Temperature dependent vapor pressures of chlorinated catechols, syringols,and syringaldehydes

The vapor pressures of nine chlorinated catechols, syringols, and syringald ehydes were determined as a function of temperature with a gas chromatograp hic retention time technique. The vapor pressures at 298.15 K were in the r ange of 0.02-1 Pa, and the enthalpies of vaporization, between 68 and 82 kJ . mol(-1). The validity of the technique was established by a calibration involving four chlorinated phenols with well-known vapor pressures. Using t hese data and previously reported solubility data, Henry's law constants fo r these substances and some chlorinated guaiacols aad veratrols were estima ted. The vapor pressure of these substances tends to decrease with increasi ng polarity and an increasing number of chlorine atoms. Henry's law constan ts decrease sharply with increasing polarity, suggesting that methylation c an result in a significant increase in a chemical's potential for volatiliz ation from water.