Mechanism and Kinetics of the Synthesis of 1,7-Dibromoheptane

Abstract

Mechanism and the kinetic model for the synthesis of 1,7-dibromoheptane was studied. During the synthesis process of 1,7-dibromoheptane (D) from 1,7-heptanediol (A) and hydrobromic acid (B) by using acid as the reaction catalyst, the product distributions were measured. It was found that the concentration variations of components with reaction time followed the regularity of consecutive reaction. The first step is the formation of 7-bromo-1-heptanol (C) from A and B was a slow step. The second step, formation of 1,7-dibromoheptane from C and B was a fast step. Based on the S_N2 reaction mechanisms, a kinetic model of the reaction was established. The reaction rate constants (k) and activation energy (E_a) were calculated in various reaction conditions. The kinetic model was tested and verified by the experiments. At the same time, the curve between activation energy (E_a) versus mass fraction of sulphuric acid (m) gave the straight line in the reaction system. Because acid strength (H) can be expressed by mass fraction of sulphuric acid, so the reaction activation energy could be changed by adjusting acid strength (H) of catalyst.