Solutions_Manual_for_Organic_Chemistry_6th_Ed 161

Solutions_Manual_for_Organic_Chemistry_6th_Ed 161 - c...

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Unformatted text preview: c 7-4w5ithontinued rearrangement h ydride shift ( a) 7- 4 major­ Zaitsev 61, /' .... /' m ajor + (c ) � +� m aj or mInor "y minor (b) maj or + m inor only product from E2anti -coplanar is possi ble only from carbon wi thout CH3 by rem (d) major ax (e) minor N y D �� 3 ) (CH3hC -.£:::::i CI eq C l 7- 4 7 The conformation must be considered because the leaving group must be in an axi al position. The t-butyl group is so large that it must be equatori al , locking the conformation into the chair shown. As a result, only the Cl at position i s axial, so that is the one that must leave, not the one at position 3. Two isomers are possible but it is difficult to say which would be formed in greater amount. � .�H� . H V H' , H etc I 0 H 4 + H '- � _ - H20 � __ HSO4- .. .. --� - ct OSO 3H H 154 El w orks well because only one carbocation and o nly one alkene are possible. Substitution i s not a problem here. The only nuc leophiles are water, which would s i mply form starting material by a r everse of the dehydration , and bisulfate anion. Bisulfate anion is an extremely weak base and poor nucleophile; if it did attack the carbocation , the unstable product would quickly re-ionize, with no net change, bac k to the carbocation. / () +C H H '\ H ... ' • H 20 . " � ...
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This note was uploaded on 02/27/2010 for the course CHEM 140 taught by Professor Wade during the Spring '10 term at Whitman.

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