Secondary deuterium isotope effects in radical-forming reactions. V. tert-Butyl peracetate and substituted tert-butyl phenylperacetates

Abstract

The secondary deuterium isotope effects on the thermal decomposition of t-butyl peracetate (6), t-butyl p-nitrophenylperacetate (7), and t-butyl p-methoxyphenylperacetate (8) have been measured. The isotope effect for compound 6 is very small (kH/kD = 1.00 =k 0.02 in isooctane at 130.10"). The isotope effect on the decomposition of 7 is 1.10 for two deuteriums at 85 O in chlorobenzene and 1.09 at the same temperature in Nujol. Compound 8 has an isotope effect of 1.07 for two deuteriums in isooctane at 60.4", and at the same temperature in Nujol the effect is found to be 1.05. The very small isotope effect for 6 is interpreted in terms of a nonconcerted decomposition, while the larger effects observed for 7 and 8 are compared to that observed in the case of t-butyl phenylperacetate. A study of oxygen-18 scrambling in the decomposition of 6 is discussed in terms of possible mechanistic refinements for perester decompositions.he thermal decomposition of peresters has been

Thermolysis of organic peroxides in solution

“…An increase in the solvent viscosity favours reverse recombination and increases the degree of averaging of the label content. The secondary isotope effect (k H /k D ) observed in the thermal decomposition of tert-butyl peroxyacetate is equal to unity, 139 which points to a non-synchronous cleavage of the bonds in its decomposition. At the same time, the magnitude of the isotope effect for tert-butyl p-methylphenylperoxyacetate and its derivatives markedly exceeds unity [1.03 ± 1.06 per one H(D) atom], which unequivocally testifies to a synchronous mechanism of their decomposition.…”

Steric driving forces in perester decomposition. tert-Butylperoxy di-tert-butylacetate

“…(or deuterium) and Pd(II) by concerted diaxial diequatorial type shifts. 3 One way to test Scheme I is to use a reagent that will add cis to cyclohexene. If homoallylic product arises from cis palladium hydride (or deuteride) eliminations and readditions as shown in Scheme I, the arrangement of protons in the homoallylic product will be different from that found in 1.…”

Secondary α-Deuterium Kinetic Isotope Effects Signifying a Polar Transition State in the Thermolysis of Ring-Substituted tert-Butyl Phenylperacetates

“…Secondary α-deuterium kinetic isotope effects (SDKIE) were reported for 2 with substituent Y being p- OCH 3 ( k H / k D = 1.07 at 60.46 °C), p -H ( k H / k D = 1.13 at 84.98 °C), and p -NO 2 ( k H / k D = 1.10 at 85.1 °C). A k H / k D value of 1.13 for p -H could be consistent with two-bond homolysis.…”