scholarly journals HYDRIDE TRANSFER TO CARBONIUM IONS: I. THE MECHANISM OF THE REDUCTION OF TRIPHENYLMETHYL CARBONIUM ION IN FORMIC ACID

1957 ◽  
Vol 35 (8) ◽  
pp. 766-777 ◽  
Author(s):  
Ross Stewart
Keyword(s):  
Formic Acid ◽  
Kinetic Isotope Effect ◽  
Hydride Transfer ◽  
Resonance Spectroscopy ◽  
Hydride Ion ◽  
Carbonium Ion ◽  
Kinetic Isotope ◽  
Carbonium Ions ◽  
Entropy Of Activation ◽  
Rate Controlling Step

In an attempt to prove that reduction can take place by hydride transfer, the conversion of triphenyl carbinol in formic acid to triphenylmethane via the carbonium ion was examined. Kinetic and isotopic proof was obtained for the following mechanism:[Formula: see text][Formula: see text]The rate law based on the above mechanism is[Formula: see text]where R = C6H5, which leads to the integrated rate expression[Formula: see text]This equation was found to be obeyed under a variety of conditions.Anhydrous formic-d acid was synthesized in good yield by the glycerol catalyzed decomposition of oxalic acid-d2. The concentration of deuterium was shown by nuclear magnetic resonance spectroscopy to be greater than 99%. Use of this material in the reduction gave a kinetic isotope effect and led to isolation of triphenylmethane which had greater than 97% deuterium in the α-position, thus supporting the idea that a hydride ion was transferred from formate ion to the carbonium ion.The energy and entropy of activation for the rate controlling step have been found to be 18.3 kcal. per mole and −7.5 e.u. The negative ΔS‡ is presumably due to the less likely orientation for the transition state A as compared to B.[Formula: see text]

H/D kinetic isotope effect in HCOOH cis–trans conversion of formic acid in noble gas matrices

2013 ◽  
Vol 574 ◽  
pp. 47-50 ◽  
Author(s):  
Leonid I. Trakhtenberg ◽  
Anatoly A. Fokeyev ◽  
Alexander M. Mebel
Keyword(s):  
Formic Acid ◽  
Isotope Effect ◽  
Kinetic Isotope Effect ◽  
Noble Gas ◽  
Kinetic Isotope

Synthesis of 5H-dibenzo[a,d]cycloheptene-5-carboxylic acid and related compounds. 1,5-Hydride transfer to inductively destabilized carbonium ions

1968 ◽  
Vol 46 (23) ◽  
pp. 3665-3670 ◽  
Author(s):  
D. E. Horning ◽  
J. M. Muchowski
Keyword(s):  
Carboxylic Acid ◽  
Carbonyl Group ◽  
Isotope Effect ◽  
Hydride Transfer ◽  
Large Magnitude ◽  
Carbonium Ion ◽  
Carbonium Ions ◽  
Acid Catalyzed ◽  
Derivatives Of ◽  
Related Compounds

The synthesis of 10,11-dihydro-5H-dibenzo[a,d]cycloheptene-5-carboxylic acid (2) and several derivatives of 5H-dibenzo[a,d]cycloheptene-5-carboxylic acid (1; a–c) from 5-hydroxy-10,11-dihydro-5H-dibenzo[a,d]cycloheptene-5-carboxylic acid and derivatives thereof (3; a–c) is described.The p-toluenesulfonic acid-catalyzed elimination of water (at 110.6° in toluene) from the deuterated hydroxy ester (3b; C-10, 11 d2) resulted in the incorporation of deuterium at C-5 of the olefinic ester 1b with a KH/KD of 2.76. The large magnitude of this isotope effect indicated that the reaction proceeded via a rate-determining transannular 1,5-hydride transfer from one of the benzylic positions of 3b to the carbonium ion generated alpha to the methoxy-carbonyl group.

