Question

What would be the major product of the following reaction sequence? D + H20 Br2 OH heat Br Br Br -Br I II ITI IV V Select one or more ob 11 C. Od V Lev

Answer 1

Answer:

b. II

Explanation:

The given cyclopentanone (starting substrate) on reaction with Bromine in presence of acidic conditions gives the 2-bromocyclopentanone as the major organic product.

The 2-bromocyclopentanone compound on reaction with a base (OH-) at higher temperatures (heat) gives cyclopent-2-en-1-one as the major organic product (alpha,beta unsaturated cyclopentanone).

overall reaction scheme can be written as below gi -Br CH an + Brz H₂ot heat major product Mechanism: H30+ indicates acidic conditions at the first reaction. Under acidic condition the reaction occurs through the formation of enot intermediate which then reacts give the a-bromocyclopentanone a) protonation of the carbonyl group generates positive charge on carbonyl oxygen atom, which then enol intemediate form. 2:6-H. "OH2 HOH₂ H305 Enol form with bromine to :ÖH gives the + :Q: + b) sia attack by the end on Brz followed by deprotonation generates 2-byomo cyclopentanone proderet 0. + :By: :0-H By: SNA Barby: + Deprotonation :0 i -Bo

Reaction with base and heat:

one hydrogen atom and one Bromine will be removed from the substrate, so we can say dehydrohalogenation reaction. This reaction follows E2 mechanism (bimolecular elimination).

Conclusion:

Dehydrohalogenation of 2-byomo cyclopentanone gives cyclopent-2-en-1-one as major product. :0: :Q: Bri E2 . + H, O + : By: + :OH Ha Major product

Cyclopentanone under acidic conditions reacts with Br2 and gives 2-bromocyclopentanone as major product which is on further reaction with base gives the alpha beta unsaturated cyclopentanone as the major organic product.