BDEs of C-H bonds

Practically, all the hydrocarbons have BDE of C—H bonds higher than 300 kJ mol-1, and this method of calculation can be used for them. The enthalpy of reaction was calculated as AH= D(R—H)—220 (kJ mol-1). The weakest bonds participate in this reaction. The pre-exponential factor depends on the reaction enthalpy value for the reactions with high enthalpy [18]. 

The hydroxyl group of alcohol weakens the a-C—H bond. Therefore, free radicals attack preferentially the a-C—H bonds of the secondary and primary alcohols. The values of bond dissociation energy (BDE) of C—H bonds in alcohols are presented in Table 7.1. The BDE values of C—H bonds of the parent hydrocarbons are also presented. It is seen from comparison that the hydroxyl group weakens BDE of the C—H bond by 23.4 kJ mol 1 for aliphatic alcohols and by 8.0 kJ mol 1 for allyl and benzyl alcohols. 

The BDEs of a-C—H bonds of alcoholic and acidic substituents are compared with those of ethers and acids. Both types of BDE of C—H bonds are lower than those of the hydrocarbons. 

BDEs of C-H bonds 3.1 Chain saturated hydrocarbons Table 3.1 C-H BDEs in Chain Saturated Hydrocarbons ... 

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