluation of kD/kH, the ratio of specific rate constants for reaction of formic-d acid and formic acid, a 50:50 mixture of DCOOH and HC14OOH was added to enough chlorine (or bromine) to effect reaction of approximately 5% of the mixture of acids. The C14 dioxide produced was precipitated as barium carbonate-C14, of which the specific activity (S5) was then determined by radioassay of the gas released when a sample was acidified. The specific activity (S100) of the barium carbonate-C14 representing 100% reaction of a portion of the 50:50 mixture of DCOOH and HC14OOH with excess chlorine was also determined. A simple equation was derived, making the reasonable assumption that the C14 isotope effects in the two reactions mentioned are negligibly small in comparison with the deuterium isotope effects. Using the equation, kH/kD values, 2.0 and 2.7, were calculated for reactions with Cl2 and Br2 respectively. An earlier study (Ropp, Danby, and Dominey, 1957) showed that reaction with Cl2 was accompanied by a much smaller C13 kinetic isotope effect than the reaction with Br2. This was taken as an indication that the carbon-hydrogen bond is stretched more in the transition state for the Br2 reaction than for the Cl2 reaction. The difference reported here between the corresponding deuterium isotope effects is less pronounced, though in the same direction as the difference between the C13 effects. A reasonable conclusion is that bromine-hydrogen bonds formed in the transition state for the reaction with Br2 largely compensate the stretching of the carbon-hydrogen bond. (author)
Abstract (French)
On sait qu'il est utile de connaitre les rapports quantitatifs qui existent entre les effets isotopiques cinetiques primaires et secondaires du deuterium pour l'etude des reactions organiques. Il est quelquefois difficile cependant de mesurer ces rapports par des methodes directes. Une methode indirecte qui permet de tourner ces difficultes dans certains cas consiste a determiner les effets isotopiques primaires du deuterium dans les reactions suivantes en phase vapeur: HCOOH + Cl2 lumiere/visible → 2HCl + CO2 (1); HCOOH + Br2 lumiere/visible → 2HB2 + CO2 (2). Pour l'evaluation de kD/kH - rapport des constantes de vitesse de reaction de l'acide formique-D et de l'acide formique - un melange a parts egales de DCOOH et de H14COOH a ete ajoute a une quantite de chlore (ou de brome) suffisante pour faire reagir environ 5% du melange d'acides. Le 14CO2 produit a ete precipite sous forme de Ba14CO3, dont l'activite specifique (S5) a ete ensuite determinee par radioexamen du gaz degage lorsqu'on a acidifie l'echantillon. L'activite specifique (S100) du Ba14CO3 obtenu apres reaction totale d'une partie du melange a parts egales de DCOOH et de H14COOH avec un exces de chlore, a ete egalement determinee. On en a tire une equation simple en partant de l'hypothese apparemment raisonnable que les effets isotopiques du carbone-14 dans les reactions (1) et (2) sont negligeables en comparison de ceux du deuterium. L'equation donne comme valeurs de kH/kD 2,0 et 2,7 pour les reactions (1) et (2) respectivement. Une etude anterieure (Ropp, Danby et Dominey, 1957) a montre que la reaction (1) s'accompagnait d'un effet isotopique cinetique du carbone-13 bien moindre que dans la reaction (2). Les auteurs avaient interprete cela comme indiquant que la liaison carbone-hydrogene s'etend davantage, dans l'etat de transition, pour la reaction (2) que pour la reaction (1). La difference signalee dans le memoire entre les effets correspondants du deuterium est moins prononcee, encore qu'elle se manifeste dans le meme sens. Il parait raisonnable d'en conclure que les liaisons bromehydrogene formees pendant l'etat de transition dans la reaction (2) compensent largement l'extension de la liaison carbone-hydrogene. (author)Abstract (Spanish)
