Amido And Amide: Structure, Preparation, Classification, Different Types

Edited By Team Careers360 | Updated on Jul 02, 2025 05:10 PM IST

Amide is classified as any member that belongs to two classes of nitrogen campaigning compound either it can be ammonia or that can be amine. Amide that are formed by the sharing of the electrons are neutral and sometimes they are very weakly acidic substance that are formed by the replacement of hydroxyl group (-OH) of an acid with the help of the amino group (NR2) in which R represents the hydrogen atom or any other of the alkyl groups such as the methyl group or any other alkyl group).

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Structure of Amide:
Difference Between Amide And Amido Group
Preparation Of Amides :
Classification Of Amides:
Different Types Of Amide And Their Properties:

When the amides formed by the sharing of electrons are derived from the ammonia then they are solid except for the formamide which is a liquid kind amide. Amides that are derived from ammonia and those that contain less than 5 carbon numbers are usually soluble in water. These amides formed by the sharing of electrons pose no free electrons so they are the non conductor of electricity. These have usually high boiling points.

Structure of Amide:

It is defined as a compound that poses a carbonyl functional group and this carbonate functional group is linked to both the amine and hydrocarbon group of the chain. Carbonyl functional group is made up of the double bonded carbon atom and oxygen atom remains attached to that of the carbon atom.

The general structure of amide is as :

R(C=O)NR'R"

In this structure R, R' & R" represents hydrocarbons that are made up of carbon and use hydrogen as substituent.

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Difference Between Amide And Amido Group

There is not much difference between these two of the group The only difference that indicates is amido group indicates the presence of an amide group in it.

Preparation Of Amides :

1. Amine acylation :

Generally amides are formed by the reaction of an amine with the help of a carboxylic acid derivative.

In the structure of amine nitrogen possesses a lone pair of electrons and it attacks the electron deficient carbonyl carbon. Now this carbonyl carbon forms the bond with that of the nitrogen atom.

When a bond is formed the elimination of protons from the amine occur and the leaving group forms the amide.

2. Nitrile hydrolysis:

As the name suggests when the nitrile group is lysed with the help of water it is termed as the nitrile(RCN) hydrolysis.

In this reaction the amide group is formed by the partial hydrolysis of the nitriles but some basic or acidic condition should be given.

3. Beckmann rearrangement :

It is the most used amide synthesis method and the most important method.In this reaction amide is formed by the help of the oxime group. The oximes are rearranged to form the amides in the presence of many activating agents such as sulfuric acid or phosphorus chloride.

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Classification Of Amides:

Amides are generally categorized into three different categories that are :

Primary amide :

These are defined as those amides in which the nitrogen atom substitute of the amide possesses only one hydrogen atom.

Secondary amide:

Those amides in which an amide nitrogen atom is linked to the hydrocarbon substituent of the atom.

Tertiary amide:

These are defined as those amides in which the nitrogen amide is attached to the three carbon.

Cyclic amides:

Cyclic amides are also known as lactam.

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Different Types Of Amide And Their Properties:

Examples of amides

Formamide

Condensed structure : HCONH2

Melting point : 2°C

Boiling point : 193°C

Solubility in water : Yes formamide is soluble.

Acetamide

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Condensed structure : CH3CONH2

Melting point : 82°C

Boiling point : 222°C

Solubility in water : Yes acetamide is soluble.

Propionamide

Condensed structure : CH3CH2CONH2

Melting point : 81°C

Boiling point : 203°C

Solubility in water : Yes it is soluble

Benzamide

Condensed structure : C6H5CONH2

Melting point : 132°C

Boiling point : 290°C

Solubility in water : soluble only in some amount

Basicity of amides:

When compared with the amines, amides are found to be a very weak basic structure.Conjugate acid of amines possesses the pKa of roughly 9.5, and conjugate acid of an amide has a pKa of around 0.5.

So we can observe amides do not possess clear acid–base characteristics in water. The carbonyl carbon is an electron withdrawing group so it withdraws electrons from the amide and so explains the lack of basicity. But when compared with other groups such as carboxylic acids, esters, aldehydes, and ketones (their conjugate acids' pKas range from 6 to 10) aminde are found to be more basic than these groups.

