Reduction hydrochloric acid

Sodium chlorate Sodium peroxide ore reduction Hydrochloric acid ore refining... 

Clemmensen reduction Aldehydes and ketones may generally be reduced to the corresponding hydrocarbons by healing with amalgamated zinc and hydrochloric acid. 

Colourless crystals m.p. 50 C, b.p. 301 C. Basic and forms sparingly soluble salts with mineral acids. Prepared by the reduction of 1-nitronaphthalene with iron and a trace of hydrochloric acid or by the action of ammonia upon l-naphlhol at a high temperature and pressure. 

N-phenylhydroxylamine, PhNHOH and further reduction can give azoxybenzene, azobenzene, hydrazobenzene and aniline. The most important outlet commercially for the nitro-compounds is the complete reduction to the amines for conversion to dyestufTs. This is usually done in one stage with iron and a small amount of hydrochloric acid. 

Ditrophenol, -nitropbenol, C H NOj. Colourless needles m.p. 114 C. Prepared as 2-nitrophenol. Reduction with iron and hydrochloric acid gives 4-aminophenol. 

It is usually prepared by the reduction of p-nitrophenetole with iron and hydrochloric acid. 

CfiHgNj. Colourless crystals m.p. 63 C, b.p. 2%TC. Turns brown in air. Prepared by a one-stage reduction of m-dinitrobenzene with iron and hydrochloric acid. 

Benzenediazonium chloride reacts in solution with sodium sulphite to give benzenediazonium sodium sulphonate, which when treated with sulphurous acid undergoes reduction to phenylhydrazine sodium sulphonate. The latter readily hydrolyses in the presence of concentrated hydrochloric acid to give... 

Aliphatic hydrocarbons can be prepared by the reduction of the readily accessible ketones with amalgamated zinc and concentrated hydrochloric acid (Clemmensen method of reduction). This procedure is particularly valuable for the prep>aration of hydrocarbons wdth an odd number of carbon atoms where the Wurtz reaction cannot be applied with the higher hydrocarbons some secondary alcohol is produced, which must be removed by repeated distillation from sodium. 

Clemmensen reduction of aldehydes and ketones. Upon reducing aldehydes or ketones with amalgamated zinc and concentrated hydrochloric acid, the main products are the hydrocarbons (>C=0 —> >CHj), but variable quantities of the secondary alcohols (in the case of ketones) and unsaturated substances are also formed. Examples are ... 

Arylamines are generally prepared by the reduction of nitro compounds. When only small quantities are to be reduced and the time element is important and cost is a secondary consideration, tin and hydrochloric acid may be employed, for example ... 

Secondary and tertiary amines are not generally prepared in the laboratory. On the technical scale methylaniline is prepared by heating a mixture of aniline hydrochloride (55 parts) and methyl alcohol (16 parts) at 120° in an autoclave. For dimethylaniline, aniline and methyl alcohol are mixed in the proportion of 80 78, 8 parts of concentrated sulphuric acid are added and the mixture heated in an autoclave at 230-235° and a pressure of 25-30 atmospheres. Ethyl- and diethyl-anihne are prepared similarly. One method of isolating pure methyl- or ethyl-aniline from the commercial product consists in converting it into the Y-nitroso derivative with nitrous acid, followed by reduction of the nitroso compound with tin and hydrochloric acid ... 

Method B. Reduction with iron and hydrochloric acid. Place 40 ml. of water and 30 g. of grease-free iron filings (1) in a 750 or 1,000-ml. round-bottomed flask, and 25 g. (21 ml.) of nitrobenzene in a small beaker or conical flask. W arm the former on a water bnth at about 60°. Add... 

Reduction of A-nitrosomethylaniline. Into a 1 litre round-bottomed flask, fitted with a reflux condenser, place 39 g. of A-nitroso-methylaniline and 75 g. of granulated tin. Add 150 ml. of concentrated hydrochloric acid in portions of 25 ml. (compare Section IV.34) do not add the second portion until the vigorous action produced by the previous portion has subsided, etc. Heat the reaction mixture on a water bath for 45 minutes, and allow to cool. Add cautiously a solution of 135 g. of sodium hydroxide in 175 ml. of water, and steam distil (see Fig. II, 40, 1) collect about 500 ml. of distillate. Saturate the solution with salt, separate the organic layer, extract the aqueous layer with 50 ml. of ether and combine the extract with the organic layer. Dry with anhydrous potassium carbonate, remove the ether on a water bath (compare Fig. II, 13, 4), and distil the residual liquid using an air bath (Fig. II, 5, 3). Collect the pure methylaniline at 193-194° as a colourless liquid. The yield is 23 g. 

