This work investigates the phase-transfer catalytic (PTC) reaction of dichlorocycloproanation of 1,7-octadiene in an alkaline solution/organic solvent two-phase medium. The reaction is dramatically enhanced in the presence of quaternary ammonium salt. The reaction mechanism proposed is that the active dichlorocarbene (:CCl2) is first generated from the interfacial reaction of chloroform, sodium hydroxide and quaternary ammonium salt to form an active complex (QCCl(3)) of the dichlorocarbene (:CCl2) precursor. Then, this active complex QCCl(3) (or dichlorocarbene :CCl2), which transfers from the aqueous phase to the organic phase, further reacts with 1,7-octadiene to produce mono-dichlorocyclopropane and bi-dichlorocyclopropane in the organic phase. No other byproducts were detected during or after the reaction. The conversion of 1,7-octadiene is increased with the increase in the amount of NaOH in the aqueous phase. At lower alkaline concentration (30% NaOH or less), the reaction obeys a third-order rate law. However, a pseudo first-order rate law is sufficient to describe the kinetic behavior at higher alkaline concentration (>50% NaOH). Explanations are made for this discrepancy. The effects of the reaction conditions, such as quaternary ammonium salts, amount of catalyst, agitation, concentration of 1,7-octadiene, temperature, amount of chloroform, and amount of NaOH on the conversion were investigated in detail. (C) 2003 Elsevier Science B.V All rights reserved.