Hydrochloric acid elimination

Working principle of the method The level of carbonyl chloride in the polymer is determined by dissolution of the polymer in methylene chloride and concurrent derivation with 2-aminophenol to form 2-benzoxazolinone (Box) under hydrochloric acid elimination (see Fig. 10-8). 

The following compounds when heated with hydrochloric acid yield mercuric chloride and an organic acid The anhydride of o-hydroxy-mercuri benzoic acid and the anhydride of a-hydroxy mercuri- -hydroxy-j3-phenyipropionic acid, whilst o-chloromercuri benzoic methyl ester is decomposed by halogen acids, and cold dilute hydrochloric acid eliminates the acetoxymercuri group attached to the nitrogen in N-isodiacetoxymercuri anthranilic methyl ester. 

An important general method of preparing indoles, known as the Fischer Indole synthesis, consists in heating the phenylhydrazone of an aldehyde, ketone or keto-acld in the presence of a catalyst such as zinc chloride, hydrochloric acid or glacial acetic acid. Thus acrtophenone phenylhydrazone (I) gives 2-phenyllndole (I V). The synthesis involves an intramolecular condensation with the elimination of ammonia. The following is a plausible mechanism of the reaction ... 

Benzoylpropionitrile. To a mixture of 21 4 g. of p dimethylamino propiophenone hydrochloride, 13 0 g. of potassium cyanide in a 500 ml. flask, add 260 ml. of boiling water heat the heterogeneous mixture under reflux for 30 minutes. Part of the dimethylamine, which is eliminated in the reaction, distils collect this in dilute hydrochloric acid. Cool the reaction mixture in ice the oil sohdifies and crystals form from the aqueous layer. Collect the solid (crude p benzoylpropiouitrile, 10-5 g.) by suction filtration and recrystallise it from benzene - light petroleum (b.p. 40-60°) it separates as almost colourless blades, m.p. 76°. 

The first step of the reaction involves the formation of the S-C bond with the elimination of a molecule of ammonium salt. The fact that it has been possible to isolate the acyclic intermediate (176), R = Me or Ph, would confirm this hypothesis, particularly when the reaction is carried out for a short time in the cold in ethereal solution (27, 82). These intermediates (176) can be cyclized quantitatively on standing or on being treated by hydrochloric acid. However, no evidence has been advanced concerning their structures. 

Perchloric acid can be prepared by the treatment of perchlorates with sulfuric acid followed by distillation. A modification of the procedure (21) involves the reaction of ammonium perchlorate with nitric and hydrochloric acids, and then concentration at 198—200°C to eliminate the unreacted acids by vacuum distillation ... 

Both phenanthrene and anthracene have a tendency to undergo addition reactions under the eonditions involved in eertain eleetrophilic substitutions. For example, in the nitration of anthracene in the presence of hydrochloric acid, an intermediate addition product can be isolated. This is a result of the relatively close balance in resonance stabilization to be regained by elimination (giving an anthracene ring) or addition (resulting in two benzenoid rings). 

Dioxepanes 63 were hydrolyzed with aqueous hydrochloric acid to the starting diol. A thionyl chloride promoted ring-opening of dioxepane 63 to intermediate 64 has been reported. When treated with base, compound 64 can be transformed into vinylic ether 65 in 58% yield (81ZOR1047) (Scheme 31). 3-Methylfurazan-4-acetic acid was converted to the vinyl derivative 66 via an esterification, reduction, mesylation, and base elimination sequence (81JHC1247) (Scheme 31). 

The diazirines have no basic character, they are not attacked even by strong mineral acids. 3,3-Pentamethylenediazirine (68) could be recovered almost unchanged after the action of methanolic ZN hydrochloric acid for 1 hr. Strong alkalies are also without effect diazirine (67) is unchanged by passing through concentrated sodium hydroxide solution after preparation to eliminate carbon dioxide which is formed simultaneously. ... 

Upon completion of the addition, the mixture is agitated for 7 hours at ambient temperature. The solution is then poured into 3 liters of water/ice obtaining a clear solution of dark yellow color which is rendered alkaline upon phenolphthalein with 30% NaOH and extracted with ethyl ether to eliminate the majority of the pyridine. The mixture is filtered with active charcoal, the pH adjusted to 8 with hydrochloric acid 1 1 and extracted with chloroform to remove the 4,4 -dihydroxydiphenyl-(2-pyridyl)-methane which has not reacted. 

The reaction product is filtered and the filtrate is evaporated in vacuo to remove the alcohol. There remains an oily product from which the excess formyl-ethylenedlamine is removed by distillation under 1 mm Hg pressure up to 125°C. The dark yellow, residual product is treated with 10% hydrochloric acid at 100°C for 12 hours to eliminate the formyl group it is evaporated to a syrupy consistency and taken up with ethyl alcohol at the boiling point until complete miscibility is attained it is then discolored over carbon, filtered and stored at low temperature. 

