20.4 Amines and Amides
3 min read•june 25, 2024
and are crucial organic compounds with nitrogen atoms. Amines have a lone pair of electrons, making them basic and nucleophilic. They're classified as , , or based on carbon-nitrogen bonds. Their properties depend on ability.
Amides contain a carbonyl group bonded to nitrogen. They're formed by condensing carboxylic acids and amines. Amides have planar structures due to resonance, lower basicity than amines, and higher melting points. Both groups are vital in biological molecules and pharmaceuticals.
Amines
Structure and properties of amines
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- Amines are organic compounds containing a nitrogen atom bonded to carbon atoms
- Classified as primary (1°), secondary (2°), or tertiary (3°) based on the number of carbon atoms bonded to the nitrogen (, , )
- Nitrogen atom in amines has a lone pair of electrons, making amines basic compounds
- Can accept a proton () to form an ()
- Act as weak bases in aqueous solutions, with basicity increasing from 1° < 2° < 3° (pKa values: 1° ~10, 2° ~11, 3° ~10.5)
- Physical properties of amines are influenced by their ability to form hydrogen bonds
- Lower molecular weight amines are soluble in water due to hydrogen bonding with water molecules (, )
- Higher molecular weight amines are less soluble in water and have higher boiling points (, )
- Amines exhibit high due to the lone pair of electrons on the nitrogen atom
Amides
Formation and characteristics of amides
- Amides are organic compounds containing a carbonyl group (C=O) bonded to a nitrogen atom
- Formed by the between a carboxylic acid and an amine, releasing water (acetic acid + methylamine → + water)
- General formula: R-CO-NH-R' or R-CO-NR'R"
- Amides have a planar structure due to the resonance of the C-N bond
- Partial double bond character of the C-N bond restricts rotation, leading to higher stability
- Amides exhibit lower basicity compared to amines due to the electron-withdrawing effect of the carbonyl group (pKa ~15 for amides vs ~10 for amines)
- Participate in hydrogen bonding, resulting in higher melting and boiling points compared to similar-sized hydrocarbons (acetamide mp 81°C, mp 79°C)
Amines vs amides: comparison
- Functional groups:
- Amines contain a nitrogen atom bonded to carbon atoms (, , )
- Amides contain a carbonyl group bonded to a nitrogen atom (, , )
- Reactivity:
- Amines are basic and can act as nucleophiles in reactions, such as in the formation of amides (nucleophilic acyl substitution)
- Amides are less reactive compared to amines due to the resonance stabilization of the C-N bond
- Amides can undergo hydrolysis under acidic or basic conditions to form carboxylic acids and amines (acetamide + + → acetic acid + ammonia)
- Biological significance:
- Amines are found in many biologically important molecules, such as neurotransmitters (, ) and amino acids (, )
- Amides are present in the peptide bonds that link amino acids in proteins
- Peptide bonds provide stability to protein structures due to their partial double bond character
- Many pharmaceuticals and natural products contain amine or amide functional groups, contributing to their biological activity and therapeutic properties (, )
Key Terms to Review (24)
Acetamide: Acetamide is an organic compound with the chemical formula CH3CONH2. It is a simple amide derived from acetic acid and ammonia, and is a key term in the context of amines and amides, which are important functional groups in organic chemistry.
Amides: Amides are a class of organic compounds that contain a carbonyl group (C=O) bonded to a nitrogen atom. They are formed by the reaction between a carboxylic acid and an amine, and they are important in various biological processes and chemical applications.
Amines: Amines are organic compounds that contain a nitrogen atom with a lone pair of electrons. They are derivatives of ammonia (NH3) where one or more hydrogen atoms have been replaced by alkyl or aryl groups. Amines are an important class of compounds in organic chemistry and are found in various biological systems.
Ammonium Ion: The ammonium ion (NH4+) is a positively charged ion composed of one nitrogen atom and four hydrogen atoms. It is an important species in the context of amines and amides, as it is a key intermediate in various chemical reactions involving these functional groups.
Condensation reaction: A condensation reaction is a chemical process where two molecules combine to form a larger molecule, releasing a small molecule, often water, as a byproduct. This type of reaction is fundamental in the formation of various organic compounds, especially in the synthesis of biomolecules like proteins and nucleic acids. In the context of amines and amides, condensation reactions are crucial for forming these compounds from their respective functional groups.
Decyl Amine: Decyl amine is a primary aliphatic amine with a 10-carbon alkyl chain. It is an important compound in the context of amines and amides, as it serves as a precursor for various chemical reactions and has diverse applications.
Diethyl Amine: Diethyl amine is a primary aliphatic amine with the chemical formula (CH3CH2)2NH. It is a colorless, volatile liquid with a fishy or ammonia-like odor. Diethyl amine is an important organic compound that is widely used in various chemical reactions and industrial applications, particularly in the context of amines and amides.
