Protolytic

As expected, superacids were found to be extremely effective in bringing about protolytic transformations of hydrocarbons. 

This realization led me to study related possible intermolecular electrophilic reactions of saturated hydrocarbons, Not only protolytic reactions but also a broad scope of reactions with varied electrophiles (alkylation, formylation, nitration, halogenation, oxygenation, etc.) were found to be feasible when using snperacidic, low-nucleophilicity reaction conditions. 

Acid-catalyzed isomerization reactions of alkanes as well as alkylation and condensation reactions are initiated by protolytic ionization. Available evidence indicates nonlinear but not necessarily triangular... 

The reverse reaction of the protolytic ionization of hydrocarbons to carbocations, that is, the reaction of trivalent carbocations with molecular hydrogen giving their parent hydrocarbons, involves the same five-coordinate carbonium ions. 

The isomerization of butane to iso butane in superacids is illustrative of a protolytic isomerization, where no intermediate olefins are present in equilibrium with carbocations. 

Not only protolytic reactions but also a whole range of varied elee-trophilic reactions can be carried out on alkanes under superacidic conditions. 

Halonium ions, including hydrido or alkylhalonium ions, are similarly protolytically activated, indicative of protonation of the non-bonded electron pairs of their halogen atoms. 

Charge-charge repulsion effects in protolytically activating charged electrophiles certainly play a significant role, which must be overcome. Despite these effeets multidentate protolytic interactions with superacids can take plaee, increasing the electrophilie nature of varied reagents. 

Mention must be made of the u.se of o- or p-hydroxystyryl thiazolo dyes as indicators for protolytic titrations in nonaqueous media (145). and of the hypotensive action of some neotrinuclear thiazolo cyanines in experiments on animals (146). 

Several stabilization agents are available, ie, protolytic enzymes, tannic acid, or various adsorbents such as polyvinylpyrroHdinone (PvPP) and nylon-6,6 or bentonite. The stabilizing agent is normally added during the transfer to the stabilizing tank and left for some hours to react. 

In another experiment tritiated adamantane diazirine fixed to the hydrocarbon core of a membrane gave rise to carbene insertion into the catalytic subunit of ATP-ase. After protolytic degradation adjacent areas of the original structure became evident (80JBC(255)860). 

SYNTHESIS AND PROTOLYTIC PROPERTIES OF THE PERIODICALLY ORDERED MESOPOROUS ORGANOSILICAS WITH MCM-41-TYPE ARCHITECTURES FUNCTIONALISED... 

It is established, that the natural and synthetic polymers influence on spectrophotometrical, protolytical and complex-formating properties of azodyes in different degree. The result of interaction between anions of organic dyes and polymers is formation of specifical hydrophobic-hydrated adducts. Express spectrophotometrical methods of polymer content determination in water solutions with the help of polymer adducts have been elaborated. 

Hydrated alumina is one of the most widespread hydrophilic polar sorbents for concentration and separation of different substances. In water Al Oj shows cation or anion exchange properties and its protolytic and adsorption characteristics depend on a way of obtaining. 

Distribution of benzodiazepines in system micellar pseudophase - water was investigated in micellar solutions of sodium dodecylsulfate. The protonization constants of benzodiazepines were determined by the UV-spectophotometry. Values of protonization constants increase with increasing of sodium dodecylsulfate concentration. The binding constants of two protolytic forms of benzodiazepines with a micellar pseudo-phase and P, values were evaluated from obtained dependence. 

On the above basis it is, in principle, unnecessary to treat the strength of bases separately from acids, since any protolytic reaction involving an acid must also involve its conjugate base. The basic properties of ammonia and various amines in water are readily understood on the Bronsted-Lowry concept. 