Attempts made to produce an alloy more resistant to hydrochloric acid have resulted in alloys containing 17-18% silicon or 14-5% silicon and chromium plus 3% molybdenum. The first is produced in Britain, and the second in the United States. The reason for the increase in resistance to hydrochloric acid of the Fe-18 Si alloy is thought to lie primarily in the increased density of the silica-rich film left on the metal by initial corrosion. The addition of 6% chromium with some molybdenum to Fe-14-5 Si causes the formation of extremely stable complex carbides with the consequent complete elimination of graphite plus the formation of a more penetration-resistant silica film, probably containing chromium in substantial quantity. 

By monitoring the intensity of the carbonyl absorption it was observed that oxidation of methyl 4,6-0-benzylidene-2-deoxy-a-D-Zt/ ro-hexopyrano-side with chromium trioxide-pyridine at room temperature gave initially the hexopyranosid-3-ulose (2) in low concentration, but attempts to increase this yield resulted in elimination of methanol to give compound 3. However, when methyl 4,6-0-benzylidene-2-deoxy-a-D-Zt/ ro-hexo-pyranoside is oxidized by ruthenium tetroxide in either carbon tetrachloride or methylene dichloride it affords compound 2 without concomitant elimination. When compound 2 was heated for 30 minutes in pyridine which was 0.1 M in either perchloric acid or hydrochloric acid it afforded compound 3, but in pyridine alone it was recoverable unchanged (2). Another example of this type of elimination, leading to the introduction of unsaturation into a glycopyranoid ring, was observed... 

Calcium, iron, magnesium, alkali metals, and citrates do not affect the analysis. Ammonium salts interfere and must be eliminated by means of sodium nitrite or sodium hypobromite. The hydrochloric acid normally used in the analysis may be replaced by an equivalent amount of nitric acid without any influence on the course of the reaction. Sulphuric acid leads to high and erratic results and its use should be avoided. 

The monoethanolamine-hydrochloric acid buffer has a buffering capacity equal to the ammonia-ammonium chloride buffer commonly employed for the titration of calcium and magnesium with EDTA and solochrome black (compare Section 10.54). The buffer has excellent keeping qualities, sharp end points are obtainable, and the strong ammonia solution is completely eliminated. 

In the application of the polarographic method of analysis to steel a serious difficulty arises owing to the reduction of iron(III) ions at or near zero potential in many base electrolytes. One method of surmounting the difficulty is to reduce iron(III) to iron(II) with hydrazinium chloride in a hydrochloric acid medium. The current near zero potential is eliminated, but that due to the reduction of iron(II) ions at about - 1.4 volts vs S.C.E. still occurs. Other metals (including copper and lead) which are reduced at potentials less negative than this can then be determined without interference from the iron. Alternatively, the Fe3 + to Fe2+ reduction step may be shifted to more negative potentials by complex ion formation. 

The cobalt complex is usually formed in a hot acetate-acetic acid medium. After the formation of the cobalt colour, hydrochloric acid or nitric acid is added to decompose the complexes of most of the other heavy metals present. Iron, copper, cerium(IV), chromium(III and VI), nickel, vanadyl vanadium, and copper interfere when present in appreciable quantities. Excess of the reagent minimises the interference of iron(II) iron(III) can be removed by diethyl ether extraction from a hydrochloric acid solution. Most of the interferences can be eliminated by treatment with potassium bromate, followed by the addition of an alkali fluoride. Cobalt may also be isolated by dithizone extraction from a basic medium after copper has been removed (if necessary) from acidic solution. An alumina column may also be used to adsorb the cobalt nitroso-R-chelate anion in the presence of perchloric acid, the other elements are eluted with warm 1M nitric acid, and finally the cobalt complex with 1M sulphuric acid, and the absorbance measured at 500 nm. 

Dibenzo[7>,/]thiepins, e.g. 2, are obtained from 2-(arylsulfanyl)benzenepyruvic or -acetic acids by intramolecular Friedel-Crafts acylation, followed by elimination of water or hydrochloric acid.3 60... 

Optically pure vinylglycine derivatives 3 can be prepared by reacting lithiated (2aldol adducts 212. Hydrolysis of the adduct, followed by heating in 5N hydrochloric acid, effected ester hydrolysis and Peterson elimination to give the vinylglycine derivatives. 

Figure 2, it will be seen that the major maxima coincide at 550 to 560 m/. The nature of this interfering contaminant is not known, but it is readily extractable into aqueous hydrochloric acid (7). To eliminate the tedium of testing and tracing every lot of benzene, 25 ml. of 10% hydrochloric acid solution are routinely added to the sample just prior ta mincing. This procedure has effectively removed such solvent interference from consideration. 

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