Formation of salts

Anion-exchange resins contain a basic radical, such as —NH and =NH, and are prepared by the condensation of formaldehj de with amines such as m-phenylenediainine and urea. These resins can absorb acids by the formation of salts, —NH3CI and =NHjCl, and are regenerated by treatment with sodium hydroxide or sodium carbonate. 

Chemical Properties The formation of salts with acids is the most characteristic reaction of amines. Since the amines are soluble in organic solvents and the salts are usually not soluble, acidic products can be conveniendy separated by the reaction with an amine, the unshared electron pair on the amine nitrogen acting as proton acceptor. Amines are good nucleophiles reactions of amines at the nitrogen atom have as a first step the formation of a bond with the unshared electron pair of nitrogen, eg, reactions with acid anhydrides, haUdes, and esters, with carbon dioxide or carbon disulfide, and with isocyanic or isothiocyanic acid derivatives. 

Diastereoisomeric Salts. The formation of salts of optically active bases with racemic acids or of optically active acids with racemic bases leads to diastereomeric mixtures which may be resolved by the differential solubiUty of the components of such mixtures (49), ie,... 

Carboxylic Acid Group. Reactions of the carboxyl group include decarboxylation, reduction to alcohols, and the formation of salts, acyl hahdes, amides, and esters. 

Hydroxyl Group. Reactions of the phenohc hydroxyl group iaclude the formation of salts, esters, and ethers. The sodium salt of the hydroxyl group is alkylated readily by an alkyl hahde (WiUiamson ether synthesis). Normally, only alkylation of the hydroxyl is observed. However, phenolate ions are ambident nucleophiles and under certain conditions, ring alkylation can also occur. Proper choice of reaction conditions can produce essentially exclusive substitution. Polar solvents favor formation of the ether nonpolar solvents favor ring substitution. 

Antimony trioxide is insoluble in organic solvents and only very slightly soluble in water. The compound does form a number of hydrates of indefinite composition which are related to the hypothetical antimonic(III) acid (antimonous acid). In acidic solution antimony trioxide dissolves to form a complex series of polyantimonic(III) acids freshly precipitated antimony trioxide dissolves in strongly basic solutions with the formation of the antimonate ion [29872-00-2] Sb(OH) , as well as more complex species. Addition of suitable metal ions to these solutions permits formation of salts. Other derivatives are made by heating antimony trioxide with appropriate metal oxides or carbonates. 

In the hands of Collie and Tickle in 1899 this reaction gave the first crystalline pyrylium salts. The salt character of the compounds was proved by conductivity measurements the basicity of 2,6-dimethylpyrone was found to be a little higher than that of urea. Basicities of other pyrones decrease in the order 2,6-dimethyl-> 2-phenyl-6-methyl-> 2,6-diphenylpyrone, paralleling the dipole moments. These hydroxypyrylium salts hydrolyze in water to pyrones. " The formation of salts of 2,6-dimethylpyrone with organic acids was investigated by Kendall,and with mineral acids by Cook. 11 ... 

PA attacks all the commonly used metals except A1 and Sn, with the formation of salts known as picrates. These salts can also be prepd by the action of PA on hydroxides or carbonates, or by other methods. Nearly all picrates are exp , and are usually more sensitive than PA. Some picrates, eg,Pb Pi crate, can serve as initiating agents. Many picrates detonate with such... 

Sodium carbonate undergoes many of the same reactions as sodium hydroxide, for example, the formation of salts when contacted with acids. In the case of sodium carbonate, carbon dioxide gas is formed along with water. 

The effectiveness with which divalent ions cause gelation of poly(acrylic add) has been found to follow the order Ba > Sr > Ca (Wall Drenan, 1951) and this has been attributed to the formation of salt-like crosslinks. Gelation has been assumed to arise in part from dehydration of the ion-pairs (Ikegami Imai, 1962), and certainly correlates with predpitation in fairly dilute systems. Indeed, the term precipitation has sometimes been applied to the setting of AB cements derived from poly(acrylic add) as they undergo the transition from soft manipulable paste to hard brittle solid. 

The insolubilization of cations and anions during the setting and hardening process is thus paralleled by that of silica. Under add conditions orthosilicic add condenses first to form polymeric silidc add and then silica gel (Her, 1979 Andersson, Dent Glasser Smith, 1982). These processes are discussed more fully in Section 6.5.4. Gelation of silica, like the formation of salt gels, is enhanced by a reduction in the acidity of solutions. 

The reaction of 2-aminopyridine with 2-chloropyridine 102 furnishes pyrido[l,2- 3,2- ]pyrimidine derivative 104 in good yield (Scheme 10) <1998T5775, 2003CHE328>. The first step is quaternization with the formation of salt 103. Then 103 undergoes intramolecular cyclization with participation of cyano and amino groups. 

