Question

The IUPAC name of the following compound is $C{H_2} = CH - CH{\left( {C{H_3}} \right)_2}$ :
A. $1,1 - $Dimethyl $ - 2 - $ propene
B. $3 - $Methyl $ - 1 - $ butene
C. $2 - $ Vinylpropane
D. $1 - $isopropylethylene

Answer 1

Hint: In the given compound $C{H_2} = CH - CH{\left( {C{H_3}} \right)_2}$ we can see that it is a simple compound which does not contain any complex functional group. So the IUPAC nomenclature of this compound is very easy. We need to follow the basic rules of IUPAC naming.

Complete step by step answer:
So the first step is the numbering of carbon in the straight hydrocarbon chain. There is no functional group in the given compound so we will start numbering carbon from that carbon which contains double bonds. The structural representation of the compound is given below:
                                                     

Here in the given compound the longest carbon chain contains four carbon atoms so the root word would be but and there is a double bond between first and second carbon so the nature of bond will be denoted by ene . Then the second step is to identify side groups or chains. In the given compound we can see that there is a methyl group substituted on the third carbon so we will also name that , which will use $3 - $Methyl prefix. Therefore the name of the compound will be $3 - $Methyl $ - 1 - $ butene. Here in the name $1 - butene$ refers to the position of double bond in the main chain as it is between the first and second carbon.
So, the correct answer is “Option B”.

Note: We have done IUPAC naming of the given compound by following the rules of IUPAC nomenclature. We have identified the longest straight chain then we have given the name to the side group attached to the carbon of the principal chain along with the position of the side group.