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Amines and Amides

Amines

Reactions of Amines

Amides

Reactions of Amides

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Amines

• Organic compounds of nitrogen N• Classified as primary, secondary, tertiary

CH3 CH3

CH3—NH2 CH3—NH CH3—N — CH3

1° 2° 3°

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Naming Amines

IUPAC aminoalkane Common alkylamine

CH3CH2NH2 CH3—NH —CH3

aminoethane N-methylaminomethane(ethylamine) (dimethylamine)

NH2

|

CH3CHCH3

2-aminopropane Aniline N-methylaniline(isopropylamine)

NH2 NH CH3

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Practice Naming

Give the common name and classify as primary, secondary or tertiary:

A. CH3NHCH2CH3

CH3

|

B. CH3CH2NCH3

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Solution

A. CH3NHCH2CH3

N-methylaminoethane (ethylmethylamine), 2°

CH3

|B. CH3CH2NCH3

N,N-dimethylaminoethane (ethyldimethylamine), 3°

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Reactions of Amines

• Act as weak bases in water

CH3NH2 + H2O CH3NH3+ + OH–

methylammonium hydroxide

• Neutralization with acid gives ammonium salt

CH3NH2 + HCl CH3NH3+ Cl–

methylammonium chloride

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Alkaloids

• Physiologically active nitrogen-containing compounds

• Obtained from plants• Used as anesthetics, antidepressants, and

stimulants• Many are addictive

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Nicotine

N

CH3

Nicotine, leaves of tobacco plant

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Caffeine

N

N N

NCH3

O

O CH3

CH3

Caffeine, coffee beans and tea

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Procaine

NH2N

CH3CH2

CH3CH2

CH2CH2 O C

O

Procaine (novocaine), painkiller

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Practice

Write a structural formula for

A. 1-aminopentane

B. 1,3-diaminocyclohexane

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Solution

A. 1-aminopentane

CH3CH2CH2CH2CH2-NH2

B. 1,3-diaminocyclohexaneNH2

NH2

More naming practice

• Draw:

N-methyl-N-propyl-2-aminobutane

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Solution

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Properties of Amines

• When organisms decompose, large and complex molecules such as proteins are broken down into simpler amines.

• Amines often have an unpleasant odour, such as rotting fish.

• Putrescine (1,4-diaminobutane) and Cadavarine (1,5-diaminopentane) are amines produced by bacteria when animal tissue decomposes.

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Properties cntd

• Amines have higher melting and boiling points than comparable hydrocarbons as they are more polar.

• Amines with 1-5 carbons are soluble in water. When N-H bonds are present (primary or secondary amines), hydrogen bonding can occur with water.

• The N-H bond is not as polar as the O-H bond in alcohols.

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Preparing Amines

• Preparing a Primary Amine (ammonia reacts with an alkyl halide)

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Secondary Amines

• Preparing a Secondary Amine (primary amine reacts with alkyl halide)

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Tertiary Amines

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Preparing a Tertiary Amine (secondary amine reacts with alkyl halide)

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Amides

Derivatives of carboxylic acids where an amino (-NH2) group replaces the –OH group. (CON)

O O

CH3 — C—OH CH3 — C—NH2

carboxylic acid amide

acetic acid ethanamide

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Naming Amides

Alkanamide from acid name

O

methanamide (IUPAC)

HC–NH2 formamide (common)

O propanamide (IUPAC)

CH3CH2C–NH2 propionamide(common)

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Naming Amides with N-Groups

O

CH3C–NHCH3 N-methylethanamide (IUPAC)

N-methylacetamide (common) O

CH3CH2C–N(CH3)2

N,N-dimethylpropanamide

N,N-dimethylpropionamide

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Aromatic Amides

C

O

NH2

Benzamide

C

O

NHCH3

N methylbenzamide -

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Practice

Name the following amides: O

A. CH3CH2CH2C–NH2

O

B. CH3C–N(CH2CH3)2

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Solution

O

A. CH3CH2CH2C–NH2

butanamide; butryamide (common)

O

B. CH3C–N(CH2CH3)2

N,N-diethylethanamide;

N,N-diethylacetamide

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Practice

Draw the structures of

A. Pentanamide

B. N-methylbutanamide

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Solution

A. Pentanamide O

CH3CH2CH2CH2C–NH2

B. N-methylbutanamide O

CH3CH2CH2C–NHCH3

Preparing Amides

• Carboxylic Acid + Ammonia

• Carboxylic Acid with Primary or Secondary Amine

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Reactions of Amides

Amides undergo

acid hydrolysis base hydrolysis

carboxylic acid salt of carboxylic acid

ammonium salt and an amine or ammonia

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Reactions of Amides

acid hydrolysis O

O HCl + H2O CH3COH + NH4+Cl–

CH3CNH2 O

NaOH

CH3CO– Na+ + NH3

base hydrolysis

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Practice

Write the products of the hydrolysis of

N- ethylpropanamide with NaOH.

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Solution

Hydrolysis of N-ethylpropanamide with NaOH gives the following products.

O

CH3CH2CO– Na+ + CH3CH2NH2

Properties of Amides

• Amides are weak bases and generally insoluble in water. Smaller amides are slightly soluble in water due to hydrogen bonding with NH group of amide and OH group of water.

• Amides whose N atoms are bonding to two H atoms have higher melting and boiling points than those with more alkyl groups attached due to more hydrogen bonding.

• Amide functional groups (CON) are an important linkage in proteins.

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