As nouns the difference between mercaptan and aliphatic is that mercaptan is mercaptan while aliphatic is a compound of this type.
As an adjective aliphatic is (organic chemistry) of a class of organic compounds in which the carbon atoms are arranged in an open chain.
(chemistry) Any of a class of organic compounds of sulphur, ( R1.S.R2 ); they tend to be foul-smelling. When R2 is a hydrogen atom, they are termed thiols or thioalcohols.
(organic chemistry) Of a class of organic compounds in which the carbon atoms are arranged in an open chain.
A compound of this type.
(chiefly, in the plural) A petroleum fraction containing no aromatic compounds