Hydrogen chloride preparation

Hydrogen chloride prepared by dropping concentrated sulfuric acid into a mixture of sodium chloride and concentrated hydrochloric acid may be used directly without diying. 

A solution of (R)-5-trans-(2-phenylsulfonylethenyl)-3-(N-methylpyrrolidin-2-ylmethyl)-lH-indole and 10% Pd/C in ethanolic hydrogen chloride (prepared from absolute ethanol and acetyl chloride and N,N-dimethylformamide was shaken under a hydrogen atmosphere at room temperature). The resultant reaction mixture was filtered through diatomaceous earth (Celite trademark), washed with absolute ethanol, and the combined filtrates were evaporated under reduced pressure. The residue was partitioned between ethyl acetate and water. The organic phase was separated, washed with water, brine, dried... 

Utilization of Liberated Hydrogen Chloride. Preparation of Alkyl Halides. By causing the hydrogen chloride split off in direct chlorinations to react with compatible alcohols, it is not necessary to employ oxidants to obtain a maximum utilization of the chlorine introduced. Thus, methanol can be introduced into the chamber containing hydrogen chloride, hydrocarbon, and chlorinated hydrocarbon and is converted to methyl chloride. The principal reactions involved may be represented as follows ... 

CaHjNCO, PhNCO. A pungent lachrymatory almost colourless liquid m.p. — 33 "C, b.p. 162°C. Used as a dehydrating agent and for characterization of alcohols. Prepared from aniline and phosgene in the presence of hydrogen chloride. 

Aluminium chloride can be prepared not only by the direct combination of the elements but also by the passage of dry hydrogen chloride over heated aluminium ... 

This chloride is prepared by dissolving tin in concentrated hydrochloric acid on cooling, the solution deposits crystals of hydrated tin(II) chloride. SnClj. 2H2O ("tin salt ). The anhydrous chloride is prepared by heating tin in a current of hydrogen chloride ... 

Arsenic forms a volatile trifluoride, ASF3, and a fairly volatile trichloride, ASCI3, which fumes in air. The latter is prepared by passing dry hydrogen chloride over arsenic(lll) oxide at 500 K ... 

Uses of hydrogen chloride—Hydrogen chloride is sometimes used in the preparation of an ester, for example ethyl benzoate, where it acts as both an acid catalyst and a dehydrating agent. Hydrochloric acid is used primarily to produce chlorides, for example ammonium chloride. It is extensively used in the manufacture of anilme dyes, and for cleaning iron before galvanising and tin-plating. 

The tribromobenzene obtained in this way should be entirely free from unchanged tribromoaniline. To test its purity, dissolve a small quantity in hot dry benzene and pass in hydrogen chloride gas from a Kipp s apparatus no trace of crystals of tribromoaniline hydrochloride should appear. Note also that although the m.p.s of the two compounds are almost identical, that of the recrystallised product from the above preparation is considerably depressed by admixture with tribromoaniline. 

Cinnamic acid can be readily esterified by the Fischer-Speier method without any risk of the addition of hydrogen chloride at the double bond. Proceed precisely as for the preparation of ethyl benzoate (p. 104), using 20 g. of cinnamic acid and 20 ml. of rectified spirit. When the crude product is poured into water, a sharp separation of the ester is not readily obtained, and hence the addition of about 10 ml. of carbon tetrachloride is particularly desirable. Finally distil off the carbon... 

Lucas reageut is prepared by dissolving 68 g. (0-5 mole) of anhydrous zinc chloride (fused sticks, powder, etc.) in 62 6 g. (0 6 mole) of concentrated hydrochloric acid with cooling to avoid loss of hydrogen chloride. 

In a 1500 ml. round-bottomed flask, carrying a reflux condenser, place 100 g. of pure cydohexanol, 250 ml. of concentrated hydrochloric acid and 80 g. of anhydrous calcium chloride heat the mixture on a boiling water bath for 10 hours with occasional shaking (1). Some hydrogen chloride is evolved, consequently the preparation should be conducted in the fume cupboard. Separate the upper layer from the cold reaction product, wash it successively with saturated salt solution, saturated sodium bicarbonate solution, saturated salt solution, and dry the crude cycZohexyl chloride with excess of anhydrous calcium chloride for at least 24 hours. Distil from a 150 ml. Claisen flask with fractionating side arm, and collect the pure product at 141-5-142-5°. The yield is 90 g. 

An alternative method of conducting the preparation consists in treating 100 g. of cycZohexanol with 250 ml. of concentrated hydrochloric acid, refluxing slowly whilst a stream of hydrogen chloride gas is passed into the mechanically stirred... 

