A theoretical approach to substituent effects: Stabilities and conformational preferences in β-substituted ethyl radicals |
| |
Authors: | Addy Pross Leo Radom |
| |
Affiliation: | Research School of Chemistry, Australian National University, Canberra, A.C.T. 2600, Australia |
| |
Abstract: | Ab initio molecular orbital theory is used to study substituent effects in a series of β-substituted Et radicals XCH2CH2. For X = BH2 (plan.), CH3, NH2, OH and F, only slight conformational preferences and weak stabilizations are indicated. Such behaviour may be rationalized, using a PMO model, in terms of opposing changes, accompanying variation in X, in positive and negative hyperconjugation between the XCH2 group and the CH2 centre. On the other hand, for groups containing an appropriately oriented, low-lying vacant orbital, viz. X = Li, BeH and BH2 (perp.), there is a pronounced preference for the perpendicular conformation of the radical. This is attributed to 1,3-interaction between the singly-occupied 2p(C) orbital and the vacant 2p(X) orbital. |
| |
Keywords: | Permanent address: Department of Chemistry Ben Gurion University of the Negev Beer Sheva Israel. |
本文献已被 ScienceDirect 等数据库收录! |
|