Protogen

Proton donors (protogenic solvents) H2SO4, carboxylic acids. 

These four solvents can thus be termed protogenic solvents, whilst bromine trifluoride and sulphur dioxide which do not contain hydrogen are non-protonic solvents. Non-ionising solvents include hydrocarbons, ethers, esters and higher alcohols the lower alcohols, especially methanol and ethanol, do show slight ionising properties with appropriate solutes. 

Protogenic solvents are acidic in nature and readily donate protons. Anhydrous acids such as hydrogen fluoride and sulphuric acid fall in this category because of their strength and ability to donate protons they enhance the strength of weak bases. 

Amphiprotic solvents consist of liquids, such as water, alcohols and weak organic acids, which are slightly ionised and combine both protogenic and protophilic properties in being able to donate and to accept protons. 

Solder analysis of by EDTA, (ti) 337 Solochrome black 317, 692 Solochrome (Eriochrome) cyanine R 678 Solochrome dark blue 318 Solubility product 24 calculations involving, 25 importance of, 26 principal limitations of, 24 Solution of sample 110 Solvents amphiprotic, 282 aprotic, 282 ionising, 18 non-protonic, 18 protogenic, 18, 282 protophilic, 282... 

There are gegen ions, e.g. (BF3OH) ion, which cannot form a bond with a carbonium ion. Protogenic acids yielding such gegen ions are on the whole better initiators of carbonium ion polymeri-... 

The rate of protonation may vary according to the structure of the light-emitter and the environment around the light emitter. In the case of chemiluminescence reactions in solutions, the hydrophobicity, permittivity (dielectric constant) and protogenic nature of the solvent are important environmental factors. In the case of bioluminescence involving a luciferase or photoprotein, the protein environment surrounding the light-emitter will be a crucial factor. 

Table 6 gives the data obtained with f-BuX/Et2 All initiator system using MeCl solvent. Et2AlI was found to induce polymerization even in the absence of purposefully added t-BuX. As these experiments were carried out in a dry box, traces of moisture (< 30 ppm) may have functioned as protogenic initiators. The data obtained in these experiments, i.e. in the absence of f-BuX, are shown in columns 9 and 10 in Table 6. 

In Fig. 4.1a one sees the occurrence of an increasing levelling effect on the acid side when changing from protogenic solvents via neutral to proto-philic solvents (dotted lines below). 

Strehlow standard ferrocene-ferrocinium+ electrode and obtained a value of - 0.228 V, i.e., a positive pH shift of 3.85. Theoretically the pH range of pyridine is unlimited on the basic side, but in practice it is limited somewhere in that area as a consequence of the protogenic effect of contaminating traces of water. 

In order to increase our knowledge of the complex electrochemistry in non-aqueous media, we shall consider the phenomena that occur during titrations in solvents with very low e in this connection, it is useful to treat these titrations separately for protogenic and the aprotic solvents, with the latter being subdivided into protophilic and inert solvents. 

Acid-base titrations in protogenic solvents with low e... 

HOAc in the equations of the original papers will be replaced in our description by HS as a designation of protogenic solvents in general (see later its use for m-cresol). 

Although m-cresol shows predominant acidity, and so is mainly protogenic, its basicity is still appreciable (cf., Ka = 2 10 19) and therefore it belongs to Bronsted class 5 further, it shows excellent solubility for a wide range of organic compounds. 

Substances capable of splitting off a proton, i.e. proton donors, are termed protogenic and, on the other hand, substances accepting protons, i.e. proton... 

Most protic solvents have both protogenic and protophilic character, i.e. they can split off as well as bind protons. They are called, therefore, amphiprotic. These include water, alcohols, acids (especially carboxylic), ammonia, dimethylsulphoxide and acetonitrile. Solvents that are protogenic and have weak or practically negligible protophilic character include acid solvents, such as sulphuric acid, hydrogen fluoride, hydrogen cyanide, and formic acid. 

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 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... 

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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