Chemistry > Alcohols, Phenols and Ethers > 11.0 Epoxides
Alcohols, Phenols and Ethers
1.0 Alcohols
2.0 Classification of alcohols
3.0 Physical properties of the alcohol
3.0 Physical properties of the alcohols
4.0 Preparation of Alcohol
4.1 By hydrolysis of alkyl halide
4.2 Acid catalysed hydration of alkenes
4.3 Oxymercuration Demercuration
4.4 Hydroboration-oxidation
4.5 Hydroxylation of alkenes
4.6 From organometallic compounds
4.6 Reduction of Esters
5.0 Grignard reagent
5.1 Reaction & Mechanism
5.2 Product of Grignard reagent
5.3 Planning a Grignard synthesis
5.4 Restriction of the use of Grignard reagents
6.0 Chemical properties of alcohols
6.1 Acidic character
6.2 Dehydration
6.3 Reaction with phosphorus trihalide or thionyl chloride
6.4. Reaction with hydrogen halide
6.5 Oxidation of Alchols
7.0 Tests for Alchols
8.0 Ethers
9.0 Chemical Properties of Ethers
10.0 Aryl Ethers
11.0 Epoxides
12.0 Phenols
13.0 Preparation of Phenol
14.0 Physical Properties of Phenol
15.0 Chemical properties of phenols
11.1 Reactions of Epoxides
4.2 Acid catalysed hydration of alkenes
4.3 Oxymercuration Demercuration
4.4 Hydroboration-oxidation
4.5 Hydroxylation of alkenes
4.6 From organometallic compounds
4.6 Reduction of Esters
5.2 Product of Grignard reagent
5.3 Planning a Grignard synthesis
5.4 Restriction of the use of Grignard reagents
6.2 Dehydration
6.3 Reaction with phosphorus trihalide or thionyl chloride
6.4. Reaction with hydrogen halide
6.5 Oxidation of Alchols
The highly strained three-membered ring is molecules of epoxides make them much more reactive towards nucleophilic substitution than other ethers.
1. Acid catalysed ring opening of epoxide: Acid catalysis assists epoxide ring opening by providing a better leaving group at the carbon atom undergoing nucleophilic attack
2. Base catalysed ring opening of Epoxides: Epoxides can also undergo base catalysed ring opening such reactions do not occur with other ethers provided that the attacking nucleophile is also a strong base such as alkoxide ion or hydroxide ion.
If the epoxide is unsymmetrical, in base catalysed ring opening attack by the alkoxide ions occurs primarily at the less substituted carbon atom.
Because reaction is ${S_N}2$ reaction and primary substrates reacts more rapidly in ${S_N}2$ reaction because they are less sterically hindered. In the acid catalysed ring opening of an unsymmetrical epoxide the nucleophile attacks primarily at the more substituted carbon atom.
The bonding in the protonated epoxide is unsymmetrical with more highly substituted carbon atom bearing aconsiderable positive charge the reaction is SN1 like. The nucleophile therefore attacks this carbon atom even though it is more highly substituted. Which bears a greater positive charge because it resembles more stable tertiary carbocation.
