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Bond Energies

Bond energies can be very useful for providing estimates of the favourability of reactions by comparing the new bonds made in a reaction (exothermic) with the bonds broken during that reaction (endothermic).

Study Tip:
Remember that bond energies are the energy required to break a bond, that's an endothermic process .... it requires an energy INPUT.
The table shows some representative examples of some of the more common bonds.
 


kJ/mol kcal/mol
Homonulcear diatomics H-H 435
104
F-F 159 38
Cl-Cl 242 58
Br-Br 192 46
I-I 150 36




H-X bonds H-F  568 136 
H-Cl 431 103
H-Br  366 87.5
H-I  297 71
H-OH  497 119
CH3O-H 426 102




C-H bonds CH3-H  435 104
CH3CH2-H  410 98
(CH3)2CH-H  397 95
(CH3)3C-H  380 91
C=C-H  450 108
C≡C-H 535 128
Ar-H 460 110
C=CCH2-H  368 88
ArCH2-H  355 85




C-C bonds CH3-CH3 368 88
CH3CH2-CH3 355 85
(CH3)2CH-CH3 351 84
(CH3)3C-CH3 334 80




C-X bonds CH3-NH2  364  
87
CH3-OH   380 
91
CH3-F  451 108
CH3-Cl  349 83.5
CH3-Br  293 70
CH3-I  234 56
Multiple bonds C=C
 611 
146
C≡C 837 200
C=N  615 147
C=N 891 213
C=O 749 179

© Dr. Ian Hunt, Department of Chemistry, University of Calgary