. ▁ ▁An ▁example ▁of ▁a ▁reaction ▁proceed ing ▁in ▁a ▁SN 1 ▁fashion ▁is ▁the ▁synth esis ▁of ▁ 2 , 5 - d ich lor o - 2 , 5 - dim eth yl hex ane ▁from ▁the ▁corresponding ▁di ol ▁with ▁concentr ated ▁hydro ch lor ic ▁acid : ▁ ▁As ▁the ▁alpha ▁and ▁beta ▁substitution s ▁increase ▁with ▁respect ▁to ▁leaving ▁groups ▁the ▁reaction ▁is ▁di vert ed ▁from ▁SN 2 ▁to ▁SN 1 . ▁ ▁S tere och em istry ▁The ▁car b ocation ▁intermediate ▁is ▁formed ▁in ▁the ▁reaction ' s ▁rate ▁determ ining ▁step ▁is ▁an ▁sp 2 ▁hy brid ized ▁carbon ▁with ▁trig onal ▁plan ar ▁mole cular ▁geometry . ▁This ▁allows ▁two ▁different ▁ways ▁for ▁the ▁nucle oph il ic ▁attack , ▁one ▁on ▁either ▁side ▁of ▁the ▁plan ar ▁mole c ule . ▁If ▁neither ▁way ▁is ▁prefer entially ▁fav ored , ▁these ▁two ▁ways ▁occur ▁equally , ▁yield ing ▁a ▁rac em ic ▁mixture ▁of ▁en anti om ers ▁if ▁the ▁reaction ▁takes ▁place ▁at ▁a ▁s tere oc enter . ▁This ▁is ▁illustrated ▁below ▁in ▁the ▁SN 1 ▁reaction ▁of ▁S - 3 - ch lor o - 3 - m eth yl hex ane ▁with ▁an ▁i od ide ▁ion , ▁which ▁yields ▁a ▁rac em ic ▁mixture ▁of ▁ 3 - iod o - 3 - m eth yl hex ane : ▁ ▁However , ▁an ▁excess ▁of ▁one ▁s tere ois omer ▁can ▁be ▁observed , ▁as ▁the