SOLVOLYSIS RATES AND BETA-DEUTERIUM SECONDARY KINETIC ISOTOPE EFFECTS OF SOME TERTIARY AND SECONDARY ALK-5-ENYL DERIVATIVES - EVIDENCE FOR PI-PARTICIPATION

Tertiary 1,1-dimethylalk-5-enyl chlorides solvolyze in 80% v/v ethanol with no or moderate rate enhancements attributable to pi-participation. However, secondary beta-deuterium kinetic isotope effects (KIE, two deuterated methyl groups) are significantly reduced (k(H)/k(D) = 1.22-1.57) relative to the saturated analogues (k(H)/k(D) = 1.80), indicating participation of the double bond. Secondary 1-methylalk-5-enyl tosylates show the same trends, i.e., no or very moderate rate enhancements but reduced beta-deuterium secondary KIE relative to the saturated analogue.