AMINES

Chemistry of Amines
Ch. 24 of McMurry

Classification: NH3= ammonia NR4+ X- = quaternary ammonium salt
(tetraalkylammonium)
NH2R = 1o NHR2 = 2o NR3 = 3o
Nomenclature
Primary amines: 1) Hydrocarbon portion is named with “amine” added as a suffix
2) When other FG present, name “amino” group as substituent
2o and 3o: 1) If symmetrical, use prefix “di” or “tri” before alkyl group name
2) Unsymmetrical: smaller groups are named as N-substituents
Aromatic amines: Named as derivatives of aniline with o, p system or with amino group as C1
Properties of amines
1) Physical:
Polarity: Due to polarity of N – H bonds, 1o and 2o amines can hydrogen-bond
Elevated boiling points: amines > alkanes
Water-solubility: 5C or smaller amines and ammonium salts are highly soluble, aromatic are moderately soluble
Odor: fishy or rotten smell; diamines form from lysine in rotting flesh (cadaverine)
Pharmacological effects: Many amines resemble amine neurotransmitters and affect nervous system functioning by mimicking or blocking these NTs
2) Chemical: Basicity and nucleophilicity
Due to lone pair of e- on N, amines are good electron-donors (nucleophilic)
and can accept protons (basic)
How do substituents affect basicity?
? Nonaromatic amines: basicity isn’t affected much by the nature of alkyl groups
? Aromatic (anilines) & heterocyclic amines are much less basic than alkylamines
1) The hybridization of the N atom:
In heterocyclic aromatic amines the lone pair of e- may be part of the aromatic pi electron system as in pyrrole, or held tightly in an sp2 orbital as in pyridine.