Frequently Asked Questions (FAQs)

1. What are the properties of covalent amides?

2. What are polyamides?

When many amide groups are joined together by the help of covalent bonds these are termed as polyamides. They are present in a protein rich diet.

3. What is the hybridization of amides?

Hybridization is defined as the intermixing of atomic orbitals to form a hybrid orbital. Hybridization of amides is found out to be sp3. We can explain it as the electrons of three p orbitals are engaged on three atoms: oxygen, carbon and nitrogen and s orbital of hydrogen are on the same plane and delocalized.

4. Write about the solubility of amides?

Lower amides that are amides with lower number of carbon atoms are highly soluble in water as they are involved in hydrogen bonding with that of water. They act both as electron donor and electron acceptor as they have presence of both Nitrogen and oxygen.

5. Write the name of cyclic amides?

Lactam amides are known as cyclic amides.

6. What is the difference between an amide and an imide?

An amide contains one carbonyl group attached to a nitrogen, while an imide contains two carbonyl groups attached to the same nitrogen atom. Imides are typically cyclic compounds and are more acidic than amides due to the increased electron-withdrawing effect of the two carbonyl groups.

7. How does the reactivity of amides compare to that of carboxylic acids?

Amides are generally less reactive than carboxylic acids. This is due to the resonance stabilization in amides, which makes the carbonyl carbon less electrophilic. As a result, amides are more resistant to nucleophilic attack and require harsher conditions for hydrolysis compared to carboxylic acids.

8. How does the presence of electron-withdrawing or electron-donating groups affect the reactivity of amides?

Electron-withdrawing groups attached to the carbonyl carbon increase the electrophilicity of the carbonyl group, making the amide more reactive towards nucleophiles. Conversely, electron-donating groups on the nitrogen can increase electron density in the amide, making it less reactive. These effects can significantly influence the rate and ease of amide hydrolysis and other reactions.

9. What is the Hofmann rearrangement, and how is it relevant to amides?

The Hofmann rearrangement is a reaction where primary amides are converted to primary amines with one fewer carbon atom. It involves treating the amide with bromine and a strong base, typically sodium hydroxide. This reaction is relevant to amides as it provides a method for synthesizing primary amines and demonstrates the unique reactivity of the amide functional group.

10. What is the Gabriel synthesis, and how does it relate to amides?

The Gabriel synthesis is a method for preparing primary amines using phthalimide as a key intermediate. While not directly involving amides, it's related to amide chemistry as phthalimide is a cyclic imide (a type of amide). The method involves forming an N-alkyl phthalimide, which is then hydrolyzed to yield a primary amine. This synthesis is valuable because it allows for the selective preparation of primary amines.

11. What is the difference between an amide and an amido group?

An amide is a functional group consisting of a carbonyl (C=O) bonded to a nitrogen atom, while an amido group is a functional group derived from ammonia by replacing one hydrogen atom with an acyl group. The key difference is that amides are compounds, while amido groups are substituents within larger molecules.

12. How does the basicity of the nitrogen in amides compare to that in amines?

The nitrogen in amides is significantly less basic than in amines. This is because the lone pair on the nitrogen in amides is delocalized into the carbonyl group through resonance, making it less available for protonation. As a result, amides are very weak bases compared to amines and do not typically form stable salts with acids.

13. How does the presence of an amide group affect the NMR spectrum of a molecule?

The presence of an amide group significantly affects the NMR spectrum:

14. What is the difference between an amide and a lactam?

An amide is a general term for compounds containing the RCONR'R" functional group, while a lactam is a specific type of cyclic amide. In lactams, the amide group is part of a ring structure. Lactams are important in organic synthesis and are found in many natural and synthetic compounds, including some antibiotics.

15. How does the structure of an amide influence its ability to act as a ligand in coordination chemistry?

Amides can act as ligands in coordination chemistry through their carbonyl oxygen, which can donate a lone pair to a metal center. The planar structure of amides allows for good orbital overlap. However, amides are generally weaker ligands compared to amines due to the reduced electron density on the oxygen caused by resonance with the nitrogen. The ability to act as a ligand can be enhanced by nearby electron-donating groups.

