Protolysis

Protoiiation (and protolysis) of alkanes is readily achieved with superacids. The protonation of methane itself to CH5, as discussed earlier, takes place readily. 

The superacid-catalyzed cracking of hydrocarbons (a significant practical application) involves not only formation of trivalent carbo-cationic sites leading to subsequent /3-cleavage but also direct C-C bond protolysis. 

These reactions involve the intermediate formation of thiols, followed by condensation to the sulfides. The observation of isomerized products in suitable cases indicates the intermediate formation of carbocations, either by protolysis of alkanes by the superacid or reversible ionisation of the thiol products (149). 

The polar tellurium(II)-nitrogen bond is readily susceptible to protolysis by weakly acidic reagents. Eor example, the reaction of [Te(NMe2)2]oo with two equivalents of Ph3CSH produces the monomeric thiolato derivative Te(SCPh3)2. Alkynyl tellurides may be prepared by the reaction of terminal acetylenes with arenetellurenamides (Eq. 10.13). ... 

The 12,21 reaction is sometimes called neutralization, the 13,31 reaction is protolysis, and the 23,32 reaction is hydrolysis. 

Another phenomenon that is closely associated with acid-base equilibria is the so-called hydrolysis of metal cations in aqueous solution, which is probably better considered as the protolysis of hydrated cations, e.g. ... 

DFT molecular dynamics simulations were used to investigate the kinetics of the chemical reactions that occur during the induction phase of acid-catalyzed polymerization of 205 [97JA7218]. These calculations support the experimental finding that the induction phase is characterized by the protolysis of 205 followed by a rapid decomposition into two formaldehyde molecules plus a methylenic carbocation (Scheme 135). For the second phase of the polymerization process, a reaction of the protonated 1,3,5-trioxane 208 with formaldehyde yielding 1,3,5,7-tetroxane 209 is discussed (Scheme 136). 

Research into the mechanism of diazotization was based on Bamberger s supposition (1894 b) that the reaction corresponds to the formation of A-nitroso-A-alkyl-arylamines. The TV-nitrosation of secondary amines finishes at the nitrosoamine stage (because protolysis is not possible), but primary nitrosoamines are quickly transformed into diazo compounds in a moderately to strongly acidic medium. The process probably takes place by a prototropic rearrangement to the diazohydroxide, which is then attacked by a hydroxonium ion to yield the diazonium salt (Scheme 3-1 see also Sec. 3.4). 

The first one, (A), includes (b) insertion of CO into the Pd-S bond (c) insertion of the C C triple bond of the enyne into the Pd-C(0)SR bond whereby Pd binds to the terminal carbon and the RSC(O) group to the internal carbon, and (d) C-H bond-forming reductive elimination or protolysis by the thiol to form 29 (Scheme 7-7). 

In 1996, Ogawa et al. reported the hydrothiolahon of an allene catalyzed by Pd(OAc)2 to provide 32, whose formahon can be explained as follows (1) insertion of the allene into the Pd-S bond of Pd(SPh)2 to give a tt-allyl palladium thiolate 33, and (2) protolysis by PhSH to form 32 and Pd(SPh)2 (Eq. 7.24) [35], The authors proposed the direct reachon of a o-aHyl palladium with PhSH before the formation of 33. 

These reactions could proceed either via (1) insertion of the alkyne or the allene into the M-Se bonds, and (2) C-H bond-forming reductive elimination (or protolysis by selenol) or via (1) insertion of the alkyne or the aUene into the M-H bond, and (2) C-Se bond-forming reductive elimination. 

Dienols with 2 equiv. of 1 gave the corresponding bimetallic alkoxide organozir-conocene complexes however, protolysis allowed recovery of the alcohol functionality (Scheme 8-29) [107]. Alcohols can also be easily converted to ethers. Alkyl, aryl, silyl [85,112,183, 210] and THP [17, 153, 211, 219] ethers are stable under hydrozirconation conditions side products were observed only with the trimethylsUyl group [220, 221]. 

