10/29/2023 0 Comments Peptide backbone nitrogen atom![]() ![]() This moderate acidity makes them ideal candidates for ionized drug molecules, which are typically more soluble that their non-ionized counterparts.Īmides are easily detectable with spectroscopic methods due to the presence of two well understood functional groups. This leads to much less acidic behavior than a carboxylic acid (pKa of 4-5) but more acidic than the amine functional group, which typically acts as a base. The ability of primary and secondary amides to donate and accept hydrogen bonds with water also contributes to their solubility.Īmides have a pKa of roughly 16, meaning that they do not want to readily donate a hydrogen molecule. The amide group has a polar surface area of 29 square angstroms, which is less than the comparable carboxylic acid functional group but more than the amine group. This usually makes small molecules containing amides soluble in polar solvents, including water. The amide group is reasonably polar due to the high electronegativities of the oxygen and the nitrogen. This will be explored in the Amides in Proteins paragraph. In biologics, amides are ubiquitous in peptide (protein) drugs as they form the backbone of small proteins. Ubiquitously found in medicinal molecules, amides can hydrogen bond with amino acids in the protein target, ensuring a strong and potent bond with the protein. Note the many amides connecting the repeating units of each polymer. Figure 5: The polymer structure of nylon (top) with the structure of Kevlar (bottom) with hydrogen bonds shown. The below molecules are Nylon (top) and Kevlar (bottom). Exploiting the hydrogen bonding ability of amides (and some clever spacing) creates rigid forces between polymer chains that give Kevlar its strength. On the other hand, Kevlar, one of the strongest synthetic materials, also contains many amides. One of the most common plastics, nylon, is replete with secondary amides, combining flexible carbon groups in between giving nylon its flexible characteristic. Polymers often contain amides for this connective ability. Amides are the most abundant functional group in medicinal molecules, proteins, and plastics due to their versatility as a ‘linker’ to connect two or more moieties. Figure 4: Amide Naming Examples of Molecules with an Amide Functional GroupĪmides are a key organic functional group and form important pieces of both synthetic and natural molecules. To illustrate this, examples of two molecules containing an amide functional group are shown below. Finally, the molecule should end with the suffix -amide. Following IUPAC nomenclature, one should name the rest of the carbon chain appropriately. You should name any substituents attached to the N molecule with the N- prefix. When naming a molecule with an amide functional group, the chain numbering starts at carbonyl carbon and counts away following standard IUPAC chain naming procedures. However, IUPAC has very specific nomenclature for naming amides. When writing out a molecule linearly, amides are written as CON. This discrepancy is caused by the partial delocalization of the carbonyl pi bond to the C-N bond to form an imine. Figure 2: Carboxylic Acid (Left), Amines (Center), Amides (Right)Īmides typically have a C-N bond length of 132 to 134 picometers, shorter than an amine C-N bond. Amides are also similar to amines, which consist of only a nitrogen atom bonded to at least one carbon atom. Note that the quaternary amine carries a positive formal charge, making it useful to form ionic bonds with an anion.Īmides are most structurally similar to carboxylic acids, which have a second oxygen in place of the nitrogen. Figure 1: Primary Amide (Left) Secondary Amide (Center Left) Tertiary Amide (Center Right) Quaternary Amide (Right Based on the number of non-hydrogen groups attached to the nitrogen atom, amides are either classified as primary, secondary, tertiary, or even quaternary. Amide functional groups have a specific layout of atoms, where the nitrogen bonds to the carbonyl carbon. Topics Covered In Other ArticlesĪmides are an organic functional group that consist of a carbon, oxygen, and nitrogen atoms. In this article, the structure, atomic properties, synthesis, reactions, and role in peptide bonding of the amide functional group are explored. Amides are a common and useful organic functional group consisting of a carbon, oxygen, and nitrogen atom. ![]()
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