Chapter 20, Problem 20.75AP

Interpretation Introduction

Interpretation: The fuel values of leucine and isoleucine are to be estimated by considering the average bond energies and without doing the actual calculation. The validation of the fact that the fuel values of the two amino acids be the same is to be stated. The explanation corresponding to the fact that the actual calorimetric measurements show that isoleucine has a lower fuel value than leucine is to be given.

Concept introduction: A fuel is a substance which releases energy on combustion. The released energy may in the form of heat, light or may in other form. Fuel value is one of the basic characteristic of the fuel. It is defined as the amount of energy released by the fuel when $1\text{g}$ of the substance/fuel undergoes complete combustion. Fuel value is calculated by the formula,

$\text{Fuel}\text{value}=\frac{\Delta H_{\text{combustion}}^{\text{°}}}{M}$ (1)

Where,

• $\Delta H_{\text{combustion}}^{\text{°}}$ is the standard enthalpy of combustion.
• $M$ is the molar mass of the hydrocarbon.

To determine: The fuel values of leucine and isoleucine by considering the average bond energies; If the fuel values of the two amino acids be the same; The explanation corresponding to the fact that the actual calorimetric measurements show that isoleucine has a lower fuel value than leucine.