Amine Structure

8 Key excerpts on "Amine Structure"

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  eBook - ePub

  Principles of Organic Chemistry

  • Robert J. Ouellette, J. David Rawn(Authors)
  • 2015(Publication Date)
  • Elsevier

    (Publisher)

  3 hybrid orbitals. As expected from VSEPR theory, these orbitals point to the corners of a tetrahedron. Three are half-filled. They form three covalent bonds. The fourth orbital contains a pair of nonbonded electrons.

  12.3 Structure and Classification of Amines and Amides

  In the simplest amine, methylamine (CH3 NH2 ), one hydrogen atom of ammonia has been replaced by a methyl group (Figure 12.2 ). The nitrogen atom of methylamine and other amines has five valence electrons in four sp3 hybrid orbitals that are directed to the corners of a tetrahedron. Three of these orbitals are half-filled; the fourth contains a nonbonding pair of electrons that plays an important role in the chemical properties of amines.

  Figure 12.2 Structure of Methylamine

  Amines are classified by the number of alkyl (or aryl) groups attached to the nitrogen atom. Note that amines are not classified like alcohols. (The classification of alcohols is based on the number of groups attached to the carbon atom bearing the hydroxyl group.) For example, tert -butylamine has a tert -butyl group attached to an –NH2 group. However, the amine is primary because only one alkyl group is bonded to the nitrogen atom. In contrast, tert -butyl alcohol is a tertiary alcohol because the carbon atom bonded to the –OH group is bonded to three alkyl groups. Trimethylamine is a tertiary amine because the nitrogen atom is bonded to three alkyl groups.

  The nitrogen atom of an amine may be contained in a ring, a common feature of nitrogen compounds in nature. The simplest five- and six-membered nitrogen-containing heterocyclic compounds are pyrrolidine and piperidine.

  Problem 12.2 Classify the nitrogen-containing functional groups in Mepivacaine®, a local anesthetic.

  Amides have an amino group or a substituted amino group bonded to a carbonyl carbon atom. The other two bonds of the nitrogen atom may be to hydrogen atoms, alkyl groups, or aryl groups. Amides are classified based on the number of carbon groups (including the acyl group) bonded to the nitrogen atom.

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  eBook - ePub

  Organic Chemistry Study Guide

  Key Concepts, Problems, and Solutions

  • Robert J. Ouellette, J. David Rawn(Authors)
  • 2014(Publication Date)
  • Elsevier

    (Publisher)

  23

  Amines and Amides

  Keys to the Chapter

  23.1 Organic Nitrogen Compounds

  Because nitrogen has five valence shell electrons, it can form three covalent bonds in neutral compounds, leaving one nonbonding electron pair. These bonds can be three single bonds as in amines and amides, one double bond and a single bond in imines, or a triple bond in nitriles.

  Nitrogen is found in many biologically important compounds that have a wide range of physiological properties. However, once a nitrogen-containing functional group is identified, its chemical reactions can often be predicted since the functional groups in these compounds, whose structures are often complex, have the characteristic reactivities of much simpler compounds.

  23.2 Bonding and Structure of Amines

  Amines are pyramidal at the nitrogen atom, with approximately tetrahedral bond angles to all bonded atoms. The nitrogen atom in amines is sp3 hybridized. However, the configuration of an amine is not static. Amines undergo nitrogen inversion to give mixtures of mirror images. The process occurs via a planar transition state. The energy barrier to inversion is low, and nitrogen inversion is rapid so that amines with chiral nitrogen atoms cannot be isolated.

  23.3 Classification and Nomenclature of Amines

  Amines are classified according to the number of alkyl or aryl groups bonded to the nitrogen atom. Primary, secondary, and tertiary amines have 1, 2, and 3 groups bonded, respectively. Amides are classified the same way, with the acyl group counting as one of the carbon groups bonded to the nitrogen atom. Abbreviations for the classes of amines and amides are 1°, 2°, and 3°.