Davidson and Hantzsch (1898) and later Engler and Hantzsch (1900) investigated this system on the supposition that it corresponds to that of the common dibasic acids. From conductivity measurements they calculated basic dissociation constants for the diazohydroxides, but it is now known that their assumptions were incorrect. In fact, at the turn of the century it was practically impossible to reach the right solution. On the one hand, Hantzsch did not have at his disposal the current poten-tiometric technique for protolytic equilibria, and on the other hand, the system of Scheme 5-1 is a special case for a dibasic acid, the principle of which was not grasped in Hantzsch s time. 

A. Nucleophilic Attack on Carbon. —(/) Activated Olefins. A study of triarylphosphine-catalysed dimerization of acrylonitrile to 2-methylene-glutaronitrile (26) and 1,4-dicyano-l-butene (27) has established a balance between phosphine nucleophilicity and protolytic strength of the solvent. The reaction of methyl vinyl ketone with triphenylphosphine in triethyl-silanol gave only 3-methylene-2,6-heptadienone (28). 

Nonaqueous electrolyte solutions are analogous to aqueous solutions they, too, are systems with a liquid solvent and a solute or solutes dissociating and forming solvated ions. The special features of water as a solvent are its high polarity, e = 78.5, which promotes dissocation of dissolved electrolytes and hydration of the ions, and its protolytic reactivity. When considering these features, we can group the nonaqueous solvents as follows ... 

Protic, which are analogous to water, have polar character, and are involved in protolytic reactions... 

An important experimental rule for protolytic reactions was estabhshed by Johannes Nicolaus Brpnsted in 1918 (it was later extended to other reactions). He showed that for a series of reactions of the same type, the rate constants and the equilibrium constants are related simply as... 

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 ... 

Aprotic solvents are not protogenic, but can be protophilic, e.g. acetone, 1,4-dioxan, tetrahy drof uran, dimethy If ormamide, hexamethylphos-phortriamide, propylene carbonate and sulpholane. Solvents that do not participate in protolytic reactions, i.e. do not donate or accept a proton, are usually chemically inert, such as benzene, chlorobenzene, chloroform, tetrachloromethane, etc. 

If an amphiprotic solvent contains an acid and base that are neither mutually conjugate nor are conjugated with the solvent, a protolytic reaction occurs between these dissolved components. Four possible situations can arise. If both the acid and base are strong, then neutralization occurs between the lyonium ions and the lyate ions. If the acid is weak and the base strong, the acid reacts with the lyate ions produced by the strong base. The opposite case is analogous. A weak acid and a weak base exchange protons ... 

Reaction (II) could be the neutralization of acetic acid by potassium hydroxide, yielding potassium acetate which can be isolated in the crystalline state. On dissolution in water the K+ cation is only hydrated in solution but does not participate in a protolytic reaction. In this way, the weak base CH3COO is quantitatively introduced into solution in the absence of an equilibrium amount of the conjugate weak acid CH3COOH. Thus... 

If the dielectric constant of an amphiprotic solvent is small, protolytic reactions are complicated by the formation of ion pairs. Acetic acid is often given as an example (denoted here as AcOH, with a relative dielectric constant of 6.2). In this solvent, a dissolved strong acid, perchloric acid, is completely dissociated but the ions produced partly form ion pairs, so that the concentration of solvated protons AcOH2+ and perchlorate anions is smaller than would correspond to a strong acid (their concentrations correspond to an acid with a pK A of about 4.85). A weak acid in acetic acid medium, for example HC1, is even less dissociated than would correspond to its dissociation constant in the absence of ion-pair formation. The equilibrium... 

The protolytic reaction between two molecules must be formulated as the formation of the pair... 

Protolytic reactions can also occur in fused salts. The solvent participates in these reactions provided that at least one of its ions has protogenic and/or protophilic character. An example of a solvent in which the cation is aprotic and the anion protophilic is ethylpyridinium bromide (m.p. 114°C). The acid HA is protolysed in this solvent (HA -I- Br HBr + A"). Hydrogen bromide acts as a solvated proton and the acidity is expressed as... 

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