Salts as bases

ROH primary and secondary alcohol, R X primary halide Mel, CS2CO3 

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Since, generally, any base stronger than OH will react with water to produce OH we must use another solvent to observe very strong bases. The high base strengths of the hydride ion and the oxide ion can best be observed in molten salts as solvents, since hydrides and ionic oxides are either insoluble in ordinary solvents or attack them. 

By analogy, ammonium salts should behave as acids in liquid ammonia, since they produce the cation NH4 (the solvo-cation ), and soluble inorganic amides (for example KNHj, ionic) should act as bases. This idea is borne out by experiment ammonium salts in liquid ammonia react with certain metals and hydrogen is given off. The neutralisation of an ionic amide solution by a solution of an ammonium salt in liquid ammonia can be carried out and followed by an indicator or by the change in the potential of an electrode, just like the reaction of sodium hydroxide with hydrochloric acid in water. The only notable difference is that the salt formed in liquid ammonia is usually insoluble and therefore precipitates. 

Liquid ammonia, like water, is only a poor conductor of electricity. Ammonium salts dissolved in water behave as acids giving the ion NH4, whilst amides which give the ion NHj behave as bases. Thus the reaction ... 

The Lassaigne procedure for detecting nitrogen in organic compounds frequently gives unsatisfactory results with explosive compounds (diazonium salts, polynitro compounds and the like) and with certain volatile nitrogenous substances, such as bases, their acyl derivatives or their salts. These difficulties... 

The value of the second-order rate constant for nitration of benzene-sulphonic acid in anhydrous sulphuric acid varies with the concentration of the aromatic substrate and with that of additives such as nitromethane and sulphuryl chloride. The effect seems to depend on the total concentration of non-electrolyte, moderate values of which (up to about 0-5 mol 1 ) depress the rate constant. More substantial concentrations of non-electrolytes can cause marked rate enhancements in this medium. Added hydrogen sulphate salts or bases such as pyridine... 

The primary use for 2,4-di-/ f2 -butylphenol is in the production of substituted triaryl phosphites. 2,4-Di-/ f2 -butylphenol reacts with phosphoms trichloride typically using a trialkylamine or quaternary ammonium salt as the catalyst. Hydrogen chloride is formed and either complexed with the amine or Hberated as free hydrogen chloride gas forming the phosphite ester, tris(2,4-di-/ f2 -butylphenyl)phosphite [31570-04-4] (58). The phosphite-based on... 

The selection of a particular metal salt is based on such factors as local availabiUty, convenience, economics, and effectiveness for the specific treatment problem. 

Naphthol AS Coupling Components. Naphthol AS components are the aryhdes of either o-hydroxyarylcarboxycHc acids or acylacetic acids. They are free of sulfo and carboxyl groups, but form salts with bases these salts dissolve in water to give colloidal solutions, which couple with diazo components to form colored pigments. The whole class derives from the anilide of 3-hydroxy-2-naphthoic acid [92-70-6] Naphthol AS (85) (Cl Azoic Coupling Component 2). 

Calcination or dead burning is used extensively to dehydrate cements (qv) and hygroscopic materials such as MgO, and to produce a less water sensitive product. Calcination is also used to decompose metal salts to base oxides and to produce multicomponent or mixed oxide powders for... 

Although there is very little scope for reactions of the above types with 1,2-benzisoxazole derivatives, the quaternary salts such as 2-methyl-3-phenyl-l,2-benzisoxazolium salt underwent base-catalyzed isomerization to the 1,3-benzoxazine shown in Scheme 83. This reaction is analogous to the formation of (202) above (67AHC(8)277). 

Sulphonie aeids are water soluble, viseous liquids. Their aeidity is akin to that of sulphurie aeid they form salts with bases but fail to undergo esterifieation with aleohols. Their properties vary aeeording to the nature of R some are prone to thermal deeomposition. They are used as surfaetants and in the dye industry some have biologieal uses. 2-Amino-ethanesulphonie aeid is the only naturally oeeuning sulphonie aeid. 

The most demanding test of cesium carbonate as base was with 2,3-dihydroxypyridine (3-hydroxypyridone). The cesium salt was found to be fairly unstable, apparently oxidizing quite rapidly. Model reactions suggested that alkylation would occur 1,3 (N, 0) to give the substituted pyridone. Nevertheless, on the basis of UV and H-nmr analysis, the product of reaction between 2,3-dihydroxypyridine and tetraethylene glycol dibromide was assigned as the pyridocrown (23% yield, mp 77—78.5°) as shown in Eq. (3.60). 

