Relaxation studies on aromatic aldehydes in a polystyrene matrix
- 1 January 1978
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in Journal of the Chemical Society, Faraday Transactions 2: Molecular and Chemical Physics
- Vol. 74, 727-733
- https://doi.org/10.1039/f29787400727
Abstract
Dielectric absorption studies have been made of aldehyde group relaxation of terephthaldehyde, 2-furanaldehyde, 4-biphenylcarboxaldehyde and 2-fluorocarboxaldehyde in a polystyrene matrix. Only group relaxation occurs in terephthaldehyde; the Eyring parameters are ΔHE= 29 ± 1 kJ mol–1, and ΔSE= 15 ± 6 J K–1 mol–1(95 % confidence intervals). The enthalpy of activation for aldehyde group relaxation in 4-biphenylcarboxaldehyde and 2-fluorocarboxaldehyde is 27 kJ mol–1; the values for molecular relaxation are 72 and 76 kJ mol–1 respectively and are of the magnitude to be expected for such molecules. Examination of 2-furanaldehyde revealed both a group and a molecular process with ΔHE values of 41 and 14 kJ mol–1 respectively. The value for the group process in 2-furanaldehyde is of the same magnitude as the ultrasonic and n.m.r. value; its higher ΔHE may be accounted for by the increased conjugation of the group with the ring system over that in the three other aromatic aldehydes.Keywords
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