Relative volatilities of some onion flavour components

The volatilities of propanethiol, 2,5-dimethylthiophene, methyl propyl sulphide, dimethyl disulphide, dipropyl disulphide, allyl methyl sulphide, diallyl sulphide, diallyl disulphide, acetaldehyde, propionaldehyde, methanol, ethanol, 1-propanol and 2-propanol in dilute water solutions were studied experimentally by gas chromatography. The volatilities of these compounds varied appreciably. They were higher for thiols, thiophenes, and monosulphides, than disulphides, aldehydes or alcohols. The results for aldehydes and alcohols confirm earlier theoretical predictions by other authors that at 25°C the volatility, in very dilute solution, increases as the carbon chain gets longer.