Electro negativity of N>S

Positive charge on N will make Methyl group more electron deficient than positive charge on 'S'. Therefore (a) will undergoSN² reaction more rapidly than (c)

(CH₃)₃C - MgCl + D₂O  → (CH₃)₃C - D + Mg(OD)Cl

Dipole moment decreases with decrease in electronegativity of halogen. Fluorides have lower dipole moment than chlorides because of smaller C-F bond length which outweights the effect of greater electronegativity

When  2 molecules of same aryl halides  reacts  in presence of Na metal  the reaction is called as Fittig reaction

Chloroform on nitration with nitrating mixture gives chloropicrin

Conversion of α,ω-dihalogen derivatives to cycloalkanes using Na and ether is Freund’s reaction.

The outgoing nucleophile does not leave the reactant and therefore, attack is mainly from backside .