Amines An amine is part of the nitrogenous organic family. (i.e. it contains Nitrogen) Amines can be thought of as ammonia (NH 3 ) with one, two or all three of its hydrogens replaced by alkyl groups. These are classified as primary, secondary or tertiary amines respectively. Like always, the alkyl groups in the amine may be identical or different

Amines Low molecular-weight amines tend to have sharp, penetrating odors similar to ammonia Higher molecular-weight amines often smell like rotting fish, and are often found in decaying animal tissues.

Naming Amines Locate the hydrocarbon parent chain. The NH 2 group is treated like an alkyl group and given the name “amino” The amino group is given the lowest possible number in the parent chain (but not over other functional groups) The rest of the molecule is named in the usual way. Molecules with 2 amino groups are called diamines. Use the di, tri, tetra, etc. prefixes to denote the number of amines. For secondary and tertiary amines, the alkyl groups which are attached to the N are given the prefix N rather than a number. (Note: CAPITAL N and it comes before any #s) N-methylaminoethane

Naming Amines Cont’d The common way of naming amines is to put the alkyl groups in alphabetical order and add the suffix amine. This is usually done for lower amines Aromatic amines are based on the structure aniline (aminobenzene) and named as such. 3-methylaniline N,N,3-trimethylaniline ethylmethylamine aniline

More Naming Practice Name the following: 1,3-diaminobutane N, N-dimethylaminomethane 6-amino-2-heptanone OR trimethylamine

More examples! 3-ethyl-N,N,5-trimethylaniline N-methylaniline Draw: 3-amino-1-propanol N-methyl-2-chloroaniline

Properties of Amines Amines are polar because of the polarity of the N-C bond and the N-H bond. However because N is not as electronegative as O the N-H bonds are not as polar as a O-H bond. 1° and 2° amines can hydrogen bond with themselves and with water. 3° amines cannot hydrogen bond with itself (no N-H bond) but because of the lone pair of electrons on N can accept H-bonds from water. Low molecular weight amines are therefore soluble in water; solubility decreasing with size. Amines (1° and 2°) have lower boiling points than alcohols of similar sizes, 3° amines have boiling points similar to hydrocarbons of the same size. (Lower than 1° and 2°)

Properties of Amines Cont’d Arrange the following compounds in order of increasing boiling point. (All of the compounds have about the same molecular weight.) propanoic acid, diethylamine, 1-butanol, ethyldimethylamine ethyldimethylamine, diethylamine, 1-butanol, propanoic acid Which member of each of the following pairs of compounds would you expect to have a higher boiling point? 2-aminopropane or 2-aminohexane triethylamine or 1-aminohexane propanoic acid or diethylamine 1-pentanol or 1-aminopentane

Some Important Alkaloids Alkaloids are N containing, weakly basic organic compounds; thousands of these substances are known.

Preparation of Amines Amines are prepared by reacting an alkyl halide with ammonia (ammonia remember is a weak base, therefore so are amines.) Reacting the 1° amine with more alkly halide produces a 2° amine

Preparation of Amines Cont’d The 2° amine can then be further reacted with more alkyl halide to produce a 3° amine From the above we can see that adding ammonia to alkyl halide will produce a mixture of amines. Chemists are able to these can be separated using different methods (e.g. based on boiling points)

Amine Reactions As we see in the next section amines are used to produce amides.