The reactions of 4-chloro-2-butanol and 3-chloro-1-butanol with aqueous sodium hydroxide, and 1-chloro-2-propanol and 2-chloro-1-propanol with isopropyl amine

The total reaction of 4-chloro-2-butanol 1 with NaOH(aq) is dominated (74%) by intramolecular substitution (S(N)i), besides which bimolecular substitution (S(N)2, 12%) and 1,4-elimination (i. e. fragmentation, contrary to earlier arguments) exhibit a significant contribution (11%). The total reaction of 3-chloro-1-butanol 2 instead is dominated by 1,4-(72%) and 1,2-elimination (25%), the substitution reactions being just observable (S(N)i 2% and S(N)2 1%). In 1 both the +I-effect and the conformational factors in the intermediate gamma-chloroalkoxy anion favour the S(N)i-reaction, whereas in 2 the situation is opposite and the location of Cl on a secondary carbon also makes the S(N)i-reaction less favourable. The relative proportions of 1,4-and 1,2-eliminations for 2 can be explained by thermodynamic basis since the consequent products are more stable than the corresponding products from 1. 1-chloro-2-propanol 3 and 2-chloro-1-propanol 4 both react with isopropyl amine giving the same product, namely 1-isopropylamino-2-propanol, which indicates that the reaction proceeds through the propylene oxide intermediate. Compound 1 also reacted with isopropyl amine predominantly via S(N)i-reaction, giving first 2-methyloxetane which then further gave 4-isopropylamino-2-butanol, whereas 2 gave 3-isopropylamino-1-butanol through a direct S(N)2-reaction.