Reaction Pathway and Selectivity Control of Tetraethyl Thiuram Disulfide Synthesis with NaHCO3 as a pH Regulator.

ABSTRACT

The selectivity of a chemical reaction is related to the effective utilization of raw materials as well as the cleanliness and economy of the process. Herein, it has been first proposed to synthesize tetraethyl thiuram disulfide (TETD) with sodium bicarbonate as the pH regulator with a reaction selectivity of ∼100%. The existence of a reaction intermediate, a sodium salt of diethyl dithiocarbamoylsulfenic acid (NaEt2DTCS), has been proved by experiments and theoretical calculations. The results indicate that TETD can not only be generated from NaEt2DTCS oxidized by H2O2 directly, but also from the conjugation of NaEt2DTC and NaEt2DTCS generated in the first stage of oxidation meanwhile. Accordingly, an oxidation reaction pathway has been proposed. The reaction selectivity with NaHCO3 or CO2 as the pH regulator has been compared, and the selectivity control mechanism is discussed. At relatively higher pH values with NaHCO3 as the pH regulator, peroxidation could be almost avoided.