16-1

Principles and Applications ofInorganic, Organic, and Biological

ChemistryDenniston, Topping, and Caret

4th ed

Chapter 16

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Power Point to Accompany

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Amines have these structures:RNH2, R2NH, R3N (R is aliphatic or

aromatic)Amines, like alcohols, can be put into

classes. Class depends on the number of carbons directly bonded to the nitrogen atom: a primary amine has one bond, a secondary two, etc.

RNH2, R2NH, R3N

1o 2o 3o

16.1 Amines

16-3

Amines: Physical properties

Most amines up to 5 or 6 carbons are water soluble due to hydrogen bonding with the water molecule.

CH3NH

HH

OH

HO

H

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Amines: Physical properties-2Amines have boiling points between

alkanes and alcohols. They hydrogen bond but not as strongly as alcohols. Tertiary amines cannot hydrogen bond to each other and boil lower then 1o or 2o of similar molecular weight.

C4H8 (58), bp 0 oC

C3H7NH2 (59), bp 48 oC

C3H7OH (60), bp 97 oC

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Amine names: Chem AbstractsPrimary aliphatic amines are named by

dropping the final –e of the parent name and adding the suffix -amine.

Name: CH3CH2NH2

ethanamine

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Amine names: Chem Abstracts-2

The prefix N-alkyl is added to the name of the parent for 2o and 3o amines. Name:

CH3CH2N

H

CH2CH3

N-ethylethanamine

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Amine names: IUPACFor primary amines, the prefix amino

and a number designates the position of the amino group on an alkane parent chain. A substituent on the N uses the –N prefix as with the Chem Abstracts system.

CH3CH CH3NH2

CH3CH CH3NH CH3

2-aminopropane

N-methyl-2-aminopropane

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Amine names: Common NamesName the alkyl groups attached to the N

in alphabetical order and add –amine. The name is continuous, no spaces between groups. Name:

CH3CH2CH CH3

NHCH3

Methylsec-butylamine

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Amine names

Aromatic amines are named as N-substituted derivatives of aniline. (See aromatics) Name a) and b):

NH CH3NH2

NO2a) b)

a) m-nitroaniline

b) N-methylaniline

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Reactions of Amines: PreparationAliphatic amines are prepared via reduction of amides. E. g.

CH3CH2CO

CH3NH[H]

CH3CH2CH2 CH3NH

Aromatic amines are prepared via reduction of nitro compounds. E. g.

NO2

[H]NH2

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Reactions of Amines: BasicityAmines are weak bases. They accept protons from water making solutions basic.

CH3CH2NH2+ H2O CH3CH2NH3

+

+ OH-

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Reactions of Amines: Neutralization

Amines form salts by accepting a proton from strong mineral acids.

Converting amines to salts often makes insoluble amines soluble!!!!!

CH3CH2CH2NH2

+ HClCH3CH2CH2NH3

+Cl-

Name amine salts by replacing the suffix –amine with ammonium and the name of the anion.

E. g. propylammonium chloride

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Reactions of Amine Salts: Neutralization

Amine salts revert to the amine (donate a proton) in strong base.

NH3

+

NO2

NH2

NO2

Cl-

+ NaOH + NaCl + H2O

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Amine Reactions: “Quats”3o amines react with alkyl chlorides to give quaternary ammonium salts which are very important in biochemistry.

CH3 N

CH3

CH3

CH3Cl+ CH3 N

CH3

CH3

CH3+

Cl -

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“Quats” cont.

Benzalkonium chloride (ZephiranTM) and choline are important examples.

CH3N+

CH3

CH3

CH2CH2OHCl-

Cl-

C18H37 N+

CH3

CH3

CH2

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16.2 Heterocyclic AminesHeterocyclic amines have at least one

nitrogen in the ring. MANY are physiologically active and many are critical in biochemistry.

