(a) When the rate of oxidation of isopropyl alcohol to acetone is compared with the rate of oxidation of a deuterated derivative, a primary isotope effect (Sec. 9.5D) is observed (see part (a) of Fig. P10.60). Assuming that the mechanism is the same as the one shown in Eqs. 10.52a–c, which step of this mechanism is rate-limiting?

(b) When either (S)- or (R)-1-deuterioethanol is oxidized with PCC in CH₂Cl₂, the same product mixture results and it contains significantly more of the deuterated aldehyde A than the undeuterated aldehyde B (see part (b) of Fig. P10.60). Explain why the deuterated aldehyde is the major product.

(c) Explain why, in the oxidation of (R)-1- deuterioethanol with alcohol dehydrogenase and NAD⁺, none of the deuterated aldehyde is obtained.

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(a) (b) CH3 H₂C-C-OH H CH3 T H3C-C-OH T D H H₂C-C-OH D 1-deuterioethanol H₂CRO4 Figure P10.60 H₂CrO4 PCC H₂C H3C-C=O + H₂C-C=0 LIT D A (mostly) CH₂Cl2 H3C H₂C H3C C=O relative rate = 6.6 C=O relative rate = 1.0 H B