Question

The number of C atoms present in allyl vinyl acetylene is ----- and it has ----- degree of unsaturation.
(A). 7 and 4
(B). 7 and 3
(C). 5 and 4
(D). 5 and 3

Answer 1

- Hint: This question can be solved by drawing the structure of the compound. The number of double bonds is also called the degree of unsaturation. Sometimes, it is also denoted by the index of hydrogen deficiency.

Complete step-by-step solution -
In this particular compound, there are three types of carbon class of compounds present and they are-allylic, vinylic and acetylene carbon.
First let us know what is allylic carbon. These are the compounds in which the functional group or any other element other than carbon atom is bonded to the $\text{s}{{\text{p}}^{3}}$hybridized carbon atom next to carbon-carbon double bond (C=C) i.e. to an allylic carbon.
Now, Vinylic carbon are the compounds in which the functional group or any other element is present other than carbon is bonded to an $\text{s}{{\text{p}}^{2}}$-hybridised carbon atom of a carbon-carbon double bond (C=C).
Here, the structure of the compound is Alkyl vinyl acetylene
$\text{C}{{\text{H}}_{2}}=\text{CH-C}{{\text{H}}_{2}}-\text{C}\equiv \text{C-CH=C}{{\text{H}}_{2}}$
Here, the number of carbon atoms is 7 and the degree of unsaturation is the number of $\pi$ bonds which is equal to 4.
Thus, the number of C atoms present in allyl vinyl acetylene is 7 and it has 4 degrees of unsaturation.

Note: We should know the term Index of Hydrogen Deficiency. It is a count of how many molecules of ${{\text{H}}_{2}}$ need to be added to a structure in order to obtain the corresponding saturated, acyclic species.