Amines are a class of organic compounds derived from ammonia, involved in both natural processes and industrial synthesis. These compounds are characterized by a nitrogen atom that possesses a lone pair of electrons. This structure allows for a wide range of derivatives found in everything from amino acids to manufactured goods.
Defining the Structure of a Tertiary Amine
A tertiary amine is an organic compound in which a nitrogen atom is bonded to three carbon-containing groups. These groups can be alkyl groups (chains of carbon and hydrogen atoms) or aryl groups (based on aromatic rings like benzene). This complete substitution is the defining feature of a tertiary amine.
To visualize this structure, one can imagine the nitrogen atom as a central hub, giving the molecule a pyramidal shape. The angle between the carbon-nitrogen bonds is approximately 107 degrees, slightly less than the 109.5-degree angle of a perfect tetrahedron due to the lone electron pair on the nitrogen atom.
This configuration distinguishes tertiary amines from primary and secondary amines. Primary amines have only one carbon group attached to the nitrogen, while secondary amines have two carbon groups and one hydrogen atom. The absence of a hydrogen atom bonded directly to the nitrogen is a consequence of this structure.
Distinctive Chemical Characteristics
The absence of a hydrogen atom on the nitrogen gives tertiary amines specific chemical properties. Unlike primary and secondary amines, tertiary amines cannot act as hydrogen bond donors because they lack an N-H bond. This results in tertiary amines having lower boiling points compared to primary or secondary amines of similar molecular weight.
Despite this, the lone pair of electrons on the nitrogen atom allows tertiary amines to act as hydrogen bond acceptors with molecules that do have available hydrogen atoms, such as water. This interaction explains why smaller tertiary amines exhibit some solubility in water. The solubility decreases as the size of the carbon groups increases.
Tertiary amines are weak bases because the lone pair of electrons on the nitrogen can accept a proton from an acid. Many simple tertiary amines, such as trimethylamine, are also known for their distinct and often unpleasant odors, which are commonly described as fishy.
Prominent Examples and Natural Occurrence
Tertiary amines are widespread in both simple synthetic forms and complex natural products. A common example is trimethylamine, the compound largely responsible for the smell of decaying fish. Another example is triethylamine, which is frequently used in organic chemistry laboratories as a solvent and a base.
Nature provides more complex examples of tertiary amines, particularly within a class of plant-derived compounds known as alkaloids. Many alkaloids possess physiological effects and have historical and medicinal relevance. For instance, nicotine, the stimulant found in tobacco plants, features a tertiary amine within its structure.
Another natural tertiary amine is atropine, extracted from the deadly nightshade plant, which has medical uses as an antidote to certain nerve agents. Morphine, a powerful pain reliever from the opium poppy, also contains a tertiary amine structure that is part of its activity.
Applications in Industry and Medicine
The properties of tertiary amines make them valuable in a wide range of industrial and medical contexts. In manufacturing, they are frequently used as catalysts to facilitate chemical reactions, such as in the production of polyurethane foams for insulation and furniture. They also serve as curing agents for epoxy resins, which are strong adhesives used in construction and electronics.
The tertiary amine structure is a common feature in pharmaceuticals, with more than 60 percent of amine-containing drugs being tertiary amines. This includes many common medications, such as the antihistamine diphenhydramine (found in Benadryl) and anesthetics like novocaine. Their structure often helps with a drug’s solubility and its ability to interact with biological targets.
Beyond these roles, tertiary amines serve as intermediates in the synthesis of other chemical products. They are starting materials for making quaternary ammonium compounds, which are used as disinfectants and surfactants. They are also used in the manufacturing of dyes for textiles and in the formulation of some pesticides and corrosion inhibitors.