The case of dehydration of alcohol takes place most easily in case (c). In all cases during dehydration carbocation is formed. In case (a), carbocation destabilise by NO2(−I) group hence, dehydration reaction proceed with difficulty. In case (b) dehydration reaction takes place less difficulty than case (a) because Cl group show (-I) and (+ R) effect. In case (c) dehydration reaction proceed easily because carbocation is stabilised by OCH3(+R) group.