Amine
Organic compounds with carbon–nitrogen bonds derived from ammonia.
Amines are organic compounds that contain carbon–nitrogen bonds, formed when one or more hydrogen atoms in ammonia are replaced by alkyl or aryl groups. They are classified into primary, secondary, and tertiary amines based on the number of substituents on the nitrogen atom, and include both aliphatic and aromatic varieties, such as aniline, the simplest aromatic amine.
- classification
- Primary (1°), secondary (2°), tertiary (3°) amines
- functional_group
- Amino group (−NH2) in primary amines
- key_example
- Aniline (C6H7N) as simplest aromatic amine
- basicity
- Weaker bases than alkali metal hydroxides
- common_physical_state
- Methyl and ethyl amines are gases under standard conditions
Lore & Background
Amines are formed by replacing hydrogen atoms in ammonia with alkyl or aryl groups. They are organized into three subcategories: primary (one substituent), secondary (two substituents), and tertiary (three substituents). A fourth subcategory, cyclic amines, includes secondary or tertiary amines such as aziridine and piperidine. Related compounds include amides, where nitrogen is attached to a carbonyl group, and quaternary ammonium salts, which have four organic substituents on nitrogen.
Reader's Guide
Amines are significant in chemistry due to their basicity, which is influenced by electronic effects and solvation. Alkyl groups enhance basicity, while aryl groups diminish it; solvation effects dominate in aqueous solutions, making tertiary amines less basic than secondary in water, though the reverse is true in the gas phase. Their physical properties, such as hydrogen bonding and solubility, vary with structure: primary and secondary amines form hydrogen bonds, while aromatic amines like aniline have reduced hydrogen bonding due to conjugation. Amines are also chiral when the nitrogen center bears four distinct substituents, though inversion barriers are low except in constrained cyclic structures.
Did You Know?
- Amines possess a characteristic ammonia smell, and liquid amines have a distinctive fishy and foul smell.
- The nitrogen atom in an amine features a lone pair of electrons that can bind H+ to form an ammonium ion.
- Primary amines exhibit two N–H bands in their infrared spectrum, while secondary amines exhibit only one.
- The energy barrier for nitrogen inversion in a trialkylamine is about 7 kcal/mol.
Frequently Asked Questions
What is Amine in chemistry fundamentals?
Amine refers to a family of organic molecules built around a carbon–nitrogen bond, essentially created by swapping one or more hydrogens on ammonia for alkyl or aryl groups. They sit at the heart of nitrogen-containing organic chemistry and appear in everything from simple gases to complex aromatic systems.
How are Amines classified by structure?
They fall into three tiers—primary, secondary, and tertiary—depending on how many carbon groups are attached to the nitrogen atom. A primary amine carries the classic −NH₂ amino group, while secondary and tertiary amines have progressively more organic substituents replacing the hydrogens.
What is the simplest aromatic amine?
Aniline (C₆H₇N) holds that title, consisting of a benzene ring directly bonded to an amino group. It serves as the go-to reference point when distinguishing aromatic amines from their aliphatic cousins.
Are Amines strong bases?
Not particularly—they are noticeably weaker bases than alkali metal hydroxides like sodium or potassium hydroxide. Their nitrogen lone pair can accept a proton, but the overall basicity falls short of those inorganic hydroxide compounds.
What state of matter are common small amines in at room temperature?
Methylamine and ethylamine are both gases under standard conditions, which is why they're often encountered in fume hoods or sealed containers rather than as liquids on a bench. Larger, heavier amines tend to be liquids or solids instead.
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