More Substitutes

A single-bonded carbon chain as a substituent is called an alkyl group. There are many other kinds of substitution besides hydroxy and alkyl groups. A nitrogen atom bonded to up to two hydrogens is called an amino group, and a molecule having an amino group is called an amine. Examples include methylamine CH₃NH₂, also called aminomethane; butylamine CH₃CH₂CH₂CH₂NH₂, also called 1-amino butane; and 1,4-butanediamine H₂NCH₂CH₂CH₂CH₂NH₂ also called 1,4-diamino butane or putrescine. Putrescine and its close relative cadaverine (1,5-pentanediamine, H₂NCH₂CH₂CH₂CH₂CH₂NH₂) are famously part of the smell of death, but also are made by the body and occur even in living tissues.

An amine does not have to have two hydrogens on its nitrogen atom, because those hydrogens can be substituted as well, e.g. dimethylamine CH₃NHCH₃, trimethylamine CH₃N(CH₃)CH₃, triethylamine CH₃CH₂N(CH₂CH₃)CH₂CH₃, and so on. If an amine has substituents on its nitrogen atom, it is common to use a capital letter N in the name to indicate that that's where the substitutions are attached, e.g. N,N-dimethyl butylamine CH₃CH₂CH₂CH₂N(CH₃)₂. This is not the same N as the n- in for example n-butane, even though this specific example does include an n-butyl group.

Methylamine, butylamine, putrescine, and cadaverine are primary amines, with only one substituent on the amino group. Dimethylamine is a secondary amine with two substituents, and trimethylamine and triethylamine are tertiary amines with three substituents.

Other common substituents include: thiol (-SH), as in methanethiol CH₃SH (pronounced methane-thigh-all); chloro, as in dichloromethane ClCH₂Cl (also called methylene chloride); alkoxy, as in ethoxyethane CH₃CH₂OCH₂CH₃ (more commonly called ether or diethyl ether); alkylthio, as in methylthio methanethiol CH₃SCH₂SH, and some more that I will cover later on.

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