Amines in Organic Chemistry

Study Notes

• Trimethylaminuria is a rare genetic disorder where the body cannot produce the enzyme to oxidize trimethylamine, resulting in a fish-like body odor. • Trimethylamine is a compound produced from trimethylamine oxide by enzymes and bacteria, and is used as a marker of freshness in fish. • Amines are important in biochemistry, medicine, and agriculture, and are involved in various reactions. • There are two naming systems for amines: common names and IUPAC names. • Primary amines have one alkyl or aryl group attached to the nitrogen, secondary amines have two, and tertiary amines have three. • The NH2 group is low priority in IUPAC nomenclature, often seen as a prefix "amino" when there are higher priority functional groups. • Diamines are used as monomers to prepare polymers like nylon and have a strong smell. • Amines have a trigonal pyramidal geometry, with the nitrogen atom being sp3 hybridized. • Amines are weak bases, with the lone pair of electrons on the nitrogen accepting a proton to form a conjugate acid (ammonium ion). • The pKa of the ammonium ion determines the basicity of the amine, with lower pKa values indicating higher acidity. • Substituting additional alkyl groups can increase the basicity of an amine, as they are electron-donating and help stabilize the positive charge. • Resonance can also affect the basicity of amines, such as in aniline, which is a weaker base than alkyl amines. • Nitrogen-containing heterocycles can be aromatic or non-aromatic, with aromatic ones being weaker bases due to sp2 hybridization. • Pyridine is a useful molecule in the lab, used as a precursor to produce herbicides, insecticides, and antiseptics, but has a strong, unpleasant smell. • Amines can be synthesized using nucleophilic substitution reactions and reductions, but may require additional steps to prevent over-alkylation or explosive reactions. • The Gabriel synthesis is a method that uses thalamide to add nitrogen and provides a built-in amine protecting group.- Primary amines can be obtained by reacting a compound with hydrazine.

Reducing a nitrile group with a haloalkane can also produce a primary amine with a bonus carbon atom.
Lithium aluminum hydride can be used to reduce amides to primary amines, and also provides a path to secondary and tertiary amines by making amides with alkyl groups substituting for hydrogen atoms.
Reacting an ester with a primary or secondary amine can produce an amide, which can then be reduced to a secondary or tertiary amine.
Reductive amination is a reaction that uses a mild reducing agent to add additional alkyl groups to an amine.
In reductive amination, a hydride is added to the electrophilic carbon of an iminium ion, allowing customization of the alkyl group attached to the nitrogen.
Iminium ions play a role in the synthesis of penicillin V, where the lone pair on the nitrogen attacks the carbonyl carbon, and a proton jumps to an acetate ion, forming the iminium ion.
Various nucleophiles can add to iminium ions, including hydroxide ions, which can grab the hydrogen from the thio group and attach the sulfur to the iminium ion carbon.
Quaternary ammonium salts can be used as leaving groups, and the Hoffman elimination reaction can be used to produce an alkene, water, and a tertiary amine.
Enamines are molecules with a carbon-carbon double bond next to an amine, and can be formed by reacting an aldehyde or ketone with a secondary amine.
Enamines can act as nucleophiles, similar to enolates, and can be used in alkylation and aldol reactions, with advantages over enolates including avoiding over-alkylation.
Enamines can be used in carbon-carbon bond-forming reactions, and can be hydrolyzed to reform an aldehyde or ketone.

Description

This quiz covers the properties, synthesis, and reactions of amines in organic chemistry, including their structure, basicity, and uses in various reactions. It also explores the different types of amines, such as primary, secondary, and tertiary amines, and their applications in different fields.