Question

The total number of possible dichloro derivatives of n-butene are:
(A) 2
(B) 4
(C) 5
(D) 6

Answer 1

Hint: We need to check the position of chlorine with respect to the double bond in the structure of n-butene. As the question is asked about n-butene which means we can place the double bond in three positions with respect to chlorine atoms and no branches will be introduced to the carbon chain. The number of possible structures for n-butene are as follows:

But-1-ene

But-2-ene

Complete Step by Step Solution:
n-Butene or normal butene are considered as the stable compounds but the unsaturated carbon-carbon double bonds which consists of $\pi $ electrons make them more reactive due to the attack of electrophile becomes easy due to the presence of cloud of electrons, as compared to similar alkanes as which are more inert compounds in various ways. As per the number of structures of n-butene, the possible constitutional dichloro derivatives of n-butene are as follows:
a) 1,1-dichlorobut-1-ene

b) 1,1-dichlorobut-2-ene

c) 1,2-dichlorobut-1-ene

d) 4,4-dichlorobut-1-ene

e) 1,3-dichlorobut-2-ene

f) 1,3-dichlorobut-1-ene


Hence, the total number of possible constitutional dichloro derivatives of n-butene are 6. Therefore, option (D) is the correct answer.

Note: It is important to note that the answer in such questions may vary due to the possibility of stereoisomerism in the compound. So, whenever the question is asked in general, only constitutional isomers of the compound are included. The possible stereoisomers that can be formed in case of alkene are E-Z geometrical isomerism that are similar in molecular structure but differ in arrangement of atoms in space.