Question

how the leaving group affect the behavior of the alkyl halide in mixture of NaI/ Acetone and in mixture of AgNO3/ Ethanol?

Answer 1

A mixture of Sodium iodide in acetone [NaI/ Acetone] is a polar aprotic solvent and it favours SN2 reactions and the reaction is faster for a leaving group attached to a primary carbon atom in primary alkylhalides. The order of the SN2 reaction for alkyl halides is 1^o>2^o>3^o. So if the alkyl halide is in a mixture of [NaI/ Acetone], it will undergo SN2 reactions .

SN1 reactions takes place in polar protic solvents like silvernitrate in ethanol   [ AgNO3/ Ethanol]. Here the reaction is faster for a leaving group attached to a tertiary carbon in tertiary alkylhalides . The reason is that tertiary alkyl halides will easily form the stable tertiary carbocations. Here the order of SN1 reaction for alkylhalides is 3^o >2^o>1^o

To   identify SN1 or SN2 reactions the main point is to identify the leaving group in the alkyl halide and check to which carbon the leaving group is attached, that is whether it to a primary , secondary or tertiary carbon atom.

For SN2 reactions solvents used are polar aprotic solvents like NaI/ Acetone and the reactions is faster for primary alkylhalides in which the leaving group is attached to primary carbon atom.

For SN1 reactions the solvents used are polar protic solvents like AgNO3/ Ethanol and the reaction takes place faster for tertiary alkyl halides where the leaving group is attached to tertiary carbon atom.