Final - Fall 200610

Final - Fall 200610 - a) (1 S , 2 R ) and (1 R , 2 S ) b)...

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10 23. (4 pts) Select the substrate which would react fastest in the substitution reaction under the indicated conditions (at 25 o C)? MeNH 2 CH 3 CN ? Br OTos Br I a) c) b) d) Comments: S N 2 reactivity patterns are tested here. The tested factors include leaving groups and steric effects in the electrophile. There are several examples of this type of questions in the practice set: TS4: 55, 58, 59-62, PE4A: 22-25. 24. (4 pts) (1 S , 2 S )-1-Bromo-1-deutero-2-methylbutane is converted to 1-deutero-2-methylbutanol in a two-step process. What is the stereochemistry of the major products ? Note: deuterium, D = 2 H, has a higher priority than hydrogen, 1 H, in assigning the absolute configurations. Br t- BuOK t- BuOH BH 3 /THF H 2 O 2 /NaOH D OH D
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Unformatted text preview: a) (1 S , 2 R ) and (1 R , 2 S ) b) (1 S , 2 R ) and (1 R , 2 R ) c) (1 S , 2 R ) and (1 S , 2 S ) d) (1 S , 2 S ) and (1 R , 2 R ) Comments: This question tests stereochemistry of reaction with know mechanism. There are several question of this type in the practice set, and one 14 on PE4C is almost identical. Other examples include: TS4: 30, 38, PE4A: 17, PE4B: 27, PE4C 7, 14. Br t-BuOK t-BuOH BH 3 /THF H 2 O 2 /NaOH D H H D H HO H H D 1R, 2S + mirror image Elimination has to be antiperiplanar, giving E alkene which adds HOH syn (through hydroboration). The addition can take place from either face of the double bond, giving the two enantiomers (one shown)....
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