Los valores medidos de las razones de los efectos isotopicos cineticos primarios y secundarios del deuterio son de evidente utilidad para el estudio de las reacciones organicas. Pero algunas veces es dificil medir estas razones por metodos directos. La determinacion de los efectos isotopicos primarios del deuterio en las siguientes reacciones en fase vapor constituye un ejemplo ilustrativo de un metodo indirecto que puede utilizarse para subsanar algunas dificultades: HCOOH+ Cl2 luz/visible → 2HCl + CO2 (1), HCOOH + Br2 luz/visible 2HBr + CO2 (2). Para evaluar el cociente kD/kh, esto es, la razon de las constantes especificas de velocidad de reaccion de los acidos formico-D y formico, el autor anadio una mezcla 50:50 de DCOOH y H14COOH a una cantidad suficiente de cloro (o de bromo) para que reaccione aproximadamente el 5 por ciento de la mezcla de acidos. Precipita como Ba14CO3 el 14CO2 que se forma y determina su actividad especifica (S5) analizando por metodos radioanaliticos el gas que se desprende al acidificar la muestra. Determina tambien la actividad especifica (S100) del Ba14CO3, que representa la reaccion total de una parte de la mezcla 50:50 de DCOOH y H14COOH con un exceso de cloro. Dedujo una ecuacion simple suponiendo licitamente que los efectos isotopicos del carbono-14 en las reacciones 1) y 2) son despreciables en comparacion con los efectos isotopicos del deuterio. Partiendo de esa ecuacion, calculalos valores 2,0 y 2,7 para los cocientes kH/kD correspondientes a las reacciones 1) y 2) respectivamente. Un estudio anterior (Ropp, Danby y Dominey, 1957) permitio comprobar que en la reaccion 1) el efecto isotopico cinetico del carbono-13 es mucho menor que el correspondiente a la reaccion 2). Este hecho se tomo como indicacion de que, en el estado de transicion, el enlace carbono-hidrogeno sufre un alargamiento mayor en la reaccion 2) que en la reaccion 1). La diferencia entre los correspondientes efectos isotopicos del deuterio que menciona la presente memoria es menos pronunciada, pero tiene la misma direccion que la diferencia entre los efectos del carbono-13. Conclusion logica es que los enlaces bromo-hidrogeno creados en el estado de transicion correspondiente a la reaccion 2) compensan en gran medida el alargamiento del enlace carbono-hidrogeno. (author)Abstract (Russian)
Shiroko izvestna poleznost' izmereniya obemov pervogo i vtorogo poryadka sootnoshenij kineticheskogo vozdejstviya izotopov dejteriya pri izuchenii organicheskikh reaktsij. Odnako izmereniya takikh sootnoshenij pryamymi sposobami v nekotorom rode zatrudneny. Primenenie kosvennogo metoda, kotoryj mozhet byt' ispol'zovan dlya togo, chtoby preodolet' trudnosti v ryade sluchaev, demonstriruetsya na opredelenii vozdejstvij izotopov dejteriya pervogo poryadka v sleduyushchikh reaktsiyakh paroobraznoj fazy: H COO H + Cl2 vidimyj/svet → 2 HCl + CO2 (1), H COO H + Br2 vidimyj/svet → 2HBr + CO2 (2). Dlya togo, chtoby proizvesti otsenku kD/kH-koehffitsienta spetsificheskoj skorosti konstant dlya reaktsij murav'inoj-d i murav'inoj kislot k dostatochnomu kolichestvu khlora (ili broma) dobavlyaetsya smes' 50:50 DCOOH i HC14OOH