Formation of a Salt

Please pass the sodium chloride It is amazing that food is seasoned with an ionic compound that is composed of two deadly elements— sodium and chlorine. The gain or loss of electrons can make a big difference in properties. Reacting sodium hydrogen carbonate, which is baking soda, with hydrochloric acid (HCI), the acid found in your stomach, produces salt, carbon dioxide, and water, according to the following equation  

If we evaporate the water, then all that should remain is the salt, NaCI. 

6M HCI NaHC03 100-mL beaker 10-mL graduated cylinder dropper phenol red indicator 

Identify the noble gases that Na+ and Cl resemble in their electron configurations. 

Place 0.50 g of sodium hydrogen carbonate (NaHC03) into the beaker. 

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Flurbiprofen and indomethacin, which comprise the third class of inhibitors, cause a slow, time-dependent inhibition of COX-1 and COX-2, apparently via formation of a salt bridge between a carboxylate on the drug and Arg , which lies in the tunnel. 

Poloxamers are used primarily in aqueous solution and may be quantified in the aqueous phase by the use of compleximetric methods. However, a major limitation is that these techniques are essentially only capable of quantifying alkylene oxide groups and are by no means selective for poloxamers. The basis of these methods is the formation of a complex between a metal ion and the oxygen atoms that form the ether linkages. Reaction of this complex with an anion leads to the formation of a salt that, after precipitation or extraction, may be used for quantitation. A method reported to be rapid, simple, and consistently reproducible [18] involves a two-phase titration, which eliminates interferences from anionic surfactants. The poloxamer is complexed with potassium ions in an alkaline aqueous solution and extracted into dichloromethane as an ion pair with the titrant, tet-rakis (4-fluorophenyl) borate. The end point is defined by a color change resulting from the complexation of the indicator, Victoria Blue B, with excess titrant. The Wickbold [19] method, widely used to determine nonionic surfactants, has been applied to poloxamer type surfactants 120]. Essentially the method involves the formation in the presence of barium ions of a complex be-... 

The Usanovich theory is the most general of all acid-base theories. According to Usanovich (1939) any process leading to the formation of a salt is an acid-base reaction. The so-called positive-negative definition of Usanovich runs as follows. 

Operations which involve any reaction between a base and nitroethane should be carried out in such a way that the formation of a salt in the dry state is impossible, othenwise it will detonate. 

The arylation of common heteroarenes could be governed by the choice of conditions. Free (NH)-heteroarenes were C-arylated via selective catalytic C-H bond functionalizations. The key to these transformations was the use of MgO, which enabled the formation of a salt of the heteroarene, hence offering N-protection in situ (Equations (84) and (85)). a... 

Solid-state metathesis reactions. For a number of compounds, solid-state metathesis (exchange) reactions have the advantages of a rapid high-yield method that starts from room-temperature solids and needs little equipment. The principle behind these reactions is to use the exothermicity of formation of a salt to rapidly produce a compound. We may say that for instance a metal halide is combined with an alkali (or alkaline earth) compound of a /7-block element to produce the wanted product together with a salt which is then washed away with water or alcohol. Metathesis reactions have been used successfully in the preparation of several crystalline refractory materials such as borides, chalcogenides, nitrides. 

K. -Y. Lee and M. M. Stinecipher, Propellants, Explosives, and Pyrotechnics, 14, 241 (1989). Handrick (Reference 2b) spoke of a salt link or correction of ca 67 kJ mol 1 associated with the formation of a salt from the reaction of an acid and base. From the enthalpy of formation of ethylenediamine from Pedley and of the ethylenediammonium salt of 3-nitro-l,2,4-triazol-5-one from the current reference, and the suggested salt link (x2), the enthalpy of formation of 3-nitro-l,2,4-triazol-5-one is predicted to be —135 kJ mol-1. This is in wonderful agreement with that reported in Reference 103. 

Fig. 7 Scheme illustrating anion exchange by means of the formation of a salt between an anionic and a cationic surfactant in LDHs. Reprinted with permission from [122], Copyright RSC... 

There are at least three possibile ways in which the inhibitor can bind to the active site (1) formation of a sulfide bond to a cysteine residue, with elimination of hydrogen bromide [Eq. (10)], (2) formation of a thiol ester bond with a cysteine residue at the active site [Eq. (11)], and (3) formation of a salt between the carboxyl group of the inhibitor and some basic side chain of the enzyme [Eq. (12)]. To distinguish between these three possibilities, the mass numbers of the enzyme and enzyme-inhibitor complex were measured with matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI). The mass number of the native AMDase was observed as 24766, which is in good agreement with the calculated value, 24734. An aqueous solution of a-bromo-phenylacetic acid was added to the enzyme solution, and the mass spectrum of the complex was measured after 10 minutes. The peak is observed at mass number 24967. If the inhibitor and the enzyme bind to form a sulfide with elimination of HBr, the mass number should be 24868, which is smaller by about one... 

