12 Amines and Introductory Organic Synthesis Free Online FlashCards

How are primary, secondary, and tertiary amines classified?

Primary, secondary, and tertiary amines have one, two, and three carbon groups attached to nitrogen, respectively.

What distinguishes a quaternary ammonium ion from a typical amine?

A quaternary ammonium ion has four carbon groups attached to nitrogen and no lone pair. If all four groups differ, it can be configurationally stable.

Why are amines with three different groups on nitrogen usually not isolated as enantiomers?

A typical amine nitrogen rapidly inverts through a nearly planar arrangement, so amines with three different carbon groups on nitrogen usually cannot be isolated as separate enantiomers.

How is a simple amine named when the amine is the principal functional group?

Use the suffix “-amine” and number the chain to give the amine the lowest possible locant, as in propan-1-amine.

What does a higher conjugate-acid $pK_\mathrm{a}$ indicate about an amine?

A higher conjugate-acid $pK_\mathrm{a}$ corresponds to a stronger amine base.

Why is aniline less basic than an alkylamine?

Aniline is less basic because its nitrogen lone pair is delocalized into the aromatic ring and is less available to bind a proton.

How can acid–base extraction separate an amine from neutral compounds?

Aqueous acid protonates the amine, forming a water-soluble ammonium salt that moves into the aqueous layer. Adding base then regenerates the neutral amine.

Why can direct amine alkylation give a mixture of products?

The first alkylation product remains nucleophilic and can react again, producing more highly alkylated amines or quaternary ammonium salts.

Why don’t tertiary amines form neutral amides by acylation?

Tertiary amines lack a hydrogen attached to nitrogen, so they do not form neutral amides by this reaction.

What amine class results from reductive amination of ammonia, a primary amine, or a secondary amine?

Reductive amination converts ammonia to a primary amine, a primary amine to a secondary amine, or a secondary amine to a tertiary amine.

How does Gabriel synthesis make a primary amine?

A phthalimide anion displaces the halide from a suitable primary alkyl halide by an $S_\mathrm{N}2$ reaction; hydrolysis then releases a primary amine.

What carbon-skeleton change occurs in the Hofmann rearrangement?

It converts a primary amide into a primary amine with one fewer carbon atom.