As a consequence of the high conductivities of H30+ and OH in comparison with those of Na+ and Cl, eqns. 2.28 and 2.29 will yield straight lines with negative and positive slopes, respectively. In practice, therefore, both straight lines are drawn through a sufficient number of measuring points for extrapolation to yield an intersection at, the equivalence point. According to eqn. 2.30, at A (see Fig. 2.4) some curvature may occur as a consequence of the protolysis... 

This equation corresponds to today s general convention of expressing base strength also be means of pKa, where K is considered in the sense of the Bronsted acid-base theory as a protolysis constant of the following protolytic reactions for acids ... 

The proton exchange is called protolysis solvation as a general term means hydration in the case of water, the dielectric constant (e = 78) of which is so high... 

In amphiprotic solvents protolysis of acids and bases takes place. This reaction is also termed solvolysis, classically dissociation. The degree of solvolysis depends on the nature of both the dissolved acid or base and on the solvent. 

If the solvent is not protogenic but protophilic (acetone, dioxan, tetrahydrofuran, dimethylformamide, etc.), self-ionization obviously does not occur. Consequently, the dissolved acids are dissociated to a greater or lesser degree but dissolved bases do not undergo protolysis. Thus, there can exist only strong acids but no strong bases in these solvents. The pH is not defined for a solution that does not contain a dissolved acid (i.e. in the pure solvent or in the solution of a base). The pKA value can be defined but not... 

As expected, the high reactivity of the polar Si=P bond favors protolysis reactions with HX (X = OH, OMe, Cl), in which the phosphorus is protonated and the silicon center bonds to X (Eq. 5).IOa... 

Curioni, A., W. Andreoni, J. Hutter, H. Schiffer, and M. Parrinello. 1994. Density-Functional-Theory-Based Molecular Dynamics Study of 1,2,5-Trioxaneand 1,3-Dioxane Protolysis. J. Am. Chem. Chem. Soc. 116, 11251. 

In a molecule of 2-phenyl-l-boraadamantane there are two markedly different types of B-C bonds two of them are boron-alkyl and one is boron-benzyl. On treatment of THF complex 34 with 8-hydroxyquinoline at 20 °C, mpture of the 1-boraadamantane core takes place, resulting in a mixture of boron chelates 52-54 (Scheme 16). When trimethylamine adduct 16 is used as the starting compound, reaction takes place only in boiling toluene. Interestingly, all the products result from the protolysis of B-CH2 bonds only <2006UP1>. 

Two additional problems in understanding heterogeneous catalytic CO reduction concern the means by which MrO bonds are cleaved to produce alcohols and the fate of the metal oxides once formed. In regard to the former issue, most metal alkoxides (including those of actinides) readily undergo protolysis to form alcohols (97) (eq.(31)). The source of the protons could be... 

The equilibrium constants given above for the hydrolysis and protolysis reactions of cis- and trans-DDP can be employed to construct distribution diagrams of various species as a function of the pH. In human blood plasma ([Cl-] = 0.1 M) the dichloro species predominates at about pH 7.4 for both cis- and frans-DDP (Figure 4). By contrast, in intracellular conditions ([Cl ]ambient = 0.004 M) the hydrolysis products dominate, but the distribution behavior of the two isomers is quite... 

Note Had you been given the choice, CH3Br, you would not choose it due to a possible Baker-Nathan effect (no-bond resonance). In base, one result is protolysis ... 

Earlier pioneering work by Eigen (56) showed that the exchange process of a proton in aqueous acidic/basic medium between species MOH and MO - can in general be represented by Scheme 4 (which can also be adapted to include the proton transfer between a [MOH2] and a [MOH] species). This mechanism, involving protolysis and hydrolysis (acid and base catalysis) and direct proton transfer, can be... 

---