16. Why are amides generally more stable than esters?

Amides are generally more stable than esters due to the resonance stabilization between the nitrogen lone pair and the carbonyl group. This resonance creates a partial double bond character between C and N, making the amide linkage stronger and more resistant to hydrolysis compared to esters.

17. How does the basicity of amides compare to that of amines?

Amides are generally much less basic than amines. This is because the lone pair on the nitrogen in amides is delocalized into the carbonyl group through resonance, making it less available for protonation. In contrast, the lone pair in amines is more readily available, making them stronger bases.

18. What is the key structural feature that distinguishes primary, secondary, and tertiary amides?

The key structural feature that distinguishes primary, secondary, and tertiary amides is the number of substituents on the nitrogen atom. Primary amides have two hydrogens on the nitrogen, secondary amides have one hydrogen and one carbon-containing group, and tertiary amides have two carbon-containing groups and no hydrogens on the nitrogen.

19. How does the structure of an amide contribute to its unique properties?

The structure of an amide includes a planar arrangement around the nitrogen atom due to resonance. This results in a partial double bond character between the carbon and nitrogen, leading to restricted rotation around the C-N bond. This structural feature contributes to the high boiling points and polarity of amides.

20. How does the presence of an amide group affect the solubility of a molecule?

The presence of an amide group generally increases the solubility of a molecule in polar solvents like water. This is due to the amide group's ability to form hydrogen bonds with water molecules through both its N-H and C=O portions. However, the overall solubility also depends on the rest of the molecule's structure.

21. What is the primary method for preparing amides in the laboratory?

The primary method for preparing amides in the laboratory is the reaction between carboxylic acids (or their derivatives like acid chlorides) and amines. This reaction, known as amide synthesis or condensation, involves the nucleophilic addition of the amine to the carbonyl group, followed by the elimination of water or HCl.

22. What is the Beckmann rearrangement, and how does it relate to amides?

The Beckmann rearrangement is a reaction that converts oximes to amides. It involves the migration of a group from the carbon atom to the nitrogen atom, with the simultaneous loss of water. This reaction is important in organic synthesis as it provides a method for preparing amides, especially cyclic amides (lactams), from ketones via their oximes.

23. What is the Ugi reaction, and how does it relate to amide synthesis?

The Ugi reaction is a multi-component reaction that forms a bis-amide product from a carboxylic acid, an amine, an aldehyde or ketone, and an isocyanide. It's a powerful method for synthesizing complex amides in a single step, allowing for the rapid generation of diverse amide-containing compounds. This reaction is particularly useful in combinatorial chemistry and drug discovery due to its versatility and efficiency.

24. What is transamidation, and why is it important in organic synthesis?

Transamidation is a reaction where the nitrogen component of an amide is exchanged with another amine. This reaction is important in organic synthesis because it allows for the modification of existing amides without affecting the carbonyl portion. It's particularly useful in the synthesis of complex amides and in the modification of peptides and proteins.

25. What is the mechanism of amide hydrolysis under basic conditions?

The mechanism of amide hydrolysis under basic conditions involves:

26. What is the significance of the planarity in amide structures?

The planarity in amide structures is significant because it allows for maximum overlap between the nitrogen's lone pair and the π-system of the carbonyl group. This results in resonance stabilization, which contributes to the amide's stability, influences its reactivity, and affects its physical properties like boiling point and solubility.

27. What is the significance of cis-trans isomerism in amides?

Cis-trans isomerism in amides is significant because the C-N bond in amides has partial double bond character, restricting rotation. This can lead to distinct cis and trans isomers, particularly in N-substituted amides. This isomerism can affect the physical properties, reactivity, and biological activity of amides, and is particularly important in peptide chemistry.

