Question

2. Isomers A and B undergo dehydrohalogenation when treated with sodium methoxide (NaOme); however, one isomer reacts > 1000 times faster than the other. Identify the more reactive isomer and justify your answer using chair structures (1 pt).

Answer 1

Isomer (A) The bulky group like tert-butyl always occupy equatorial position. On reaction of isomer A! with Na Oct leads to dehydrohalogenation by | Ez - elimination mechanismº A ka path (a) a path (b) less stable More stable.

To carry out dehyrohalogenation reaction by E-2 mechanism the geometry of 2 leaving groups should be anti periplanar. which is clearly possible in isomer A than isomer B. In isomer A out of the 2 possible product the alkene that is more substituted will be major product according to Saytzeff rule

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Pace No. Date . * Ich (B) of be In isomer B there are two hydrogen that can be eliminate ring flepping will not be favourable buor the bulky group ends up in axial position which is highly unstable In order to carry out dehydrohalogenation the two leaving gp should be in anti-pertplanai cohich is not possible in this case ttb y no pet

Ring flipping in isomer 2 will lead bulky group like tert butyl in axial position which is highly unstable.

Hence isomer A will react greater than 1000 times compared to isomer B