Amines
ORGAIC CEMISTRY 20.1 omenclature
ORGAIC CEMISTRY Amines are classified as primary (R 2 ), secondary (R 2 ), or tertiary (R 3 ), depending on the number of organic substituents attached to nitrogen. C 3 2 (C 3 ) 2 (C 3 ) 3 Methylamine Dimethylamine Trimethylamine primary secondary tertiary ( ) ( ) ( )
ORGAIC CEMISTRY ote When we speak of a tertiary alcohol or alkyl halide, we refer to the degree of substitution at the alkyl carbon atom. When we speak of a tertiary amine, however, we refer to the degree of substitution at the nitrogen atom. C 3 C 3 C 3 C 3 C O C 3 C 3 C 2 C 3 C 3 C 3 tert-butyl alcohol Trimethylamine tert-butylamine (a tertiary alcohol) (a tertiary amine) (a primary amine)
ORGAIC CEMISTRY omenclature of Amines Common nomenclature: alkylamines (the suffix -amine is added to the name of the alkyl substituent.) Systematic nomenclature: the name of the parent compound e -amine
ORGAIC CEMISTRY C 3 C 2 2 Ethylamine (ethanamine) C 3 Primary Amines C C 3 C 2 2 Isobutylamine (2-methyl-1-propanamine) 2-1- C 3 C 3 C 2 C 3 tert-butylamine (2-methyl-2-propanamine) 2-2- 2 2 2 Cyclohexylamine (cyclohexanamine) 1,4-Butanediamine 1,4-
ORGAIC CEMISTRY Secondary and Tertiary Amines Common nomenclature: symmetrical secondary and tertiary amines are named by adding the prefix di- or tri- to the alkyl group. Systematic nomenclature: named as - substituted primary amines. The largest alkyl group is chosen as the parent name, and the other alkyl group are considered -substituents on the parent ( since they re attached to nitrogen).
ORGAIC CEMISTRY C 3 C 2 C 3 Ethylmethylamine (-methylethanamine) (C 3 C 2 ) 2 Diethylamine (-ethylethanamine) (C 3 C 2 ) 3 Triethylamine (,-diethylethanamine) - -,- C 3 C 3 C 2 C 2 (C 3 ) 2 C 2 C 3 Dimethylpropylamine (,-Dimethyl-1-propanamine),- -1- Ethylmethylcyclohexylamine (-Ethyl--methylcyclohexanamine) - --
ORGAIC CEMISTRY An 2 group, when not the principal group, is named by the prefix amino-. CO 2 2 CO 2 2 2-Aminobutanoic acid 2 2,6-Diaminobenzoic acid 2-2,6- O 2 4-Amino-2-butanone 4- -2-2 C 2 C 2 O 2-Aminoethanol 2-
ORGAIC CEMISTRY 20.1A Arylamines 2 2 2 2 Benzenamine 1-aphthalenamine 1,3-benzenediamine C 6 5 -Phenylbenzenamine -Phenyl-2-naphthalenamine
ORGAIC CEMISTRY Three common arylamines have the following names: 2 C 3 2 2 C 3 OC 3 Aniline -Methylaniline p-toluidine p-anisidine (benzenamine) (-methylbenzenamine) (4-methylbenzenamine) (4-methoxybenzenamine)
ORGAIC CEMISTRY 20.1B eterocyclic Amines The important heterocyclic amines all have common names. In systematic replacement nomenclature the prefixes aza-, diaza-, and triaza- are used to indicate that nitrogen atoms have replaced carbon atoms in the corresponding hydrocarbon. 4 3 4 3 5 2 5 2 5 2 1 1 1 Pyrrole Pyrazole Imidazole (1-aza-2,4-cyclopentadienepentadienepentadiene) (1,2-diaza-2,4-cyclo- (1,3-diaza-2,4-cyclo- (1- -2,4- ) (1,2- -2,4- ) 4 3
ORGAIC CEMISTRY 5 4 3 O 1 2 Oxazole (1-oxa-3-aza-2,4-cyclopentadiene) (1,3- -2,4- ) Pyrrolidine (azacyclopentane) ( ) 5 6 4 7 5 4 3 S 1 2 1 3 Thiazole (1-thia-3-aza-2,4-cyclopentadiene) (1,3- -2,4- ) 2 Indole (1-azaindene) (1- )
ORGAIC CEMISTRY 5 4 3 6 2 1 Pyridine Pyridazine Pyrimidine Pyrazine (azabenzene) (1,2-diazabenzene) (1,3-diazabenzene) ( ) (1,2- ) (1,3- ) (1,3-diazabenzene) (1,3- ) 8 Piperidine Quinoline 6 7 (azacyclohexane) ( ) 5 4 1 3 2 (1-azanaphthalene) (1- ) Isoquinoline Purine
ORGAIC CEMISTRY 20.2 Physical Properties and Structure of Amines
ORGAIC CEMISTRY 20.2A Physical Properties Moderately polar substances Boiling points: alcohol > amine > alkane Form strong hydrogen bonds to each other (1 and 2 ) Form hydrogen bonds to water or other hydroxylic solvents. Very water soluble (low molecular weight amines).
