What is peptide bond? How is it formed? Write the name and formula of the reagent used to convert alkylhalide to nitroalkane.

Answer: Peptide bond is the −CO−NH− amide link between amino acids; the reagent is silver nitrite, AgNO₂.

Peptide bond: The amide linkage (−CO−NH−) formed between the −COOH group of one α-amino acid and the −NH₂ group of another α-amino acid.

Formation: by condensation with loss of a water molecule, e.g. glycine + alanine:

\(\mathrm{H_2N\text{-}CH_2\text{-}COOH + H_2N\text{-}CH(CH_3)\text{-}COOH \rightarrow H_2N\text{-}CH_2\text{-}CO\text{-}NH\text{-}CH(CH_3)\text{-}COOH + H_2O}\)

The product (Gly-Ala) is a dipeptide.

Reagent: Silver nitrite, AgNO₂ (alcoholic). \(\mathrm{R\text{-}X + AgNO_2 \rightarrow R\text{-}NO_2 + AgX}\)