Comparison of methods employing gas chromatography retention data to determine vapour pressures at 298 K.

Validity of five models suggested for expressing the relationship between vapour pressures and GC retention times measured on a non-polar capillary column were tested on a common set of compounds [five homologous series of the type H-(CH2)n-Y, where Y denotes Cl, Br, CHO, OCOCH3 and COOCH3, and n varies from 6 to 14]. Standard methods of statistical analysis, as well as vapour pressure values obtained independently from direct vapour pressure measurements were used as validity criteria. For the 40-compound data set examined, the methods provided vapour pressures agreeing within 9.2-24.7% (average absolute percent error) with direct experimental data.

New mimics of the acetate function in pheromone-based attraction.

Several analogues of (Z)-8-dodecenyl acetate (1a), the major pheromone component of the Oriental fruit moth, Cydia molesta, with chloroformate and lactone functional groups in place of the acetate moiety, were synthesized and investigated for their biological activity at four evaluation levels, i.e. by electroantennography (EAG), electrosensillography (ESG), short-range sexual stimulation and activation in the flight-tunnel. We found very strict requirements on the shape as well as on the electron distribution of the acetate group for a productive interaction with the receptor. The behavioral results showed that, among the analogues investigated, the chloroformate 1b, alken-4-olide 2a and also dodecyl acetate (1c) possess significant (60-85%) inhibitory activities. Based on electrophysiological evidence demonstrating that (i) only 1b is competing with the major pheromone component 1a for the same receptor sites on the male antennal sensilla, (ii) 1c elicits moderate EAG but no ESG responses and (iii) 2a does not produce any electrophysiological response at all, three possible inhibitory mechanisms by which these analogues are acting could be distinguished.

Behavioral observations and measurements of aerial pheromone in a mating disruption trial against pea mothCydia nigricana F. (Lepidoptera, Tortricidae).

Synthetic sex pheromone of the pea mothCydia nigricana. (E,E)-8,10-dodecadien-1-yl acetate (E8,E10-12 : Ac), was applied in a 3-ha pea field at a rate of 17 g/ha, in two different dispenser formulations. Aerial concentrations within pea canopy, as determined by a field electroantennogram (EAG) apparatus, were 2 and 3 ng/m(3) in the two dispenser treatments. The validity of the EAG measurements was corroborated by sampling of field air, followed by gas chromatographic quantification ofE8,E10-12 : Ac. Males were attracted to fresh dispensers releasingE8,E10-12 : Ac plus less than 2% of the antagonisticE, Z; Z, E; andZ, Z isomers. Two days after placement, the proportion of these isomers had increased to 6%. Males were then no longer attracted to the dispensers, but were observed to fly out of the treated field. Male attraction to calling females was almost entirely suppressed, and attraction to traps baited with synthetic pheromone was significantly reduced. Larval infestation in the pheromone-treated field was 2%, compared to 36% in a control field.

Propheromones derived from codlemone.

Tricarbonyl [(8,9,10,11-η-8,10-dodecadien-l-ol] iron and the corresponding acetate prepared from 8,10-dodecadien-1-ol or its acetate, comprise the protected double-bond system of the molecule. After coming in contact with ambient oxygen, the iron complexes in question slowly release the corresponding pheromones of, for example, the codling moth,Cydia pomonella, and the pea moth,Cydia nigricana in highE,E purity and amounts that are sufficient for pest monitoring. A simple dispenser for propheromone application is proposed. Results of release rates in laboratory conditions and field trials are given.

Haloacetate analogs of pheromones: Effects on catabolism and electrophysiology inPlutella xylostella.

A series of mono-, di-, and trihalogenated acetate analogs of Zl 1-16: Ac were prepared and examined for electrophysiological activity in antennae of males of the diamondback moth,Plutella xylostella. In addition, two potential affinity labels, a diazoacetate (Dza) and a trifluoromethyl ketone (Tfp), were evaluated for EAG activity. The Z11-16∶Ac showed the highest activity in EAG assays, followed by the fluorinated acetates, but other halo-acetates were essentially inactive. The polar diazoacetate and the trifluoromethyl ketone were also very weak EAG stimulants. The effects of these analogs on the hydrolysis of [(3)H]Z11-16∶Ac to [(3)H]Z11-16∶OH by antennal esterases was also examined. The three fluorinated acetates showed the greatest activity as inhibitors in competition assays, with rank order F2Ac > F(3)Ac > FAc > Ac > Cl2Ac > ClAc > Dza > Br2Ac > BrAc > Tfp > I > Cl3Ac > Br3Ac > OH. The relative polarities of the haloacetates, as determined by TLC mobility, are in the order mono- > di- > trihalo, but F, Cl, Br, and I all confer similar polarities within a substitution group. Thus, the steric size appears to be the predominant parameter affecting the interactions of the haloacetate analogs with both receptor and catabolic proteins inP. xylostella males.