Z-Ecgonine, CgHigOgN. HjO. This substance was first obtained I Lossen as the final basic hydrolytic product of the action of acids c cocaine, and is obtainable in like manner from several of the alkaloii occurring with cocaine (see above). It crystallises from dry alcohol i monoclinic prisms, m.p. 198° (dec.), 205° (dry), [a]n — 45-4°, is soluble i water, sparingly so in alcohol, insoluble in most organic liquid Eegonine forms Salts with bases and acids the hydrochloride crystallis... 

The carbanionic species thus formed is protonated to give the final product 3. The use of an alkoxide as base leads to formation of a carboxylic ester as rearrangement product use of a hydroxide will lead to formation of a carboxylic acid salt ... 

The Glaser coupling reaction is carried out in aqueous ammonia or an alcohol/ammonia solution in the presence of catalytic amounts of a copper-I salt. The required copper-II species for reaction with the acetylide anion R-C=C are generated by reaction with an oxidant—usually molecular oxygen. For the Eglinton procedure, equimolar amounts of a copper-II salt are used in the presence of pyridine as base. 

The general procedure is to heat a mixture of aldehyde 1 and carboxylic anhydride 2 together with a base to a temperature of 170-200 °C for several hours. As base the sodium salt of the carboxylic acid corresponding to the anhydride is most often used. 

Amino acid zwitterions are internal salts and therefore have many of the physical properties associated with salts. They have large dipole moments, are soluble in water but insoluble in hydrocarbons, and are crystalline substances with relatively high melting points. In addition, amino acids are amphiprotic they can react either as acids or as bases, depending on the circumstances. In aqueous acid solution, an amino acid zwitterion is a base that accepts a proton to yield a cation in aqueous base solution, the zwitterion is an add that loses a proton to form an anion. Note that it is the carboxylate, -C02-, that acts as the basic site and accepts a proton in acid solution, and it is the ammonium cation, -NH3+, that acts as the acidic site and donates a proton in base solution. 

The thermolabile, unsubstituted 3-benzothiepin (3) can be synthesized by a double Wittig reaction, in analogy to the Knoevenagel condensation (vide supra). This is achieved by condensation of phthalaldehyde with the bis(triphenylphosphonium) salt of bis(bromomethyl) sulfide in the presence of lithium methoxide as base at — 30"C.68... 

Most of the salts described below can be prepd by interaction of PA with the corresponding inorganic salt or base. Inasmuch as PA is only sparingly sol in w, it is advisable to dissolve the metallic salt (or base) in w, and then introduce the PA in a finely divided state. For 4 example,the Ksalt (see below) can be prepd by saturating a hot K carbonate soln with powdered PA 2C6H2(N02)30H+K2C03 2C6 H2(NO 2) 30K+H20+C02. When the liq is cooled, pale yel acicularcrysts separate out... 

Most of the chemistry of PA is determined by its acidic nature. It is a strong acid whose ionization constant of 1.6 x 10"1 (Ref 31) makes it comparable in acid strength to pyrophosphoric acid and trichloroacetic acid. PA readily forms salts with bases and esters with alcohols. The salts are known as Picrates. Many of them are expl and will be described in a separate article in this Vol. The esters are phenol ethers, eg, Trinitro-anisolc (see Vol t, A450-L)... 

A completely different method of synthesis of azo compounds from diazonium salts involving radical intermediates was found by Citterio et al. (1980, 1982 c), Cit-terio and Minisci (1982), and Fontana et al. (1988). It is a new general synthesis of arylazoalkanes based on the addition of an alkyl radical to an arenediazonium ion followed by reduction of the intermediate azo radical cation adduct by a metal salt (Scheme 12-80). The preferred source for the alkyl radical R in this reaction is an alkyl iodide, which gives rise to alkyl radicals cleanly in the presence of an arenediazonium salt and a Ti3+ or Fe2+ salt as in Scheme 12-81. The overall stoichiometric equation is therefore as given in Scheme 12-82. The yields vary between 36% and 79% (with respect to alkyl iodide). 

To avoid side reactions, like the formation of diglycolic acid disodium salt, a reaction is described whereby instead of NaOH as base a so-called hindered base (e.g., tert-butoxide) is used [16]. 

However, thermolysis of the phosphonium salts (X=+PPh3) leads directly to the indolic products without need of acid catalyst or PPh3, and thus may not proceed via a normal Wittig pathway. Alternatively, Hughes has effected a solid-phase version of this reaction employing a polymer-hound phosphonium salt and potassium tert-butoxide as base <96TL7595>. In this case, the phosphine oxide by-product remains bound to the polymer resin. 

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