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Henry's Law Constant: Calculated HLC for linear and essentially-linear isomers of alcohols at environmental temperature (12°C): 4.8 Pa m3/mol (C12); 13 Pa m3/mol (C13); 7.5 Pa m3/mol (C14); 5.5 Pa m3/mol (C15).

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Additional information

The transfer of a substance from the water phase to the gas phase can be estimated by means of the Henry’s Law Constant (HLC). No measured value for this parameter is available. The HLC can be estimated from the ratio of the vapour pressure (VP) to the water solubility (WS).

HLC = (VP x MW)/WS

Where MW is molecular weight.

The calculated HLC values for the constituents of Alcohols, C12 -15 -branched and linear at environmental temperature (12°C) are moderate, in the range 4.8 - 13 Pa m3/mol (taken from EUSES 2.1.2).

The SRC HenryWin Bond method, which is a technique allowing prediction directly from the chemical structure, shows results consistent with the VP/WS ratio method in this range of carbon chain length. Using this technique, the predicted HLC values for essentially-linear structures are not different from those of linear alcohols of the same carbon number. This supports the equivalence of essentially-linear isomers with the linear alcohols.

Discussion of trends in the Category of C6-24 linear and essentially-linear aliphatic alcohols:

The Henry’s Law constant (HLC) describes the potential for volatilisation from water. No measured values are available, hence the HLC can be estimated, e.g. from the values of vapour pressure and water solubility. Values calculated in this way range between approximately 0.7 – 80 Pa.m3/mol (for 1-docosanol and 1-octadecanol respectively). Other category members have intermediate values. These values suggest low to moderate volatility from water, however fugacity modelling shows that a negligible proportion of the substance will be volatilised in the environment based on the overall equilibrium and taking into account degradation rates.