Halogen Alkane
General Formula of Alkene: CnH2n+1 X, where n=1,2,3,4,5,6,7,8,9,10 and X is the halogen.
Halogenoalkanes undergo nucleophilic substitution reactions.
Halogenoalkanes can be classified into three types:
1. Primary halogenoalkanes - Halogenoalkanes that have the halogen bonded to a carbon that has two hydrogens bonded to it.
2. Secondary halogenoalkanes - Halogenoalkanes that have the halogen bonded to a carbon which has one hydrogen bonded to it.
3. Tertiary halogenoalkanes - Halogenoalkanes that have the halogen bonded to a carbon that has no hydrogen bonded to it.
There are two mechanisms of Nucleophilic substitution reaction:
(a) SN1
(a) SN2
Primary halogenoalkanes undergo SN1 reaction mechanism.
Tertiary halogenoalkanes undergo SN2 reaction mechanism.
Secondary halogenoalkanes can undergo both SN1 and SN2 reaction mechanism.
Reactions of halogenoalkanes:
1. Halogenoalknes can react with aqueous sodium hydroxide to make alcohol and sodium chloride.
For this reaction, the reactants are needed to be heated under reflux
2. Halogenoalknes can react with aqueous sodium hydroxide in the presence of an alcohol to make alkene.
These reactions are called elimination reactions.
3. Halogenoalkanes react with excess ammonia in ethanol to make amine.
High pressure is needed for this reaction.
**It is important to use excess ammonia otherwise a mixture of amines will be formed.
4. Halogenoalkanes react with potassium cyanide in ethanol to make nitrile.
For this reaction, the reactants are needed to be heated under reflux
Reaction Mechanisms
SN1
This is called a nucleophilic substitution reaction.
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