Hydrohalide acid

Hydrobromic acid is used in the production of inorganic bromides as well as in organic brominations, particularly in the production of pesticides. Some physical properties of the hydrohalide acids are summarized in Table 6. 

Indium (I) halides can be prepared by dissolving an excess of indium in hydrohalide acid or reduction of trUialides with metal. The structures of the bromides have been... 

The chemistry of alkali amides was well investigated in the early twentieth century [3, 4], especially, sodium amide (NaNH2) has been used as a reagent in synthetic organic chemistry because of its ability to promote condensation reactions, to introduce amino groups into a molecule, and to remove the elements of water or of a hydrohalide acid. Lithium nitride has also been investigated for more than 50 years [5]. 

Frigden [429] has addressed the underlying causes of the differing hydrohalide acidities in terms of the physical properties of the compounds. As shown in Table 7.2, several properties such as the trend to lower bond dissociation energies (BDEs) and smaller differences in X-H electronegativi-ties fAri ) as one proceeds down a group in the periodic table are consistent... 

Among these, carboxylic acid esters have gained importance in the field of wood preservation, because they are of lower volatility and water-solubility, but higher thermal stability than TBTO. From comparison data it can be concluded that the tributyltin (TBT) moiety of the TBT esters determines their antimicrobial effectiveness and also their oral toxicity. This is in line with the fact that the TBT esters tend to dissociated into the hydrated TBT cation and the respective anion. Due to the lower TBT content compared with TBTO greater quantities of TBT carboxylic acid ester therefore have to be used to achieve sufficient antimicrobial effectiveness. Hydrohalide acid esters of practical importance as microbicides have been tributyltin fluoride (19.6.6.) and triphenyltin chloride (19.6.7.). 

When the preceding rules lead to inconvenient names, then (1) the unaltered name of the base may be used followed by the name of the anion or (2) for salts of hydrohalogen acids only the unaltered name of the base is used followed by the name of the hydrohalide. An example of the latter would be 2-ethyl-p-phenylenediamine monohydrochloride. 

For this reaction to proceed it is obviously necessary to remove the hydrochloric acid formed, preferably by means of hydrohalide acceptor. 

Because of the cost of pyridine the phosgenation process may be carried out with a mixture of pyridine and a non-hydrohalide-accepting solvent for the polymer and the growing complexes. Suitable solvents include methylene dichloride, tetrachlorethane and chloroform. Although unsubstituted aromatic hydrocarbons may dissolve the solvent they are not effective solvents for the acid chloride-pyridine complexes. 

The hydrohalide is usually prepared by passing hydrogen chloride into a solution of masticated high-grade raw rubber in benzene at 10°C for about six hours. Excess acid is then neutralised and plasticisers and stabilisers are added. The benzene is removed by steam distillation and the product washed and dried. Alternatively the solution is cast on to a polychloroprene rubber belt, leaving a tough film after evaporation of the solvent. 

The hydrohalide is liable to dehydrochlorination, particularly when moist acid is used in its preparation, so that hydrochloric acid acceptors such as lead carbonate are useful stabilisers. Dibutyl phthalate and tritolyl phosphate are effective plasticisers. Rubber hydrochloride is used as a packaging film (Pliofilm) and as a rubber-to-metal bonding agent (e.g. Typly). 

Amine-phosphorus halide reactions involve hydrogen halide (or amine hydrohalide) formation. They can be complicated through acid catalysis or side reactions. Thus, the possible formation of skeletally stabilized products through transamination reactions in which no hydrohalide products are obtained is of interest. 

Although the synthesis is completed in very few steps, oxidation of 1,4-xylene to the corresponding terephthalic acid does not afford a uniform product. Partial dihalogenation gives rise to side products. The condensation reaction requires two equivalents of arylamine per halogen atom. One equivalent is needed to neutralize the generated hydrohalogen acid, which is subsequently separated as aryl-amine-hydrohalide and recycled as hydrohalide and arylamine. 

The catalytic effect of quaternary ammonium salts in the basic liquid liquid two-phase alkylation of amines [1-3] is somewhat unexpected in view of the low acidity of most amines (pKfl>30). Aqueous sodium hydroxide is not a sufficiently strong base to deprotonate non-activated amines in aqueous solution and the hydroxide ion is not readily transferred into the organic phase to facilitate the homogeneous alkylation (see Chapter 1). Additionally, it is known that ion-pairs of quaternary ammonium cations with deprotonated amines are decomposed extremely rapidly by traces of water [4]. However, under solidrliquid two-phase conditions, the addition of a quaternary ammonium salt has been found to increase the rate of alkylation of non-activated amines by a factor of ca. 3-4 [5]. Similarly, the alkylation of aromatic amines is accelerated by the addition of the quaternary ammonium salt the reaction is accelerated even in the absence of an inorganic base, although under such conditions the amine is deactivated by the formation of the hydrohalide salt, and the rate of the reaction gradually decreases. Hence, the addition of even a weak base, such as... 

