Alkylhalides: Introduction

Alkylhalides: an initiation

Background information

Alkylhalides are compounds (in this case salts) that consist of an alkyl group and an halogen (seventh row in the table of Mendeljev). 

Alkylhalides have good leaving groups, these groups are the atoms (or the atom) that will be substituted or eliminated during elimination or substitution reactions on the molecule. This fenomenon is caused by the polar bond formed between the halogen and the alkyl group, making the halogen more afferent to be attacked (substituated / eliminated) by a nucleophile.

Nucleophile substitution reaction (SN2 reaction)

A nucleophile 'attacks' the alkylhalide, the leaving group - in this case the halogen - will be taken of the compound and will be replaced (SUBSTITUTED) by the nucleophile (hense the reaction its name). This reaction however is characterized and depended by several factors including:

• the solvent in which the reaction is taking place
• the reactivity or activity of the attacking nucleophile
• the concentration and amount of added nucleophile
• the structure and compound of the alkylhalide

Experiments have shown that the Sn2 reaction really takes place by noticing following measures:

• the configuration of the substituted product is inverted (contrary) to the original reacting chiral configured alkylhalide
• if the alkylhalide is more branched off at the reaction center, the reaction rate of the attacking nucleophile will go down thus resulting in a much slower reaction (slow tertiary < secondary < primary fast)
• logic: the reaction rate is dependent on the concentration of both compounds (alkylhalide and nucleophile)