Question

Give the common name for each of the following amines: (a) \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{NH}_{2}\) (b) \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{NH}_{2}\)

Short answer

(a) Ethylamine, (b) Propylamine.

Step-by-step solution

Recognize the Structure and Functional Group

Examine the given structures to identify the functional group present. Both structures are amines, characterized by the presence of an \(-\mathrm{NH_2}\) group attached to an alkyl chain. The challenge is to name these compounds using common nomenclature for amines.

Name the Alkyl Group for Part (a)

For the compound \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{NH}_{2}\), first identify the alkyl group. The chain has two carbon atoms, which forms an ethyl group. Using common naming, we write this as "ethylamine," where the prefix "ethyl" comes from the two-carbon alkane, "ethane." The \(-\mathrm{NH_2}\) group is implied in names of simple amines.

Name the Alkyl Group for Part (b)

Examine the compound \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{NH}_{2}\). The straight chain has three carbon atoms, which is a propyl group. The common name for this amine is derived from "propyl" and "amine." Thus, it is called "propylamine." Like before, the \(-\mathrm{NH_2}\) group is implicitly present.

Review and Validate Your Answer

Ensure the names derived match with typical common nomenclature for amines. Ethylamine and propylamine are correctly named based on their respective alkyl chains attached to the amino group.

Key concepts

Understanding Common Nomenclature for Amines

When naming organic compounds, especially amines, it is essential to understand common nomenclature. Common nomenclature is a traditional way of naming compounds, often simpler than systematic IUPAC naming. Amines are organic compounds characterized by having one or more alkyl groups attached to a nitrogen atom. In common nomenclature, amines are named by identifying the alkyl groups attached to the nitrogen and simply appending the suffix "amine."

• For single-chain alkyl amines, the compound's name typically starts with the name of the alkyl group, followed by "amine." For example, if the alkyl group is derived from ethane, the name will be "ethylamine."
• Common names are derived from the parent alkane chains, with carbon chains identified using prefixes like methyl, ethyl, or propyl.
• It is important to remember that the common naming in simpler amines automatically implies the presence of an amine functional group.

Understandably, common names are preferred in less complex amines due to their simplicity, allowing for easier communication between chemists.

Alkyl Group Naming in Amines

Alkyl groups are fundamental parts of amine structures, and recognizing them is crucial for naming purposes. Alkyl groups are fragments of alkanes—saturated hydrocarbons—that have one hydrogen atom less, which allows them to connect to other groups. This is important in amines since the alkyl groups decide their common names.

Identifying Alkyl Groups

The first step in naming amines is recognizing how many carbon atoms are in the alkyl chain. This helps in selecting the appropriate prefix:

• "Meth-" for a single carbon alkyl group (methylamine).
• "Eth-" for a two-carbon alkyl chain (ethylamine).
• "Prop-" for a three-carbon chain (propylamine).

Once identified, these prefixes are combined with "amine" to create the name. Understanding these basics makes naming straightforward and eliminates confusion.

Exploring the Amine Functional Group

Amines are easily identified by their functional group, characterized by the presence of the nitrogen atom typically attached to alkyl or aryl groups. In organic chemistry, understanding functional groups is essential as they define the chemical properties and reactivity of the compound.
The amine functional group, denoted as \(\text{RNH}_2\), \(\text{R}_2\text{NH}\), or \(\text{R}_3\text{N}\) based on substitution level, is essentially an amino group that is prevalent in a wide range of chemical reactions.

• Primary amines have the structure \(\text{RNH}_2\), involving one alkyl group attached to the nitrogen.
• Secondary amines have the formula \(\text{R}_2\text{NH}\), with two alkyl groups bonded to the nitrogen atom.
• Tertiary amines are represented as \(\text{R}_3\text{N}\), where three alkyl groups are bonded.

This group is responsible for the characteristic reactions that define amines, including their basicity and nucleophilicity, making them vital in both biological and industrial chemical processes.