Question

Give the expected major product of reaction of 2,2-dimethyloxacyclopropane with each of the following reagents.

Give the expected major product of reaction of 2, 2-dimethyloxacydopropane with each of the following reagents. dilute H_2SO_4 in CH_3OH NaOCH_3 in CH_3OH Dilute aqueous HBr concentrated HBr CH_3Mgl, then H^+/H_2O C_6H_5Li, then H^+/H_2O

Answer 1

Consider the product formed by the given reaction as shown below: In the presence of acid, oxygen atom will get protonated first. As methanol is a weak nucleophile therefore, w attack from the more substituted carbon, that is, the mechanism follows S pathway as shown below: : O dil. H2SO4 CH; CH3 CH CH 2,2-dimethyloxacyclopropane CH,OH но CH3 ÖCH3 Major product

In basic epoxide ring opening reaction, the attack of nucleophile takes place from the less substituted carbon as shown below: он CH3OH CH3 CH2ONa H3CO CH CH, Major product 2,2-dimethyloxacyclopropane In the presence of dilute aqueous HBr, oxygen atom will get protonated first and bromide ion will get trapped by the water molecules, thus water will act as a nucleophile (weak) and attack will take place from more substituted carbon as shown below: : O HBr CH3 CH3 CH3 2,2-dinethyloxacyclopropane H2O

но CH3 CH3 он Major product In the presence of concentrated HBr, oxygen atom will get protonated first and bromide ion which is present in excess will act as a nucleophile and attack will take place from more substituted carbon as shown below: : O HBr CH3 CH3 CH3 2,2-dimethyloxacyclopropane Br

но CH CH3 Major product Grignard reagent will act as strong nucleophile thus, attack the epoxide ring from less substituted carbon as shown below: он H3Mgl CH3 CH CH CH3 Major product 2,2-dimethyloxacyclopropane Grignard reagent will act as strong nucleophile thus, attack the epoxide ring from less substituted carbon as shown below: он C6H,Li CH3 CH3 CH3 СНз 2,2-dimethyloxacyclopropane Major product