Alcohols

📘 1. Definition of Alcohol

• Alcohols are a homologous series of organic compounds that contain the hydroxyl (-OH) functional group attached to a carbon atom.
• They are derivatives of alkanes where one hydrogen atom is replaced by an –OH group.

Example: Ethanol – CH₃CH₂OH

🧪 2. Functional Group of Alcohols

• The functional group of alcohols is the hydroxyl group (-OH).
• It is responsible for the physical and chemical properties of alcohols.

🧮 3. General Formula

• The general formula for aliphatic (straight-chain) alcohols is: C_nH_2n+1OH or C_nH_2n+2O

Examples:

• Methanol: CH₃OH
• Ethanol: CH₃CH₂OH
• Propanol: CH₃CH₂CH₂OH

🧬 4. Isomers of Butanol (C₄H₁₀O)

There are four isomers of butanol:

a. butan-1-ol (n-butanol): CH₃CH₂CH₂CH₂OH

b. butan-2-ol: CH₃CH₂CHOHCH₃

c. 2-methyl propan-1-ol: (CH₃)₂CHCH₂OH

d. 2-methyl propan-1-ol: (CH₃)₃COH

These isomers differ in the position of the –OH group and the branching of the carbon chain.

🍬 5. Preparation of Ethanol from Glucose (Fermentation)

Word Equation:

Glucose → Ethanol+Carbon dioxide

C₆H₁₂O₆→2C₂H₅OH+2CO₂

Conditions:

• Yeast as an enzyme
• Temperature around 30°C
• Anaerobic (no oxygen)
• Neutral pH

🧪 6. Preparation of Alcohol from Alkenes (Hydration of Ethene)

Reaction:

CH₂=CH₂+H₂O → CH₃CH₂OH

Condition: H₃PO₄ catalyst, 300°C, 60 atm

• This is called hydration of ethene.
• It is an addition reaction where water adds across the double bond.

🧠 7. Reactions of Alcohols

a. Reaction with Sodium Metal (similar to water)

2CH₃CH₂OH+2Na→2CH₃CH₂ONa+H₂↑

• Sodium reacts with alcohol to form sodium ethoxide and hydrogen gas.
• Observation: effervescence due to hydrogen gas.

b. Oxidation of Alcohols (using oxidizing agents like acidified potassium dichromate)

Primary Alcohol (e.g., Ethanol):

CH₃CH₂OH+[O]→CH₃COOH+H₂O

• Ethanol is oxidized to ethanoic acid.

Observation: Orange dichromate turns green.

Secondary Alcohol: oxidized to ketone

Tertiary Alcohol: generally resistant to oxidation

🧪 8. Esterification Reaction (Alcohol + Carboxylic Acid)

General Reaction:

Alcohol+Carboxylic Acid → conc. H₂SO₄ Ester+Water

Example:

CH₃CH₂OH+CH₃COOH → CH₃COOCH₂CH₃ + H₂O

(Ethanol + Ethanoic Acid → Ethyl Ethanoate + Water)

• Catalyst: concentrated sulfuric acid
• Reversible reaction

Esters have a pleasant smell (used in perfumes and flavorings)

🧰 9. Uses of Alcohols

1. As fuels (ethanol as biofuel)
2. As solvents (in perfumes, inks, medicines)
3. In alcoholic drinks (ethanol)
4. In antiseptics (e.g., hand sanitizers)
5. In making esters for perfumes and flavorings

📝 Summary Chart:

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