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35 Cl NQR studies of 1‐chloro‐2,4‐dinitrobenzene and 1,2‐dichloro‐3‐nitrobenzene as a function of pressure and temperature
Author(s) -
Srinivas Jandhyala,
Subramanian Raman K.,
Ramesh Keralapura P.,
Ramakrishna Jandhyala,
S. Suresh Kalkunte,
Raghavendra Rao Chdaghatta
Publication year - 2002
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/mrc.1016
Subject(s) - chemistry , nitrobenzene , nuclear quadrupole resonance , relaxation (psychology) , atmospheric temperature range , nitro , spin–lattice relaxation , activation energy , molecule , thermodynamics , nuclear magnetic resonance , analytical chemistry (journal) , organic chemistry , psychology , social psychology , physics , alkyl , catalysis
The temperature and pressure dependences of 35 Cl nuclear quadrupole resonance (NQR) frequency and spin–lattice relaxation time ( T 1 ) were investigated for 1‐chloro‐2,4‐dinitrobenzene and 1,2‐dichloro‐3‐nitrobenzene. T 1 was measured in the temperature range 77–300 K. Furthermore, the NQR frequency (ν) and T 1 for these compounds were measured as a function of pressure up to 5.1 kbar at 300 K. Relaxation was found to be due to the torsional motion of the molecule and the reorientation motion of the nitro group. By analysing the temperature dependence of T 1 , the activation energy for the reorientation motion of the nitro group was obtained. The temperature dependence of the average torsional lifetimes of the molecules and the transition probabilities W 1 and W 2 for the Δ m = ±1 and Δ m = ±2 transitions, were also obtained. Both compounds showed a non‐linear variation of NQR frequency with pressure. The pressure coefficients were observed to be positive. A thermodynamic analysis of the data was carried out to determine the constant‐volume temperature coefficients of the NQR frequency. The spin–lattice relaxation time T 1 for both the compounds was found to be weakly dependent on pressure, showing that the relaxation is mainly due to the torsional motions. Copyright © 2002 John Wiley & Sons, Ltd.