. ▁▁ ▁N uc le oph il ic ▁attack : ▁the ▁car b ocation ▁react s ▁with ▁the ▁nucle oph ile . ▁If ▁the ▁nucle oph ile ▁is ▁a ▁neutral ▁mole c ule ▁( i . e . ▁a ▁sol vent ) ▁a ▁third ▁step ▁is ▁required ▁to ▁complete ▁the ▁reaction . ▁When ▁the ▁sol vent ▁is ▁water , ▁the ▁intermediate ▁is ▁an ▁ox on ium ▁ion . ▁This ▁reaction ▁step ▁is ▁fast . ▁▁ ▁De pro ton ation : ▁Rem oval ▁of ▁a ▁pro ton ▁on ▁the ▁pro ton ated ▁nucle oph ile ▁by ▁water ▁acting ▁as ▁a ▁base ▁forming ▁the ▁alco hol ▁and ▁a ▁hyd ron ium ▁ion . ▁This ▁reaction ▁step ▁is ▁fast . ▁ ▁S cope ▁ ▁The ▁SN 1 ▁mechanism ▁tends ▁to ▁domin ate ▁when ▁the ▁central ▁carbon ▁atom ▁is ▁surrounded ▁by ▁bul ky ▁groups ▁because ▁such ▁groups ▁ster ically ▁h inder ▁the ▁SN 2 ▁reaction . ▁Additionally , ▁bul ky ▁subst itu ents ▁on ▁the ▁central ▁carbon ▁increase ▁the ▁rate ▁of ▁car b ocation ▁formation ▁because ▁of ▁the ▁relief ▁of ▁ster ic ▁stra in ▁that ▁occurs . ▁The ▁result ant ▁car b ocation ▁is ▁also ▁stabil ized ▁by ▁both ▁induct ive ▁stabil ization ▁and ▁hyper con j ug ation ▁from ▁attached ▁alk yl ▁groups . ▁The ▁Hamm ond – Le ff ler ▁post ulate ▁suggests ▁that ▁this ▁too ▁will ▁increase ▁the ▁rate ▁of ▁car b ocation ▁formation . ▁The ▁SN 1 ▁mechanism ▁therefore ▁domin ates ▁in ▁re actions ▁at ▁t ert i ary ▁alk yl ▁cent ers