Question

What is the product of reaction and its formation of selectivity

Answer 1

Hint: The reaction is an example of the Wittig reaction. The given ketone will react with triphenyl phosphonium ylide which is also known as Wittig reagent. Firstly we will make this Wittig reagent and then it will attack on the ketonic group of the compound and hence after rearrangement of atoms we will get our desired product A.

Complete answer:
Here the given compound consists of both alcohol and carbonyl. But when we add $$Cr{O}_3$$ to the compound then oxidation of alcohol takes place and we get another carbonyl group. $$Cr{O}_3$$ is a strong oxidising agent, therefore it will convert alcohol directly into a carbonyl group.

Now we will take the reagent and make a finalized product which will react with our oxidized product. The reaction between the reagents can be represented in steps ass,
Step $$1.$$ Tri-methoxy phosphorus will react with phenyl methyl iodide and form an intermediate.
Step $$2.$$ This intermediate will further react with the base known as $$n-BuLi$$ and it will develop a negative charge on the carbon atom.

Therefore we get ylide which will react with our oxidized product and will form alkene by rearrangement of atoms. This reagent will attack on that carbon which is more electron deficient, thus which decides its selectivity of the formed product.

Thus we get our product A which is an alkene.

Note:
The reagent will attack on that carbonyl group which is more deficient of electrons which is also known as selectivity principle. The Wittig reaction is used for manufacturing the alkene from ketones or aldehydes. We must take care of rearrangement of atoms.