Thioacetamide

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Thioacetamide is an organosulfur compound with the formula CH3CSNH2. This white crystalline solid is soluble in water and serves as a source of hydrogen sulfide in the synthesis of organic and inorganic compounds. It is a prototypical thioamide.

Coordination chemistry

Thioacetamide was widely used in classical qualitative inorganic analysis as an in situ source for sulfide ions. Thus, treatment of aqueous solutions of many metal cations to a solution of thioacetamide affords the corresponding metal sulfide:

M2+ + CH3C(S)NH2 + H2O → MS + CH3C(O)NH2 + 2 H+ (M = Ni, Pb, Cd, Hg)

Related precipitations occur for sources of soft trivalent cations (As3+, Sb3+, Bi3+) and monovalent cations (Ag+, Cu+).

Preparation

Thioacetamide is prepared by treating acetamide with phosphorus pentasulfide as shown in the following idealized reaction:[1]

CH3C(O)NH2 + 1/4 P4S10 → CH3C(S)NH2 + 1/4 P4S6O4

Structure

The C2NH2S portion of the molecule is planar; the C-S and C-N distances are 1.713 and 1.324 Å, both indicating multiple bonding.[2]

Safety

Thioacetamide is carcinogen class 2B.

References

  1. ^ George Schwarz (1955). "2,4-Dimethylthiazole". Organic Syntheses; Collected Volumes, vol. 3, p. 332.
  2. ^ Mary R. Truter "An accurate determination of the crystal structure of thioacetamide" Journal of the Chemical Society, 1960, pp. 997-1007. DOI: 10.1039/JR9600000997