ORGAIC CEMISTRY 20.2B Structure of Amines sp 3 hybridized R' R" R" R' C 3 C 3 C3 R Interconversion of amine enantiomers R R' R" R R'" R"' R" R' Quaternary ammonium salts such as these can be resolved R
ORGAIC CEMISTRY 20.3 Basicity of Amines: Amine Salts
ORGAIC CEMISTRY R 2 + O R 2 + O In the gas phase: 3 > 2 > 1 > 3 In aqueous solution: 2 > 1 > 3 > 3
ORGAIC CEMISTRY 20.3A Basicity of Arylamines Arylamines are much weaker bases than corresponding nonaromatic amines 2 2 C 3 2 pk a 10.64 4.58 5.08 2 2 2 2 2 1 2 3 4 5 1. Delocalization of the electron pair stabilizes aniline. 2. Aryl groups are electron-withdrawing groups.
1. ORGAIC CEMISTRY 20.3B Amines versus Amides Basicity : nonaromatic amines > arylamines > amides. The pk a of the conjugate acid of a typical amide is about 0. Amide O R C 2 -Protonated Amide O R C 2 O R C 3 O R C 2 O R C 3 Larger resonance stabilization Smaller resonance stabilization 2. The powerful electron-withdrawing effect of the carbonyl group of the amide. O O O R C 2 R C 2 R C 2 Protonated on the oxygen atom
ORGAIC CEMISTRY 20.3C Aminium Salts and Quaternary Ammonium Salts ( ) When 1, 2, and 3 amines act as bases and react with acids, they form compounds called aminium salts. Aminium salt + attached to at least one. C 3 C 2 2 + Cl (C 3 C 2 ) 2 + Br (C 3 C 2 ) 3 + I 2 O C3 C 2 3 Cl Ethylaminium chloride 2 O (C3 C 2 ) 2 2 Br Diethylaminium bromide 2 O (C3 C 2 ) 3 3 I Triethylaminium iodide
ORGAIC CEMISTRY When + is not attached to a. the compound is called a quaternary ammonium salt. (C 3 C 2 C 2 C 2 ) 4 Br Tetrabutylammonium bromide (TBAB) (a quaternary ammonium salt) Quaternary ammonium hydroxides ( ) are strong bases as strong as ao or KO. (C 3 ) 4 O + Cl (C 3 ) 4 Cl + 2 O
ORGAIC CEMISTRY 20.3D Solubility of Amines in Aqueous Acids Almost all alkylaminium chlorides, bromides, iodides and sulfates are soluble in water. Distinguishing amines from nonbasic compounds Separating amines from nonbasic compounds Water-insoluble amine + X X (or 2 SO 4 ) (or SO 4 ) Water-soluble aminium salt Water-insoluble amides do not dissolve in dilute aqueous acid solution.
ORGAIC CEMISTRY 20.3E Amines as Resolving Agents Enantiomerically pure amines are often used to resolve racemic form of acidic compounds. aturally occurring optically active amines such as ( )-quinine, ( )-strychnine, and ( )-brucine are often employed as resolving agents for racemic acids. O O ( )-Strychnine C 3 O C 3 O O O ( )-Brucine
ORGAIC CEMISTRY 20.4 Some Biologically Important Amines
ORGAIC CEMISTRY 2-Phenylethylamines O O C C 2 R O R = C 3, Adrenaline (epinephrine) R =, oradrenaline (norepinephrine) C 2 C C 3 2 Amphetamine (benzendrine) C 2 C 2 2 O C 2 C 2 2 2-Phenylethylamine 2 O Dopamine
ORGAIC CEMISTRY C 3 O C 3 O RO O O OC 3 Mescaline C 2 C 2 2 C 3 R =, Morphine R = C 3, Codeine O C 3 O C 2 C 2 2 Serotonin 5 O C ( )-Quinine
ORGAIC CEMISTRY O Vitamins and Antihistamines( ) C 2 O C 2 O C 2 Cl C 3 S C 2 C 2 O C 3 C 3 2 Pyridoxine Thiamine chloride (vitamin B 6 ) (vitamin B 1 ) C 3 icotine CO 2 icotinic acid (niacin) C 2 C 2 2 istamine
ORGAIC CEMISTRY Cl CC 2 C 2 (C 3 ) 2 Chlorpheniramine Tranquilizers ( ) C 3 Cl O Chlordiazepoxide (Librium)
ORGAIC CEMISTRY eurotransmitters ( ) O C 3 C OC 2 C 2 (C 3 ) 3 Acetylcholine + 2 O acetylcholinesterase C 3 CO 2 + OC 2 C 2 (C 3 ) 3 Choline