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Ch. 25 - Amines: Structure, Reactions, and Synthesis
Mullins - Organic Chemistry: A Learner Centered Approach 1st Edition
Mullins1st EditionOrganic Chemistry: A Learner Centered ApproachISBN: 9780137566471Not the one you use?Change textbook
All textbooksMullins 1st EditionCh. 25 - Amines: Structure, Reactions, and SynthesisProblem 9
Chapter 24, Problem 9

Label the amines shown as a 1° amine, 2° amine, 3° amine, or 4° ammonium ion.
a. Structural representation of a 2° amine with a nitrogen atom bonded to two carbon chains.
b.
c. Chemical structure of a cyclohexane with an attached primary amine group (NH2) indicated.
d. Chemical structure of a hexagonal ring with an amine group (NH) labeled for identification as a functional group.

Verified step by step guidance
1
Step 1: Understand the classification of amines. Amines are classified based on the number of alkyl or aryl groups attached to the nitrogen atom. A 1° (primary) amine has one alkyl/aryl group, a 2° (secondary) amine has two, a 3° (tertiary) amine has three, and a 4° (quaternary) ammonium ion has four groups attached to the nitrogen atom, along with a positive charge.
Step 2: Analyze structure (a). The nitrogen atom is bonded to three ethyl groups. Since there are three alkyl groups attached to the nitrogen, this is a 3° (tertiary) amine.
Step 3: Analyze structure (b). The nitrogen atom is bonded to four alkyl groups and carries a positive charge. This makes it a 4° (quaternary) ammonium ion.
Step 4: Analyze structure (c). The nitrogen atom is bonded to one alkyl group (cyclohexyl) and two hydrogen atoms. This makes it a 1° (primary) amine.
Step 5: Analyze structure (d). The nitrogen atom is bonded to one alkyl group (cyclohexyl) and one hydrogen atom. This makes it a 2° (secondary) amine.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Classification of Amines

Amines are classified based on the number of carbon groups attached to the nitrogen atom. A primary (1°) amine has one carbon group, a secondary (2°) amine has two, a tertiary (3°) amine has three, and a quaternary ammonium ion (4°) has four carbon groups, with the nitrogen carrying a positive charge.
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Structure of Amines

The structure of amines is characterized by the presence of a nitrogen atom bonded to hydrogen and/or carbon atoms. The geometry around the nitrogen is typically trigonal pyramidal due to the lone pair of electrons, which influences the physical and chemical properties of the amine.
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Functional Groups in Organic Chemistry

Functional groups are specific groups of atoms within molecules that are responsible for the characteristic chemical reactions of those molecules. In the case of amines, the amine group (-NH2, -NHR, or -NR2) is the functional group that defines their reactivity and properties, distinguishing them from other organic compounds.
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Related Practice
Textbook Question

Draw a constitutional isomer for C4H11N containing a 1° amine at a

(a) 1° carbon,

(b) 2° carbon, and

(c) 3° carbon.

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Textbook Question

Give an acceptable name for each amine.

(c)

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Textbook Question

We usually calculate Keq for acid–base reactions using pKa values.

(a) Derive an equation to calculate Keq using pKb values, then

(b) use it to calculate the equilibrium constant for the following reaction.

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Textbook Question

Which would you expect to be a stronger nucleophile, ethyl amine or diethyl amine? Why?

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Textbook Question

Given the following names, draw the structure of the molecule.

c. (S)-2-methyloctan-4-amine

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Textbook Question

Give an acceptable name for each amine.

(b)

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