Alcohols can be prepared in many ways in the laboratory and industry. Here’s a structured explanation:
Methods of Preparation of Alcohols
1. From Alkenes
- Hydration of alkenes: Adding water to alkenes in the presence of an acid catalyst gives alcohols.
- Hydroboration-oxidation: A two-step reaction that converts alkenes to alcohols, usually giving anti-Markovnikov products.
2. From Haloalkanes
- Haloalkanes (alkyl halides) react with aqueous alkali (like NaOH or KOH) to form alcohols by substitution.
3. From Grignard Reagents
- Reaction of Grignard reagents with carbonyl compounds, followed by hydrolysis, produces different alcohols:
- With formaldehyde → primary alcohol.
- With other aldehydes → secondary alcohol.
- With ketones → tertiary alcohol.
4. From Aldehydes and Ketones
- Reduction of aldehydes gives primary alcohols.
- Reduction of ketones gives secondary alcohols.
- Common reducing agents: catalytic hydrogen, lithium aluminium hydride, or sodium borohydride.
5. From Carboxylic Acids and Esters
- Reduction of carboxylic acids or esters also produces alcohols.
6. Fermentation of Sugars (Industrial Method)
- Glucose and other sugars undergo fermentation in the presence of enzymes to produce ethanol.
- This is the most important industrial method for alcohol production.
In short: Alcohols can be prepared from alkenes, haloalkanes, Grignard reagents, aldehydes, ketones, carboxylic acids, esters, and by fermentation of sugars.