Chapter 18, Problem 42P

Interpretation Introduction

(a)

Interpretation:

The structure for the eight constitutional isomers of molecular formula C₄H₁₁N should be drawn.

Concept Introduction:

There are three types of amines as primary, secondary and tertiary. Primary amine has one C-N bond. Secondary amine has two C-N bonds. Tertiary amine has three C-N bonds. Constitutional isomers are defined as compounds that have same molecular formula with different connectivity.

Answer to Problem 42P

The structures for the eight constitutional isomers of molecular formula C₄H₁₁N are represented as follows:

  

  

  

Explanation of Solution

Four structures of primary amines can be drawn with the formula C₄H₁₁N.

  

  

Three structures of secondary amines can also be drawn.

  

A tertiary structure can also be drawn as follows:

  

Interpretation Introduction

(b)

Interpretation:

The systematic name for each amine should be given.

Concept Introduction:

In nomenclature of primary amine, the longest carbon chain bonded to nitrogen is determined and the −e ending of the parent alkane is replaced by the suffix −amine. Usual rules are used in numbering and naming substituents. In nomenclature of secondary or tertiary amines identical alky groups are named by using a prefix such as di- or tri-. If there are different kinds of alkyl groups they are named as N-substituted primary amines.

Answer to Problem 42P

The name of amines are as follows:

  

1-butanamine 2-methylpropan-1-amine butan-2-amine

  

2-methylpropan-2-amine N-ethylethanamine N-methylpropan-1-amine

  

N-methylpropan-2-amine N,N-dimethylethanamine

Explanation of Solution

  

The longest carbon chain has four carbons. So the alkane name is butane. N is attached to C-1. Therefore, the systematic name of the amine is butanamine.

  

The longest carbon chain has three carbons. There is a methyl group at C-2. So the parent name is 2-methylpropanamine. The N atom is bonded to C-1. Therefore, the name become 2-methylpropan-1-amine.

  

The longest carbon chain bonded to amine group has four carbons. The parent name is butanamine. The N atom is bonded to C-2. Therefore, the systematic name of the amine is butan-2-amine.

  

The longest carbon chain bonded to amine group has three carbons. There is a methyl group at C-2. The parent name is 2-methylpropanamine. The N atom is bonded to C-2. Therefore, the systematic name of the amine is 2-methylpropan-2-amine.

  

The secondary amine has the longest carbon chain with 2 carbons. So, the parent name is ethanamine. The N atom has bonded to C-1 and has 1 ethyl group as a substituent. Therefore, the systematic name become N-ethylethanamine.

  

The secondary amine has the longest carbon chain with 3 carbons. So, the parent name is propanamine. The N atom has bonded to C-1 and has 1 methyl group as a substituent. Therefore, the systematic name become N-methylpropan-1-amine.

  

The secondary amine has the longest carbon chain with 3 carbons. So, the parent name is propanamine. The N atom has bonded to C-2 and has 1 methyl group as a substituent. Therefore, the systematic name become N-methylpropan-2-amine.

  

The tertiary amine has the longest carbon chain with 2 carbons. So the parent name is ethanamine. N atom has bonded to C-1 and has two methyl groups and 1 ethyl group as substituents. So, the systematic name of the amine is N,N-dimethylethanamine.

Interpretation Introduction

(c)

Interpretation:

The chirality center present in one of the amines should be identified.

Concept Introduction:

An atom that has four different groups bonded to it is referred to as chirality center. A chiral molecule has a non-superimposable mirror image.

Answer to Problem 42P

  

Explanation of Solution

Butan-2-amine has long carbon chain with 4 carbons and amine group is bonded to C-2. This C-2 carbon has four different groups bonded to it as 1 ethyl group, 1 methyl group, 1 amine group and a hydrogen. So, C-2 carbon is a chirality center.