Amphiprotic protogenic solvents

In Ref. 26c, solvents are classified as follows protic solvents [amphiprotic hydroxylic solvents (water, methanol, glycols), amphiprotic protogenic solvents (CH3COOH, HF), proto-philic H-bond donor solvents (FA, NMF, NH3) dipolar aprotic solvents [aptotic proto-philic solvents (DMF, DMSO, Py), aprotic... 

Amphiprotic protogenic solvents have higher acidic properties, but lower basic ones (always in comparison to water). Examples are formic and acetic acid. Amphiprotic protophilic solvents have lower acidity and higher basicity than water, with formamide or ethanolamine as examples. Aprotic dipolar solvents have low acidity and (occasionally) basicity as well, with A,A-dimethylformamide and dimethylsulfoxide as examples for protophilic dipolar solvents and acetonitrile for a protophobic dipolar solvent. 

Amphiprotic protogenic solvents have higher acidic properties, but lower basic ones (always in comparison to... 

Water is the prototype of an amphiprotic solvent and all other solvents with similar acid-base properties are called neutral solvents. Solvents which are much stronger acids and much weaker bases than water are called protogenic solvents, while those which are much stronger bases and much weaker acids than water are designated protophilic solvents. 

Using water as reference, an amphiprotic solvent having an acidity and a basicity comparable to those of water is called a neutral solvent, one with a stronger acidity and a weaker basicity than water is called a protogenic solvent, and one with a weaker acidity and a stronger basicity than water is called a protophilic solvent. The solvent with relatively strong acidity usually has in its molecule a hydrogen atom... 

Among amphiprotic solvents of high permittivities, there are water-like neutral solvents (e.g. methanol and ethanol), more acidic protogenic solvents (e.g. formic acid), and more basic protophilic solvents (e.g. 2-aminoethanol). There are also amphiprotic mixed solvents, such as mixtures of water and alcohols and water and 1,4-dioxane. The acid-base equilibria in amphiprotic solvents of high permittivity can be treated by methods similar to those in aqueous solutions. If the solvent is expressed by SH, the acid HA or BH+ will dissociate as follows ... 

Types of Solvent.—In order that a particular solvent may permit a substance dissolved in it to behave as an acid, the solvent itself ifiust be a base, or proton acceptor. A solvent of this kind is said to be proto-philic in character instances of protophilic solvents are water and alcohols, acetone, ether, liquid ammonia, amines and, to some extent, formic and acetic acids. On the other hand, solvents which permit the manifestation of basic properties by a dissolved substance must be proton donors, or acidic such solvents arc protogenic in nature. Water and alcohols arc examples of such solvents, but the most marked protogenic solvents are those of a strongly acidic character, e.g., pure acetic, formic and sulfuric acids, and liquid hydrogen chloride and fluoride. Certain solvents, water and alcohols, in particular, are amphiprotic, for they can act both as proton donors and acceptors these solvents permit substances to show both acidic and basic properties, whereas a purely protophilic solvent, e.g., ether, or a completely protogenic one, e.g., hydrogen fluoride, would permit the manifestation of either acidic or basic functions only. In addition to the types of solvent already considered, there is another class which can neither supply nor take up protons these are called aprotic solvents, and their neutral character makes them especially useful when it is desired to study the interaction of an acidic and a basic substance without interference by the solvent. 

In this section we shall consider the state of protonic acids in the pure state and in solutions of three classes of solvents (i) amphiprotic-protogenic (mineral and carboxylic acids), (ii) aproticdipolar-protophobic (e.g., acetonitrile and nitromethane), and (iii) aprotic-inert (aliphatic and aromatic hydrocarbons and their haloderivatives). While classes (ii) and (iii) represent the only two families of solvents relevant to cationic polymerisation (with the possible exception of the polymerisation of N-vinylcarbazole, wdiich can be carried out in certain dipolar-protophilic solvents), class (i) is interesting because it represents the interaction between two Br nsted acids, the initiator and the solvent, as a direct source of protonating species. Althou the latter combination has not been used in cationic polymerisation, we will discuss its potentials and possible drawbacks. 

The earliest advantages recognized arose from the use of amphiprotic solvents, those that have both acidic and basic properties. The prototype is water. Significant differences in acid-base properties are seen in the case of either protogenic solvents (more acidic than water), for example acetic acid, or protophilic solvents (more basic than water), for example ethylenediamine. In the protogenic cases it was found that bases too weak to be titrated in water could be successfully titrated with a strong acid dissolved in the same solvent. For example, primary, secondary, and tertiary amines can be titrated in acetic acid with perchloric acid in acetic add as titrant. Medicinal sulfonamides, which have a primary amino group, can be titrated... 

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... 

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. 

A term applied to a solvent that can act as a proton donor. Water and ethanol are both protogenic and proto-philic. See Protophilic Amphiprotic... 

Neutral solvents The term neutral solvent applies here to solvents not predominately either acidic (protogenic) or basic (protophilic) in character. Some are weakly basic but not appreciably acidic (ethers, dioxane, acetone, acetonitrile, esters), some aprotic (benzene, carbon tetrachloride, 1,2-dichloroethane), and some amphiprotic solvents (ethanol, methanol). Aprotic solvents are used mainly in mixed solvents to alter the solubility characteristics of the reactants. 

A protic (or protogenic) substance possesses dissociable protons (e.g., HCl, benzoic acid) and can therefore undergo self-ionization in the form of autoprotolysis. Conversely, aprotic solvents cannot undergo autoprotolysis and examples include pentane, carbon tetrachloride, and diox-ane. Amphiprotic (or amphoteric) substances can serve either as Brpnsted acids or bases (e.g., water, ammonia). Autoprotolysis involves a proton transfer between two identical molecules ... 

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