Only a few reactions of imidazo[2,l-h][l,3,4]oxadiazoles have been reported. The basicity of these compounds is rather low hydrohalides cannot be isolated (69ZC337). Protonation of 23 with strong acids occurs at position 7, giving, for example, 24 (mp 212°C with explosion ). With aqueous base 24 is converted back to 23 (72BSF3968). On alkylation of 23 the quaternary salts 25 are obtained (72BSF3968). Reaction of 25 (R = Et) with ethyl cyanoacetate (Et3N/EtOH) yields 26, albeit in low yield (3.8%) (72BSF3968). 

Kaupp et al. also exploited heterogeneous reactions with CICN and BrCN in the quantitative synthesis of cyanamides, cyanates, thiocyanates and derivatives [26]. Gaseous acids were shown to form salts with strong and weak solid nitrogen bases. Solid hydrohalides are formed quantitatively by reaction with vapours of HCl, HBr and HI the same applies to di-bases such as o-phenylen-diamines. The products are much more easily handled than when they are formed in solution. The solid products can in turn be used in reactions with gaseous acetone to form the corresponding dihydrohalides of 1,5-benzodi-azepines [27]. 

Equally important is the salt formation of solid bases with gaseous acids. An example has been cited above (30 31). This type of reaction is quite general. Strong and very weak bases react quantitatively and the gas-solid technique does not have problems with moisture. Amino acids such as L-phenylalanine, D-penicillamine (42), DL-penicillamine, L-cysteine, L-leucine, L-proline, DL-ty-rosine and others are quantitatively converted into their hydrohalides with... 

Methyl-1,2,4-triazolo[ 1,5-a]pyrimidin-7-on is amphoteric and can be titrated with perchloric acid in glacial acetic acid (61JOC3834). Some derivatives form isolable hydrohalides (75PHA134). Glier et al. (72T5789) formulated a cationic structure at pH 1 from the UV spectrum contrary to that of Hill et al. (61JOC3834). 

Many analytical methods depend on the conversion of the tellurium in the sample to tellurous acid, H2Te03. Should tellurous acid precipitate on dilution, it can be redissolved with hydrochloric acid. Although tellurium is not as readily volatile as selenium, precautions should be taken to prevent the volatilization of tellurium when halogen or hydrohalide media are used during sample decomposition. 

When an axiridine is treated w>th an acid, the resulting protonnted axiridine (XLI) is usually toe reactive to be isolated, and rapidly under goes solvolyais, isomerizatioin or polymerization. Thus the isolation of stable crystalline axiridine hydrohalides is seldom mentioned in the literature. 88... 

Although HI addition to alkenes and alkynes is faster than that of the other hydrohalides and free radical anti-Maikovnikov additions are not a problem, this reaction has received less attention than the others.173 The hydroiodination of alkenes is most commonly run using concentrated HI in water or acetic acid at or below room temperature. While the early literature suggests that simple terminal alkenes afford small amounts of anti-Markovnikov products, only Markovnikov products have been reported in the more recent literature (equations 125-129).67 176-179... 

Nevertheless, if the cyclization of the succinonitrile with this acid is carried out in the presence of thiolacetic acid, 2-imino-5-thioxo-pyrrolidine hydrohalides (121) are obtained in good yield.98 These compounds very readily convert benzaldehyde to thiobenzaldehyde trimer. 

Nakazawa and Tanaka described a potentiometric titration of salts of organic bases in non-aqueous solvents with the addition of bismuth nitrate [16], The base halide or hydrohalide (0.7 mequiv.) is dissolved in 40 mL of anhydrous acetic acid, and then 40 mL of 1,4-dioxane and 2.5 mL of 5% Bi(N03)3 solution in acetic acid are added. The Bi(N03)3 prevents interference by the halide. The solution is titrated to a potentiometric endpoint with 0.1 M HC104 (a blank titration is also carried out). Results of purity assays of acetylcholine chloride and other compounds were tabulated, and it was found that the coefficient of variation was 0.18%. 

Hydrohalides dissolve easily in water to form hydrohalic acids and undergo virtually complete ionic dissociation (equation 84). All the hydrohalic acids, except HF, are very strong acids. Although AHF is one of the most acidic liquids, as measured by its Hammett function, hydrofluoric acid is a weak acid. 

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