HARDMCQ SINGLEJEE Mains ChemistryInorganic ChemistryGOCAchiever Section
Which of the following compounds possesses the C—H bond with the lowest bond dissociation energy?
A.Toluene✓ Correct
B.Benzene
C.n-pentane
D.2,2-dimethyl propane
Explanation
Toluene is a tertiary free radical. The structure is shown below- Toluene has lowest dissociation energy. Bond dissociation energy depends on the stability of free radical formed after homolytic fission of C-H bond. Higher the stability of free radicals, lesser will be the bond dissociation energy. The order of the stability of free radicals is given by- Toluene >2,2-dimethylpropane > n-pentane > benzene The bond dissociation energy of GENERAL ORGANIC CHEMISTRY 74 6 5 3 6 6 3 2 2 2 3 C H CH 85kcal/mol C H 110kcal/mol CH CH CH CH CH 98kcal/mol Thus, the correct option is (a) Toluene.
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