0243Pb77an-09.cwk (WP)

0243Pb77an-09.cwk (WP) - is also as shown but we will...

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Answer to Problem 77. Chemistry 0243, 2009 Addition of bromine in the presence of water gives the bromohydrin. Opening of the bromonium ion by an S N 2 reaction of water ensures the stereochemistry shown: Br Br CH 3 CH 3 Br+ CH 3 Br OH 2 CH 3 Br OH OH 2 S N 2 + A C 7 H 13 BrO Treatment of this alcohol with base generates the alkoxide which is in perfect position to displace bromide from the rear (S N 2 again) to give the epoxide: CH 3 Br O H CH 3 Br O CH 3 O .. H B C 7 H 12 O _ S N 2 _ A Finally, cyanide ion opens the epoxide through another S N 2 reaction to give the final product. Of course the S N 2 opening must occur with inversion; this ensures the stereochemistry shown. The regiochemistry
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Unformatted text preview: is also as shown but we will accept the other with a good explanation. CH 3 O CH 3 O CN CH 3 OH CN C C 8 H 13 NO H 2 O _ _CN S N 2 B (b) The first step is an S N 2 displacement to make the quaternary ammonium iodide: N(CH 3 ) 2 CH 3 I N(CH 3 ) 3 I _ D C 10 H 22 N + _ I + S N 2 .. Hofmann elimination leads to the less substituted alkene, and hydroboration gives the anti-Markownikoff alcohol. N(CH 3 ) 3 OH D + I _ KOH/H 2 O 1. B 2 H 6 2. HOOH H 2 O/HO-E C 7 H 12 F C 7 H 14 O...
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