Question

Find the formula of C and structure of B in above reaction and determine the degree of unsaturation in compound B.
(Enter your answer as integer)

Answer 1

Cyclopentene (compound B) reacts with bromine water mixture (C) to form bromohydrin. In this reaction, HOBr is added to the carbon-carbon double bond in trans manner.

Degree of unsaturation (DOU) in B:
Corresponding alkane of $B$ is $C_n{H}_{2n+2}=C_5{H}_{12}$

Actual formula of B is $C_5{H}_8$
$DOU=\frac{12-8}{2}=2$
One DOU is due to the double bond and another is due to the cyclic structure.
Answer-$2$