Six related oxiranes (thecisandtransisomers derived from 3-methoxycyclopentene and from 3-methoxycyclohexene, as well as the oxiranes from the corresponding unsubstituted olefins) were each treated under the same conditions with an acidic solution containing charged and uncharged nucleophiles (chloride ion, water, and methanol). The corresponding perchloric acid catalyzed scissions were also carried out. Accurate and reproducible methods of product analysis for the reaction mixtures were developed. In this way, nucleophilic attacks upon different oxiranes were compared directly. Attacks by different nucleophiles upon the same oxirane, or by a single nucleophile upon different positions of the same oxirane, were compared in the very same solution. The results are considered to provide the most extensive demonstration of the effects of charge orientation yet available. The synthesis of some new isomeric 1,2,3-trisubstituted diols and dimethoxyalcohols are reported.