Dielectric dispersion and relaxation mechanism in some trichloro esters at microwave frequencies

Abstract

The permittivity and dielectric loss of three trichloro esters, namely methyl trichloroacetate, ethyl trichloroacetate, and n-propyl trichloroacetate have been measured at frequencies 1 MHz, 9.83, 18.26, 24.50 GHz, and optical frequency at 35 °C. The permittivity and dielectric loss at different frequencies have been plotted against concentration (weight fraction). The slopes of these straight lines have been used for complex plane plots (a″ vs. a′). There are two possible relaxation processes in these molecules, i.e. overall rotation of the molecule and intramolecular group rotation —CCl3 around C—C bond. Whereas the relaxation time for overall rotation is dependent on temperature the relaxation time for group rotation is practically independent of temperature.

Microwave‐Material Interactions and Dielectric Properties, Key Ingredients for Mastery of Chemical Microwave Processes

“…Figure 1.7 gives relaxation frequency range for classical organic functions: alkanes [33,34], alcohols [35][36][37][38][39], alcohol ether [40], acid chlorides [41,42], esters [43,44], aliphatic [45][46][47][48][49][50][51][52][53][54] and aromatic halogens [55,56], aliphatic [57,58], aromatic ketones [59], nitriles [60], and aliphatic [61,62] and aromatic amines [63].…”

“…This character is further accentuated by the three electron attracting halogen group. This positive carbonyl carbon interacts strongly with the oxygen lone-pair electrons in dioxane and the p electrons of the benzene ring forming complexes with these solvents and resulting in large value of relaxation time [54].…”