James G. Traynham

Chemical releasers of social behaviour—VI. The relation of structure to activity of ketones as releasers of alarm for Iridomyrmex pruinosus (Roger)☆

Abstract 2-Heptanone, the alarm pheromone produced by Iridomyrmex pruinosus, is a powerful attractant for workers of this dolichoderine species. I. pruinosus also appears to employ this alarm pheromone for defense. The possible origin of alarm pheromones from defensive secretions is discussed. The abilities of 49 ketones to produce typical alarm behaviour in I. pruinosus were determined in order to establish the relationship between chemical structure and alarm-releasing activity. Ketones in the range C3 to C13 were tested on both laboratory and strong field colonies. In the series of 2-alkanones, activity was present in the C5 to C10 ketones, the most pronounced activity occurring in the range C6 to C9. The corresponding cycloalkanones showed no activity. In general, movement of the carbonyl group toward the centre of the hydrocarbon chain caused at least a slight diminution in activity. The introduction of a second carbonyl group either had no effect or produced a slight drop in the ability of the compound to release alarm. Unsaturation in the aliphatic chain either slightly increased or did not alter the activity of the synthetic pheromones. Branched methyl groups produced compounds which were generally less active than their unbranched isomeric counterparts, although this relationship was not absolute, especially in the C7 to C9 ketones. Activity was also present in some phenyl alkyl ketones, which suggests that the aromatic ring can correspond to an aliphatic portion of an alkanone. These results are discussed in terms of the absolute structural requirements of a maximally active alarm pheromone for I. pruinosus. The data demonstrate that alarm releasers, in common with other types of pheromones, require a degree of structural specificity in order to manifest maximum activity.

n-Tridecane and trans-2-Heptenal in Scent Gland of the Rice Stink Bug Oebalus pugnax (F.)

The scent-gland secretion of the rice stink bug Oebalus pugnax (F.) is composed of a liquid two-phase system. The saturated hydrocarbon n-tridecane accounts for 60 percent of the secretion. In the other phase, the major organoleptic compound is the trans form of 2-heptenal.

Honey bee sex attractant: Conformational analysis, structural specificity, and lack of masking activity of congeners

Abstract Nineteen alkenoic acids closely related to 9-oxo- trans -2-decenoic acid, the sex pheromone of the honey bee, were evaluated as sex attractants for this insect. All structural modifications resulted in a complete loss of attractant activity. The absolute structural specificity of this pheromone is analysed in terms of its preferred minimum energy conformer and a theoretical model of a suitable and complementary olfactory receptor cell is presented. Intra-atomic distances in the sex pheromone molecule are calculated and silhouettes of the molecule along its three main axes are presented. trans -Alkenoic acids closely related to the sex pheromone do not mask its sex attractant activity. 9-Oxo- cis -2-decenoic acid, the geometric isomer of the natural attractant, has no activity as a masking agent. The inability of congeners to mask the sex attractant is analysed in terms of the highly specific receptor sites on the antennae which complement only the rigid spatial conformation of the pheromone molecule.

Linear Correlations of Substituent Effects in 1H, 19F, and 13C Nuclear Magnetic Resonance Spectroscopy

Nuclear magnetic resonance (nmr), from its inception, has provided useful and sometimes unique information about molecules. Nuclear shielding and spin-spin coupling data could lead to a complete understanding of the electronic environment of magnetic nuclei. This potential, however, has been only partly realised, primarily because theoretical interpretations of magnetic phenomena have not yet been as successful as empirical ones in providing information about the nature of electronic environments in and the transmission of electronic effects through a molecule.

A short guide to nomenclature of radicals, radical ions, iron-oxygen complexes and polycyclic aromatic hydrocarbons

Abstract This article summarizes and illustrates by examples the principal official rules for naming some species used by research writers in the field of free radical biology.