24: Amines and Heterocycles
- Page ID
- 448816
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)When you have completed Chapter 24, you should be able to
- fulfill all of the detailed objectives listed under each individual section.
- design a multi-step synthesis that involves the use of any of the reactions described in this unit, and any of the reactions described in any previous unit.
- solve road-map problems that require a knowledge of amine chemistry in addition to any of the chemistry discussed in previous units.
- define, and use in context, the key terms introduced.
Amines are the first nitrogen-containing compounds that we study in detail in this course. We begin the chapter with an explanation of the differences in structure among primary, secondary and tertiary amines. We explain the nomenclature of aliphatic and arylamines, and examine the structure and bonding of these compounds, relating these features to their physical properties and basicity. We describe the use of amines to resolve racemic mixtures of chiral carboxylic acids.
Amines may be prepared by a number of different synthetic methods. We describe each of these methods and assess the relative merits of each. After a description of the reactions of aliphatic amines, we devote sections to a discussion of the use of tetraalkylammonium salts as phase-transfer agents. The chapter concludes with a summary of the spectroscopic properties of amines.
- 24.0: Why This Chapter?
- This chapter introduces the importance of amines and heterocycles in organic chemistry. It outlines their diverse applications in pharmaceuticals, agriculture, and materials science. The chapter sets the stage for understanding the structure, properties, and reactions of amines and heterocyclic compounds, emphasizing their significance in both biological systems and synthetic chemistry.
- 24.1: Naming Amines
- The section on naming amines explains the systematic approach to naming these compounds. Amines are classified based on the number of carbon-containing groups attached to the nitrogen atom—primary, secondary, or tertiary. The IUPAC naming convention includes using "amine" as a suffix, and when substituents are present, they are prefixed with their respective names, indicating the positions on the carbon chain.
- 24.2: Structure and Properties of Amines
- The section on naming amines details the classification of amines as primary, secondary, or tertiary based on the number of carbon groups attached to the nitrogen. It explains the IUPAC naming conventions, where "amine" is used as a suffix, and substituents are named and numbered according to their positions on the carbon chain.
- 24.3: Basicity of Amines
- The section on the basicity of amines discusses how the basicity of amines arises from the lone pair of electrons on the nitrogen atom, which can accept protons. It highlights factors affecting basicity, such as electronegativity and steric hindrance. Primary amines are generally more basic than secondary and tertiary amines due to less steric hindrance, while aromatic amines are less basic because of resonance stabilization.
- 24.4: Basicity of Arylamines
- This section examines the basicity of arylamines, which is influenced by the resonance of the aromatic ring. In arylamines, the lone pair of electrons on the nitrogen can delocalize into the ring, reducing its availability to accept protons and thus decreasing basicity compared to aliphatic amines. Factors such as electron-withdrawing groups further reduce basicity by stabilizing the lone pair through resonance. The relative basicity of arylamines is crucial for understanding their chemical beha
- 24.5: Biological Amines and the Henderson-Hasselbalch Equation
- This section discusses biological amines, which play significant roles in various physiological processes. It highlights the importance of the Henderson-Hasselbalch equation in determining the pH of solutions containing these amines, especially in biological systems. The equation helps explain how the protonation state of an amine affects its biological activity. Understanding this relationship is crucial for fields like pharmacology and biochemistry.
- 24.6: Synthesis of Amines
- This section covers various methods for synthesizing amines, including reductive amination of carbonyl compounds, nucleophilic substitution reactions, and the reduction of nitro compounds. It emphasizes the significance of amines in organic synthesis and their applications in pharmaceuticals and agrochemicals. Understanding these synthetic pathways is essential for developing new amine compounds for various uses.
- 24.7: Reactions of Amines
- This section discusses the reactions of amines, including their role as nucleophiles in various chemical reactions. It highlights amines' ability to undergo acylation, alkylation, and oxidation. Additionally, it explores the formation of salts when amines react with acids. The significance of these reactions in organic synthesis and pharmaceuticals is emphasized, showcasing amines' versatility and importance.
- 24.8: Reactions of Arylamines
- This section focuses on the unique reactions of arylamines, highlighting their reactivity compared to aliphatic amines. It discusses electrophilic aromatic substitution reactions, where arylamines can act as nucleophiles, and their ability to form diazonium salts. The section also notes that the presence of the amino group can influence the reactivity of the aromatic ring, impacting various chemical transformations.
- 24.9: Heterocyclic Amines
- This section covers heterocyclic amines, which are organic compounds featuring nitrogen atoms within a ring structure. It discusses their diverse structures, reactivity, and biological importance, such as the roles of pyridine, pyrrole, and imidazole. These heterocyclic amines are significant in pharmaceuticals, agrochemicals, and as biomolecules like nucleic acids. The section also highlights their synthesis and reactions.
- 24.10: Spectroscopy of Amines
- This section explains how amines can be identified and analyzed using various spectroscopic methods such as infrared (IR), nuclear magnetic resonance (NMR), and mass spectrometry. Key features include the N-H stretching vibrations in IR, the characteristic chemical shifts in NMR, and the fragmentation patterns in mass spectrometry. These methods help in determining the structure and properties of amines in both simple and complex compounds.
- 24.11: Chemistry Matters - Green Chemistry II- Ionic Liquids
- The section highlights the use of ionic liquids as a sustainable alternative to conventional solvents in chemical processes. Ionic liquids are non-volatile, recyclable, and can be engineered for specific tasks, reducing environmental impact. They are especially useful in organic reactions, separation processes, and catalysis. This approach aligns with green chemistry principles aimed at reducing waste and hazards in chemical production.
- 24.13: Summary
- We’ve now seen all the common functional groups that occur in organic and biological chemistry. Of those groups, amines are among the most abundant and have among the richest chemistry. In addition to proteins and nucleic acids, the majority of pharmaceutical agents contain amine functional groups and many of the common coenzymes necessary for biological reactions are amines.
- 24.14: Summary of Reactions
- The summary of reactions involving amines and heterocycles highlights key transformations such as the synthesis of amines from alkyl halides and the reduction of nitro compounds. It covers the preparation of heterocycles through methods like cyclization and substitution reactions. The text also addresses the behavior of amines in acid-base reactions, their role as nucleophiles, and how heterocycles can participate in electrophilic aromatic substitution. For a detailed overview, visit the origina