3 out of 3 points Electrophilic addition of hydroiodic acid to (3s)-3-tert-butox

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 ratiol .A The same reaction carried out on (38)-3-methoxy-pent-1-ene also gave to this process: which is the major product for Reaction 2? t in a much lower ratio [Reaction 1, 55:45 ratio]. Answer the following questions related 55:45 HI H3C CH3 H3C CH OCH3 OCH3 OCH3 Reaction1 OtBu = Product 1 Product 2 CH3 99:1 OCH3 CH3 HI CH3 H3C H3C CH3 Reaction 2 H3C OtBu OtBu Product 3 Product 4

Explanation / Answer

The major product of the reaction 2, is product 3.

The above addition reaction follow Markonikov's rule.

Obeys markonikovs rule: the negative part (I-)of HI adds to the double bonded carbon having least number of hydrogen. But here the stability of the product (stable compound is always the major product of a reaction) depends upon the steric factor.

I,e one of the product is sterically hinder (less stable) hence becomes minor product while the other gets sterically favoured (more stable) hence becomes the major product.

Steric factor: the OtBut on the neighboring carbon is a bulky group which is above the plane hinders the attack of Iodide ion above the plane as iodide ion is also a larger ion.

There is a Steric hindrance created between them. Hence the iodide ion attacks the carbon containing least no. Of hydrogens below the plane instead of attacking from above, forming a stable compound product 3. hence becomes the major product of the reaction 2.

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