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Amides

Amides. Session 40. Amides. Amides derive from the carboxylic acids, in which the hydroxyl group (-OH) of the carboxylic group has been substituted for a amine group (-NH2). The general formula is: R – C – NH2 O

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Amides

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  1. Amides Session 40

  2. Amides Amides derive from the carboxylic acids, in which the hydroxyl group (-OH) of the carboxylic group has been substituted for a amine group (-NH2). The general formula is: R – C – NH2 O The link between the carbon and the nitrogen atom in amide molecule, is known as the amide or amino bond. It is very stable and it is found as a repetitive bond in the large molecules like proteins and industrial polymers, like nylon.

  3. Nomenclature IUPAC System Amides are named changing the end of the name of the hydrocarbon for ine. The carbon of the amide group is considered part of the hydrocarbon base. CH3- CONH2 CH3CH2CH2CONH2 Ethanamine Butanamine Common names come from the carboxylic acids with the same number of carbon atoms, taking away the word acid and changing the end of the word for amide. CH3- CONH2 CH3CH2CH2CONH2 Acetamine Butyramine

  4. Physical Properties The majority of amides are solids at room temperature. Amides with smaller chains are soluble in water, due to the presence of the polar group amide. This solubility decreases as the molecular weight increases. The boiling and fusion points of amides are generally higher then the corresponding acids. This elevated fusion and boiling points are the result of bonds by hydrogen bridges between the polar amide groups within the amide molecules.

  5. Chemical Properties Reduction with hydride of lithium and aluminum. In this reaction the carbonyl group is reduced to methylene. R – CONH2 + LiAlH4  R – CH2 – NH2 + H2O Hydrolysis to obtain acids: In an acid environment R – CONH2 + H2O + HCl  R – COOH + NH4Cl In a basic environment R – CONH2 + NaOH  R – COONa + NH3

  6. Importance and Applications Urea is a diamide of carbonic acid it is the final product of the metabolism of the proteins of mammals and it is found in urine. Acetaminophen in a substitute analgesic of aspirin. All the proteins are polymers of amino acids bonded by links of amides named peptide.

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