Vapour pressures, aqueous solubilities, Henry’s Law constants, and octanol/water partition coefficients of a series of mixed halogenated dimethyl bipyrroles

Basic physical–chemical properties of five bromine and chlorine containing mixed halogenated dimethyl bipyrroles (HDBPs) were determined using established methods. Subcooled liquid vapour pressures image, aqueous solubilities (Sw,25), and octanol/water partition coefficients (Kow) were determined using the gas chromatography-retention time, generator column, and slow-stirring methods, respectively. Henry’s Law constants (H25) were estimated using experimentally-derived image and Sw,25 data. Values of all four properties were generally similar to those reported for other polyhalogenated aromatic compounds [image Pa; Sw,25 = (1.0–1.9) × 10−5 g/l; log Kow=6.4–6.7; H25 = 0.0020–0.14 Pa m3/mol]. The effect of replacing a chlorine with a bromine atom significantly decreased image (image (# bromine atoms) − 2.643, p < 0.01) and H25 (log H25 = −0.508 (# bromine atoms) + 0.394, p < 0.02). There were no significant effects of bromine/chlorine substitution on Sw,25 or Kow. A simple Level I equilibrium partitioning model predicted the environmental behaviour of HDBPs to be similar to a tetrabrominated diphenyl ether. Only slight differences in behaviour amongst HDBP congeners were predicted since substitution of a bromine for a chlorine (Cl/Br substitution) atom had less effect than H/Cl or H/Br substitution on image, Sw,25, H25, and Kow.