In general, barbiturates—thiopental in particular—change into soluble form on treatment with bases. Therefore, thiopental often appears in the market under the name sodium thiopental. In this case, the formation of a salt occurs due to the sulfur atom in an enethi-olate form. The most common synonyms for thiopental are pentothal, trapanal, farmotal, intraval, and others. 

Trimethylenetriamine Ammonia also forms during this reaction, but it is absorbed by acid with formation of a salt... 

Compounds that are more polar, and which can better hydrogen-bond with water, require less drastic alterations to the solvent environment to cause dissolution to occur. On the right side of Figure 3, we associate solute polarity with each formulation concept. Drugs that are good hydrogen donors, in the extreme sense, have acidic properties. Likewise, those that are very good acceptors have basic properties. For these compounds, formation of a salt by protonation or deprotonation is a feasible route. 

The large number of newly developed COX-2 inhibitors demonstrates how promising this field of anti-inflammatory agents is expected to be. More than 1000 COX-2 inhibitors have been described over the past few years (Prous database, March 2002). The chemical structures of COX-2 inhibitors are heterogenic. Contrary to the classical NSAIDs, this new class of enzyme inhibitors lacks a carboxylic acid group, thus effecting COX-2 affinity by a different orientation within the enzyme without formation of a salt bridge in the hydrophobic channel of the enzyme. 

Another extreme is the formation of a salt bridge between, say, an ammonium ion and a carboxylate (equation 11.12). There are two good hydrogen bonds on each side,... 

When amino acid ester prodrugs of acetaminophen were prepared (Kovach et al., 1975 Pitman, 1976), the hydrobromide salt of the glycine ester showed enhanced solubility in water, but the hydrochloride salt of th -aspartic acid ester exhibited a solubility lower than that of the parent compound. The enhanced solubility resulted from the formation of a salt, while the parent drug is a weakly acidic phenol and behaves as essentially a neutral molecule in solution. The reduced solubility in the case of th0-aspartic acid ester resulted from ionization of the terminal carboxylic acid, which, with the protonated amine, gives a zwitterionic compound. The zwitterion also behaved as a molecule with an overall neutral character, as is commonly observed with zwitterion behavior in aqueous media, but its larger size resulted in a further reduced solubility. 

Enantioselective catalytic alkylation is a versatile method for construction of stereo-genic carbon centers. Typically, phase-transfer catalysts are used and form a chiral ion pair of type 4 as an key intermediate. In a first step, an anion, 2, is formed via deprotonation with an achiral base this is followed by extraction in the organic phase via formation of a salt complex of type 4 with the phase-transfer organocata-lyst, 3. Subsequently, a nucleophilic substitution reaction furnishes the optically active alkylated products of type 6, with recovery of the catalyst 3. An overview of this reaction concept is given in Scheme 3.1 [1],... 

Partial racemization of the ester obtained can be explained by the intermediate formation of a salt of type V which undergoes methano-lysis with inversion of configuration at the phosphoryl center. 

X-ray studies show the silicon to be trigonal bipyramidal coordinated with the oxygen and chlorine in the apical positions.46 48 Variations in the substitution at silicon are reflected in variations in the strength of the O — Si coordination bond, sometimes resulting in the loss of the pentacoordination at silicon and formation of a salt.49 These studies have been reviewed.50... 

The process occurs through the formation of a salt, trifluoropropylmag-nesiumchloride, which does not react fully therefore, to destroy the unreacted salt, the reactive mixture is neutralised by 2-3% hydrochloric acid ... 

The synthesis of amides directly from carboxylic acids is not easy because the reaction of an amine with a carboxylic acid is a typical acid-base reaction resulting in the formation of a salt (Following fig.). Some salts can be converted to an amide by heating strongly to expel water. 

Treatment of a quaternary halide salt Q+X with a Lewis acid MX results in the formation of a salt with the composition Q+MX +i . In general, more than just one anion species is formed, depending on the relative proportions of MX and the halide salt Q X. A representative example is the reaction of l-ethyl-3-methylimidazolium chloride [EMIMJC1 with AICI3 (Scheme 2.3). 

The reaction between a carboxylic acid (an acid) and an amine (a base) results in the formation of a salt. The product salts are diastereomers (R,S and S,S) and can be separated by various methods. 

Electrodes of many metals can undergo corrosion or passivation— formation of a salt film on the surface—and other reactions, depending on the medium and experimental conditions. Electrochemical techniques can be used to investigate the mechanisms of these processes. 

Poisoning by water vapor is a reversible effect and can be overcome by redrying the catalyst. Alkali poisoning, on the other hand, is permanent and may involve the formation of a salt, such as a manganite or cobaltite in the surface layer. In such cases, the manganese or cobalt atom is more completely coordinated and the reactivity of the surface considerably lessened thereby. Carbon monoxide is therefore oxidized only stoichiometrically by poisoned Mn02. 

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