Influence of the chemical structure on the odor qualities and odor thresholds of guaiacol-derived odorants, Part 1: Alkylated, alkenylated and methoxylated derivatives.

Guaiacol and its derivatives are commonly found in nature and are known for their characteristic smoky, clove-like and vanilla-like smells. However, there is no systematic investigation of the smell properties of structurally related guaiacol derivatives. In order to establish a comprehensive database on this olfactorily interesting substance class, odor thresholds in air and odor qualities of guaiacol and its alkylated, alkenylated, and methoxylated derivatives were determined by means of gas chromatography-olfactometry. All compounds elicited characteristic smoky/smoked ham-like, vanilla-like/sweet and/or clove-like smell impressions. The odor thresholds of the compounds were generally very low, ranging from 0.00018 to 111ng/L. The lowest thresholds were determined for 5-methoxyguaiacol and guaiacol, followed by 4-ethyl- and 4-vinylguaiacol. Some inter-individual differences in the threshold values between panelists were observed, with highest variation in the individual values of cis-6-propenyl-, trans-6-propenyl- and 3-vinylguaiacol. The smell impressions, on the other hand, were quite consistent.