Kinetic isotope effect and tunnelling in the proton transfer reaction between 2,4,6-trinitrotoluene and 1,1′,3,3′-tetramethylguanidine in dimethylformamide solvent

1979 ◽  
Vol 57 (6) ◽  
pp. 669-672 ◽  
Author(s):  
Arnold Jarczewski ◽  
Przemyslaw Pruszynski ◽  
Kenneth T. Leffek
Keyword(s):  
Proton Transfer ◽  
Isotope Effect ◽  
Kinetic Isotope Effect ◽  
Transfer Reaction ◽  
Proton Transfer Reaction ◽  
Deuterium Isotope Effect ◽  
Kinetic Isotope ◽  
Enthalpy Of Activation ◽  
Entropy Of Activation ◽  
Large Primary

The proton transfer reaction between 2,4,6-trinitrotoluene and 1,1′,3,3′-tetramethylguanidine in dimethylformamide solvent shows a large primary deuterium isotope effect, kH/kD = 24.3 at 0 °C and 16.9 at 20 °C. The enthalpy of activation difference (ΔHD≠ − ΔHH≠) = 2.6 ± 0.4 kcal mol−1 and the entropy of activation difference (ΔSD≠ − ΔSH≠) = 3.4 ± 1.3 cal mol−1 K−1. This isotope effect, when fitted to Bell's equation, indicates that there is a considerable contribution to this reaction from tunnelling of the proton through the potential energy barrier.

Hydride transfer reactions. A kinetic study of oxidation of 10-methyl-9-phenylacridan by some π acceptors and a one-electron oxidant

1985 ◽  
Vol 63 (8) ◽  
pp. 2237-2240 ◽  
Author(s):  
Allan K. Colter ◽  
A. Gregg Parsons ◽  
Karen Foohey
Keyword(s):  
Kinetic Study ◽  
Kinetic Isotope Effect ◽  
Isotope Effects ◽  
Hydride Transfer ◽  
Transfer Reactions ◽  
Kinetics Of Oxidation ◽  
Kinetic Isotope ◽  
One Step ◽  
The One ◽  
Kinetics Of

The kinetics of oxidation of 10-methyl-9-phenylacridan (1(H)) and 9-deuterio-10-methyl-9-phenylacridan (1(D)) to 10-methyl-9-phenylacridinium ion (3) by eight oxidants have been investigated. The oxidants included the π-acceptors 1,4-benzoquinone (BQ), 7,7,8,8-tetracyanoquinodimethane (TCNQ), p-bromanil (BA), p-chloranil (CA), tetracyanoethylene (TCNE), 2,3-dicyano-1,4-benzoquinone (DCBQ) and 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) in acetonitrile (AN), BQ in 50:50 (v/v) AN-water, and the one-electron oxidant tris(2,2′-bipyridyl)cobalt(III), [Formula: see text] in AN. The seven π acceptors cover a 109-fold range of reactivity from BQ to DDQ and the deuterium kinetic isotope effect varies from 11.9 (BQ in AN) to 5.8 (DDQ). For π acceptors (BQ, TCNQ, CA, TCNE, and DCBQ) previously investigated with 10-methylacridan (NMA), 1(H) is less reactive than NMA by factors ranging from 9.1 (BQ) to 1.7 × 102 (TCNE). The isotope effects and relative reactivities for the π acceptor oxidations are most simply explained by a one-step hydride transfer mechanism.

Hydride transfer from NADH analogues to a nonheme manganese(iv)–oxo complex via rate-determining electron transfer

2014 ◽  
Vol 50 (85) ◽  
pp. 12944-12946 ◽  
Author(s):  
Heejung Yoon ◽  
Yong-Min Lee ◽  
Wonwoo Nam ◽  
Shunichi Fukuzumi
Keyword(s):  
Electron Transfer ◽  
Charge Transfer ◽  
Isotope Effect ◽  
Kinetic Isotope Effect ◽  
Hydride Transfer ◽  
Charge Transfer Complexes ◽  
Kinetic Isotope ◽  
Transfer Step

Hydride transfer from NADH analogues to a nonheme Mn(iv)–oxo complex, [(Bn-TPEN)MnIV(O)]2+, proceeds via a rate-determining electron transfer step with no deuterium kinetic isotope effect (KIE = 1.0 ± 0.1) and via charge-transfer complexes formed in the reactions of Mn(iv)–oxo and NADH analogues.

Sign in / Sign up

Export Citation Format

Share Document