The specific rates of solvolysis have been determined for chloromethyl ethyl ether (3) and chloromethyl octyl ether (4) at −10.0 °C and for chloromethyl methyl sulfide (5) at 25.0 °C in a variety of pure and binary solvents. These values were used for a correlation analysis treatment using the extended Grunwald–Winstein equation incorporating literature values for solvent nucleophilicity (NT) and solvent ionising power (YCl). Appreciable values were found for the sensitivities towards changes in both NT and YCl values. Using a literature specific rate of hydrolysis at 25.0 °C for fluoromethyl methyl ether (2), the required value for chloromethyl methyl ether (1) was obtained from use of NT and YCl values and the sensitivities for 3 to changes in their values, to adjust an experimental specific rate value for 1 in 100% ethanol to the corresponding value in 100% water. In this way, an estimated kCl/kF of 1.2 × 105 was obtained, essentially identical to values for the solvolyses of tert-butyl halides. A unimolecular mechanism for the solvolyses, with appreciable nucleophilic solvation of the developing carbocation, is proposed. Electronic supplementary information provides, for several solvents, specific rates of solvolysis for 3, 4, and 5 at additional temperatures and the calculated activation parameters.