Hydrogen halides bond strengths

Table 1.6 Hydrogen-Halogen Bond Lengths and Bond Strengths Hydrogen halide Bond length...

Bond Strength The effect of bond strength is easy to see by comparing the acidities of the hydrogen halides... 

Open-chain alkanes, alkyl halide reduction, 29-31 Organosilicon hydrides bond strengths, 5-6 hypervalent silicon species, 9-11 ionic hydrogenation, 5 trivalent silicon species, 7-9 Orthoesters, reduction of, 97-99 Oxime reduction, 102... 

Because of the lower metal-carbon and metal-hydrogen bond strength, organolead hydrides are particularly unstable species and represent the least stable of those of the group 14 elements. Triorganolead hydrides are obtained at low temperatures by reduction of the halides with LiAlH4 (equation 45), but they decompose at 0 °C. 

These equilibrium constants vary with molarity of the HF solution. Measured values corrected for zero ionic strength at 25 °C are = 6.71 x 10 4 mol 1, K2=3.86 1 mol-1, and K3=2.71mor1 [BrlO, Iul, Wall], implying a dissociation of only a few percent. This unusual behavior is still controversial and has been attributed to the greater strength of the H-F bond compared to the other hydrogen halides [Pal], to the presence of the dimer (HF)2 [Wal], or to polymers that may... 

Variations in atomic radii also contribute to the trend in bond becomes larger, strengths. If the nuclei of the bonded atoms cannot get very close to the electron pair lying between them, the two atoms will be only weakly bonded together. For example, the bond strengths of the hydrogen halides decrease from HF to HI, as shown in Fig. 2.13. 

The amount of adsorbed hydrogen decreases in the presence of halide ions [395, 396]. This is due to a decrease in the M-H adsorption energy induced by ion-specific adsorption with partial charge transfer. The decrease in M-H bond strength results in an increase of overpotential. The effect is lower for Cl and higher for I -. However two joint effects are operative one due to electronic modifications, and the other one of an electrostatic nature related to a change in the local electric potential... 

A selection of the CBE values calculated by Pearson and Mawby are presented in Table ll8). In addition values of CBE for the hydrogen halides have been entered, calculated by the present author9). The values entered are the enthalpy change for the total reaction of n steps. Division of these values by n will give an average CBE per bond which should be possible to use for a fairly just comparison of the strength of the acceptor to donor bond in halides of different types. 

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