NQR frequencies are studied in 6 compounds at 77°K and room temperature. The frequencies of the substituted chlorobenzene derivatives are compared with values calculated using the σ andk values of Hammett and Biedenkapp and Weiss respectively. The poor agreement between observed and calculated values is ascribed to the presence of two or more substituent groups other than chlorine and the consequent interaction between them. The poor agreement with Nagarajan’s equation at room temperature is ascribed to the increase in temperature. The σ andk values for the orthobenzamide group are estimated from the observed frequencies as 0.275 and 0.369 respectively.