Question

Choose the correct option for - which is not the structure of ${C_4}{H_9}Br$
(A) $1 -$ Bromobutane
(B) $2 -$ Bromobutane
(C) $1 -$ Bromo - $2 -$ methylpropane
(D) Isobutane

Answer 1

Hint : Bromobutane is a colourless liquid, but its impure sample can be seen as slightly yellow in colour. Bromobutane is an organobromine compound with a molecular formula of ${C_4}{H_9}Br$ and the boiling point of around $100 - {205^o}C$ .

Complete Step By Step Answer:
To solve this question we should have some insight regarding the conformation of structures.
Looking at our options - $1 -$ Bromobutane and $2 -$ Bromobutane, let’s have a look at their structure for the better understanding –


As, it is evident from the diagram above, that $1 -$ Bromobutane and $2 -$ Bromobutane fits completely into the formula ${C_4}{H_9}Br$ . All the valencies of all the atoms are completely satisfied and have a stable structure under this formula - ${C_4}{H_9}Br$ .
Similarly. $1 -$ Bromo - $2 -$ methyl propane – also has a stable structure satisfying all the valences of each atom.
But, coming to our option D , it is isobutane . It has a molecular formula of ${C_4}{H_{10}}$ . Isobutane does not consist of bromine atoms. So it does not fit in our given formula ${C_4}{H_9}Br$ .
So, the correct option to our question is D i.e. isobutane.

Note :
For ${C_4}{H_9}Br$ we have four possible structural isomers and they are - $1 -$ Bromobutane and $2 -$ Bromobutane, $1 -$ Bromo - $2 -$ methylpropane, these three we just read above, but the fourth isomer that is possible is – tert-butyl bromide or $2 -$ Bromo - $2 -$ methylpropane. These bromobutane are less soluble in water and are denser than water.