Differences in sample size, shape and composition can also affect heating rates. The last case particularly applies when ionic conduction becomes possible through the addition or formation of salts. For compounds of low molecular weight, the dielectric loss contributed by dipole rotation decreases with rising temperature, but that due to ionic conduction increases. Therefore as an ionic sample is microwave-irradiated, the heating results predominantly from dielectric loss by dipole rotation initially, but the contribution from ionic conduction becomes more significant with temperature rise. 

The use of high-temperature water as a reaction medium can be beneficial in that regard. For reactions necessitating addition of acid or base, less agent is usually required for high temperature processes than for those at and below 100 °C and the reactions often proceed more selectively. At the end of the process, the requirement for less neutralizing agent lowers the formation of salt [6]. 

The solubility of a drug candidate may not always be sufficient for its intended pharmacological purpose, and in such cases the solubility may need to be modified (either increased or decreased). These concerns are especially important for parenterals when the active substance does not exhibit the desired level of solubility. The solubility of a given compound can be profoundly altered in a number of ways, such as through the formation of salt species or drug-substrate complexes, or through the use of surfactants or cosolvents [43], In the majority... 

Lowry praised the 1916 memoir of the American chemist Lewis as a "turning point in the history of chemistry" with its "plausible theory" of the electronic origin of the different types of chemical affinity and a clear differentiation between two kinds of valence, ionic and covalent. It is customary in mineral chemistry, he said, to consider reactions that occur between ions to be instantaneous, without attaching any importance to ionization in organic chemistry, except for the formation of salts from organic acids. 

Yatsimirskii, K.B. "Thermochemical Radii of Ions and Heats of Formation of Salts, "Izvest. Akad. Nauk. S.S.S.R., Otdel. 

An application to one binary mixture of a volatile electrolyte and water will illustrate the choice of parameters H and K, an approach is proposed to represent the vapor-liquid equilibrium in the whole range of concentration. Ternary mixtures with one acid and one base lead to the formation of salts and high ionic strengths can be reached. There, it was found useful to take into account... 

It is possible that this theory can be adapted to explain molten metal-water thermal explosions although many needed data are still unavailable. One might presume that, at the molten metal-wet surface interface, there is some chemical reaction. Possibly that of the metal plus water or metal plus surface to lead to localized formation of salt solutions. These may then superheat until homogeneous nucleation occurs. The local temperature and pressure would then be predicted to be far in excess of the critical point of pure water (220 bar, 647 K) and a sharp, local explosion could then result. Fragmentation or subsequent other superheat explosions would then lead to the full-scale event. 

A further synthesis of thiazolo[3,2-6][l,2,4]triazoles starts with 2,3-diaminothiazoles. Treatment of 2-aminothiazole with O-mesitylensulfonyl-hydroxylamine results in the formation of salt 171, which on heating with acetic anhydride (140-150°C) gives a mixture of 172 and 173. 2-Phenylthia-zolo[3,2-h]-5-triazole could be obtained from 171 and benzoylchloride ( 200°C) in 68% yield. When 2-acylamino-3-aminothiazolium salts 174 are heated 20-30°C above their melting point for 1 h the corresponding thiazolo[3,2-h]-5-triazoles were obtained. Much better results were achieved by using PPA (100-110°C, 1.5 h 97% yield) (73JHC947). 

An elegant variation of this procedure is to carry out the polycondensation with the salt of a diamine and a dicarboxylic acid (see Example 4-10). In this case, the formation of salt (which is also the first step in the direct polycondensation of a diamine and a dicarboxylic acid) and the polycondensation are carried out as two separate steps. The salts can be obtained in good crystalline form most simply by mixing equimolar amounts of diamine and dicarboxylic acid in a solvent in which the salt formed is insoluble (e.g., ethanol). In order to attain high molecular weights by such polycondensations the salts should be as neutral as possible (exactly equivalent amounts of diamine and dicarboxylic acid) and very pure (recrystallize, for example, from mixtures of ethanol/water). 

Neutralizing acids created during processing can cause the formation of salts that can plug reactor components. 

Hydroxides. The generic name for compounds of the type Ma(OH) where M is a metal and a b are integers. Most hydroxides are insol or sparingly sol in water but are sol in aq acid with the formation of salts. Most hydroxides have been used in neutralizing nitrated explosives made by mxied acid or nitric acid nitration although bicarbonates are more commonly employed. The more common hydroxides are listed below ... 

Hypochlorous acid reacts with inorganic bases with the formation of salts, called hypochlorites. 

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