In an early study of the stereochemistry of nucleophilic displacements, optically pure (R)-1-deuterio-1-pentanol was treated with 4-methylphenylsulfonyl (tosyl) chloride to make the corresponding tosylate. The tosylate was then treated with excess ammonia to convert it to 1 -deuterio,- 1 -pentanamine:

(a) Describe the stereochemistry that you expect to observe at Cl of both the intermediate tosylate and the final amine?
(b) When the reaction sequence is actually carried out, the expected results are not obtained. Instead, the final amine is isolated as a 70:30 mixture of (5)-and (R)-1-deuterio-1-pentanamine. Suggest a mechanistic explanation?

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-SO,CI Excess NH, (R)-CH-CH-CH,CH.CHDOH (R)-1-Deuterio-1-pentanol CHCHCHCH.CHDNH, 1-Deuterio-1-pentanamine →