The behavior and origin of the excess wing in DEET (N,N-diethyl-3-methylbenzamide)

Abstract

Broadband dielectric spectroscopy along with a high pressure technique and quantum-mechanical calculations are employed to study in detail the behavior and to reveal the origin of the excess wing (EW) in neat N,N-diethyl-3-methylbenzamide (DEET). Our analysis of dielectric spectra again corroborates the idea that the EW is a hidden β-relaxation peak. Moreover, we found that the position frequency of the β peak corresponds to the position of the primitive relaxation of the Coupling Model. We also studied the possible intramolecular rotations in DEET by means of DFT calculation. On that basis we were able to describe the EW as the JG β-relaxation and find the possible origin of the γ-relaxation visible in DEET dielectric spectra at very low temperatures.