Table 2 Enthalpy changes for the H-bond competing processes (A + B ↔ C + D) of strong ionic H-bonds (ΔH, in kilocalories per mole).

On the basis of the H-bond energies given (25), we list H-bond competing processes, the energy of each H-bond, and the enthalpy change (ΔH) of each process. The strongest H-bond of each process is D, which is on the right side of the process. Because all processes have negative ΔH values, we conclude that the reversible H-bond competing process favors the s-s/w-w H-bond pairing in enthalpy. A, B, C, and D denote the hydrogen bonds of the H-bond competing processes. EA, EB, EC, and ED denote the hydrogen bond energy of A, B, C, and D in kilocalories per mole.

ABCDEAEBECEDΔH
1Cl…H-ClF…H-FCl…H-FF…H-Cl23.138.621.859.8−19.9
2Cl…H-BrF…H-FCl…H-FF…H-Br29.038.621.865.0−19.2
3Cl…H-IF…H-FCl…H-FF…H-I32.038.621.872.0−23.2
4Cl…H-CNF…H-FCl…H-FF…H-CN21.038.621.839.5−1.7
5Br…H-ClF…H-FBr…H-FF…H-Cl19.038.617.059.8−19.2
6Br…H-BrF…H-FBr…H-FF…H-Br20.038.617.065.0−23.4
7Br…H-CNF…H-FBr…H-FF…H-CN16.038.617.039.5−1.9
8I…H-ClF…H-FI…H-FF…H-Cl13.038.615.059.8−23.2
9CN…H-ClF…H-FCN…H-FF…H-Cl37.038.621.159.8−5.3
10F…H-FCN…H-BrCN…H-FF…H-Br38.642.021.165.0−5.5
11CN…H-CNF…H-FCN…H-FF…H-CN20.038.621.139.5−2.0
12Cl…H-IF…H-ClCl…H-ClF…H-I32.059.823.172.0−3.3
13Cl…H-ClF…H-CNCl…H-CNF…H-Cl23.139.521.059.8−18.2
14Br…H-BrF…H-ClBr…H-ClF…H-Br20.059.819.065.0−4.2
15Br…H-ClF…H-CNBr…H-CNF…H-Cl19.039.516.059.8−17.3
16CN…H-ClF…H-CNCN…H-CNF…H-Cl37.039.520.059.8−3.3
17Cl…H-IF…H-BrCl…H-BrF…H-I32.065.029.072.0−4.0
18Cl…H-BrF…H-CNCl…H-CNF…H-Br29.039.521.065.0−17.5
19Br…H-BrF…H-CNBr…H-CNF…H-Br20.039.516.065.0−21.5
20F…H-CNCN…H-BrCN…H-CNF…H-Br39.542.020.065.0−3.5
21Cl…H-IF…H-CNCl…H-CNF…H-I32.039.521.072.0−21.5
22Br…H-BrCl…H-FBr…H-FCl…H-Br20.021.817.029.0−4.2
23I…H-ClCl…H-FI…H-FCl…H-Cl13.021.815.023.1−3.3
24CN…H-FCl…H-ClCl…H-FCN…H-Cl21.123.121.837.0−14.6
25CN…H-FCl…H-BrCl…H-FCN…H-Br21.12921.842.0−13.7
26Br…H-BrCl…H-ClBr…H-ClCl…H-Br20.023.119.029.0−4.9
27CN…H-CNCl…H-ClCl…H-CNCN…H-Cl20.023.121.037.0−14.9
28Br…H-BrCl…H-CNBr…H-CNCl…H-Br20.021.016.029.0−4.0
29CN…H-CNCl…H-BrCl…H-CNCN…H-Br20.029.021.042.0−14.0
30I…H-ClBr…H-FI…H-FBr…H-Cl13.017.015.019.0−4.0
31Br…H-ClCN…H-FBr…H-FCN…H-Cl19.021.117.037.0−13.9
32Br…H-BrCN…H-FBr…H-FCN…H-Br20.021.117.042.0−17.9
33Br…H-BrCN…H-ClBr…H-ClCN…H-Br20.037.019.042.0−4.0
34Br…H-ClCN…H-CNBr…H-CNCN…H-Cl19.020.016.037.0−14.0
35CN…H-CNBr…H-BrBr…H-CNCN…H-Br20.020.016.042.0−18.0
36I…H-ClCN…H-FI…H-FCN…H-Cl13.021.115.037.0−17.9