Dissociation of dimers

Couthon, R Clottes, E. Vial, C. High salt concentrations induce dissociation of dimeric rabbit muscle creatine kinase. Physico-chemical characterization of the monomeric species. Biochim. Biophys. Acta, 1339, 277-288 (1997)... 

There is very little experimental evidence relating to the energetics of dissociation of poly(dienyl)lithium species. From the temperature dependence of the flow times of the concentrated solution viscosities of hexane solutions of poly(isoprenyl)lithium, Morton and Fetters 47) reported an estimate of 37 kcal/mole for the dissociation of dimers (Eq. (5)). 

Pyridinyl radicals are prepared primarily by reduction of the corresponding pyridi-nium ions, but may also be generated for special types of experiments by dissociation of dimers and disproportionation of pyridinium ions and dihydropyridines... 

AlEt2Cl listed in Table 9.4 are the effective values and include the equilibrium constant for dissociation of dimers into monomeric species, i.e.. 

Similar to the bipyrimidine palladium complex, Bercaw and coworkers demonstrated that hydroxy-bridged dimers [ (diimine)Pd(OH) 2]2+ 11 could also effect activation of the allylic C-H bond [25]. Mechansitic studies revealed that the solvent (trifluoroethanol or MeOH) assisted dissociation of dimer 11 to monoca-tionic monomer 12, followed by the rate-limiting -coordination of indene to palladium center, and finally by fast C-H activation (Scheme 9). 

We shall use the following further notation Wy mass of benzene (at equilibrium) containing phenanthrene tffy mass of benzene (at equilibrium) containing benzoic acid M 2 molar mass of phenanthrene M3 molar mass of benzoic acid monomer a degree of dissociation of dimer. 

As indicated in Sections II and III, it is desirable to have a free monomer for reaction. Thus, we have seen that dissociation of dimers... 

BenzoimidazoT2-ylidenes lose less aromatic stabilisation than imidazoT2-ylidenes when they dimerise, and unhindered examples exist as dimers at ambient temperatures. However, two studies have demonstrated that equilibria can be established at higher temperatures. Dissociation of dimer 30 in... 

Rates of formation, and of dissociation, of dimeric iron(m) complexes of cydta, edta, and hedta have been determined as a function of pH. This represents a contribution to the knowledge of the kinetic behaviour associated with M-O-M and M-OH-M systems, to complement the long-known thermodynamic properties of such complexes. T-Jump studies of the dimerisation of iron(m)-edta show one relaxation, ascribed to the equilibrium... 

The step of cationic initiation can be subdivided into two separate reactions. The first one consists of formation of ionic species and the second one of reactions of these ionic species with the olefins, a cationization process. This reaction, termed priming by Kennedy and Marechal, is a process of ion formation in a non-nucleophilic media through (1) dissociation of protonic acids to form protons and counterions, (2) reactions of Lewis acids with Bronsted acids, (3) dissociation of dimeric Lewis acids, (4) complexation of Lewis acids with water or with alkyl halides or with ethers, and so on. These reactions may take place through a series of complicated steps. The second reaction, the cationization of the olefins, may also include several intermediate steps that will eventually lead to propagating species. 

M McLachlan calculation of spin densities and determination of thermodynamic parameters for dissociation of dimer. 

Dissociation of dimers followed by ligand exchange in monomers... 

M. Snels and R. Fantoni, IR dissociation of dimers of high symmetry molecules SFe, SiF4 and SiH4, Chem. Phys. 109 67 (1986). 

If A5a and AZfa are respectively the entropy and enthalpy of dissociation of dimer to momomer, A5r and Hr are the corresponding quantities for r-mer to monomer, and b is the co-volume then the following equations apply. 

At room temperature in cyclohexane, about 15% of the compound is in the form of the simple monomer (Me5C5)2LuCH3. The values of AH and AS for dissociation of dimer to monomer in cyclohexane are 12.6 kcal/mol and 32.8 eu, respectively [198]. 

Cu2(2,2 -0 CsH4 CH=N CH2CH2N=CH-C6H4-0-)2] 394j solution CHCI3 77 811=2.24 81 = 2.03 360 9.18 considerable dissociation of dimeric units in solution 70C1... 

HF/6-31G calculations have been performed to determine thermodynamic parameters for the dissociation of dimeric associates of crotyllithium and 1-lithium-2,6-octadiene and for crotyllithium complexes of butadiene. An equilibrium constant within an order of magnitude of the experimentally determined value for the dissociation was obtained. 

ATP affects only the second process during the dissociation of phos-phofructokinase (Parr and Hammes, 1976). It only delays dissociation of dimer into monomers at the concentration of 50 mM, but neither dissociation of tetramer into dimer nor the conformational change which occurs in the monomer are influenced by the presence of ATP. 

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