Amines The organic bases Categorizing Amines n Amines
Amines The organic bases
Categorizing Amines n Amines are categorized by the number of alkyl groups attached to nitrogen: 1º 2º 3º 4º (primary amine) (secondary amine) (tertiary amine) (quaternary amine salt) RNH 2 R 2 NH R 3 N R 4 N +
Naming simple amines n Simple 1º amines are named as “alkylamine” q n Examples: n methylamine CH 3 NH 2 n ethylamine CH 3 CH 2 NH 2 n butylamine CH 3 CH 2 CH 2 NH 2 Symmetrical 2º or 3º amines are named as “dialkylamine” or “trialkyamine” q Examples: n diethylamine (CH 3 CH 2)2 NH; trimethylamine (CH 3)3 N
Naming more complex amines n Amines with more than one type of alkyl group may be named as N-substituted primary amines. The longer alkyl chain determines the base name. q n Examples n N-methylpropylamine CH 3 NHCH 2 CH 3 N, N-dimethylamine (CH 3)2 NCH 2 CH 3
Naming more complex amines n Amines that have more than one functional group may be named using “amino” as a substituent on the parent molecule. q Examples: n 2 -aminoethanol H 2 NCH 2 OH n 4 -aminobutanoic acid H 2 NCH 2 CH 2 CO 2 H
Heterocyclic amines n Some amines have a nitrogen as part of a ring. These generally have common (non-systematic) names, which should be memorized: aniline quinoline pyridine pyrimidine pyrrole indole imidazole benzimidazole
Structure of amines n n n Amines have an sp 3 hybridized nitrogen In principle, tertiary amines with three different R groups should be chiral (i. e. , have a stereocenter). However, rapid pyramidal inversion of the amine nitrogen prevents isolation of the enantiomers except where the nitrogen is part of a ring or has other geometrical constraint. fast
Properties of amines n n Amines are moderately polar and are capable of hydrogen bonding. Low MW amines (up to about C 5) are soluble in water; higher MW amines will dissolve in acidic solution (as their conjugate acid). Many amines have foul odors. Amines are weak bases.
Example of biologically active amines
…More biologically active amines
…More biologically active amines
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