6-59 continued (b) In order to undergo substitution and therefore inversion, HO-wouid have to be the leaving group, but HO- is never a leaving group in SN2. No reaction can occur. (c) Once the OH is protonated, it can leave as H20. Racemization occurs in the SN1 mechanism because of the planar, achiral carbocation intermediate which "erases" all stereochemistry of the starting material. Racemization occurs in the SN2 mechanism by establishing an equilibrium of Rand S enantiomers, as explained in 6-59(a). (b) (c) HO-C-H --..:: H+ \:::) HO-C-H + H-C-OH racemic mixture The carbocation produced in this E l elimination is 30 and will not rearrange. The product ratio follows the Zaitsev rule. trace-from unrearranged 20 carbocation minor trace amount from either unrearranged 20 carbocation or rearranged 30 carbocation from rearranged 30 carbocation
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