[Correlation between odor thresholds and saturated vapor pressures of odorants]

The purpose of our work is to develop an estimation method for odor thresholds on the basis of physicochemical properties of odorous compounds. In this report, we examined the correlation between odor thresholds (Cth) and the saturated vapor pressures (Pvp) of various odorants. Results. 1) There were very good correlations between Pvp and k. k represents an indicator of lipid affinity. In our earlier report, k was obtained by the analysis of the gas chromatography with a column packed with a support coated by a phospholipid. Accordingly the correlations show that Pvp may be an indicator of solubility into the lipid phase. 2) It was found that correlations between Pvp and Cth were very good in several homologous series of aliphatic compounds. However ionized substances, such as acids and amines, and sulfur compounds had no good correlations. 3) In odorants having more than 3-5 carbon atoms, odor thresholds of normal types were higher than those of iso types. 4) In the series of amines, the relationship between Cth and Pvp depended upon the length and the number of alkyl chains combined with the contained nitrogen atom. 5) In the series of alcohol and aldehyde, the decrease of Cth in the rate became smaller with the decrease of Pvp.