s tem, chtoby proizvesti reaktsiyu s priblizitel'no 5 % smesi kislot. Poluchennyj dioksid ugleroda-14 vydelyaetsya v osadok v-vide karbonata bariya-C14, spetsificheskaya aktivnost' (S5) kotorogo zatem zameryaetsya pri analize na radioaktivnost' vysvobozhdennogo gaza v moment okisleniya obraztsa. Takzhe opredelyaetsya spetsificheskaya aktivnost' (S100) karbonata bariya-C14, predstavlyayushchego 100%-nuyu reaktsiyu chasti smesi 50:50 DCOOH i HC14OOH s izlishnim khlorom. Bylo vyvedeno uravnenie, chto dalo vozmozhnost' sdelat' obosnovannoe utverzhdenie o tom, chto vozdejstvie izotopov ugleroda-14 v reaktsiyakh (1) i (2) ochen' malo v sravnenii s vozdejstviem izotopov dejteriya. Ispol'zuya uravnenie (3), byli podschitany KH/KD obemov 2,0 i 2,7 sootvetstvenno dlya reaktsij (1) i (2). Rannie issledovaniya (Ropp, Denbi i Dominej, 1957 god) pokazali, chto reaktsiya (1) prokhodila pri znachitel'no men'shem kineticheskom vozdejstvii izotopa ugleroda-13, chem reaktsiya (2). EHto bylo prinyato v kachestve pokazatelya togo, chto uglerodno-vodorodnaya svyaz' bolee usilivaetsya v perekhodnoj stadii v reaktsii (2), chem v reaktsii (1). Otmechaemoe v nastoyashchem issledovanii razlichie mezhdu sootvetstvuyushchimi izotopami dejteriya menee vyrazheno, khotya ono idet po tomu zhe napravleniyu, chto i razlichie mezhdu vozdejstviyami ugleroda-13. Delaetsya obosnovannyj vyvod o tom, chto bromo-vodorodnye svyazi, obrazuyushchiesya v perekhodnoj stadii dlya reaktsii (2), v znachitel'noj stepeni kompensiruyut uvelichenie uglerodno-vodorodnoj svyazi. (author)Additional details
Additional titles
- Original title (English)
- Evaluation a l'aide du
Publishing Information
- Publisher
- Globus, Druck- und Verlagsanstalt
- Imprint Place
- Vienna (International Atomic Energy Agency (IAEA))
- Imprint Title
- Radioisotopes in the Physical Sciences and Industry. Proceedings of the Conference on the Use of Radioisotopes in the Physical Sciences and Industry. V. III
- Imprint Pagination
- 652 p.
- Series
- Proceedings Series
- Journal Page Range
- p. 235-242
- ISSN
- 0074-1884
Conference
- Title
- Conference on the Use of Radioisotopes in the Physical Sciences and Industry
- Dates
- 6-17 Sep 1960
- Place
- Copenhagen (Denmark)
INIS
- Country of Publication
- International Atomic Energy Agency (IAEA)
- Country of Input or Organization
- International Atomic Energy Agency (IAEA)
- INIS RN
- 43113020
- Subject category
- S37: INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; S07: ISOTOPES AND RADIATION SOURCES;
- Resource subtype / Literary indicator
- Conference
- Descriptors DEI
- BARIUM CARBONATES; BROMINE; CARBON; CARBON 14; CARBON DIOXIDE; CHLORINE; DEUTERIUM; FORMIC ACID; HYDROBROMIC ACID; HYDROCHLORIC ACID; ISOTOPE EFFECTS; PHOTOCHEMICAL REACTIONS; REACTION KINETICS
- Descriptors DEC
- ALKALINE EARTH METAL COMPOUNDS; BARIUM COMPOUNDS; BETA DECAY RADIOISOTOPES; BETA-MINUS DECAY RADIOISOTOPES; BROMINE COMPOUNDS; CARBON COMPOUNDS; CARBON ISOTOPES; CARBON OXIDES; CARBONATES; CARBOXYLIC ACIDS; CHALCOGENIDES; CHEMICAL REACTIONS; CHLORINE COMPOUNDS; ELEMENTS; EVEN-EVEN NUCLEI; HALOGEN COMPOUNDS; HALOGENS; HYDROGEN COMPOUNDS; HYDROGEN ISOTOPES; INORGANIC ACIDS; INORGANIC COMPOUNDS; ISOTOPES; KINETICS; LIGHT NUCLEI; MONOCARBOXYLIC ACIDS; NONMETALS; NUCLEI; ODD-ODD NUCLEI; ORGANIC ACIDS; ORGANIC COMPOUNDS; OXIDES; OXYGEN COMPOUNDS; RADIOISOTOPES; STABLE ISOTOPES; YEARS LIVING RADIOISOTOPES
Optional Information
- Notes
- 1 fig, 1 tab, 9 refs
- Secondary number(s)
- STI/PUB--20(Vol.3)