Electrochemical studies of amine salts of monothiocarbamates

Abstract

The electrochemical behaviour of the amine salts of morpholyl-, pyrrolidyl- and piperidyl-mono- thiocarbamates (morpholinium morpholine-4-carbothioate, piperidinium piperidine-1-carbothioate and pyrrolidinium pyrrolidine-1-carbothioate) at the mercury electrode has been studied by means of d.c. polarography and cyclic voltammetry. All three exhibited a well defined anodic wave, but the pyrrolidyl derivative (pymtc) gave an additional wave. The main wave in each case was found to be diffusion-controlled. Temperature coefficients showed erratic behaviour at higher temperatures which was thought to be due to decreasing availability of reactive material because of decomposition. Controlled potential coulometry gave n = 1 per mole for the main wave of each compound. The behaviour was similar to that of the dithiocarbamate ligands under the same conditions and the small pre-wave in the polarograms of pymtc is attributed to the formation of a mercuric pyrrolidyl monothiocarbamate, which, unlike the mercuric complex of the other two ligands is structurally ordered and able to form a compact layer with the electrode.

Cyclic voltammetric results supported the findings of polarography and confirmed the following mechanism:

mtc^- + Hg → Hg(mtc) + e' (1)

2Hg(mtc) → Hg(mtc)_{2 +} Hg (2)