Heterolytic Bond Cleavages

When heterolytic bond cleavage is favored, the configuration energies as functions of intemuclear distance vary as shown below. 

Configuration correlation diagram for a homonuclear case in which heterolytic bond cleavage is energetically favored. 

State correlation diagram for heteronuclear case in which both heterolytic bond cleavage products are energetically favored relative to homolytic cleavage. 

FIGURE 2.3. The energetics of a heterolytic bond cleavage reaction in a polar solvent. The specific example shown corresponds to the CH3OCH3— CH3 + CH30 reaction in water. The energy of the covalent state does not include the effect of the solvent on this state, but a more consistent treatment (e.g., eq. (2.21) should account for the polarization of the solvent toward the charges of the ionic state. This would result in destabilization of H31. 

In order to clarify the implementation of the LD model in VB calculations, it is useful to apply this model to the heterolytic bond cleavage of... 

Chemical reaction rate, see Rate of reaction Chemical reactions condensed phases, 42-46 enzymatic, see Enzymatic reactions gas phase, see Gas-phase reactions heterolytic bond cleavage, 46, 47, 51,... 

Heitler-London wave function, 15-16 Helium atom, wave function for, 3 Heterolytic bond cleavage, 46, 51, 47,53 Histidine, structure of, 110 Huckel approximation, 8,9,10,13 Hydrocarbons, force field parameters for, 112... 

Excited states can also decay by means of chemical reaction via heterolytic bond cleavage, leading to ions, or by homolytic bond cleavage generating free radicals. 

It is convenient to separate heterolytic bond cleavage and bond formation (ki and k-i) from the transport steps k-, k and k ) for Scheme 2. The values of... 

B. Cases in Which Heterolytic Bond Cleavage is Favored... 

If Figure 3.9a represents bond formation between two molecules, the reverse process would correspond to heterolytic bond cleavage. One notes, however, that in the gas phase heterolytic bond cleavage is never observed. As we shall see, the interaction depicted in Figure 3.9a is the primary interaction between any pair of molecules whether it leads to bond formation or not. It is responsible for van der Waals attraction and hydrogen bonding. 

In heterolytic bond cleavage, both electrons end up on system B. The energy change associated with the bond dissociation is just the difference between electron energies before (2sl) and after (2 ), equation (4.1) and Figure 4.1 ... 

These equations involve bond cleavages of the type shown in color in figure 10.3d. Pyridoxal-5 -phosphate promotes these heterolytic bond cleavages by stabilizing the resulting electron pairs at the a- or /3-carbon atoms of a-amino acids. To do this, the aldehyde group of the coenzyme first reacts... 

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