Answer to Question #301921 in Organic Chemistry for Karly

Question

4.1 Use electronic factors to explain why methyl carbanion is more stable than tertiary butyl

carbanion.

4.3 Reaction of 2-methyl-1,3-butadiene with bromine yields a mixture of products: 3,4-

dibromo-2-methyl-1-butene (3 %), 3,4-dibromo-3-methyl-1-butene (21 %) and 1,4-

dibromo-2-methyl-2-butene (76 %).

a) Identify all products as either 1,2 or 1,4 adducts.

b) Propose mechanisms for the formation of all 3 products.

c) Explain why 3,4-dibromo-3-methyl-1-butene (21 %) predominates over 3,4-dibromo-2-

methyl-1-butene (3 %).

Answer 1

Assertion : tert-Butyl carbanion is more stable than methyl carbanion. <br> Reason : The +I effect of the three methyl groups in tert-butyl carbanion tends to make it more stable than methyl carbanion. ... <br> Reason: The +1-effect of the CH3 groups tends to stablize the tert-butyl carbanion.