Question

How many straight chain isomers are there of hexene ${{C}_{6}}{{H}_{12}}$ ?

Answer 1

Hint:Compounds that have the same molecular formula but differs in the arrangement of constituent atoms are called isomers. Two main types of isomers are structural isomers and stereoisomers.

Complete step-by-step answer:Isomers will have the same formula, but they will differ in the arrangements of atoms or bonds. Alkenes can have various isomers, but the question asks about the straight chain isomers.
Straight chain isomers of alkenes are only possible when the double bond changes its position. For every change in the position of double bond in alkenes we get a new isomer.
In the given question, we are asked to find out the straight chain isomers of hexene. Hexene is a type of alkenes. And in hexene straight isomers will only be possible when the double bond changes the position.
The straight chain isomers of the compound hexene are represented as follows:
1. $C{{H}_{2}}=CH-C{{H}_{2}}-C{{H}_{2}}-C{{H}_{2}}-C{{H}_{3}}$
The above isomer is 1-Hexene.
2. $C{{H}_{3}}-CH=CH-C{{H}_{2}}-C{{H}_{2}}-C{{H}_{3}}$
The above isomer represents 2-Hexene
3. $C{{H}_{3}}-C{{H}_{2}}-CH=CH-C{{H}_{2}}-C{{H}_{3}}$
The above isomers represent 3-Hexene
Now, please note that if we shift the double bond between the last second and last third carbon, we will get the same structure as isomer 2. There will be no difference, or we can say both will be replicas of each other. And in chemistry we do not write two same isomers of a single compound.

Therefore, hexene has three straight chain isomers.

Note:Students should note that there is no shortcut or formula to find the number of isomers of a given compound. We can just draw the isomers based on few knowledge and facts, just like we used the double bonds position in this question. And this comes with the practice. So, practice is must.