Allyl Chloride. Comparatively poor yields are obtained by the zinc chloride - hydrochloric acid method, but the following procedure, which employs cuprous chloride as a catalyst, gives a yield of over 90 per cent. Place 100 ml. of allyl alcohol (Section 111,140), 150 ml. of concentrated hydrochloric acid and 2 g. of freshly prepared cuprous chloride (Section II,50,i one tenth scale) in a 750 ml. round-bottomed flask equipped with a reflux condenser. Cool the flask in ice and add 50 ml. of concen trated sulphuric acid dropwise through the condenser with frequent shaking of the flask. A little hydrogen chloride may be evolved towards the end of the reaction. Allow the turbid liquid to stand for 30 minutes in order to complete the separation of the allyl chloride. Remove the upper layer, wash it with twice its volume of water, and dry over anhydrous calcium chloride. Distil the allyl chloride passes over at 46-47°. 

Commercial preparations of acetyl chloride are best freed from volatile phos. phorus compounds and dissolved hydrogen chloride by redistillation from 5-10 per cent, of the volume of pure dimethylaniline. 

To prepare the solid phenyldlazonlum chloride or sulphate, the reaction is conducted in the absence of water as far as possible. Thus the source of nitrous acid is one of its organic esters (e.g., amyl nitrite) and a solution of hydrogen chloride gas in absolute alcohol upon the addition of ether only the diazonium salt is precipitated as a crystalline solid, for example ... 

The phenyl propionate may be prepared by slowly adding 196 g. (120 ml.) of redistilled thionyl chloride to a mixture of I50g. of pure phenol and 132 g. (133 ml.) of propionic acid (compare Fig. 111,31, 1), warming to drive all the sulphur dioxide and hydrogen chloride, and distilling 190 g. of phenyl propionate, b.p. 202-212° (the pure substance boils at 211°) are obtained. 

CAUTION. The preparation of o-nitrobenzoyl chloride, o-nitrophenacetyl chloride and all o nitroacid chlorides should not be attempted by the above methods a violent explosion may occur upon distilling the product or when the last traces of thionyl chloride are removed in vacuo at 100°. Perhaps the safest method is to treat the pure acid in benzene solution with 1 1 mols of thionyl chloride and to reflux until evolution of sulphur dioxide and hydrogen chloride has ceased the solution of the acid chloride in benzene may then bo employed for most reactions. 

Vinyl compounds. Vinyl chloride (prepared from acetylene and hydrogen chloride) 3 ields polyvinyl chloride (P.V.C.), which is employed as a rubber substitute and for other purposes. Vinyl acetate (from... 

The reason for this is that reaction (i) is usually much slower than (ii) and (iii) so that the main reaction appears to be (Iv) (compare the preparation of tertiary butyl chloride from tertiary butyl alcohol and concentrated hydrochloric acid, Section 111,33). If the reaction is carried out in the presence of P3rridine, the latter combines with the hydrogen chloride as it is formed, thus preventing reactions (ii) and (iii), and a good yield of the ester is generally obtained. The differentiation between primary, secondary and tertiary alcohols with the aid of the Lucas reagent is described in Section III,27,(vii). 

Phenylpropanolamine. - With catalyst prepared as previously described from 0.5g of palladium chloride and 3g of charcoal, it was possible to reduce two portions of 9.8g of isonitrosopropio-phenone (0.06 mol), dissolved in 150 cc. of absolute alcohol containing 7. Og of hydrogen chloride, to phenylpropanolamine in from 145 - 190 minutes with yields of the isolated chloride from 9.4g to 11. Og, or 84 to 98% of the theoretical. After recrystallization from absolute alcohol the salt melted at 191°. The free base was obtained by treating an aqueous solution of the hydrochloride with alkali on cooling, the liberated amino alcohol solidified and after recrystallization from water melted at 103°."... 

Halide derivatives may be fluorides, chlorides, or bromides. Fluorides are best prepared by the reaction of hydroxy groups with (diethylamino)sulfur trilluoride ( DAST M. Sharma, 1977) or of glycosyl thioethers with DAST/NBS (K.C. Nicolaou, 1990 B). The other halides are usually only introduced at the glycosidic position, where treatment with hydrogen chloride... 

Urea derivadves are of general interest in medicinal chemistry. They may be obtained cither from urea itself (barbiturates, sec p. 306) or from amines and isocyanates. The latter are usually prepared from amines and phosgene under evolution of hydrogen chloride. Alkyl isocyanates are highly reactive in nucleophilic addidon reactions. Even amides, e.g. sulfonamides, are nucleophilic enough to produce urea derivatives. 

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