Reactions of cyclic alkyl radicals. Part 3.—Kinetics of decomposition of bi-cyclopropylformyl peroxide

Abstract

The thermal decomposition of bicyclopropylformyl peroxide in p-cymene solution has been studied in the temperature range 70-113°C. Values of log A(sec-') = 14.05 and E(kca1 mole-') = 29.8 have been obtained for the Arrhenius parameters for the decomposition reaction : D COO. OCO 0 +2 D COZ. Cyclopropyl radicals are generated by the subsequent decarboxylation of the cyclopropylcarboxyl radicals and dimerize forming bicyclopropyl, and to react by hydrogen atom abstraction with the solvent with an estimated activation energy of 7.3 kcal mole-'.We have studied previously the gas-phase reactions of cyclopropyl radicals, generating them by the methyl-radical-sensitized decomposition of cyclopropane carboxaldehyde and also by the direct photolysis of the aldehyde.2 Our results indicated that cyclopropyl radicals abstracted hydrogen atoms readily from the aldehyde, dimerized to yield bicyclopropyl, isomerized to allyl radicals with an activation energy of ca. 20 kcal mole-l and that cyclopropylcarbonyl radicals were appreciably more stable than other acyl radicals.Bi-acyl peroxides are 3-5 good sources of alkyl radicals, the initial 0-0 bond fission (reaction (1)) being followed by extensive decarboxylation of the acyloxy radical (reaction (2)) thereby generating an alkyl radical :

Orbital symmetry, orbital stability, and orbital pairing rules for organic reactions in the ground state

“…However the forbidden character of the former mode is more marked that the latter, suggesting the following reactivity order: (i) abstraction (FA), (ii) disrotatory opening (FF), and (iii) conrotatory opening (AF) [58]. This is in accord with experiments [62] and other theoretical results [63-681. However, substituted cyclopropyl radicals (23) were ring-opened to the corresponding allyl radicals (24) [66,67].…”

Conversion of benzo- and naphthonorcaradien-7-yl to benzo- and naphthotropyl radicals

“…We examined the hydrocarbon products, 2,3-benzonorcaradiene (11) and 1,2-benzotropilidene (12) from 7 and 9, and 2,3-(2',3'-naphtho)norcaradiene ( 14) and 1,2-(2,,3,-naphtho)tropilidene (15) "R = benzo for 7 and 9 and R = 2,3-naphtho for 8 and 10. 6 Consists of material which was insoluble in benzene and of a large number of other compounds none of which amounted to more than a few percent. Because of the small amount of each component, none was identified.…”

“…The yellow solid residue was dissolved in the minimum amount of CHCI3 and petroleum ether (bp 30-60 °C) was added until the solution was turbid. Cooling afforded tan crystals of 2,3-(2',3'-naphtho)norcaradiene-7-carbonyl chloride (1.2 g, 82%); mp 153-155°C;IR(Nujol) 1760 cm"1; NMR (CDCI3) 7.5 (m, 6, Ar//), 6.2 (m, 2, -CH=CH-), 3.3 (m, 1, Ar-C//-CH-), 2.9 (m, 1, =CH-C//-CH-), 1.3 (t, 1, >C//-COCl) ppm. ferf-Butyl 2,3-(2',3'-Naphtho)norcaradiene-7-percarboxylate (8).…”

“…This is in spite of the known aromaticity of the tropyl radical. 8 This paper describes our attempts to observe the ring opening of the 2,3-benzonorcaradien-7-yl radical (3) to produce the benzotropyl radical (4) and also the ring opening of the 2,3-(2',3'-naphtho)norcaradien-7-yl (5) radical to produce the naphthotropyl radical (6). We felt that ring opening might 3, R = benzo 4, R = benzo 5, R = 2,3-naphtho 6, R = 2,3-naphtho be observable under an appropriate set of conditions since these should be highly exothermic reactions.…”

Photolysis of 1,1,1-trifluoromethylazocyclopropane. Fate of the N.N-c-C3H5 radical

“…Free cyclopropyl radicals should readily abstract hydrogen from 2,3-dimethylbutane. 13 The isolation of CF3-c-C3H6 from the products of liquidphase photolysis could be interpreted as evidence for the formation of c-C3H6, i.e., the rearrangement of the diazonium radical might compete with its decomposition into N2 + • <(|.…”