chapter19

chapter19 - Amines Chapter 19 19-1 19- Structure &...

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19- 19- 1 Amines Amines Chapter 19 Chapter 19
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19- 19- 2 Amines are classified as 1°, 2°, or , 3° amines: 1°, 2°, or , 3° amines: amines in which 1, 2, or 3 hydrogens of NH 3 are replaced by alkyl or aryl groups Methylamine (a 1° amine) Dimethylamine (a 2° amine) Trimethylamine (a 3° amine) CH 3 -NH 2 CH 3 -NH CH 3 -N CH 3 CH 3 CH 3 : :
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19- 19- 3 Amines are further divided into aliphatic, aromatic, and heterocyclic amines: aliphatic aliphatic amine: amine: an amine in which nitrogen is bonded only to alkyl groups aromatic amine: aromatic amine: an amine in which nitrogen is bonded to one or more aryl groups Aniline (a 1° aromatic amine) N-Methylaniline (a 2° aromatic amine) B enzyldimethylamine (a 3° aliphatic amine) NH 2 N-H CH 2 -N-CH 3 CH 3 CH 3 :
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19- 19- 4 heterocyclic amine: heterocyclic amine: an amine in which nitrogen is one of the atoms of a ring Pyrrole Piperidine Pyrrolidine Pyridine (heterocyclic aliphatic amines) (heterocyclic aromatic amines) N N N H H N H
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19- 19- 5 Structure & Classification Structure & Classification Aliphatic amines: replace the suffix - e e of the parent alkane by - amine amine 1,6-Hexanediamine (S)-1-Phenyl- ethanamine 2-Propanamine NH 2 NH 2 NH 2 H 2 N
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19- 19- 6 Nomenclature Nomenclature The IUPAC system retains the name aniline 3-Methoxyaniline ( m- Anisidine) 4-Methylaniline ( p- Toluidine) Aniline 4-Nitroaniline ( p- Nitroaniline) NH 2 NH 2 CH 3 OCH 3 NH 2 NO 2 NH 2
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19- 19- 7 Nomenclature Nomenclature Among the various functional groups discussed in the text, -NH 2 is one of the lowest in order of precedence COOH H 2 N OH NH 2 H 2 N OH 4-Aminobenzoic acid 2-Aminoethanol (S)-2-Amino-3-methyl- 1-butanol
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19- 19- 8 Nomenclature Nomenclature Common names for most aliphatic amines are derived by listing the alkyl groups bonded to nitrogen in one word ending with the suffix - amine amine CH 3 NH 2   N H Et 3 N NH 2 Triethylamine Dicyclopentylamine Methylamine tert- Butylamine
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19- 19- 9 Chirality of Amines Chirality of Amines if we consider the unshared pair of electrons on nitrogen as a fourth group, then the arrangement of groups around N is approximately tetrahedral an amine with 3 different groups bonded to N is chiral and exists as a pair of enantiomers and, in principle, can be resolved N Et Me H N Et Me H the unshared  electron pair in the fourth  sp 3 hybrid orbital ( S )-Ethylmethylamine ( R )-Ethylmethylamine
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19- 19- 10 10 Chirality of Amines Chirality of Amines in practice, however, they cannot be resolved because they undergo pyramidal inversion, which converts one enantiomer to the other N Et Me H N Et Me H N S  Enantiomer R  Enantiomer sp 3 sp 3 sp 3 Unhybridized 2 p  orbital The transition state has a plane of  symmetry; it is achiral
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19- 19- 11 11 Chirality of Amines Chirality of Amines
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chapter19 - Amines Chapter 19 19-1 19- Structure &...

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