Key Properties and Classifications of Amides
Amide is a nitrogen-containing compound that belongs to one of two classes: ammonia and amines. When the hydroxyl group (OH) of an acid is replaced by an amino group, the result is a neutral or very weakly acidic compound (NR2, in which R may represent either as a hydrogen atom or an organic combining group, which is such as methyl, CH3). The most important group is carboxamides (R′CONR2), which are derived from carboxylic acids (R′COOH). Sulfonamides (RSO2NR2) are related to sulfonic acids in structure (RSO3H).
Ionic amides, also known as saltlike amides, are extremely alkaline compounds made by reacting ammonia, an amine, or a covalent amide with a reactive metal such as sodium. The amide formula or the amide group formula is CO-NH.
Covalent Amides
With the exception of formamide, which is a liquid, covalent amides produced from ammonia are solids; those with fewer than five carbon atoms are water soluble. They are nonconductors of electricity and are both organic and inorganic solvents.Even covalent amides with low molecular weight have high boiling points.
Although polyamides (amides joined together to create huge molecules called polymers) are abundant as the protein of living systems, there are no practicable natural sources of simple covalent amides. Simple amides are usually created by reacting acids or acid halides with ammonia or amines. They can also be created when water reacts with nitriles.
Hydrolysis (a chemical reaction with water) is the reaction by which covalent amides are changed to acids and amines; this reaction is usually slow unless it is catalysed by a strong acid, an alkali, or an enzyme. Amides can also be dehydrated to produce nitriles. Amides are difficult to oxidise or reduce, however hydrogenation (the addition of hydrogen at high temperatures and pressures) will convert most carboxylic acid amides to amines in the presence of a catalyst.
Lithium aluminium hydride, a powerful reducing agent, converts amides to amines. Imides are compounds having two carbonyl (CO) groups linked to the same nitrogen atom created by reacting amides with acid chlorides or anhydrides.
Acetamide, also known as ethanamide (CH3CONH2), and dimethylformamide HCON(CH3)2, which are used as solvents, sulfa drugs, and nylons, are among the commercially important amides. Urea, also known as carbamide [CO(NH2)2], is a crystalline compound produced as a byproduct of protein synthesis and removed in the urine of mammals. It's made from ammonia and carbon dioxide in large quantities for use in fertilisers, animal feed, and the production of urea-formaldehyde resins, which are used to make plastics.
Amide Nomenclature
Let us study what is an amide and the amide nomenclature. The term "amide" is added to the stem of the parent acid's name in standard nomenclature. Acetamide, for example, is the amide derived from acetic acid (CH3CONH2). Although the IUPAC recommends ethanamide, this and other formal names are rarely used. The nitrogen substituents occur first in the name of an amide produced from a primary or secondary amine.
The amide formula or the acid amide formula is CO-NH.
N,N-dimethylacetamide (CH3CONMe2, where Me = CH3) is the amide formed from dimethylamine and acetic acid. Even the name is usually shortened to dimethylacetamide. Lactams are cyclic amides that are either secondary or tertiary in nature.
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Production of Amide
Amides are compounds with nitrogen atoms attached to the carbonyl group's carbon atom. Various nomenclature requirements apply to amides, just as they do to amines, but they all include the class-specific suffix –amide:
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In the process of amidation, carboxylic acids react with amines or ammonia to produce amides. The amide is formed from the residual bits of the carboxylic acid and the amine when a water molecule is removed from the reaction:
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The production of amides from amines and carboxylic acids is a biologically relevant process. Amino acids (molecules with both amine and carboxylic acid substituents) link together in a polymer to make proteins through this process.
Types of Amides
When visiting an amide, there are a few things you should know about nomenclature, whether it's a name or a structure. Primary amine, secondary amine, and tertiary amine are the three types of amines based on their names. The differences are classified according to the position of the nitrogen atom in relation to the carbon atom in the chain of a molecule. When identifying a primary amide, use 'ic acid' or 'oic acid' at the end, followed by a 'amide'.
To show that nitrogen is related to an alkyl group, the Secondary amide is termed by integrating an N. A hydrocarbon chain with hydrogen and carbon atoms is known as an alkyl group.
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Amide Functional Group
The amide functional groups lead to the identification and recognition of a specific group of atoms within a larger molecule. Alkanes to alcohols, including our special friend, amide, are examples of functional groups. An amide is a functional group with a carbonyl group and a nitrogen atom that can be generated from various carboxylic acid functional groups.
Amide Structure
Let us look at the amide structure.
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To remember the amide structure, all you need to remember is that an amide compound must have a nitrogen atom.
The carbonyl group is composed of two carbon atoms that are double bonded to an oxygen atom.
The amine group, in which a nitrogen atom shares a single bond with R groups, is the second. R groups can be regarded of as substituents for other atoms or molecules in a structure.
Finally, there is a single bond, which is also an amide's defining functional group.
