Overview
CHEM 205 Worksheet (WS5)
56 Points Total
Key Topics: Nucleophilic Substitution Reactions (SN1 or SN2, Reactions using PBr3, SOCl2, or TsCl.
1. Consider the scheme below then complete the following parts.
(a) (4pts) The stereochemistry expected for Product A has not been shown clearly. Using the template
provided in the box above, complete the Fischer projection of Product A to show the stereochemistry of
this product clearly.
(b) (12pts) Based on the following information, complete the Fischer projections for Product B, Product
C, and Product D below.
• Product A when treated with NaSCH2CH3 gives Product B (optical rotation D = +25°).
• Optically pure (R)-(-)-2-butanol when treated with PBr3 gives Product C (D = +38°).
• Product C when treated with NaSCH2CH3 gives Product D (optical rotation of D = -25°)
(c) (2pts) What is the absolute configuration of Product B? ________________
(d) (2pts) What type of mechanism is involved in the formation of Product C? ________________
(e) (4pts) Propose an arrow-pushing mechanism to clearly illustrate the mechanistic step indicated in part
(d) that is also consistent with the stereochemical information provided. You do not need to show the
entire mechanism. Just show the step that is relevant to setting the stereochemistry observed in the
product.