ORIENTATION OF OLEFIN-FORMING ELIMINATION IN REACTIONS OF 2-SUBSTITUTED HEXANES WITH POTASSIUM T-BUTOXIDE IN DIMETHYL SULFOXIDE

Compositions of the olefin product mixtures from the action of t-BuO-K+-dimethyl sulfoxide on 13 2-substituted hexanes are reported. Reactions were carried out under continuous flushing with nitrogen gas, and product isomerization was negligible. In most cases, the fractional yield of 1-hexene is lower in this system than in t-BuO-K+-t-BuOH. 2-Hexene trans/cis ratios vary dramatically. The very high transjeis ratios of about 5.0 from 2-hexyl chloride, bromide, and iodide suggest that syn elimination occurs, while the very low ratios of about 0.4 from 2-hexyl fluoride and 2-hexyl phenyl ether suggest exceptional solvation of transition states when the leaving groups detach as highly basic ions of low polarizability. In a general way, positional orientation seems to correlate with the ease or difficulty of detaching the leaving group, and therefore with the relative degrees of breaking of the Cβ-H and Cα-X bonds in the transition state. © 1969, American Chemical Society. All rights reserved.