  The common names of simple amines are based on the identity of the alkyl or aryl groups bonded to the nitrogen atom. The names of the alkyl groups are written in alphabetical sequence as one word, followed by the word amine.

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  Chemistry for Today

  General, Organic, and Biochemistry

  • Spencer Seager, Michael Slabaugh, Maren Hansen, , Spencer Seager, Spencer Seager, Michael Slabaugh, Maren Hansen(Authors)
  • 2021(Publication Date)
  • Cengage Learning EMEA

    (Publisher)

  16.1 Classification of Amines Learning Objective 1 Classify amines as primary, secondary, or tertiary on the basis of given structural formulas. Amines are organic derivatives of ammonia, NH 3 , in which one or more of the hydrogens are replaced by an aromatic or alkyl group (R). Like alcohols, amines are classified as primary, secondary, or tertiary on the basis of molecular structure. However, the classification is done differently. When classifying amines, the number of groups (R) that have replaced hydrogens in the NH 3 is counted. The nitrogen atom in a primary amine is bonded to one R group. The nitrogen in secondary amines is bonded to two R groups, and that of tertiary amines is bonded to three R groups. These amine subclasses are summarized in Table 16.1. amine An organic compound derived by replacing one or more of the hydrogen atoms of ammonia with alkyl or aromatic groups, as in RNH 2 , R 2 NH, and R 3 N. primary amine An amine having one alkyl or aromatic group bonded to nitrogen, as in R—NH 2 . secondary amine An amine having two alkyl or aromatic groups bonded to nitrogen, as in R 2 NH. tertiary amine An amine having three alkyl or aromatic groups bonded to nitrogen, as in R 3 N. TABLE 16.1 Subclasses of Amines Subclass General Formula Example Primary (1°) Secondary (2°) Tertiary (3°) N R H H N CH 3 H H N R R′ H N CH 3 CH 3 H N R R′ R″ N CH 3 CH 3 CH 3 Example 16.1 Classifying Amines Serotonin, an amine involved in the transmission of nerve impulses, contains two nitro- gen atoms in its structure. Classify each of the following nitrogens as primary, second- ary, or tertiary. NH 2 H N CH 2 CH 2 Copyright 2022 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience.

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  Introduction to General, Organic, and Biochemistry

  • Morris Hein, Scott Pattison, Susan Arena, Leo R. Best(Authors)
  • 2014(Publication Date)
  • Wiley

    (Publisher)

  An amine (pronounced ameen) is a substituted ammonia molecule with basic properties and has the general formula RNH 2 , R 2 NH, or R 3 N, where R is an alkyl or an aryl group. Amines are classified as primary (1°), secondary (2°), or tertiary (3°), depending on the number of hydrocarbon groups attached to the nitrogen atom. Some examples include the following: KEY TERM urea KEY TERMS amine heterocyclic compound A Biochemical Perspective: Silk, a natural fiber, is a polyamide composed of amino acids—a protein. During World War II, ladies valued nylon stockings more than gold. The stock of early Remington 22- caliber rifles was very popular and was made of nylon. Instead of urea, uric acid is excreted by birds and reptiles. LEARNING OBJECTIVE LEARNING OBJECTIVE Crops are often fertilized with urea. Lloyd Sutton/Masterfile 25.5 • Amines: Nomenclature and Physical Properties 649 H N H H CH 3 N H H ammonia methylamine (1� amine) N CH 2 CH 3 H CH 3 ethylmethylamine (2� amine) CH 3 CH 2 N CH 2 CH 3 CH 2 CH 3 triethylamine (3 amine) NH 2 aniline (1° amine) NH 2 cyclohexylamine (1° amine) More Practice? Try Paired Exercises 13–16. P R A C T I C E 2 5 . 4 Identify these compounds as 1°, 2°, or 3° amines: (a) CH 3 CH 2 CH 2 NH 2 (e) CH 3 CH 2 NCH 2 CH 3 CH 3 (b) NH 2 CH 3 C CH 3 CH 3 (f) CH 3 CH 2 NHCH 2 CH 3 (c) N H (g) CH 2 NH 2 (d) NH 2 P R A C T I C E 2 5 . 5 Application to Biochemistry The following amines are synthesized by humans: (a) N H CH 2 ¬ CH 2 ¬ NH 2 ¬ (b) CH ¬ CH 2 ¬ NH ¬ CH 3 OH OH HO ¬ “ CH 3 NH 2 ¬ CH ¬ (c) tryptamine epinephrine (adrenaline) alanine C OH O Identify each amine functional group as 1°, 2°, or 3°. Health Connection: Some tertiary amines put a stop to pain The history of local anesthetics traces a path taken in many drug discoveries, that is, starting with a natural molecule that has a desired physiological impact and making it better using organic chemistry. Surprisingly, cocaine, a much-abused narcotic, is also a very good local anesthetic.

