Question

A decapeptide $\left(Mol. wt. 796\right)$ on complete hydrolysis gives glycine $\left(Mol. wt. 75\right)$, alanine and phenylalanine. Glycine contributes $47.0\%$ to the total weight of the hydrolysed products. Calculate the number of glycine units present in the decapeptide.

Answer 1

Molecular weight of decapeptide $ = 796 g/mol$
Total bonds to be hydrolysed $ = \left(10 - 1\right) = 9$ per molecule
Total weight of $H_{2}O$ added $ = 9 \times 18 =162 g/mol$
Total weight of hydrolysis products $ = 796 + 162 = 958 g$
Total weight $\%$ of glycine (given) $ = 47\%$
Total weight of glycine in product
$= \frac{958 \times47}{100}g =450g$
Molecular weight of glycine $ = 75 g/mol$
Number of glycine molecules $= \frac{450}{75} = 6$