Organophosphorus compounds, vapor pressures

Boublik, T., Fried, V., Hala, E. (1984) The Vapor Pressure of Pure Substances, 2nd revised Edition, Elsevier, Amsterdam, The Netherlands. Bowman, B. T., Sans, W. W. (1983) Determination of octanol-water partitioning coefficient (KqW) of 61 organophosphorus and carbamate insecticides and their relationship to respective water solubility (S) values. J. Environ. Sci. Health B18, 667-683. Bradley, R. S., Cleasby, T. G. (1953) The vapour pressure and lattice energy of some aromatic ring compounds. J. Chem. Soc. 1953, 1690-1692. 

Pyrethroids generally have low vapor pressures. Although empenthrin (20) volatilizes at room temperature without external energy and is 31 times more volatile than allethrin, its vapor pressure is only 1/88 that of dichlorvos, a volatile organophosphorus compound. As profluthrin (40) is 13 times more volatile than allethrin and volatilizes gradually for 6 months to 1 year at room temperature, it is suitable as an insecticide for the protection of clothes. The vapor pressure of profluthrin is 10 mPa/25°C, almost the same as that of glycerin. 

Fumigant action of some organophosphorus compounds was related to their vapor pressures and the water content of the soil. Phorate, disulfoton, and dimethoate were equally eflEective in soils in wet years, but only phorate and disulfoton were eflEective in dry years (326). Phorate and disulfoton provided much vapor action in dry years because of their high vapor pressures whereas dimethoate did not. 

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