The structure of three different types of amides is shown in the diagram above. For three different amides, the nitrogen atom is not in the same position. In the case of a primary amide, a nitrogen atom is linked to a single carbon atom. In the case of secondary amine, the nitrogen atom is linked to two carbon atoms. The nitrogen in tertiary amide is linked to three carbon atoms.
Basicity
Amides are very weak bases as compared to amines. An amine's conjugate acid has a pKa of roughly 9.5, whereas an amide's conjugate acid has a pKa of around 0.5. As a result, amides don't have as clear acid–base characteristics in water. The carbonyl withdraws electrons from the amine, which explains the relative lack of basicity. Amides, on the other hand, are far more powerful bases than carboxylic acids, esters, aldehydes, and ketones (their conjugate acids' pKas range from 6 to 10).
Key Points of Amide
A nitrogen atom is bonded to a carbonyl carbon atom in the typical structure of amides.
The acid amide formula or the amide group formula is CO-NH.
An amide's functional group is as follows:
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The -ic acid of the common name or the -oic ending of the IUPAC for the corresponding carboxylic acid is replaced by -amide in the names for amides.
FAQs on Amide: Definition, Structure & Importance
1. What is an amide in chemistry?
An amide is an organic compound derived from a carboxylic acid, featuring a nitrogen atom bonded to a carbonyl group (C=O). The general formula for a primary amide is R-CO-NH₂, where 'R' can be a hydrogen atom, an alkyl group, or an aryl group. They are a fundamental class of compounds in organic chemistry.
2. What is the main difference between an amide and an amine?
The key difference is the presence of a carbonyl group. An amine has a nitrogen atom bonded to carbon and/or hydrogen atoms (e.g., R-NH₂). An amide has a nitrogen atom bonded directly to a carbonyl group (R-CO-NH₂). This structural difference makes amides significantly less basic than amines because the nitrogen's lone pair of electrons is delocalised by resonance.
3. How does the structure of the amide functional group affect its properties?
The structure of the amide functional group (-CONH-) leads to unique properties due to resonance. The delocalisation of the nitrogen's lone pair of electrons into the carbonyl group creates a partial double bond character in the C-N bond. This results in several key characteristics:
- Planarity: The atoms involved in the amide group lie in the same plane, which is crucial for the structure of proteins.
- Reduced Basicity: The nitrogen atom is not a good proton acceptor, making amides neutral compounds, unlike basic amines.
- High Boiling Points: Amides form strong intermolecular hydrogen bonds, leading to higher boiling points compared to carboxylic acids of similar molecular mass.
4. What are some common real-world examples of amides?
Amides are found in many natural and synthetic materials. Simple laboratory examples include acetamide (CH₃CONH₂) and benzamide (C₆H₅CONH₂). Important large-scale examples include:
- Proteins: The peptide bonds linking amino acids are amide linkages.
- Nylon: A synthetic polymer widely used in textiles and engineering, which is a polyamide.
- Urea: A simple diamide that is a major organic component of human urine.
- Pharmaceuticals: Many drugs, such as Paracetamol, are amides.
5. How are amides typically prepared according to the CBSE syllabus?
As per the NCERT curriculum for the 2025-26 session, amides can be synthesised using several key methods:
- From Carboxylic Acids: Reacting a carboxylic acid with ammonia or an amine, followed by heating to dehydrate the intermediate ammonium carboxylate salt.
- From Acid Derivatives: Reacting acid chlorides or acid anhydrides with ammonia or amines (ammonolysis). This is a very efficient method.
- Partial Hydrolysis of Nitriles: Controlled hydrolysis of nitriles (cyanides) using an acid or base can yield amides.
6. Why are amides considered neutral or only very weakly basic?
Amides are neutral because the lone pair of electrons on the nitrogen atom is not available to accept a proton (H+). This is due to resonance. The electron-withdrawing effect of the adjacent carbonyl oxygen pulls the lone pair into the C=O bond, delocalising it across the O-C-N system. This makes the nitrogen electron-deficient and thus unable to act as a significant base.
7. What is the primary application of the Hofmann bromamide degradation reaction?
The Hofmann bromamide degradation reaction is a vital method in organic synthesis used to prepare primary amines from amides. When an amide is treated with bromine in an aqueous solution of NaOH, it forms a primary amine that has one carbon atom less than the starting amide. This makes it an excellent 'step-down' reaction for shortening a carbon chain in a molecule.
8. What are the products when an amide undergoes hydrolysis?
When an amide is heated with an aqueous solution, it undergoes hydrolysis, breaking the amide bond. The products depend on whether the conditions are acidic or basic:
- In an acidic medium (e.g., with aq. HCl), the products are a carboxylic acid and an ammonium salt.
- In a basic medium (e.g., with aq. NaOH), the products are a salt of the carboxylic acid (a carboxylate) and ammonia gas.
