Protons formation

Positive charge, 77, see also Proton formation of, 242 Positive ions. 207 charge to mass ratio, 243 "seeing, 242 Positron, 218... 

In principle, reactions can be carried out in UHV similarly to the proton formation reaction. By performing experiments in UHV rather than in situ one can manipulate the interface with a high level of precision, and the interface can be probed using the surface techniques mentioned in 4.3, which cannot be used in situ. In practice, the low temperature requirement of UHV and the lack of bulk solution are obstacles not easily overcome.50... 

In the absence of more easily oxidized substrates, residual water in aprotic solvents will undergo oxidation at platinum anodes. However, the mechanism of proton formation is not necessarily by simple water oxidation with the evolution of O2 but may involve radical reactions of the solvent or oxidation of supporting electrolyte anions [6, 7]. The protons produced, together with the most basic species in solution, form... 

In the initiation step, the monomer, M, is initiated by intermediate protonation followed by the formation of a carbocation, H-M+. Propagation can be terminated by anionic or nucleophilic species, A . If a hydroxy-functional compound (ROH) is present, chain transfer can occur via proton formation. 

Table 2. Competition between C-protonation (formation of nitro compounds 45) and O-proton-ation (formation of the Nef-product 47) in the protonation of nitronate ions 44 (s. Scheme 8). The percentage of C-protonated product 45 for different buffers (pyridine/p-toluenesulfonic acid) and unbuffered p-toluenesulfonic acid (48) is listed...

We conclude that the neutral substrate enters 1 to form a host-guest complex, leading to the observed substrate saturation. The encapsulated substrate then undergoes encapsulation-driven protonation, presumably by deprotonation of water, followed by acid-catalyzed hydrolysis inside 1, during which two equivalents of the corresponding alcohol are released. Finally, the protonated formate ester is ejected from 1 and further hydrolyzed by base in solution. The reaction mechanism (Scheme 7.7) shows direct parallels to enzymes that obey Michaelis-Menten kinetics due to the initial pre-equilibrium followed by a first-order rate-limiting step. 

The predominant isomer of protonated formate esters has been assigned structure (5) by the methods used to distinguish the isomers of the protonated acid, described above the coupling constants are almost identical in the two cases. 

The E2 reaction is a concerted process, with a bimolecular rate-determining step. In this case, concerted means that bonding of the base with a proton, formation of a double bond, and departure of the leaving group all occur in one step. 

In the following sections we consider the equilibria involved in the titration of a base B with perchloric acid, a reaction of practical interest the titration of acids with acetic acid as solvent is unimportant. The acidity of the solutions can be determined by an indicator or by the change in potential of an electrode responsive to free solvated protons. In water these two methods give the same results. In acetic acid, measurements of potential depend on the extent of formation of free solvated protons, whereas indicators respond to the extent of proton formation whether ion-paired or not thus two different measures of acidity are possible. The constant for ion-pair generation sometimes may be large, but the constant for dissociation to free ions never is. We discuss here the change in acidity during a titration as it would be obtained potentio-metrically and consider the behavior of indicators in Section 4-11. 

Proton formation in cluster synthesis and Hj reduction of metal cations-oxide cluster (M O ) were reported, and it was suggested that the protons are attached to zeolite interior lattice oxygen, giving acidic OH groups (3800-36(X) cm ) which may accommodate the prepared cluster anions inside zeolite cages ... 

The synthesis of conjugated diynes via the Glaser coupling reaction " is the classical method for homocoupling of terminal alkynes. The coupling reaction is catalyzed by CuCl or Cu(OAc)2 in the presence of an oxidant and ammonium chloride or pyridine to yield symmetrically substituted diynes. " The oxidative dimerization appears to proceed via removal of the acetylenic proton, formation of an alkynyl radical, and its dimerization. 

Fig. 1. Quantum yield of proton formation using several sensitizer and I

In Fig. 5, a correlation between t and l//o is given. The linearity of the plot demonstrates that Eq. 5 is fully obeyed. Under these conditions it is possible to determine the rate of acid formation (R by means of Eq. 6. The given examples demonstrate that polymerization takes place under nearly ideal conditions. Under these circumstances one must find the kinetics of the sensitized proton formation. Using Eqs. 4 and 6 one can formulate ... 

Upon decomplexation, using various methods, cyclopropane products are obtained (see Section 5.2.6.1.1). As an example, synthesis of homotropone (9 bicyclo[5.1.0]octa-3,5-dien-2-one) is achieved starting from cyclooctatetraenetricarbonyliron complex via protonation, formation of the bicylo[5.1.0]octadienylium cation complex 8, nucleophilic addition of sodium hydroxide and oxidative decomplexation. ... 

Accumulated protons generated within the pores of a catalyst cause the formation of a proton gradient. The extent of such a gradient is predominantly a matter of the proton formation rate, which is dependent on the immobilized enzyme s activity and the mass transfer driven transport of protons to the outside of the catalyst particles. At steady state a mass balance occurs. 

Like electrons, protons, muons, and quarks are formed by the interaction of gamma rays, photons, and neutrinos with a particular amount of energy. The situation for proton formation, for example, involves the interaction of gamma rays and neutrinos with a total energy of about 1,000 MeV ... 

Figure 34. Hydrogen-bonded layer in 2(C2Hs)4N HC02-2(NH2)2CS HC02H (2.11) formed by ribbons constructed from thiourea dimers and protonated formate trimers. Broken lines represent hydrogen bonds.

Relevant to water radiolysis in nuclear reactor, G-values of the water decomposition by fast neutrons have been determined by using a fast reactor at elevated temperatures [59]. Since fast neutron radiolysis is equivalent to proton radiolysis because of the recoil proton formation through the elastic collision of fast neutrons with H2O molecules [60], an alternative approach as a model experiment is the ion beam radiolysis with different LET particles from accelerators at elevated temperatures [61]. 

In solution yellow iron(II) species containing one a,a -diimine ligand can be obtained from an excess of Fe + in an acidified solution of the ligand (which controls the amount of available free ligand via protonation). Formation constants for many such complexes of substituted 1,10-phenanthrolines have been reported and tabulated. The rate of formation of [Fe(phen)(H20)4] is rapid and has a very unfavourable entropy of activation ( = 53.6 kJ mol , A5 = — 66.9 J K mor Kinetics of the corresponding reactions with 2,2 -bipyridine have also... 

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