What is the Difference Between Lactam and Lactim

The key difference between lactam and lactim is that lactam is a class of cyclic amides that occurs as nitrogen analogs of lactones, whereas lactim is a class of cyclic hydroxyl-imides (enols) that occurs tautomeric with lactams.

Lactam and lactim are organic compounds that are related to each other. Lactam is a type of amide that is formally derived from an amino alkanoic acid. Lactim is a cyclic carboximidic acid consisting of an endocyclic carbon-nitrogen double bond.

1. Overview and Key Difference
2. What is Lactam
3. What is Lactim
4. Lactam vs Lactim in Tabular Form
5. Summary – Lactam vs Lactim

What is Lactam?

Lactam is a type of amide formally derived from an amino alkanoic acid. It is a cyclic amide compound. According to its ring size, there are different lactam molecules named using Greek prefixes: alpha-lactam (contains rings with three atoms), beta-lactam (contains rings with four atoms), gamma-lactam (contains atoms with five atoms), etc.

There are several general synthetic methods for the organic synthesis of lactams. Some examples are as follows:

Preparation by the acid-catalyzed rearrangement reaction of oximes in the process of Beckmann rearrangement
Preparation from cyclic ketones and hydrazoic acid during the process of Schmidt reaction
Formation from the cyclization of amino acids
Formation from the intramolecular attack of linear acyl derivatives from the nucleophilic abstraction reaction
During the iodolactamization process
Formation from the copper-catalyzed 1,3-dipolar cycloaddition of alkynes and nitrones during the Kinugasa reaction

Figure 01: Iodolactamization Reaction

Lactim is a derivative of lactam that forms from the tautomerization of lactams. Moreover, lactams can undergo polymerization to form polyamides.

Generally, beta-lactam compounds are useful as antibiotics for the prevention and treatment of bacterial infections that are caused by susceptible organisms. Two examples of this type of antibiotic include penicillins and cephalosporins

What is Lactim?

Lactim is a cyclic carboximidic acid consisting of an endocyclic carbon-nitrogen double bond. These compounds form on the tautomerization of lactam compounds. We can simply define lactim as any of a class of cyclic hydroxyl-imides (or else we call them enols) that occurs as a tautomeric product of lactams.

Moreover, we can describe it as a special case of amide-imidol tautomerism. The tautomerism between lactam and lactim occurs because of the migration of a hydron between the oxygen and nitrogen atoms of these compounds.

What is the Difference Between Lactam and Lactim?

Lactams are related to lactim compounds. These are cyclic organic compounds. Lactam is a type of amide formally derived from an amino alkanoic acid. Lactim is a cyclic carboximidic acid consisting of an endocyclic carbon-nitrogen double bond. The key difference between lactam and lactim is that a lactam is any of a class of cyclic amides that occurs as the nitrogen analogs of lactones, whereas lactim is any of a class of cyclic hydroxyl-imides (enols) that occurs tautomeric with lactams.

Below is a summary of the difference between lactam and lactim in tabular form in tabular form for side by side comparison.

Summary – Lactam vs Lactim

Lactam is a type of amide formally derived from an amino alkanoic acid. Lactim is a cyclic carboximidic acid consisting of an endocyclic carbon-nitrogen double bond. The key difference between lactam and lactim is that lactam is any of a class of cyclic amides that occurs as the nitrogen analogs of lactones, whereas lactim is any of a class of cyclic hydroxyl-imides (enols) that occurs tautomeric with lactams.

Reference:

1. “What Is Lactam Lactim Tautomerism?” BYJUS, 10 Dec. 2020.
2. Peng, Chunte Sam, and Andrei Tokmakoff. “Identification of Lactam–Lactim Tautomers of Aromatic Heterocycles in Aqueous Solution Using 2D IR Spectroscopy.” The Journal of Physical Chemistry Letters, vol. 3, no. 22, 2012, pp. 3302–3306., https://doi.org/10.1021/jz301706a.