The kinetics for dichlorocyclopropanation of 1,7-octadiene with an excess of chloroform has been studied under phase-transfer catalysts and ultrasound irradiation conditions using aqueous sodium hydroxide as the base. The reaction was carried out at 30 degrees C and a pseudo-first order rate is used to describe the reaction rate at high alkaline concentration (>50 wt.%). Kinetics of the reaction including the effects of the reaction conditions on the conversion of 1,7-octadiene was investigated. A rational explanation was made for a peculiar phenomenon that the conversion of 1,7-octadiene was increased and then decreased with an increase in the amount of sodium hydroxide and the amount of phase-transfer catalyst, benzy1triethylammonium chloride (BTEAC). (C) 2007 Elsevier B.V All rights reserved.