Exchange reaction equations

Even under the most inert atmosphere conditions, the 31CP/MAS spectrum of the immobilized ligand showed a major signal at 6 = 42 ppm (wrt 85% H3POO characteristic of phosphine oxide rather than phosphine. This could be quantitatively reduced by HSiCl3 and this surface reaction monitored by NMR but the subsequent exchange reaction (equation [5]) generated substantial quantities of phosphine oxide and a number of different isomeric complexes were f ormed. 

Fig. 2.2 Iii(Keq) for the isotope exchange reaction, equation 2.15 plotted vs. 1,000/T (lighter...

The difference of the translation and rotation energy is more or less the same among the compounds appearing at the left- and right-hand side of the exchange reaction equation, except for hydrogen, where rotation must be taken into account. This... 

Klumpp and Sinnige proceeded similarly, using ec-butyl alcohol to protodelithi-ate the anisoles and other lithiated aryl ethers in di-n-butyl ether. The protodelithiation enthalpies for all the lithiated aryl ethers, as monomers, from the latter study are listed in Table 3. The reaction enthalpies for the o- and p-lithioanisoles are ca 20 kJmop more negative from Reference compared to the ones from Reference, presumably due to differences in the reaction media. From the exchange reaction, equation 17, and the enthalpies of formation of phenyl lithium, benzene and the relevant aryl ether, the enthalpies of formation of the lithiated aryl ethers can be derived. The calculated values are shown in Table 3. 

In 1931 Pr6vost reported the reaction of cinnamyl bromide (13) to cinnamyhnagnesium bromide (14), which was the first example of a bromine-magnesium exchange reaction (equation 10). ... 

Cyclopropyl iodides like 70 and bromides are good substrates for the exchange reaction (equation 44)77,82,83 reaction is stereoselective and sufficiently fast at low temperatures, thus allowing the preparation of functionalized compounds. If a coordinating group like an ester is present in a. gem-dihalocyclopropane like 71, the cA-halogen substituent is exchanged selectively in ether (equation 45). ... 

Recently, the preparation of functionalized benzyUc magnesium reagents 73 could be realized by using a new sulfur-magnesium exchange reaction (equation 47). I/Mg... 

An intramolecular 1,5-C,H insertion reaction was reported from substituted bromo-iodoalkane and halogen-magnesium exchange reaction (equation 24) °. Indeed, treatment of bromoiodoalkane (86) with i-PrMgCl in ether at —78°C to —20°C resulted in the formation of magnesium carbenoid 87. The 1,5-C,H insertion of 87 took place to afford a cyclopentane derivative (88) however, the yield was not satisfactory. 

Monobenzo fused borepins have been prepared by tin-boron exchange reactions (equation 18). Different stabilities to air were noted (208 R = OH) was air-sensitive <7lCC29l), but (208 R = Ph) had an unusual stability (67TL1263). 

Influence ofX Variation on Reaction Rates. The reaction that has been studied most extensively is the ligand exchange reaction (Equation 2), most frequently with the leaving ligand L = (CH30)3P. Using NMR... 

Lithiotrisilanes, which are used as precursors to polysilane dendrimers, have been obtained by a mercury-lithium exchange reaction (equation 25)56,61. The terminally metalated trisilane Me3Si(Me2Si)2Li has been synthesized analogously56. 

The reaction of trimethylgermyllithium with silicon tetrachloride, because of steric hindrance, gave a low yield of tetra(trimethylgermyl)silane, and hexamethyldigermane was obtained as the major product. The digermane resulted from a lithium/halogen exchange reaction (equation 123)32. 

Using the results obtained in the previous section, one can state that as a rule, for the ion-exchange reaction (Equation 7.1) in the case of zeolites with high Si/Al ratio, that is, zeolites with low TEC, AH is not very important. Because the aluminum content in the zeolite is low, the negative charge in the framework is low, and, consequently, the framework electrostatic interaction with the... 

These concepts are illustrated in Fig. 3.10 for the reductive dissolution of hematite (a-Fe,03) in the presence of ascorbic acid at pH 3.26 In this example, Mox = Fe(III), MRed = Fe(II), and LRed = HA, where A2 is the ascorbate anion (log K = -4 for the dissociation of H2A°, but dissociation is invoked nonetheless to promote a ligand-exchange reaction). Equation 3.46 becomes... 

The best results have been obtained in the non-polar solvents heptane or 0-xylene. Polar aprotic solvents such as Me2CO, MeCN, DMSO or dioxane gave poor yields and byproduct formations. Water-free conditions to avoid hydrolysis of BC14- have been necessary. The best fluorination yields have been achieved in the 373-393 K temperature interval (in 0-xylene with TBAF, tetrabutylammonium fluoride). An increase in the yield was observed if an excess of the diazonium salt was used. The total labelling procedure took 50 min. The tetrachloroborate incorporates fluoride by a halide exchange reaction (equation 3)9 10. 

The title compounds 135 have been synthesized176 in up to 85% yields by a facile 18F-for-19F exchange reaction (equation 87) carried out in DMSO or in wet acetonitrile. The [18F]fluoride ion has been prepared also as TBAF salt or as a polymer-bound species177. The possible uses of aryl ethers for synthesis of radiopharmaceuticals are under investigation176. 

Since the values of K s in Equations 2.6-2.8 cannot be determined directly for a given cation, they are calculated from the equilibrium constants (Chapter 1, Equation 1.77) of cation-exchange reactions (Equations 2.9 and 2.10) ... 

Ge dialkoxides, Ge(OR)2, are polymeric if the R groups are small. Ge(0-t-Bu)2 is a cyclic dimmer. When R groups are even bulkier, monomeric compounds, which can usually be sublimed in vacuum, will result readily, examples include R = C-t-Bu3 and C6H2-t-Bu3-2,4,6. They are usually made from GeCh-dioxane, or by exchange reactions (equation 25). ... 

The state splittings discussed above for rl are based on individual reactants which, aside from the bond length constraint (r1 ), are otherwise non-interacting. If we now consider the full initial and final states associated with the exchange reaction (Equations 2-7), we note that the relative energies of high-spin and low-spin states in the bimolecular transition-state complex may be affected by differences in initial and final state coupling, as represented by the electron-transfer matrix element, Hj f, discussed in the introduction. While for the "three-electron ... 

Diols can react with acyclic dialkoxy compounds to effect an exchange reaction (equation 86 ). 

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