NH N

pyrrole

pyrimidinepurine

N

N

NH

NN

N

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Examples of Heterocyclic Amines

N

N

CH3

nicotineN

N

H

CH2CH2NH2

histamine

NH

OH CH2 CH2 NH2

serotonin,a neurotransmitter

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Examples of Heterocyclic Amines-2

O

OCH3

OHNCH3

Codine

pyridoxaminea B vitamin

NCH3

OHCH2 NH2

CH2OH

OH

OH CH2 CH2NH2dopamineneurotransmitter

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16.3 AmidesMost amides are solids at room temperature due

to internal hydrogen bonding.They are not bases. A resonance structure

shows why the N lone pair is unavailable to accept a proton.

CH3C

O

NH2 CH3C

O

NH2

+

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Amide NamesNames are derived from the acid.Remove –ic acid (common) or –oic acid

(IUPAC) and replace with –amide.Nitrogen substituents are prefixed to the

name and indicated by N.

CH3C

O

NH2

CH2C

O

NHCH3 CH3

ethanamideoracetamide

N-methylpropanamide

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Preparation of Amides1o and 2o amines react with acid chlorides to give amides.

CH3C

O

Cl

NH2

+ NCH3C

O H

+ HClThe acid chloride transfers its acyl group to the N of the amine.

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Preparation of Amides-21o and 2o amines react with acid anhydrides to give amides. E. g. with acetic anhydride.

CH3CO

OCO

CH3 NH2 CH3+

NCH3CH3COH

+CH3CO

OH

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Amino Acids and Proteins

An alpha amino acid is a carboxylic acid with an amino group on the carbon alpha to the carboxylic acid .

The alpha carbon also has an R group side chain except for glycine which has two Hs.

C C

R1

H

NH3

+O

OGeneric aminoacid at physiologicalpH. C

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PeptidesA peptide is a polymer of about 2-100

amino acids linked by the peptide(amide) bond. As the amino group and the carboxyl group link, water is lost.

C C

R1

H

NH3

+O

O

Peptide bonds

C C

R1

H

NH3

+O

OC C

R1

H

NH3

+O

O

C C

R1

H

NH3

+O

C C

R1

H

NH

OC C

R1

H

NH

OO

-H2O -H2O

C C

R1

H

NH3

+O

O

Peptide bonds

C C

R1

H

NH3

+O

OC C

R1

H

NH3

+O

O

C C

R1

H

NH3

+O

C C

R1

H

NH

OC C

R1

H

NH

OO

-H2O -H2O

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Hydrolysis of Amidesa) Amides hydrolyze with acid to give the

carboxylic acid and the amine salt.

b) Amides hydrolyze with base to give the carboxylic acid salt and the amine.

CH3CH2CC

NHCH3 CH3CH2CC

OH

NH3

+CH3

+H3O+

+

CH3CH2CC

NHCH3 CH3CH2CC

ONa

NH2 CH3

+NaOH

+

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16.4 Amino Acids and Protein Synthesis

-amino acids are attached to transfer RNA molecules (t-RNA). The acyl group ( and the amino acid) are transferred to the nitrogen of another amino acid to form a peptide (amide) bond.

RC C

Ctransfer RNANH2

H

Aminoacyl groupfrom amino acid

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16.5 NeurotransmittersNeurotransmitters carry signals from a nerve

cell to a target They can be excitatory or inhibitory. All contain nitrogen.

catecholaminesA deficiency in dopamine results in

Parkinson’s disease. Too much is associated with schizophrenia. It is also associated with the “high” of drugs.

OH

OH

CH2CH2NH2

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Neurotransmitters-cont.Catecholamines-cont.

Epinephrine (adrenaline) and norepinephrine are involved in the fight or flight response.

Serotonin

A deficiency is associated with depression, bulemia and anorexia nervosa. It also affects pain perception, thermoregulation, and sleep.

OH

OH

CH CH2NH

OH CH3

epinephrine(nor=no CH3)

serotoninNH

OH CH2CH2NH3

+

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Neurotransmitters-cont.Histamine is released during an allergic response.

Benadryl is a typical antihistamine used for colds and other allergic responses.

Acetylcholine functions at the neuromuscular junction to cause muscles to contract.

histamineNH NH

+

CH2CH2NH3

+

acetyl cholineCO

CH3 O CH2CH2N+

CH3 3

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Amines and Amides

The End