Classification Alcohols, Phenols, and Ethers Formula

Alcohols: Organic compounds containing hydroxyl (-OH) group as a functional group bonded to a saturated carbon atom.

Example: CH ₃ OH (Methanol)

Phenols: Compounds in which the hydroxyl group is directly attached to an aromatic ring.

Example: C ₆ H ₅ OH (Phenol)

Ethers: Compounds that contain an oxygen atom bonded to two alkyl or aryl groups.

Example: CH ₃ OCH ₃ ​ (Dimethyl ether)

Classification of Alcohols

Primary (1°): The carbon atom bonded to the -OH group is bonded to only one other carbon atom.

Example: Ethanol CH ₃ CH ₂ OH

Secondary (2°): The carbon atom bonded to the -OH group is bonded to two other carbon atoms.

Example: Isopropanol CH ₃ CHOHCH ₃ ​

Tertiary (3°): The carbon atom bonded to the -OH group is bonded to three other carbon atoms.

Example: Tert-butanol (CH ₃ ) ₃ COH

Phenols: Typically not classified in the same way as alcohols since the -OH is always attached to an aromatic ring.

Ethers: Symmetrical (Simple) Ethers: Same alkyl groups on both sides of the oxygen.

Example: Dimethyl ether CH ₃ OCH ₃ ​

Unsymmetrical (Mixed) Ethers: Different alkyl or aryl groups on either side of the oxygen.

Example: Ethyl methyl ether CH ₃ OCH ₂ CH ₃ ​

Nomenclature

Alcohols: Named with the suffix "-ol" added to the name of the parent alkane.

Example: CH ₃ CH ₂ OH is Ethanol.

Phenols: The word "phenol" itself is used if there are no substituents. If substituents are present, their positions are indicated using numbers.

Example: C ₆ H ₄ (OH)(CH ₃ ) can be named as m-cresol where the methyl group is meta to the hydroxyl group.

Ethers: In the common naming system, name the two alkyl or aryl groups alphabetically and add "ether".

Example: CH ₃ OCH ₂ CH ₃ ​ is ethyl methyl ether. In the IUPAC system, it's named as alkoxyalkanes. For example, the above can be named as methoxyethane.

Preparation of Alcohols

From Alkenes:

Acid-catalyzed hydration.

CH ₂ =CH ₂ ​ + H ₂ O → CH ₃ CH ₂ OH (in the presence of acid)

From Grignard Reagents:

CH ₃ MgBr + H ₂ O→ CH ₄ ​ + Mg(OH)Br

Reduction of Carbonyl Compounds: Using reducing agents like LiAlH ₄ or NaBH ₄ .

RCHO + 2[H] → RCH ₂ OH

Also Check – Acids and Bases Formula: Types of Reaction

Preparation of Phenols

From Halobenzenes: Using aqueous NaOH at high temperatures (called the Dow process).

C ₆ H ₅ Cl + NaOH → C ₆ H ₅ OH + NaCl

From Benzene Sulphonic Acid: Through fusion with NaOH.

C ₆ H ₅ SO ₃ H + 3NaOH → C ₆ H ₅ OH + 3NaHSO ₃ ​

Also Check – PH of Weak Acid Formula

Physical and Chemical Properties of Alcohols and Phenols

Boiling Point:

Alcohols and phenols have higher boiling points than their corresponding hydrocarbons due to hydrogen bonding.

Acidity:

Phenols are more acidic than alcohols due to the delocalization of the negative charge over the aromatic ring in the phenoxide ion.

Reaction with Halides:

Alcohols react with halide ions in the presence of acids to form haloalkanes.

ROH + HX → RX + H ₂ O

This is termed as the Lucas Test when using anhydrous ZnCl ₂ with alcohols to distinguish between primary, secondary, and tertiary alcohols.

Ester Formation:

Alcohols react with carboxylic acids to form esters in the presence of an acid catalyst.

RCOOH + R′OH → RCOOR ′ + H ₂ O

Oxidation:

While secondary alcohols can be oxidized to ketones, primary alcohols can be converted to aldehydes and then to carboxylic acids. Alcohols in the tertiary stage do not simply oxidize.

Reimer-Tiemann Reaction:

Phenol, when treated with chloroform in the presence of aqueous NaOH, results in the formation of salicylaldehyde. This reaction involves the formation of dichlorocarbene.

C ₆ H ₅ OH + CHCl ₃ ​ + 4NaOH → C ₆ H ₄ CHO(OH) + 3NaCl + 3H ₂ O

Williamson Ether Synthesis:

An alcohol is first converted into a sodium alkoxide, which then reacts with an alkyl halide to form an ether.

RONa + R ′ X → ROR ′ +NaX