Classification of Alcohols and Phenols

Classification of Alcohols

• Primary Alcohol: Contains one alkyl group attached to the carbon with the hydroxyl group; example: Ethanol.
• Secondary Alcohol: Contains two alkyl groups attached to the carbon with the hydroxyl group; example: 2-Propanol (isopropyl alcohol).
• Tertiary Alcohol: Contains three alkyl groups attached to the carbon with the hydroxyl group; example: 2-Methyl-2-propanol (t-butyl alcohol).

Phenols

• Structurally similar to alcohols due to the presence of a hydroxyl group.

Properties of Phenols

• More acidic than alcohols.
• Concentrated phenol solutions are toxic and can cause severe skin burns.
• Polar and generally mixes with water.

Properties of Alcohols

• Alcohols mix well with water.
• Increased number of hydroxyl groups enhances water solubility due to more hydrogen bonding.
• Also soluble in organic solvents.

Chromic Acid Test

• Distinguishes primary and secondary alcohols from tertiary alcohols.
• Uses acidified dichromate solution where:
  • Primary alcohols oxidize to carboxylic acids.
  • Secondary alcohols oxidize to ketones.
  • Tertiary alcohols do not oxidize, showing no reaction.
• The color change from red/brown to blue/green indicates oxidation.
• Phenols oxidize to a brown tarry mass.

Lucas Test

• Differentiates water-soluble primary, secondary, and tertiary alcohols using Lucas reagent (ZnCl2 in HCl).
• Tertiary alcohols react rapidly, forming an insoluble white layer immediately.
• Secondary alcohols react slowly, forming a thin white layer after slight heating within 10 minutes.
• Primary alcohols do not react.
• Positive results show a heterogeneous phase or emulsion.