OIA1012 AMIDES & AMINES

Definition of Amides

Organic compounds containing a carbonyl group (C=O) bonded to a nitrogen atom (-NH2, -NHR, -NR2).

Naming Amides

Replace "-oic acid" in carboxylic acids with "-amide" (e.g., ethanoic acid → ethanamide).

Lactams

Cyclic amides, found in antibiotics like penicillin and cephalosporins.

Physical Properties

- High boiling points due to hydrogen bonding.

- Lower amides are water-soluble; solubility decreases with size.

Resonance in Amides

Amides have partial double-bond character due to resonance, reducing basicity.

Stereochemistry of Amides

Planar structure due to resonance, with the amide hydrogen trans to the carbonyl oxygen.

Preparation from Acid Chlorides

Reaction of acid chlorides with amines forms amides.

Hydrolysis in Acidic Conditions

Produces carboxylic acid and ammonium ion (NH4+).

Hydrolysis in Basic Conditions

Produces carboxylate salt and amine; irreversible.

Amidase Enzymes in Metabolism

Enzymes hydrolyze amides in the body into acids and amines.

Dehydration to Nitriles

Treating primary amides with (P2O5) forms nitriles.

Hofmann Rearrangement

Primary amides react with bromine in alkaline solution to form amines with one fewer carbon.

Reduction to Amines

Lithium aluminum hydride (LiAlH4) reduces amides to amines.

Thioamide Formation

Amides react with (P2S5) to form thioamides (-C=S).

Definition of Amines

Organic derivatives of ammonia (NH3), classified as primary, secondary, or tertiary.

Naming Amines

- Replace "-e" in alkanes with "-amine" (e.g., ethane → ethylamine).

- For multiple functional groups, use "amino-" as a prefix.

Physical Properties

- Low molecular weight amines are gases or liquids with a fishy odor.

- Higher amines and aromatic amines have higher boiling points and lower solubility.

Basicity of Amines

- Due to the lone pair on nitrogen, amines act as proton acceptors.

- Strength increases with alkyl substitution due to electron donation.

Aliphatic vs. Aromatic Amines

- Aliphatic amines are stronger bases than ammonia.

- Aromatic amines are weaker due to delocalization of the nitrogen lone pair.

Amides vs. Amines in Basicity

- Amides are weaker bases than amines because of resonance stabilization.

Salt Formation in Pharmaceuticals

- Amines react with acids to form stable, water-soluble salts used in drugs.

Gabriel Synthesis

Produces primary amines from phthalimide.

Reduction of Nitriles and Amides

(LiAlH4) reduces nitriles and amides to amines.

Reductive Amination

Aldehydes or ketones react with ammonia or amines in the presence of reducing agents to form amines.

Hofmann Rearrangement of Amides

Converts amides to amines with loss of one carbon atom.

Reduction of Nitro Compounds

Nitrobenzenes reduce to anilines using Sn/HCl or catalytic hydrogenation.

Nucleophilic Alkylation

Amines react with alkyl halides, forming secondary and tertiary amines.

Diazonium Salt Formation

Aromatic primary amines react with nitrous acid (HNO2) to form diazonium salts.

Diazo Coupling Reactions

Aryldiazonium salts react with phenols or aromatic amines to form azo dyes.

Metabolism: Dealkylation and Oxidation

- Secondary and tertiary amines undergo dealkylation in metabolism.

- Oxidation converts amines into N-oxides or nitroso compounds.