Activating effects of unsaturated and cyclopropyl groups in gas phase pyrolysis of acetates. Paper XVIII

Abstract

The activating effects of a number of unsaturated groups and a cyclopropyl group have been evaluated in a solvent free system by determining the absolute rate constants, and energies and entropies of activation in the vapor phase pyrolysis of secondary and tertiary esters of the type RC(R'CH,)OAc where R' = H or CH, and R = c-Pr, i-Pr, CH,, CH,=CH, CH,=CHCH,, C,H, ; the cyclopropyl showed only a moderate activating effect. The results are in contrast to the very significant activating effect of a cyclopropyl group in solvolysis of cyclopropylcarbinyl derivatives. iZpparently marked activation by this group occurs only when a highly developed positive center forms adjacent to it. The lack of marked activation by the cyclopropyl group supports a mechanism for ester pyrolysis which involves a modest, but detectable, charge separation in the transition state [Z] but questions a mechanism in which a n intimate ion-pair was proposed [3].

The Thermal Decomposition of N-Arylcarbamates of t-Alcohols. 2. Effects of Solvent, Temperature, and Substituents

“…C2H5, CH=CH, respectively. These may be compared to the relative rates of 1.0 : 1.5 (5 10 K), 2.5 (584 K ) : 4.1 (570 K ) for gas-phase pyrolysis of the corresponding acetates (17,15,10).…”

Thermal decomposition products of phthalates with poly(vinyl chloride) and their mutagenicity

“…The thermal decomposition of phthalates begins by way of a cis elimination 13 and finally produces 1-olefin, phthalic anhydride and the alcohol corresponding to the side chain. The determined amount of phthalic anhydride is equivalent to the decomposed phthalate.…”

“…A silicone oil bath was heated by an immersion heater to a temperature between 150-300 o C which was maintained within · 3 o C by a temperature controller, Pulthermo (Toho Kagaku Co., Tokyo, Japan). For the identification of the decomposition products 1 H-NMR, 13 C-NMR, high-resolution MS, GC-MS and IR were used. The gas chromatography (GC) procedure for the qualitative and quantitative analyses of the thermal decomposition products is as follows:…”

Gas-phase pyrolysis kinetics of 2-substituted-2-propyl acetates. Effect of substituents on the .alpha.-carbon of tertiary acetates

“…(c) If the polarization of the C«-0 bond, in the sense of Cas+...Os~, is rate determining (1), then vinyl, phenyl, and cyclopropyl groups should interact and/or delocalize their available electrons with the p orbital of the adjacent positively charged carbon atom. 16 Therefore, these substituents should be correlated with + constants. However, + values are used for substituents on the benzene ring and not directly at the reaction site because a steric factor can simultaneously interfere in the latter case.…”