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  Pharmaceutical Chemistry E-Book

  • David G. Watson(Author)
  • 2011(Publication Date)
  • Churchill Livingstone

    (Publisher)

  Chapter 3 Amines David G. Watson Chapter contents Introduction 35 Factors affecting the p Ka value of a base 36 Alkyl groups 36 Electron withdrawing groups 39 Salt formation 48 Reactions of amines in relation to storage and formulation 48 Oxidation 48 Acylation 48 Schiff’s base formation 49 Quaternary amines 52 Introduction The amine group can be considered as the single most important group for conferring pharmacological activity. This is because it is the principle group within organic molecules that bears a positive charge. When it is present in a drug molecule it can exert biological effects through electrostatic interactions with negatively charged groups within proteins and also compete with positively charged cations such as sodium, potassium and calcium ions in biological processes. Amines are derived from ammonia and have the structures shown in Figure 3.1 for mono-, di- and trisubstituted nitrogen. Figure 3.1 Amines. The structures may look planar but, in fact, the structures of amines are more or less tetrahedral, like tetrasubstituted carbon, as shown for trimethylamine in Figure 3.2. In the case of nitrogen, the position that would be occupied by a fourth bond in tetrasubstituted carbon is occupied by a lone pair of electrons. Since nitrogen is less electronegative than oxygen the lone pair within an Amine Structure is more available than the lone pairs on an oxygen atom to interact with a proton. An approximate measure of the availability of lone pairs of electrons is given by the energy of the highest occupied molecular orbital (HOMO). The deeper the ‘energy well’ that the molecular orbital occupies the less available the electrons are for bond formation with a proton. Thus water has a HOMO of −12.5 eV while ammonia has a HOMO of −10.5 eV, and thus its electrons are more available and it protonates more readily than water

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  Organic Chemistry

  • David R. Klein(Author)
  • 2021(Publication Date)
  • Wiley

    (Publisher)

  22.1 Introduction to Amines 1055 DO YOU REMEMBER? Before you go on, be sure you understand the following topics. If necessary, review the suggested sections to prepare for this chapter: • Delocalized and Localized Lone Pairs (Section 2.13) • Brønsted–Lowry Acidity: A Quantitative Perspective (Section 3.3) • Aromatic Heterocycles (Section 17.5) • Activating Groups and Deactivating Groups (Sections 18.7 and 18.8) Take the DO YOU REMEMBER? QUIZ in the online course to check your understanding. 22.1 Introduction to Amines Classification of Amines Amines are derivatives of ammonia in which one or more of the protons have been replaced with alkyl or aryl groups. Amines Ammonia H N H H Primary (1°) H N R H Secondary (2°) R N R H Tertiary (3°) R N R R Amines are classified as primary, secondary, or tertiary, depending on the number of groups attached to the nitrogen atom. Note that these terms have a different meaning than when they were used in naming alcohols. A tertiary alcohol has three groups attached to the α carbon, while a tertiary amine has three groups attached to the nitrogen atom. Amines are abundant in nature. Naturally occurring amines isolated from plants are called alkaloids. Below are examples of several alkaloids that have garnered public awareness as a result of their physiological activity: O OH OH H N Morphine (A potent analgesic isolated from the unripe seeds of the poppy plant Papaver somniferum) N O O O O Cocaine (A potent stimulant isolated from the leaves of the coca plant) Nicotine (An addictive and toxic compound found in tobacco) N N Many amines also play vital roles in neurochemistry (chemistry taking place in the brain).

