Class 12 Chemistry - ODISHA
Alcohols, Phenols and Ethers
The chapter 'Alcohols, Phenols and Ethers' in Class 12 Chemistry for Odisha BSE students explores important classes of organic compounds containing oxygen. Alcohols and phenols are formed by replacing hydrogen atoms of hydrocarbons with hydroxyl (-OH) groups, while ethers contain an oxygen atom bonded to two alkyl or aryl groups. This chapter covers their classification, nomenclature, methods of preparation, physical properties, and distinct chemical reactions like the Reimer-Tiemann reaction and Williamson synthesis. Mastery of these topics is crucial for scoring high marks in the board exams, especially in reaction-based conversions and naming reactions.
Start Learning FreeKey Concepts
Classification of Alcohols and Phenols
Alcohols and phenols are classified as mono-, di-, tri- or polyhydric depending on the number of -OH groups attached, and further as primary, secondary, or tertiary based on the carbon atom holding the -OH group.
Acidity of Phenols vs Alcohols
Phenols are more acidic than alcohols because the phenoxide ion left after losing a proton is stabilized by resonance, whereas alkoxide ions lack this resonance stabilization.
Preparation of Alcohols
Alcohols can be prepared by the hydration of alkenes, reduction of aldehydes, ketones, and carboxylic acids, and through the reaction of Grignard reagents with carbonyl compounds.
Reimer-Tiemann Reaction
Treatment of phenol with chloroform in the presence of sodium hydroxide introduces an aldehyde group (-CHO) at the ortho position, forming salicylaldehyde.
Williamson Ether Synthesis
An important laboratory method for preparing symmetrical and unsymmetrical ethers by the reaction of an alkyl halide with a sodium alkoxide.
Important Formulas
Board Exam Info
In the Odisha BSE Class 12 Chemistry board exam, this chapter typically carries around 6 to 8 marks. Questions frequently include conversion reactions, distinguishing tests between alcohols and phenols, mechanism of acid-catalyzed hydration of alkenes, and direct questions on named reactions like Williamson synthesis and Reimer-Tiemann reaction.
Frequently Asked Questions
Why are phenols more acidic than alcohols?
Phenols are more acidic because the phenoxide ion formed after the loss of a proton is stabilized by resonance, whereas alkoxide ions from alcohols do not show resonance stabilization.
How can you distinguish between primary, secondary, and tertiary alcohols?
They can be distinguished using the Lucas test (reaction with anhydrous ZnCl2 and concentrated HCl) based on the time taken for turbidity to appear.
What is the role of pyridine in the acetylation of alcohols?
Pyridine is a base used to neutralize the HCl produced during the reaction, which shifts the equilibrium to the right and prevents the reverse reaction.
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