NEET Chemistry Notes Alcohols,Phenols and ethers – Chemical Properties of Alcohols
Chemical Properties of Alcohols
Chemical Properties of Phenols
The chemical properties of alcohol depend on the order of reactivity of alcohols as given below:
Order of reactivity of alcohols:
1° alcohol > 2° alcohol > 3° alcohol
Reactions Involving Cleavage of O—H Bond Reaction with Metals
Acidity of alcohols in decreasing order:
Primary alcohols > secondary alcohols > tertiary alcohols. Electron releasing group decreases the polarity of —OH bond. This decreases the acidic strength. Alcohols when react with carboxylic acids, acid chlorides and acid anhydrides, form esters. This reaction is called esterification
Reactions Involving Cleavage of Carbon Oxygen (C—O) Bond
Reaction with hydrogen halides
Reactivity in decreasing order 3°> 2°> 1°.
Dehydration in the presence of protic acids like cone. H2S04 or H3P04 or in the presence of catalysts such as anhy.ZnCl2 or A1203.
Mechanism of Dehydration
- Methanol and ethanol are two commercially important alcohols. Methanol is used as a solvent in paints, varnishes and mainly for making formaldehyde.
- It is highly poisonous in nature. Ingestion of even small quantities of methanol can cause blindness and large quantities cause even death.
- Ethanol is used as a solvent in paint industry and in preparation of a number of carbon compounds.
- Commercial alcohol is made unfit for drinking by mixing CuSO4 and pyridine (denaturation of alcohol).
- Ethanol is mainly used in alcoholic beverages.
Identification of Primary, Secondary and Tertiary Alcohols
With Lucas reagent (cone. HCl and ZnCl2),
- tertiary alcohols give turbidity immediately.
- secondary alcohols give turbidity with in five minutes.
- primary alcohols do not produce turbidity at room temperature.
In Victor Meyer’s test
- blood red colour indicates 1° alcohols.
- blue colour indicates 2° alcohols.
- colourless solution indicates 3° alcohols.