HELLO SIR, you told us that tertiary alkyl halides prefer to undergo Sn1 rxn and primary alkyl halides prefer to undergo Sn2 rxn. sir, may i know that what sort of rxn will be preferred by secondary alkyl halides? or is there any different mechanism for them. THANK YOU.

Secondary alkyl halide can undergo either of the SN¹ or SN² substitution depending on the reaction condition such as polarity of the solvent used in those reactions.

With polar solvents reaction took the path of SN¹ mechanism whereas with nonpolar or less polar solvents rection undergo SN² reaction.