OIA1012 ALCOHOLS

Definition of Alcohols

Definition of Alcohols

Compounds containing one or more hydroxyl (OH) groups bonded to sp3-hybridized carbons.

Classification by Hydroxyl Groups

- Monohydric: One OH group.

- Dihydric: Two OH groups.

- Trihydric: Three OH groups.

- Polyhydric: More than three OH groups.

Primary, Secondary, Tertiary Alcohols

Classification based on the number of alkyl groups attached to the carbon bonded to OH.

Naming Alcohols

Replace the "-e" in the alkane name with "-ol" (e.g., methanol).

Physical Properties of Alcohols

Higher boiling and melting points compared to alkanes due to hydrogen bonding.

Solubility Trends

- Solubility in water decreases with increasing molecular weight.

- Alcohols form hydrogen bonds with water.

Grignard Reagents for Alcohol Preparation

React with aldehydes or ketones to produce primary, secondary, or tertiary alcohols.

Reaction with Alkali Metals

Alcohols react with sodium to form alkoxides and hydrogen gas.

Ester Formation (Esterification)

Alcohol reacts with carboxylic acids in the presence of acid to form esters.

Sulphate ester Formation

Alcohols react with sulphuric acid to for alkyl hydrogen sulphate.

Reaction is used to produce sodium lauryl sulphate.

Dehydration of Alcohols

Acid-catalyzed reaction produces alkenes.

Oxidation of Alcohols

- Primary alcohols: Oxidize to aldehydes, then carboxylic acids.

- Secondary alcohols: Oxidize to ketones.

- Tertiary alcohols: Do not oxidize easily.

Alcohols in Pharmaceutical Use

Ethanol is a solvent, antiseptic, and preservative.

Benzyl Alcohol

Used as an antiseptic and local anesthetic in topical formulations.

Glycerol (Triols)

- Used as a humectant, sweetener, and laxative.

- Found in creams and syrups.

Glycols (Diols)

Dihydric alcohols - contain 2 OH groups: gem-diols (1,1-diols)

Phenol vs. Alcohol

Phenols are more acidic and reactive than alcohols due to resonance stabilization of the phenoxide ion.

Haloform Reaction

Positive for alcohols with a methyl group next to the hydroxyl group (e.g., ethanol).

Phase 1 Metabolism

Alcohols undergo oxidation catalyzed by alcohol dehydrogenase.

Phase 2 Metabolism

Conjugation with glucuronic acid increases water solubility for excretion.

Alcohol in Hangovers

Causes dehydration and acetaldehyde production.

Propanol as a Solvent

Used in the preparation of ear drops and injectable formulations.

Williamson Synthesis

Alcohol reacts with alkyl halides to form ethers.

Alcohol Dehydration and Chirality Loss

Acidic conditions can lead to the formation of achiral intermediates.

Alcohols in Topical Formulations

Glycerol and glycols are common components in ointments and creams.

Adrenaline Stability

Stability of adrenaline injectable formulations is maintained at pH 2.2–5.0.

Alcohol Toxicity

Ethanol oxidation to acetaldehyde contributes to alcohol toxicity.