Question

What will be the structural formula of But-2-ene?

Answer 1

But-2-ene is also called 1,2-dimethylethylene. Structural formula shows how the various atoms are bonded to each other. They are all connected by individual lines. Structural formulas can be easily drawn if we know the chemical formula.

Complete answer:
First we will look at the chemical formula of But-2-ene.
‘But’ is mentioned hence it is a four carbon compound and also ‘ene’ is mentioned it means that it is an alkene. Hence there will be a presence of a double bond. Also , but-2-ene shows isomerism(geometrical isomerism).
There are 2 types of geometrical isomers:
Cis-isomer: These molecules have side groups attached on the same side of the double bond.
Trans-isomer: In these molecules, side groups are attached on opposite sides of the double bond.
Let’s look at its structure :
Normally we would represent its structure as:

(In this structure we have attached a double bond at the second carbon as 2-ene has been mentioned.)
Now we will give the structures of its 2 isomers.
First we will look at cis-but-2-ene: Clearly in this image side groups are on the same side, hence it is cis-but-2-ene.

Now let us look at its trans isomer: In this structure side groups are on opposite sides.

Hence these are the 2 possible structures of But-2-ene.

Note:
Do not just write structure without showing its isomers, it would not n=be correct, show all the possible isomers of a compound. Remember that cis isomers and trans isomers are only true for double bonded carbon compounds(alkenes).