Thermal bridgehead double inversion of the 6-methylene- and 6-ethylidene-2-methylbicyclo[3.1.0]hexanes. Rotational kinetic deuterium isotope effects and the mechanism of the thermal interconversion of cis- and trans-2,3-dimethylmethylenecyclopropanes via trimethylenemethane singlet biradicals

1977 ◽  
Vol 99 (17) ◽  
pp. 5696-5707 ◽  
Author(s):  
Joseph J. Gajewski ◽  
Shine K. Chou
Keyword(s):  
Isotope Effects ◽  
Deuterium Isotope Effects ◽  
Cis And Trans

scholarly journals Deuterium Isotope Effects in the Oxidation of 2,3-Dimethyl-2-butene via the Bromohydroperoxide, by Singlet Oxygen and by Triphenyl Phosphite Ozonide

1972 ◽  
Vol 50 (24) ◽  
pp. 4034-4049 ◽  
Author(s):  
Karl R. Kopecky ◽  
Johan H. van de Sande
Keyword(s):  
Singlet Oxygen ◽  
Isotope Effect ◽  
Isotope Effects ◽  
Bond Breaking ◽  
Triphenyl Phosphite ◽  
Deuterium Isotope Effect ◽  
Major Isomer ◽  
Deuterium Isotope Effects ◽  
Oxygen Oxidation ◽  
Cis And Trans

The partially deuterated alkenes (CH3)2C = C(CD3)2 (1b) and CH3CD3C = CCH3CD3 (1c) were prepared and converted to the corresponding allylic hydroperoxides by the routes shown in the title. Two bromohydroperoxides were formed from 1b in a 1.6:1 ratio with the major isomer having the OOH group on the carbon bearing the CH3's. On treatment with base at 0° this mixture formed two allylic hydroperoxides in a 2.2:1 ratio with the major isomer having the OOH group on the carbon bearing the CD3's, showing migration of the OOH group. This isomer predominated in a 1.4:1 ratio when 1b was oxidized with singlet oxygen at 15 or −52° and in a 1.6:1 ratio when 1b was oxidized with triphenyl phosphite ozonide at −70°. Under the same conditions C—H bond breaking also predominated in the oxidation of 1c, by 2.1:1 via the bromohydroperoxide, by 1.4:1 with singlet oxygen, and by 1.3:1 with triphenyl phosphite ozonide. Migration of the OOH group in the reaction of the bromohydroperoxide of 1b does not occur by way of a 1,2-dioxetane. A perepoxide may be the intermediate. Neither perepoxides nor 1,2-dioxetanes are involved in the singlet oxygen oxidation of 1b and c. At −70° the triphenyl phosphite ozonide oxidations do not proceed by way of these intermediates, either, or by way of singlet oxygen. The intermolecular deuterium isotope effect in the singlet oxygen oxidation of both cis- and trans-2,3-diphenyl-2-butene was found to be 1.1.

Solvation differences in the hydrolysis of certain alicyclic bromides

1970 ◽  
Vol 48 (8) ◽  
pp. 1296-1301 ◽  
Author(s):  
H. S. Golinkin ◽  
D. M. Parbhoo ◽  
R. E. Robertson
Keyword(s):  
Heat Capacity ◽  
Isotope Effects ◽  
Trans Isomers ◽  
Apparent Heat Capacity ◽  
Deuterium Isotope Effects ◽  
Cis And Trans ◽  
Hydrolysis Of

A detailed study of the hydrolysis in water of the cis and trans cyclopentyl and cyclohexyl bromohydrins reveals significant differences in the apparent heat capacity of activation (ΔCp≠). The cis isomers have values of[Formula: see text]; the same value as found for cyclopentyl bromide, but more negative by 10 caldeg−1 mole−1 than that found for the hydrolysis of cyclohexyl bromide. By contrast, the corresponding value for trans isomers was about −45 cal deg−1 mole−1. The differences in ΔCP≠ can be explained in terms of different mechanisms. Secondary β-deuterium isotope effects of 2.28 for the cis-2-bromocyclopentanol-1-d and 2.45 for cis-2-bromocyclohexanol-1-d confirm hydrogen participation in these cases. The corresponding ketones were the only products detected.

Mechanism of hydration and isomerisation of 4-ethylidene-2,6-di-tert-butyl-2,5-cyclohexadien-1-one. Kinetics, acid-base catalysis and solvent deuterium isotope effects

1979 ◽  
Vol 44 (1) ◽  
pp. 110-122 ◽  
Author(s):  
Jiří Velek ◽  
Bohumír Koutek ◽  
Milan Souček
Keyword(s):  
Aqueous Medium ◽  
Rate Equation ◽  
Kinetic Data ◽  
Isotope Effects ◽  
Base Catalysis ◽  
Quinone Methide ◽  
Reaction Products ◽  
Acid Base ◽  
Deuterium Isotope Effects ◽  
Hydroxybenzyl Alcohol

Competitive hydration and isomerisation of the quinone methide I at 25 °C in an aqueous medium in the region of pH 2.4-13.0 was studied spectrophotometrically. The only reaction products in the studied range of pH are 4-hydroxybenzyl alcohol (II) and 4-hydroxystyrene (III). The form of the overall rate equation corresponds to a general acid-base catalysis. The mechanism of both reactions for three markedly separated pH regions is discussed on the basis of kinetic data and solvent deuterium effect.

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