3 out of 3 points Electrophilic addition of hydroiodic acid to (3s)-3-tert-butox
ID: 562979 • Letter: 3
Question
3 out of 3 points Electrophilic addition of hydroiodic acid to (3s)-3-tert-butoxypent-1-ene gives an unequal mixture of two products Reaction 2, 99:1 ratio].A The same reaction carried out on (33)-3-methoxy-pent-1-ene also gave two stereoisomers albeit in a much lower ratio [Reaction 1, 55:45 ratiol. Answer the following questions related to this process: Which is the minor product for Reaction 1? 55:45 HI H3C CH3 H3C CH3 OCH3 OCH3 OCH3 Reaction 1 OtBu = Product 1 Product 2 CH3 99:1 OCH3 CH3 CH3 H3C CH3 Reaction 2 H3C OtBu OtBu OtBu Product 3 Product 4Explanation / Answer
In the reaction-1, product 2 is the minor product. This is because product 2 is formed by attacking of iodide ion at secondary carbocation from the front side of the OCH3 group.
ii)
The product ratio for reaction-2 is so much lower than the product ration for reaction-1. This is because in reaction-1, OCH3 group is present adjacent to carbocation carbon and it is not so bulky. Thus attack of iodide ion can be possible from both side. Thus the product ratio, 55:45 (product 1: product 2) is obtained.
In case of reaction-2, OtBu group is present adjacent to the carbocation carbon and it is much more bulkier group. Thus attack of iodide ion occurs only from the back side of the bulkier group. Hence cis product is formed in higher yield and product ration is 99:1 (product 3: product 4).
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