Question

Name the following amines: (a) \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{NH}_{2}\) (b) \(\left(\mathrm{CH}_{3}\right)_{3} \mathrm{N}\) (c) \(\left(\mathrm{CH}_{3}\right)\left(\mathrm{C}_{2} \mathrm{H}_{5}\right) \mathrm{NH}\) (d) \(\mathrm{C}_{6} \mathrm{H}_{13} \mathrm{NH}_{2}\)

Short answer

(a) 1-Propanamine, (b) Trimethylamine, (c) N-Ethylmethylamine, (d) 1-Hexanamine.

Step-by-step solution

Identify the structure and the type of amine (a)

For the compound \( \mathrm{CH}_3 \mathrm{CH}_2 \mathrm{CH}_2 \mathrm{NH}_2 \), it consists of a chain of three carbon atoms with an amino group \( \mathrm{NH}_2 \) at the end. This structure forms a primary amine called propylamine, or more specifically, "1-propanamine" as it follows the IUPAC naming rule.

Identify the structure and the type of amine (b)

The compound \( \left(\mathrm{CH}_3\right)_3 \mathrm{N} \) consists of a nitrogen atom bonded to three methyl groups, forming a tertiary amine. The common name for this compound is trimethylamine. Due to IUPAC conventions, it retains the name "trimethylamine".

Identify the structure and the type of amine (c)

The compound \( \left(\mathrm{CH}_3\right)\left(\mathrm{C}_2 \mathrm{H}_5\right)\mathrm{NH} \) has a nitrogen atom bonded to a methyl group and an ethyl group. This is a secondary amine and is named with the groups labeled alphabetically, giving the name "N-ethylmethylamine" or more technically, "ethyl(methyl)amine".

Identify the structure and the type of amine (d)

The compound \( \mathrm{C}_6 \mathrm{H}_{13} \mathrm{NH}_2 \) consists of a six-carbon alkyl chain with an amino group. The basic structure is that of a hexane with an amine group forming a primary amine. Therefore, it is called "hexylamine" or more formally, "1-hexanamine" if following strict IUPAC naming.

Key concepts

Amines

Amines are an important class of organic compounds derived from ammonia. Imagine replacing one or more of the hydrogen atoms in ammonia (NH₃) with alkyl or aryl groups. This substitution results in compounds called amines.
Amines can be classified based on the number of hydrogen atoms replaced:

• Primary amines have one hydrogen atom replaced.
• Secondary amines have two hydrogen atoms replaced.
• Tertiary amines have all three hydrogen atoms replaced.

Amines play key roles in biological systems and many industrial applications, making their study vital in organic chemistry.

IUPAC Naming Rules

The International Union of Pure and Applied Chemistry (IUPAC) provides a standardized way to name chemical compounds, ensuring consistency worldwide. When naming amines under IUPAC guidelines, several steps are typically followed:

• Identify the longest carbon chain attached to the nitrogen atom and name it as the parent alkane.
• The suffix "amine" is added to signify the presence of an amino group.
• If there are any additional substituents, their positions are identified, and names are prefixed to the parent alkane in alphabetical order.
• For secondary and tertiary amines, the N-notation is used to indicate attachment to the nitrogen atom.

This method allows chemists to clearly communicate the molecular structure of amines.

Primary Amine

In chemistry, a primary amine is one where only one alkyl or aryl group is attached to the nitrogen atom. The general formula for a primary amine is RNH₂. For example, if we look at the compound \( \mathrm{CH}_3 \mathrm{CH}_2 \mathrm{CH}_2 \mathrm{NH}_2 \), it has a three-carbon chain attached, making it a primary amine.

In IUPAC terms, this specific compound is named "1-propanamine," indicating that the amino group is connected to the first carbon in the chain. Primary amines can vary significantly in size but share the common feature of a single substituent replacing one hydrogen in ammonia.

Secondary Amine

A secondary amine features two alkyl or aryl groups replacing two of the hydrogen atoms in ammonia. Therefore, their general structure can be represented as R₂NH. For example, in the compound \( \left(\mathrm{CH}_3\right)\left(\mathrm{C}_2 \mathrm{H}_5\right)\mathrm{NH} \), methyl and ethyl groups are attached to the nitrogen.
This structure is classified as a secondary amine, typically named with the groups alphabetically using the "N" prefix for substituents connected to nitrogen. In this case, it becomes "N-ethylmethylamine" or "ethyl(methyl)amine," showcasing its unique two-group connection and distinct structure.

Tertiary Amine

When a nitrogen atom is bonded to three alkyl or aryl groups, the result is a tertiary amine. The general formula for tertiary amines is R₃N. Let's consider the compound \( \left(\mathrm{CH}_3\right)_3 \mathrm{N} \), which has three methyl groups connected to the nitrogen.
Tertiary amines do not have any hydrogen atoms attached to nitrogen, distinguishing them from primary and secondary amines. The name "trimethylamine" is used in this case, a direct reflection of the compound's structure, as indicated by the IUPAC naming conventions. Tertiary amines often exhibit unique chemical properties due to the diverse attachments to nitrogen.