Question

Expert Q&A Done Preblem 86. In electrophilic additions to alkenes (where the alkene s bond is acting as the nucleophile. there are three general types of mochanisms: True carbocation, Bridgod Carbocation, and Conceted True Carbocation Carbocation Concerted SYN addition The meaning of these terms will become clear as weprogress ough Chllí, locture. For now we will focus on the true carbocation and concerted mechanisms, as we are already familiar with cxamples of both. a) The addition of H-X to an alkene is a True Carbocation Mechanism X: HX Use the structure of the carbocation shown to explain WHY the final product of this reaction will be a racemic mixture b) Hydroboration is a concerted mochanism. The BH and the H are added to the SAME face of the alkene (this is called "syn addition HO NaOH, H20 BH3-THF Draw both enantiomers of the final product of hydroboration-exidation of (7)-3 methylpent 2-ene
Answer all parts not just one

Answer 1

Addition to HX to an alkene gives the recemic product. As we can see that substrate have vacant 'A' (anti bonding A - orbital) which have two labels: One above the plane and one below the plane. Now According to Marconicoff's rule adition of HX over the given substrate will take place where one out of two centres will become a stereogenic centre and other will remain achiral due to presence of two hydrogen at the same carbon. Represents a stereogenic centre which generated after the addition of 'HX'. (from HX) Marconicoff's rule says that Hydrogenetic will come at the position with greatest number of hydrogen in the present alkene. \r\n Here also, two products will be formed Here also due to presence of two lobes of 'A' antibending orbital racemic Mixture is formed.