VALENT MERCAPTANS—THIO-GLYCOLS

The sulphur analogues of the glycols, i.e., thio-glycols, or di-valent mercaptans are definitely known compounds. Furthermore, it is found, that when sulphur replaces oxygen, in compounds of this class, two sulph-hydrogen groups (—SH), may be linked to one carbon atom and a stable compound result. 

Methylene mercaptan, CH2 = (SH)2, is a well known compound and may be made from formaldehyde by treatment with hydrogen sulphide  

Similarly ethylidene mercaptan may be obtained from acetaldehyde  

Mercaptals and Mercaptols.—Ethylidene mercaptan is ordinarily obtained as the thio-ether by the action of ethyl mercaptan on acetaldehyde  

Such a di-thio-ether is known as a mercaptal and this particular one is known as di-thio acetal (p. 117). Analogous compounds obtained from ketones, e.g., from acetone, are called mercaptols. 

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