28. How does the resonance in amides affect their IR spectroscopy?

The resonance in amides affects their IR spectroscopy by shifting the carbonyl stretching frequency to lower wavenumbers compared to other carbonyl compounds. This is due to the partial double bond character between C and N, which weakens the C=O bond. The N-H stretching frequency is also affected, appearing at higher wavenumbers due to hydrogen bonding.

29. How do amides participate in hydrogen bonding, and why is this important?

Amides can participate in hydrogen bonding both as donors (through the N-H bond) and acceptors (through the C=O group). This dual capability allows amides to form strong intermolecular interactions, contributing to their high boiling points and the stability of protein structures in biological systems. It's particularly important in maintaining the secondary and tertiary structures of proteins.

30. What is the importance of amide bonds in biological systems?

Amide bonds, also known as peptide bonds in biological contexts, are crucial in biological systems as they form the backbone of proteins. They link amino acids together, allowing for the formation of complex protein structures. The stability and specific geometry of amide bonds contribute to the three-dimensional structure and function of proteins.

31. How does the presence of an amide group affect the acidity of nearby protons?

The presence of an amide group can increase the acidity of nearby protons, especially those on the α-carbon (the carbon adjacent to the carbonyl). This is due to the electron-withdrawing nature of the amide group, which can stabilize the resulting anion through resonance. This effect is important in the chemistry of peptides and proteins.

32. How does the presence of an amide group affect the UV-Vis spectrum of a molecule?

The presence of an amide group can affect the UV-Vis spectrum by:

33. What is the difference between an amide and a peptide?

While both contain amide bonds, a peptide specifically refers to a short chain of amino acids linked by amide bonds (also called peptide bonds in this context). An amide is a more general term for any compound containing the RCONR'R" functional group. Peptides are a subset of amides that are biologically significant and form the building blocks of proteins.

34. How does the presence of an amide group affect the melting and boiling points of a compound?

The presence of an amide group generally increases the melting and boiling points of a compound. This is due to the strong intermolecular hydrogen bonding capabilities of amides, which can act as both hydrogen bond donors (N-H) and acceptors (C=O). These strong intermolecular forces require more energy to overcome, resulting in higher melting and boiling points compared to similar-sized molecules without amide groups.

35. How does the electronic structure of amides contribute to their stability?

The electronic structure of amides contributes to their stability through resonance. The lone pair on the nitrogen atom can delocalize into the π system of the carbonyl group, creating a partial double bond character between C and N. This resonance stabilization reduces the electrophilicity of the carbonyl carbon and the nucleophilicity of the nitrogen, making amides more stable and less reactive than many other carbonyl compounds.

36. What is the significance of amide rotamers?

Amide rotamers are different conformations that arise due to restricted rotation around the C-N bond in amides. This restriction is caused by the partial double bond character of the C-N bond due to resonance. Rotamers can have different physical and chemical properties, and their interconversion can be observed in NMR spectroscopy. Understanding rotamers is crucial in predicting and explaining the behavior of amides, especially in biological systems and in the design of drugs containing amide bonds.

37. How does the presence of an amide group affect the pKa of nearby functional groups?

The presence of an amide group can affect the pKa of nearby functional groups through inductive and resonance effects:

38. How does the presence of an amide group affect the reactivity of neighboring double bonds?

The presence of an amide group can affect the reactivity of neighboring double bonds in several ways:

39. What is the difference between an amide and a thioamide?

The main difference between an amide and a thioamide is that in a thioamide, the oxygen of the carbonyl group is replaced by a sulfur atom (R-CS-NR2). This structural change leads to several differences:

40. How does the presence of an amide group affect the acidity of carboxylic acids?

The presence of an amide group generally increases the acidity of carboxylic acids:

41. What is the Vilsmeier-Haack reaction, and how does it relate to amide chemistry?

The Vilsmeier-Haack reaction is a method for introducing an aldehyde group into an aromatic ring using a combination of phosphorus oxychloride (POCl3) and an amide, typically dimethylformamide (DMF). While not directly producing amides, this reaction showcases the unique reactivity of amides:

42. How does the presence of an amide group affect the basicity of pyridine rings?

The presence of an amide group attached to a pyridine ring generally decreases its basicity: