Allochemical effect

It is interesting that the product distribution from the reaction of the o-methoxyphenyl complex with diethylacetylene was found to be dependent on alkyne concentration. One equivalent of alkyne, slow addition of alkyne, or low absolute concentration of alkyne favors the indene product. Reactions performed with excess or high concentrations of alkyne favor benzannulation. The observation, reffered to as the allochemical effect, was explained as resulting from coordination of reaction intermediates by the alkyne. Thus excess alkyne acts as a ligand to stabilize intermediates along the path to benzannulation. Finally, it was noted that the product distribution was not substantially altered by addition of phosphines, phosphine oxides or sulfides. 

A further application of this calorimeter was for airbom irritations like attrac-tants, toxic compounds, anaesthetics or allochemicals on individual insects [47]. Larvae of the cabbage looper Trichoplusia ni) were tested against microgram amounts of benzene. They produced a strong, but short exothermic effect because the benzene was washed out by the air stream. A young male of the rootworm Diabrotica longicomis answered with a pronounced exothermic heat output to the exposure to pheromones prepared as extracts from female com rootworms. Moreover, the male moved immediately towards the source of the stimulant. 

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