Synergetic effect of two kinds of phase transfer catalysts in third phase for dehydrohalogenation of 2-bromooctane

Dehydrohalogenation of 2-bromooctane in the organic phase with dodecane sol vent by using phase transfer catalysts (PTC) was carried out in a batch rea ctor with potassium hydroxide solvent in the aqueous phase. A synergetic ef fect of PTC was observed for the combination of tetrahexyl ammonium bromide ((Hex)(4)NBr) and polyethylene glycols (PEG) in the third phase. The obser ved reaction rate constant (k(obs),), which is determined from the first or der kinetics, depends on the average molecular weight of PEG, and remarkabl y increases with the increasing KOH concentration in the aqueous phase. If the optimum combination of (Hex)(4)NBr and PEG with average molecular weigh t of 200 (PEG200) is used, the amount of quaternary ammonium salt can be si gnificantly saved (for example, by one-nineteenth). The volume of the third phase and the concentration of water in the third phase (C-H2O) were measu red and related to the reaction rate constant as well as the distribution c oefficient (K-A). Catalysts which exist in the third phase can be reused wi thout any loss of catalytic activity.