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  Organic Chemistry

  • David R. Klein(Author)
  • 2016(Publication Date)
  • Wiley

    (Publisher)

  Note that these terms have a different meaning than when they were used in naming alcohols. A tertiary alcohol has three groups attached to the α carbon, while a tertiary amine has three groups attached to the nitrogen atom. Amines are abundant in nature. Naturally occurring amines isolated from plants are called alkaloids. Below are examples of several alkaloids that have garnered public awareness as a result of their physiological activity: O OH OH H N Morphine (A potent analgesic isolated from the unripe seeds of the poppy plant Papaver somniferum) N O O O O Cocaine (A potent stimulant isolated from the leaves of the coca plant) Nicotine (An addictive and toxic compound found in tobacco) N N Many amines also play vital roles in neurochemistry (chemistry taking place in the brain). Below are a few examples: Dopamine (Regulates motor skills and emotions) HO HO N H H Adrenaline (A “fight-or-flight” hormone, first discussed in Chapter 7) HO HO N CH 3 H OH Noradrenaline (Regulates heart rate and dilates air passages) HO HO N H H OH In fact, many pharmaceuticals are amines, as we will see throughout this chapter. DO YOU REMEMBER? Before you go on, be sure you understand the following topics. If necessary, review the suggested sections to prepare for this chapter: • Delocalized and Localized Lone Pairs (Section 2.12) • Brønsted–Lowry Acidity: A Quantitative Perspective (Section 3.3) • Aromatic Heterocycles (Section 17.5) • Activating Groups and Deactivating Groups (Sections 18.7 and 18.8) Take the DO YOU REMEMBER? QUIZ in to check your understanding. 1010 CHAPTER 22 Amines Reactivity of Amines The nitrogen atom of an amine possesses a lone pair that represents a region of high electron density. This can be seen in an electrostatic potential map of trimethylamine (Figure 22.1). The presence of this lone pair is responsible for most of the reactions exhibited by amines.

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  Organic and Biological Chemistry

  • H. Stephen Stoker(Author)
  • 2015(Publication Date)
  • Cengage Learning EMEA

    (Publisher)

  Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. 218 CHAPTER 6 Amines and Amides 6-10 Selected Biochemically Important Amines L E A R N I N G F O C U S Be familiar with common heterocyclic amines that have the following functions in the human body: (1) neurotransmitter, (2) central nervous system stimulant, and (3) decongestant. Amines that contain no other functional groups than the amino group are often toxic substances and generally are not prevalent in biological systems. On the other hand, many amines that contain additional functional groups besides the amino group are physiologically active compounds that affect the functioning of the human body. Some are naturally present biosynthesized compounds, others are substances isolated from plants, and still others are laboratory-synthesized products that find use in both prescription and nonprescription drugs. In this section, amines that exert the follow-ing types of effects are considered: (1) neurotransmitters, (2) central nervous system stimulants, and (3) decongestants. Two commonly encountered “core” structures for polyfunctional amines with phys-iological effects are the phenethylamine core and the tryptamine core. These two core structures, both of which are encountered in compounds discussed in this section are: CH 2 CH 2 NH 2 CH 2 CH 2 NH 2 N H Phenethylamine core: Tryptamine core: These two structures differ in the ring structure present [benzene versus indole (Figure 6-8)] and are similar in that an ethylamine group is attached to the ring structure. Neurotransmitters Neurotransmitters are substances present in the human body that assist in passing nerve impulses from one cell to another.

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