Question

Give the common name of the following compounds. (a) \(\left(\mathrm{CH}_{3}\right)_{2} \mathrm{NH}\) (b) \(\left(\mathrm{CH}_{3}\right)_{2} \mathrm{~N}\left(\mathrm{C}_{2} \mathrm{H}_{5}\right)\) (c) \(\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{NH}_{2}\)

Short answer

The common names of the given compounds are: (a) dimethylamine, (b) N-ethyl-N,N-dimethylamine, and (c) aniline.

Step-by-step solution

Identifying Compound (a)

The compound \(\left(\mathrm{CH}_{3}\right)_{2} \mathrm{NH}\) is an amine that has two methyl groups \((\mathrm{CH}_{3})\) attached to the nitrogen atom. The common name for this compound is dimethylamine.

Identifying Compound (b)

The compound \(\left(\mathrm{CH}_{3}\right)_{2} \mathrm{~N}\left(\mathrm{C}_{2} \mathrm{H}_{5}\right)\) is an amine that has two methyl groups (\(\mathrm{CH}_{3}\)) and one ethyl group (\( \mathrm{C}_{2} \mathrm{H}_{5}\)) attached to the nitrogen atom. The common name for this compound is N-ethyl-N,N-dimethylamine based on the rule that the longest carbon chain attached to the Nitrogen atom will be considered the parent chain, which in this case is the ethyl group.

Identifying Compound (c)

The compound \(\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{NH}_{2}\) is an amine with a phenyl group attached to the nitrogen atom. The phenyl group \(\mathrm{C}_{6} \mathrm{H}_{5}\) is a cyclic compound, which has a common name as derived from Benzene. So, the compound overall is commonly known as aniline.

Key concepts

Amines

Amines are organic compounds characterized by the presence of a nitrogen atom bonded to one or more alkyl or aryl groups. They are derived from ammonia (NH₃) by replacing one, two, or three hydrogen atoms with carbon chains or groups. Depending on the number of carbon groups attached, amines can be classified into three types: primary, secondary, and tertiary amines.

• Primary amines have one carbon-containing substituent and can be represented as RNH₂, such as methylamine (CH₃NH₂).
• Secondary amines have two carbon groups and are symbolized as R₂NH, like dimethylamine ( ext{CH}_{3})_{2}NH.
• Tertiary amines, on the other hand, have three substituents of carbon, depicted as R₃N, for instance, trimethylamine.

Amines play a crucial role in both biology and industry, featuring prominently in the production of pharmaceuticals, dyes, and precursors to polymers. Understanding their nomenclature aids in identifying and categorizing these compounds effectively.

Common names in chemistry

Common names in chemistry are informal names for chemical substances that are widely used in various contexts, outside of systematic naming conventions. These names simplify communication, allowing chemists to refer to compounds easily within specific communities or industries.

For example, aniline is the common name for phenylamine, ext{C}_{6} ext{H}_{5} ext{NH}_{2}, used extensively in the dye industry. Similarly, dimethylamine is the common name for ext{(CH₃)₂NH}, where two methyl groups are attached to the nitrogen atom.

Although common names are helpful in specific fields, they may not always provide detailed information about the structure of a compound as systematic names do. Nevertheless, learning common names is often critical for students and professionals to seamlessly integrate into certain chemical sectors.

Organic chemistry nomenclature

Organic chemistry nomenclature is the systematic way to name organic compounds, ensuring consistency and clarity across international scientific communities. Developed and standardized by IUPAC (International Union of Pure and Applied Chemistry), this systematic naming follows specific rules that help convey the structure and composition of chemical compounds.

• Root names in IUPAC nomenclature indicate the number of carbon atoms in the longest continuous chain. For example, "meth-" signifies one carbon atom, as in methane (CH₄), while "eth-" indicates two, as seen in ethane (C₂H₆).
• Prefixes and suffixes are added to the root to indicate functional groups, multiple bonds, and other structural features. For amines, the suffix "-amine" is common when denoting their presence.
• When naming substituted amines, the longest carbon chain attached to the nitrogen atom is usually chosen as the parent chain. Other substituents are named as prefixes using the site's location of attachment.

This systematic approach, while sometimes complex, ensures that each compound has a unique name that provides insight into its molecular composition and structure.