SummaryThe unstrained 3-chloroalcohols l a , 2a and 3a do not undergo solvolytic fragmentation in neutral and weakly acidic 80% ethanol, only substitution and elimination products being formed by the limiting S N l -El mechanisms. This also applies to the corresponding ethers l b and 3b. Addition of sodium hydroxide causes the observed rate constants for the 3-chloroalcohols to rise steeply by factors of at least lo3 to lo5. These level off at higher base concentrations due to an opposing ionic strength effect. Whereas 3a fragments quantitatively in the presence of base, l a and 2a fragment in competition with elimination to the d3-olefins 9a and 10, respectively. 2a also yields 2% of the oxetane 6b.These results support a concerted base-induced fragmentation mechanism which competes with intramolecular base-induced elimination ( E l ) in the case of the acyclic chloroalcohols l a and 2a. The formation of small amounts of the oxetane 6b from 2a is attributed to intramolecular nucleophilic substitution at the tertiarv carbon atom.Several 3-X-substituted propanols I (Scheme I ) , where X denotes a nucleofuge such as a chlorine atom, have been reported to undergo base-induced olefin-forming fragmentation (F) [ 11 [2]. However, cyclization (C) to oxetanes, nucleophilic substitution (S) and elimination (E) often compete with fragmentation [3-51.Thus, when treated with sodium hydroxide acyclic primary chlorides I tend to undergo substitution and cyclization rather than fragmentation. Only when gemiinal alkyl groups are present at C(2) does the latter reaction occur to a larger extent ([3]. Base-induced fragmentations of acyclic secondary halides I are rare, while tertiary halides do not appear to have been studied, presumably because of their instability [5]. Base-induced fragmentation of a number of rigid secondary and tertiary cyclic 3-X-substituted alcohols has been observed [6] in cases where the sequence of atoms pO-C-C-C-X meets the well-established stereoelectronic requirements