Phenol reacts with acetone in the presence of conc. sulphuric acid to form a $ {C_{15}}{H_{16}}{O_2} $ product. Which of the following compounds is this product?
(A)
  

(B)

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(D)

Hint :To solve this question, we must first understand the whole concept of Phenol and its reactions. Then we need to use the correct reaction mechanism and then only we can have our correct answer.

Complete Step By Step Answer:
Before jumping to the solution, let’s recall the basic concepts about Phenol and its reaction:
As we know that, Phenol consists of a hydroxyl group and phenyl group attached to each other. It dissolves in water. Earlier it was used as carbolic soap. It is mildly acidic and is corrosive to the respiratory tract, eyes, and skin.
Phenol is a crystalline solid white in color and needs to be handled with care as it can cause chemical burns. It is also known as phenolic acid. If a compound consists of a six-membered aromatic ring and bonded to a hydroxyl group directly, then it can be referred to as phenol.
Let’s trace out the required reaction:
Step 1: This is the simplest approach, in which two equivalents of Phenol reacts with acetone, catalyzed by strong acid such as sulphuric acid or hydrochloric acid, gives Bisphenol A:

Here in the above reaction, the acid protonates the acetone and then 2 molecules of phenol interact with one mole of the protonated acetone and then come together and make a bond followed by removal of $ {H_2}O $ .
So clearly, we can conclude that the correct answer is Option B.
Note :
There are so many industrial uses of phenol, Phenol is so cheap it attracts plenty of small-scale applications. This compound is a part of industrial paint strippers used for removal of epoxy, polyurethane, and other chemically resistant coatings in the aviation industry.