Sensory irritating effects of allyl halides and a role for hydrogen bonding as a likely feature at the receptor site.

Allyl chloride, bromide and iodide were investigated for their properties as sensory irritants in mice. The concentrations of the chemicals necessary to depress the respiratory rate by 50% (RD50) within the first 10 min. of exposure due to irritation of the upper respiratory tract were 2330, 257 and 79.8 p.p.m., respectively. No pulmonary irritation was observed. In the period 20 to 30 min., however, pulmonary irritation was observed for allyl bromide and iodide. The effect was not prominent in non-cannulated mice probably due to the scrubbing effect of the nose. According to RD50 values, thermodynamic activity as well as apparent association rate with the receptor the sensory irritating potencies of the halides were low compared to those of allyl alcohol, acetate, and ether. A mechanistic explantation could not be ascribed to metabolites, lipophilicity or chemical reactivity. Only a hydrogen bond donor ability of the receptor offered an explanation. As many industrial chemicals e.g. alcohols, ketones and esters can function as hydrogen bond acceptors this receptor-feature cannot be overemphasized.