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

✍ Scribed by Kin K. Lum; Grant Gill Smith

• Book ID: 102926246
• Publisher: John Wiley and Sons
• Year: 1969
• Tongue: English
• Weight: 598 KB
• Volume: 1
• Category: Article
• ISSN: 0538-8066
• DOI: 10.1002/kin.550010406

✦ Synopsis

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].