Question

Aromatic carbonyl compounds having molecular formula (CH)₈O react with NH₂OH. How many oximes can be formed ?
(A) 8
(B) 10
(C) 12
(D) 6

Answer 1

Hint: This question demands the need to calculate double bond equivalent. Then, consider all the possible structures.

Formula used:Here, we are required to know the double bond equivalent.
For this, Double bond equivalent $= C - \dfrac{H}{2}+ \dfrac{N}{2} - \dfrac{X}{2} + 1$.

Complete Step by Step Answer:
It can be easily noticed that it is based on its double bond equivalent. Double bond equivalent signifies for the possible unsaturation or cyclic chain in the compound that can be formed by introduction of double bond, benzene ring, etc.Basically, it works in such a way which suggests the addition of hydrogen molecules that will convert the pi bonds to single bonds and all rings to acyclic structures. So, various structures can be formed.
For (CH)8O, double bond equivalent = 8 - 82 + 0 - 0 + 1
                                                                = 8 - 4 + 1
                                                                = 5
A molecular formula having 5 as double bond equivalent and has 8 carbons in its formula gives result in Benzene ring formation.

So, it will have benzene ring as its moiety and rest will be substituted as its side chain derivatives. Look for the required structures possible ,i.e.,provide oxides on reacting with NH₂OH and leave the rest out of count.

Note: Bear in mind,it is necessary to evaluate double bond structure rather than assuming on its own otherwise it is possible that you eliminate the possibility of some structures. Count those structures which result in oximes.