20: Amines

Last updated
Save as PDF

Page ID: 424379

\( \newcommand{\vecs}[1]{\overset { \scriptstyle \rightharpoonup} {\mathbf{#1}} } \) \( \newcommand{\vecd}[1]{\overset{-\!-\!\rightharpoonup}{\vphantom{a}\smash {#1}}} \)\(\newcommand{\id}{\mathrm{id}}\) \( \newcommand{\Span}{\mathrm{span}}\) \( \newcommand{\kernel}{\mathrm{null}\,}\) \( \newcommand{\range}{\mathrm{range}\,}\) \( \newcommand{\RealPart}{\mathrm{Re}}\) \( \newcommand{\ImaginaryPart}{\mathrm{Im}}\) \( \newcommand{\Argument}{\mathrm{Arg}}\) \( \newcommand{\norm}[1]{\| #1 \|}\) \( \newcommand{\inner}[2]{\langle #1, #2 \rangle}\) \( \newcommand{\Span}{\mathrm{span}}\) \(\newcommand{\id}{\mathrm{id}}\) \( \newcommand{\Span}{\mathrm{span}}\) \( \newcommand{\kernel}{\mathrm{null}\,}\) \( \newcommand{\range}{\mathrm{range}\,}\) \( \newcommand{\RealPart}{\mathrm{Re}}\) \( \newcommand{\ImaginaryPart}{\mathrm{Im}}\) \( \newcommand{\Argument}{\mathrm{Arg}}\) \( \newcommand{\norm}[1]{\| #1 \|}\) \( \newcommand{\inner}[2]{\langle #1, #2 \rangle}\) \( \newcommand{\Span}{\mathrm{span}}\)\(\newcommand{\AA}{\unicode[.8,0]{x212B}}\)

learning objectives

After reading this chapter and completing ALL the exercises, a student can be able to

describe the structure and physical properties of amines and ammonium salts (section 20.1)
explain and predict the relative basicity of amines using resonance, hybridization, substituent effects, and aromaticity (section 20.2)
determine the structure of amines from their elemental analysis and spectral data (MS, IR ¹H NMR & ¹³C NMR) (section 20.3)
predict the products and specify the reagents to synthesize amines (section 20.4)
predict the products and specify the reagents to synthesize primary amines (section 20.5)
predict the products and specify the reagents for reactions of amines with
- aldehydes & ketones (section 20.6)
- alkyl halides and tosylates (section 20.6)
- acyl chlorides (section 20.6)
- sulfonyl chlorides (section 20.6)
- nitrous acid (section 20.7)
- oxidizing agents via Cope Elimination (section 20.9)
explain the activating effects of aryl amines during electrophilic aromatic substitution reactions (section 20.7)
use amides as protecting groups in multiple step synthesis (section 20.7)
use diazonium salts to design multiple step syntheses using the Sandmeyer reactions (section 20.7)
specify the reagents and predict the products for Hofmann Elimination reactions (section 20.8)
Specify reagents for chemical transformations using all of the reactions studied to date
combine the reactions studied to date to develop efficient and effective multiple-step synthesis including the use of amides as protecting groups

Please note: IUPAC nomenclature and important common names of amines were explained in Chapter 3.

20.1: Structure and Physical Properties of Amines
The structure and physical properties of amines depend on their classification. For primary and secondary amines, H-bond donation distinguishes their properties and reactivity from tetiary amines.
20.2: Basicity of Amines and Ammonium Salt Formation
The basicity of amines is determined by the reactivity of the lone pair on the nitrogen atom. Amines with low water solubility can react with acids to form water soluble ammonium salts.
20.3: Spectroscopy of Amines
The influence of the electronegative nitrogen atom can be observed in the spectroscopy of amines.
20.4: Synthesis of Amines
Reductive amination and acyl reduction of amides are the major synthetic routes for amine synthesis, especially secondary and tertiary amines.
20.5: Synthesis of Primary Amines
The synthesis of primary amines is useful for multiple step synthesis of larger, more complex organic compounds.
20.6: Reactions of Amines
As weak bases, amines are good nucleophiles that can react with many of the electrophilic functional groups studied so far including aldenhydes, ketones, acid chlorides, and alkyl halides.
20.7: Reactions of Arylamines
The activating effects of amine groups during electrophilic aromatic substitution reactions may be mitigated using amides as protecting groups. The diazonium salts of aryl amines are useful reactive intermediates for the Sandmeyer reactions. The "azo" linkage (Ar-N=N-Ar') is important in the chemistry of dyes and pigments.
20.8: The Hofmann Elimination- Amines as Leaving Groups
Amines are poor leaving groups. The Hofmann Elimination reaction uses quaternary ammonium salts as the leaving group.
20.9: Oxidation of Amines - The Cope Elimination
When a tertiary amine oxide bearing one or more beta hydrogens is heated, it is converted to an alkene. The reaction is known as Cope elimination or Cope reaction, not to be confused with Cope Rearrangement.
20.10: Sulfa Drugs - a closer look
Sulfonamides are synthetic antimicrobial agents with a wide spectrum encompassing most gram-positive and many gram-negative organisms. These drugs were the first efficient treatment to be employed systematically for the prevention and cure of bacterial infections.
20.11: Additional Exercises
This section has additional exercises for the key learning objectives of the chapter.
20.12: Solutions to Additional Exercises
This section has the solutions to the additional exercises from the previous section.