Dopamine: Dopamine is a neurotransmitter that plays a crucial role in the brain's reward and motivation systems. It is involved in various physiological processes, including motor control, mood regulation, and cognitive function. In the context of amines and amides, dopamine is an important amine that has significant implications for understanding the structure, function, and behavior of these organic compounds.
Ethyl Amine: Ethyl amine is a primary amine compound with the chemical formula CH3CH2NH2. It is a colorless, flammable gas with a fishy odor and is an important organic compound in the context of amines and amides.
Glycine: Glycine is the smallest and simplest amino acid, consisting of a single hydrogen atom attached to the central carbon atom. It is a non-essential amino acid that plays crucial roles in various metabolic processes, particularly in the context of amines and amides.
Hydrogen Bonding: Hydrogen bonding is a type of dipole-dipole intermolecular force that occurs when a hydrogen atom covalently bonded to a highly electronegative element, such as nitrogen, oxygen, or fluorine, experiences an attractive force with another nearby highly electronegative element. This attractive force is significantly stronger than a typical dipole-dipole interaction and has a significant impact on the physical and chemical properties of various compounds.
Lidocaine: Lidocaine is a local anesthetic that is commonly used to numb tissue in a specific area of the body during medical procedures. It belongs to a class of compounds known as amines, which are characterized by the presence of nitrogen atoms, and it also has structural similarities to amides, making it relevant in the study of both categories.
Lysine: Lysine is an essential amino acid that plays a crucial role in various biological processes, particularly in the context of amines and amides. As one of the 20 standard amino acids, lysine is an important building block for proteins and is involved in numerous metabolic pathways within the body.
Methyl Amine: Methyl amine is a primary amine with the chemical formula CH3NH2. It is the simplest organic amine and serves as a building block for the synthesis of more complex amines and other nitrogen-containing compounds. Methyl amine is an important compound in the context of amines and amides, as it provides insight into the reactivity and properties of this class of organic molecules.
Nucleophilicity: Nucleophilicity is a measure of the reactivity and electron-donating ability of a chemical species. It is a fundamental concept in organic chemistry that describes the tendency of a molecule or ion to donate its electrons and form a new covalent bond with an electrophilic (electron-deficient) center.
Octyl Amine: Octyl amine is an organic compound with the chemical formula CH3(CH2)7NH2. It is a primary aliphatic amine, consisting of an eight-carbon alkyl chain attached to an amino group. Octyl amine is an important compound in the context of amines and amides, as it exhibits the characteristic properties and reactivity of these functional groups.
Penicillin: Penicillin is a group of antibiotics derived from the Penicillium fungus, which are widely used to treat bacterial infections. It is a key term in the context of amines and amides, as penicillin contains an amide functional group that is crucial to its antibiotic properties.
Primary: The term 'primary' refers to something that is first, fundamental, or most important in a given context. It denotes the original or principal element, as opposed to something that is secondary, derived, or supplementary.
Propanamide: Propanamide is an organic compound with the chemical formula C$_{3}$H$_{7}$NO, characterized by the presence of an amide functional group attached to a three-carbon propyl chain. It is formed by the reaction of propanoic acid and ammonia or an amine, highlighting its connection to the broader classes of amines and amides, where amides are derived from carboxylic acids and contain a nitrogen atom bonded to a carbonyl group.
Propyl Amine: Propyl amine is a primary aliphatic amine with the chemical formula CH3CH2CH2NH2. It is a colorless, flammable liquid with a strong, fishy odor. Propyl amine is an important organic compound that is relevant in the context of amines and amides, as it serves as a building block for various nitrogen-containing compounds.
Secondary: In chemistry, the term 'secondary' typically refers to a classification of amines and amides based on the number of carbon atoms attached to the nitrogen atom. Specifically, a secondary amine has two carbon groups connected to the nitrogen, while a secondary amide has a similar structure where the nitrogen is bonded to one carbon group and one hydrogen atom. This classification is crucial for understanding the reactivity and properties of these compounds.
Serotonin: Serotonin is a neurotransmitter that plays a crucial role in regulating various physiological and psychological processes in the body. It is primarily produced in the gastrointestinal tract and the central nervous system, and it is involved in the functioning of amines and amides, which are the focus of chapter 20.4.
Tertiary: Tertiary refers to the third stage or level of a sequence or hierarchy. In the context of organic chemistry, it describes the position of a functional group or substituent on a carbon atom within a molecule.
Triethyl Amine: Triethyl amine is a colorless, flammable, and volatile liquid organic compound with a strong, fishy odor. It is a tertiary amine that finds applications in various chemical processes and is an important precursor in organic synthesis.