Ch19Su08

Ch19Su08 - Amines Amines are derivatives of ammonia with...

Info iconThis preview shows pages 1–5. Sign up to view the full content.

View Full Document Right Arrow Icon
Amines Amines are derivatives of ammonia with one or more alkyl groups bonded to the nitrogen. Amines can be classified as primary, secondary or tertiary, meaning one, two and three alkyl groups bonded to the nitrogen respectively. E.g. Quaternary ammonium salts have four alkyl groups bonded to the nitrogen, and the nitrogen bears a full positive charge. E.g. f86904a488202383016d607b46d5aa11c50c6718.doc Page 1 NH 2 H 3 C C CH 3 CH 3 NH 2 Primary Amines Secondary Amines N: H CH 3 N-H Tertiary Amines N: CH 3 CH 3 N H 3 CH 2 C N CH 2 CH 3 CH 2 CH 3 CH 2 CH 3 + I - N CH 2 CH 2 CH 3 + Br -
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Amines are a very common functional group in organic chemistry, and especially so for naturally occurring compounds. E.g. Nomenclature The IUPAC nomenclature is analogous to that for alcohols, where the -e of the alkane ending is replaced with -amine. Other substituents on the carbon chain are given numbers, and the prefix N- is used for each substituent on nitrogen. E.g. f86904a488202383016d607b46d5aa11c50c6718.doc Page 2 N CH 3 H C O OCH 3 O H C O Ph N N CH 3 CH 3 CH 2 C NH 2 CH 3 H H 3 C C CH 3 H CH 2 CH 2 NH 2 CH 3 CH 2 C NH-CH 3 CH 3 H CH 3 CH 2 C H CH N(CH 3 ) 2 CH 3 CH 3 2-butanamine 3-methyl-1-butanamine N-methyl-2-butanamine 2,N,N-trimethyl-3-pentanamine
Background image of page 2
Aromatic amines are called by their historical/trivial names, with phenylamine being called aniline. Other nitrogen heterocycles have ring system names that need to be learned also. (The N is normally considered to be numbered 1). Aziridine, pyrrole, pyrrolidine, imidizole, pyridine, piperidine, pyrimidine Structures of Amines Previously we have seen that ammonia (NH 3 ) has a slightly distorted tetrahedral shape, due the compression of the ideal 109.5° angle by lone pair-bond pair repulsion. This effect is less pronounced with alkyl groups, and trimethylamine has bond angles closer to the perfect sp 3 arrangement than ammonia. Since an amine has three substituents and a lone pair, the question of chirality arises. If an amine has three different substituents (and its lone pair) can we resolve the amine into enantiomers? In most cases, this is not possible since the enantiomers can interconvert through a low energy pathway. The interconversion takes place through a nitrogen inversion , where the lone pair moves from one face of the molecule to the other, and back. f86904a488202383016d607b46d5aa11c50c6718.doc Page 3
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
The lone pair starts off in an sp 3 orbital, but in the transition state of the inversion, the nitrogen can rehybridize to sp 2 , with the lone pair in a p orbital. This is not a high energy situation, and only requires 6kcal of energy to achieve this TS (therefore easy at room temperature). At the TS, the inversion can occur or return back to the original enantiomer - single enantiomers cannot be resolved in most cases. Exceptions
Background image of page 4
Image of page 5
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 02/23/2010 for the course CHEM 202 taught by Professor Smith during the Spring '10 term at Duke.

Page1 / 39

Ch19Su08 - Amines Amines are derivatives of ammonia with...

This preview shows document pages 1 - 5. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online