Chapter 21, Problem 63A

Interpretation Introduction

Interpretation:

The name of the following condensed structural formula needs to be determined:

Concept introduction:

The hydrocarbon compounds contain compound that are made up of only hydrogen and carbon atoms. Hydrocarbon compounds that contains multiple bond(s) are said to be unsaturated hydrocarbon. Compounds containing double bonds are said to be alkene whereas compounds containing triple bonds are said to be alkyne.

Answer to Problem 63A

( 3E )-4-ethyl-3-methylhept-3-ene.

Explanation of Solution

In order to give the name to the unsaturated hydrocarbon, alkene following steps are followed:

1. The parent (longest) continuous carbon chain containing multiple bonds between the carbon atoms is selected.

2. While writing the name of alkene, the suffix “ane” of the corresponding alkane is replaced by “ene”.

3. Name should be written in alphabetical order and numbering should be done in such a way that the multiple bond and substituent group gets lowest number.

4. Hyphen is used to connect the number to the name.

For number of carbons atoms in alkane chain, the prefix is given as:

Carbon-1   meth

Carbon-2   eth

Carbon-3   prop    

Carbon-4   but      

Carbon-5   pent

Carbon-6   hex

Carbon-7   hept

Carbon-8   oct

Carbon-9   non     

Carbon-10       dec

The given structure is:

The parent chain in the given structure is of 7-carbon atoms so, prefix will be hept. Numbering is done in such a way that the multiple bond that is double bond gets lower number that is 3. A methyl substituent is present at position 3 and ethyl substituent at position 4.

So, the IUPAC name will be: 4-ethyl-3-methylhept-3-ene.

Assigning the priority to the groups around double bond as:

Since, the higher priority substituents are on opposite side so, the arrangement around double bond is E.

Hence, the correct name of the compound is ( 3E )-4-ethyl-3-methylhept-3-ene.