Bond enthalpy table

To help answer this question it is worthwhile considering the following the dissociation enthalpies of bonds such as Csp.,—C, Csp-—O, Csp.—Cl, and Cspr— Br also depend heavily on n and increase in the same order, n 3, 2, and 1. The extent of the /(-dependence of the dissocation energies depends on the element which is cleaved off. This is only possible if the -dependence reflects, at least in part, an //-dependence of the respective Cv, -element bond. (Bond enthalpy tables in all textbooks ignore this and assign a bond enthalpy to each Ovp -element bond that is dependent on the element but not on the value of n ) Hence, the bond enthalpy of every. .-element bond increases in the order n = 3,2, and 1. This is so because all Cjp..-element bonds become shorter in the same order. This in turn is due to the s character of the CJ )—element bond, which increases in the same direction. 

The bond dissociation enthalpies of bonds such as C-H, C-Cl, C=0, N=N and O-H are approximately the same in different molecules. If the values of bond dissociation enthalpy for a bond between two atoms (A and B) in several different molecules are averaged, the resulting value is called the mean bond enthalpy (Table 13.4). Mean bond enthalpies are useful in estimating enthalpy changes for reactions for which standard enthalpies of formation are unavailable, but the fact that such values may have been obtained by averaging bond dissociation enthalpies from different types of molecule may lead to substantial errors in the calculated value of AH. ... 

Use average bond enthalpies (Table 8.4) to estimate AH for the atomization of benzene,... 

Organic compounds containing C—O and C—Cl bonds are more reactive than simple alkane hydrocarbons. Considering the comparative ues of C—H,C — C, C—0,and C—Cl bond enthalpies (Table 8.4), why is this so ... 

Two compotmds are isomers if they have the same chemical formula but a different arrangement of atoms. Use bond enthalpies (Table 8.4) to estimate AH for each of the following gas-phase isomerization reactions, and indicate which isomer has the lower enthalpy ... 

When a double bond forms between two atoms, the two bonds are different. There is a strong o bond and a weaker Jt bond. Evidence supporting this model is derived from bond enthalpies (Table 14.4). 

This is a good way of estimating the reactions enthalpy of a large number of reaction using a relatively small table of average bond enthalpies. Table 2.4 lists some average bond enthalpies. With this table the reaction enthalpies of a large number of reactions can be estimated. 

---