Alkyl halides

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Definition: Compounds having general formula R-X,where R is an alkyl group or a substituted alkyl or cycloalkyl group and X is a halogen(F,Cl,Br,I)are called alkyl halides .

Preparation: 

1)From alcohols:

By the reaction of HX ( or phosphorous halides) on alcohols.
for example 


2)From alkene:
By addition of hydrogen halides or halogens to carbon-carbon double bond.for example :


3)Hunsdiecker reaction : 
alkyl bromides can be prepared by the decarboxylation of silver salt of carboxylic acid with bromine in CCl4.


Mechanism: Hunsdiecker reaction involves four step .it start with ionic mechanism followed by free radical chain mechanism as shown below.












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