Chapter 12, Problem 16P

Explain why each name is incorrect and then write a correct name. Strategy: First draw the structural formula suggested by the incorrect name. Then identify the error, for example, failure to locate the longest chain that contains the alkene functional group etc., and then write the correct name.

(a) 1-Methylpropene (b) 3-Pentene

(c) 2-Methylcyclohexene (d) 3,3-Dimethylpentene

(e) 4-Hexyne

(f) 2-lsopropyl-2-butene

Interpretation Introduction

(a)

Interpretation:

To analyse the error and write the correct IUPAC names.

Concept Introduction:

The rules to write the IUPAC names are as follows-

• The longest carbon chain is identified, and the root name is given accordingly.
• All the substituents attached to the root chain are determined.
• The position of the substituents is so assigned that the sum of their positions comes to be the least of all possible positions.
• The prefix di, tri, tetra is used if the same substituent is present two, three and four times respectively.
• All the substituents in the name are written in alphabetical order.
• For a cyclic hydrocarbon the prefix cyclo- is used.

Answer to Problem 16P

But-2-ene.

Explanation of Solution

1-Methylpropene.

Error- longest chain not correctly located.

Correct name-

But-2-ene.

But-2-ene.

Interpretation Introduction

(b)

Interpretation:

To analyse the error and write the correct IUPAC names.

Concept Introduction:

The rules to write the IUPAC names are as follows-

• The longest carbon chain is identified, and the root name is given accordingly.
• All the substituents attached to the root chain are determined.
• The position of the substituents is so assigned that the sum of their positions comes to be the least of all possible positions.
• The prefix di, tri, tetra is used if the same substituent is present two, three and four times respectively.
• All the substituents in the name are written in alphabetical order.
• For a cyclic hydrocarbon the prefix cyclo- is used.

Answer to Problem 16P

2-pentene.

Explanation of Solution

3-Pentene.

Error- Position of double bond not mentioned correctly.

Correct name-

2-Pentene.

Interpretation Introduction

(c)

Interpretation:

To analyse the error and write the correct IUPAC names.

Concept Introduction:

The rules to write the IUPAC names are as follows-

• The longest carbon chain is identified, and the root name is given accordingly.
• All the substituents attached to the root chain are determined.
• The position of the substituents is so assigned that the sum of their positions comes to be the least of all possible positions.
• The prefix di, tri, tetra is used if the same substituent is present two, three and four times respectively.
• All the substituents in the name are written in alphabetical order.
• For a cyclic hydrocarbon the prefix cyclo- is used.

Answer to Problem 16P

1-Methylcyclo-1-hexene.

Explanation of Solution

2-Methylcyclohexene.

Error- Position of methyl not correct.

Correct name-

1-Methylcyclo-1-hexene.

Interpretation Introduction

(d)

Interpretation:

To analyse the error and write the correct IUPAC names.

Concept Introduction:

The rules to write the IUPAC names are as follows-

• The longest carbon chain is identified, and the root name is given accordingly.
• All the substituents attached to the root chain are determined.
• The position of the substituents is so assigned that the sum of their positions comes to be the least of all possible positions.
• The prefix di, tri, tetra is used if the same substituent is present two, three and four times respectively.
• All the substituents in the name are written in alphabetical order.
• For a cyclic hydrocarbon the prefix cyclo- is used.

Answer to Problem 16P

3,3-Dimethyl-1-pentene.

Explanation of Solution

3,3-Dimethylpentene.

Error-position of double bond not mentioned.

Correct name-

3,3-Dimethyl-1-pentene.

Interpretation Introduction

(e)

Interpretation:

To analyse the error and write the correct IUPAC names.

Concept Introduction:

The rules to write the IUPAC names are as follows-

• The longest carbon chain is identified, and the root name is given accordingly.
• All the substituents attached to the root chain are determined.
• The position of the substituents is so assigned that the sum of their positions comes to be the least of all possible positions.
• The prefix di, tri, tetra is used if the same substituent is present two, three and four times respectively.
• All the substituents in the name are written in alphabetical order.
• For a cyclic hydrocarbon the prefix cyclo- is used.

Answer to Problem 16P

2-Hexyne.

Explanation of Solution

4-Hexyne.

Error- position of triple bond is incorrectly mentioned.

Correct name 2-Hexyne.

Interpretation Introduction

(f)

Interpretation:

To analyse the error and write the correct IUPAC names.

Concept Introduction:

The rules to write the IUPAC names are as follows-

• The longest carbon chain is identified, and the root name is given accordingly.
• All the substituents attached to the root chain are determined.
• The position of the substituents is so assigned that the sum of their positions comes to be the least of all possible positions.
• The prefix di, tri, tetra is used if the same substituent is present two, three and four times respectively.
• All the substituents in the name are written in alphabetical order.
• For a cyclic hydrocarbon the prefix cyclo- is used.

Answer to Problem 16P

3,4-Dimethyl-2-pentene.

Explanation of Solution

2-Isopropyl-2-butene.

Error- longest chain is not correctly located.

The correct name will be-

3,4-Dimethyl-2-pentene.