Q.41. - Organic Chemistry

Question

Question: Each of the following IUPAC names is incorrect. Explain why it is incorrect and give the correct IUPAC name. 

a. 2,2-dimethyl-4-ethylheptane 

b. 5-ethyl-2-methylhexane 

c. 2-methyl-2-isopropylheptane 

d. 1,5-dimethylcyclohexane 

e. 1-ethyl-2,6-dimethylcycloheptane

f. 5,5,6-trimethyloctane

g. 3-butyl-2,2-dimethylhexaneh. 1,3-dimethylbutane

Step-by-Step Solution

Answer

Answer

 

a.

 

4-ethyl-2,2-dimethylheptane

 

b.

 

2-ethyl-5-methylhexane

 

c.

 

2-isopropyl-2-methylheptane

 

d.

 

1,2-dimethylcyclohexane

 

e.

 

2-ethyl-1,4-dimethylcycloheptane

 

f.

 

3,4,4-trimethyloctane

 

g.

 

4-tert-butyloctane

 

h.

 

2-methylpentane

Step 1: Rules for IUPAC naming

The rules for IUPAC naming are given as follows:

• The functional groups or high molecular carbon groups are given priority, and the counting in the longest chain is started from the side of the priority groups.
• The naming must follow the alphabetical order.

Step 2: Explanation

a. 2,2-dimethyl-4-ethylheptane

The given name is alphabetically incorrect. The ethyl is given the first priority. Therefore, the correct name is 4-ethyl-2,2-dimethylheptane

 

b. 5-ethyl-2-methylhexane

The given name is also alphabetically incorrect. The ethyl is given the first priority. Therefore, the correct name is 2-ethyl-5-methylhexane

 

c. 2-methyl-2-isopropylheptane 

The given name is alphabetically incorrect. The isopropyl is given the first priority. Therefore, the correct name is 2-isopropyl-2-methylheptane

  

d. 1,5-dimethylcyclohexane

The given name is alphabetically incorrect. The first and fifth positions are equivalent to the first and second. Therefore, the correct name is 1,2-dimethylcyclohexane

 

e. 1-ethyl-2,6-dimethylcycloheptane

The given name is alphabetically incorrect. The first, second, and sixth positions are equivalent to the second, first, and fourth positions, respectively. Therefore, the correct name is2-ethyl-1,4-dimethylcycloheptane

 

f. 5,5,6-trimethyloctane

The given name is alphabetically incorrect. The fifth, fifth, and sixth positions are equivalent to the first, first, and second positions. Therefore, the correct name is3,4,4-trimethyloctane.

 

g. 3-butyl-2,2-dimethylhexane

The given name is alphabetically incorrect. The butyl group is given the first priority, and the methyl groups take the second position. Therefore, the correct name is4-tert butyloctane.

   

h. 1,3-dimethylbutane

The given name is incorrect. The longest chain is a five-carbon chain. Therefore, the correct name is 2-methylheptane.