Shape and interactions of the synthetic repellent DEET.

,-Diethyl-3-methylbenzamide (DEET) is the most widely used insect repellent, exhibiting high efficiency against a wide variety of species. In this work, a comprehensive isolated-molecule investigation of DEET was conducted using chirp-excitation Fourier transform microwave (CP-FTMW) spectroscopy within the frequency range of 7-14 GHz. Four out of the eight theoretically predicted conformers were detected and grouped in pairs based on their rotational constants and planar moments of inertia. We also studied the non-covalent interactions of DEET by characterizing the attractive and repulsive forces, which could explain the energetic ordering of the four conformers. In addition, DEET has a methyl top bound to the benzyl ring which is predicted to rotate almost freely with respect to the molecular framework.