Abstract: 【Aim】 The effect of association between mosquito repellents (terpenoids and DEET analogues) and attractants (L-lactic acid, carboxylic acids, etc.) was investigated in previous studies. In this study, a group of 43 amide repellents were chosen to further study bimolecular association between these repellents and ammonia as well as the effect of aggregate structures on repellency, so as to provide assistance for repellent mechanism research. 【Methods】 Geometry optimizations of the repellents and aggregate structures were done using Gaussian 03, and the QSAR model was established by Ampac and Codessa. 【Results】 Calculated results showed that the hydrogen bondings between amid repellents and ammonia were within the normal range of bond distances and bond angles (2.2-3.0 Å and 128-180°,respectively). The binding energies were 14-25 kJ/mol. The best four-parameter QSAR model had a R² value of 0.8987. These four statistic important parameters can be divided into two groups. The first two are related to repellents only, namely (1/6) X GAMMA polarizability (DIP) and ESP-minimum net atomic charge for an H atom. The other two are related to the repellent-ammonia aggregate, ESP-DPSA-2 difference in CPSAs (PPSA2-PNSA2) ［Quantum-Chemical PC］ and minimum valency of a C atom. The mean squared correlation coefficients of the training sets and the test sets were 0.9013 and 0.8666, respectively. 【Conclusion】 Weak hydrogen bonds are observed between repellents and ammonia. Polarizability of repellent molecules, dipole-dipole interactions between amide and ammonia, and charge distribution in aggregates are important factors influencing repellency. Model test shows that the four-parameter model has favorable stability and predictive ability. This study is helpful for seeking novel mosquito repellents and revealing the mechanism of mosquito repellents.

Key words: Mosquito repellents, amide repellents, attractants, repellent activity, ammonia, association, quantitative structure-activity relationship