Bimolecular nucleophilic displacement at tertiary carbon centers: Aminolyses of 2-cyano-2-propyl and 1-cyanocyclooctyl arenesulfonates
✍ Scribed by Hyuck Keun Oh; Young Bong Kwon; Dong Soo Chung; Ikchoon Lee
- Publisher
- John Wiley and Sons
- Year
- 1996
- Tongue
- English
- Weight
- 416 KB
- Volume
- 9
- Category
- Article
- ISSN
- 0894-3230
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✦ Synopsis
Kinetic studies were carried out on the reactions of anilines with 2-cyano-2-propyl and 1-cyanocyclooctyl arenesulfonates in acetonitrile at 50.0"C. The second-order rate constants for the former are in general greater than those for the latter but the rates of the two become comparable for a strong nucleofuge. The crossinteraction constants, pxz (and pXz), are considerably smaller (cu -0.04) than those for the primary (cu 0.33) and secondary (cu 0-12) compounds. The negative sign and small magnitude are consistent with a dissociative S,2 mechanism with a loose transition state structure. The uC initio MO theoretical results for CI-+ RCI-CIR + Cl-at the MP2 level (MP2/6-31+ G*//MP2/6-31+ G*) confirm the Jooseness of the transition state for the tertiary (R) alkyl compounds. The average r&l,.,cl~ value is 4.8fiiO-03 A, which is larger than those for the reactions at primary (4.68 f 0.02 A) and secondary (4.80 f 0.02 A) carbon centers. Thus a looser transition state with a smaller magnitude of pxz for the tertiary carbon centers has a larger theoretical r7c,...c,, value.