Chapter 8.1, Problem 13SSC

Interpretation Introduction

Interpretation: Relative bond dissociation energies of double and triple bonds need to be explained.

Concept Introduction: The bond length is inversely proportional to bond strength.

Answer to Problem 13SSC

Triple bond dissociation energy is always greater than double bond dissociation energy.

Explanation of Solution

In triple bond, there are $3$ bonds linked between the carbons where are in double bond there are only two. The bond dissociation energy of the triple bond is $839\text{ kJ/mole}$ . The bond dissociation energy of a double bond is $6\text{14 kJ/mole}$ . So it is always hard to break a triple bond than a double bond.

Conclusion

Bond dissociation energy needed to break $\boxed{a}$ is greater than $\boxed{b}$ ,

  $\boxed{a}\to \text{H}-\text{C}\equiv \text{C}-\text{H}$

  $\boxed{b}\to {\text{H}}_{\text{2}}\text{C}={\text{CH}}_{\text{2}}$

Note: If single bond carbons are also included then the order of the bond dissociation energy will be:

  $\text{C}\equiv \text{C}>\text{C}=\text{C}>\text{C}-\text{C}$ .