22.1 Amine Nomenclature

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June Charles
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1 Chapter 22 Amines

2 22.1 Amine Nomenclature

3 Classification of Amines Alkylamine N attached to alkyl group Arylamine N attached to aryl group Primary, secondary, or tertiary determined by number of carbon atoms directly attached to nitrogen

4 Nomenclature of Primary Alkylamines (RNH 2 ) Two IUPAC styles 1) analogous to alcohols: replace -e ending by -anamine 2) name alkyl group and attach -amine as a suffix

5 Examples: some primary alkylamines (RNH 2 : one carbon directly attached to N) CH 3 CH 2 NH 2 ethylamine or ethanamine CH 3 CHCH 2 CH 2 CH 3 NH 2 NH 2 cyclohexylamine or cyclohexanamine 1-methylbutylamine or 2-pentanamine

6 Nomenclature of Primary Arylamines (ArNH 2 ) Name as derivatives of aniline.

7 Examples: some primary arylamines (ArNH 2 : one carbon directly attached to N) NH 2 F NH 2 Br CH 2 CH 3 p-fluoroaniline 5-bromo-2-ethylaniline

8 Amino groups as substituents amino groups rank below OH groups and higher oxidation states of carbon in such cases name the amino group as a substituent O HOCH 2 CH 2 NH 2 HC NH 2 2-aminoethanol p-aminobenzaldehyde

9 Secondary and Tertiary Amines Name as N-substituted derivatives of parent primary amine. (N is a locant-it is not alphabetized, but is treated the same way as a numerical locant) Parent amine is one with longest carbon chain.

10 Examples CH 3 NHCH 2 CH 3 NHCH 2 CH 3 N-methylethylamine NO 2 4-chloro-N-ethyl-3-nitroaniline Cl CH 3 N CH 3 N,N-dimethylcycloheptylamine

11 Ammonium Salts A nitrogen with four substituents is positively charged and is named as a derivative of ammonium ion (NH + 4 ). + CH 3 NH 3 Cl CH 3 + N CH 2 CH 3 CF 3 CO 2 methylammonium chloride H N-ethyl-N-methylcyclopentylammonium trifluoroacetate

12 Ammonium Salts When all four atoms attached to N are carbon, the ion is called a quaternary ammonium ion and salts that contain it are called quaternary ammonium salts. CH 2 CH 3 + N CH 3 CH 3 I benzyltrimethylammonium iodide

13 22.2 Structure and Bonding

14 Alkylamines 147 pm

15 Alkylamines Most prominent feature is high electrostatic potential at nitrogen. Reactivity of nitrogen lone pair dominates properties of amines.

16 Geometry at N Compare geometry at N of methylamine, aniline, and formamide. H H sp 3 H sp 2 C NH 2 C O NH 2 H Pyramidal geometry at sp 3 -hybridized N in methylamine. Planar geometry at sp 2 -hybridized N in formamide.

17 Geometry at N Compare geometry at N of methylamine, aniline, and formamide. sp 3 sp 2 Pyramidal geometry at sp 3 -hybridized N in methylamine. Planar geometry at sp 2 -hybridized N in formamide.

18 Geometry at N Angle that the C N C N bond makes with bisector of H N H H angle is a measure of geometry at N. sp 3 sp 2 ~ Note: this is not the same as the H N H H bond angle

19 Geometry at N Angle that the C N C N bond makes with bisector of H N H H angle is a measure of geometry at N. sp 3 sp 2 ~

20 Geometry at N Geometry at N in aniline is pyramidal; closer to methylamine than to formamide

21 Geometry at N Hybridization of N in aniline lies between sp 3 and sp 2. Lone pair of N can be delocalized into ring best if N is sp 2 and lone pair is in a p orbital. Lone pair bound most strongly by N if pair is in an sp 3 orbital of N, rather than p. Actual hybridization is a compromise that maximizes binding of lone pair

22 Electrostatic Potential Maps of Aniline Nonplanar geometry at N. Region of highest negative potential is at N. Planar geometry at N. High negative potential shared by N and ring. Figure 22.3 (page 862)

23 22.3 Physical Properties

24 Physical Properties Amines are more polar and have higher boiling points than alkanes; but are less polar and have lower boiling points than alcohols. dipole moment (µ):( boiling point: CH 3 CH 2 CH 3 CH 3 CH 2 NH 2 CH 3 CH 2 OH 0 D 1.2 D 1.7 D -42 C 17 C 78 C

25 boiling point: Physical Properties CH 3 CH 2 CH 2 NH 2 CH 3 CH 2 NHCH 3 (CH 3 ) 3 N 50 C 34 C 3 C Boiling points of isomeric amines decrease in going from primary to secondary to tertiary amines. Primary amines have two hydrogens on N capable of being involved in intermolecular hydrogen bonding. Secondary amines have one. Tertiary amines cannot be involved in intermolecular hydrogen bonds.

Amines. Amines are bases usually the base involved in biochemical acid-base reactions.

Amines. Amines are bases usually the base involved in biochemical acid-base reactions. Amines Amines Amines are derivatives of ammonia. Amines are bases usually the base involved in biochemical acid-base reactions. Vitamins comes from the term vital amines - not all vitamins are amines.