Reduction of A-nitrosoethylaniline. Employ 38 g. of A-nitroso-ethylaniUne, 75 g. of granulated tin and 150 ml. of concentrated hydrochloric acid. After all the acid has been added, heat on a water bath for 75 minutes and allow to cool. Treat the almost solid crystalline mass... 

Reduction of methyl orange to />-aminodimethylaniline. Method 1. Dissolve 2 0 g. of methyl orange in the minimum volume of hot water and to the hot solution add a solution of 8 g. of stannous chloride in 20 ml. of concentrated hydrochloric acid until decolourisation takes place gentle boiling may be necessary. Cool the resulting solution in ice a crystalline precipitate consisting of sulphanilic acid and some p-aminodimethylaniline hydrochloride separates out. In order to separate the free base, add 10 per cent, sodium hydroxide solution until the precipitate of tin hydroxide redisaolves. Extract the cold solution with three or four 20 ml. portions of ether, dry the extract... 

It may also be prepared by the reduction of phenyldiazonium chloride with the calculated amount of a solution of stannous chloride in hydrochloric acid, but the yield is not so high as that obtained by the above sulphite method ... 

Compounds containing two primary amino groups attached to a benzene ring can be prepared by the reduction of dinitro compounds and of nitroanilines, usually with tin or stannous chloride and hydrochloric acid or with iron and very dilute hydrochloric acid. / ara-diamines may also be obtained by the reduction of aromatic amino-azo compounds (e.g., p-aminodimethylanihne from methyl orange, see Section IV,78). p-Phenylenediamine may also be prepared from p-nitroacetanilide reduction with iron and acid yields p-amino-acetaniUde,.which may be hydrolysed to the diamine. 

Reduction of anthraquinone with tin and concentrated hydrochloric acid in the presence of boiling glacial eicetic acid gives anthrone this substance (keto form) under certain conditions passes into the enol form, anthranol ... 

Reduction to hydroquinone. Dissolve, or suspend, 0-5 g. of the quinone in 5 ml. of ether or benzene and shake vigorously with a solution of 1 0 g. of sodium hydrosulphite (Na2S204) in 10 ml. of N sodium hydroxide until the colour of the quinone has disappeared. Separate the alkaline solution of the hydroquinone, cool it in ice, and acidify with concentrated hydrochloric acid. Collect the product (extract with ether, if necessary) and recrystalhse it from alcohol or water. 

One method of preparing sulphlnic acids has already been described (diazo reaction. Section IV,65). Reduction of a sulphonyl chloride with zinc powder and water affords the zinc salt of the sulphinic acid, converted by sodium carbonate to the sodium salt (in which form it is conveniently isolated), and by hydrochloric acid into the somewhat unstable sulphinic acid, for example ... 

The acetone test reagent consists of a 0 1 per cent, solution of 2 4-dinitro-phenylhydrazine and is prepared as follows Dissolve 0-25 g. of 2 4-dinitrophenyl-hydrazine in 60 ml. of water and 42 ml. of concentrated hydrochloric acid by warming on a water bath cool the clear yellow solution and dilute to 250 ml. with water. The acetone test is considered negative when 5 ml. of the reagent and 4-5 drops of the distillate give no cloudiness or precipitate of acetone 2 4-dinitro-phenylhydrazone within 30 seconds. After a negative test is obtained, it is stron y recommended that the mixture in the flask be refluxed for 5-10 minutes with complete condensation and then to collect a few drops of distillate for another test. If no acetone is now detected, the reduction is complete. 

Hydrolysis of the azlactone leads to the acylaminooinnamic acid the latter may be be reduced catal3rtlcally (Adams PtOj catalyst 40 lb. p.s.i.) and then hydrolysed by hydrochloric acid to the amino acid. Alternatively, the azlactone (say, of a-benzylaminocinnamic acid) may undergo reduction and cleavage with phosphorus, hydriodic acid and acetic anhydride directly to the a-amino acid (d/ p phenylalanine). 

Reduction of a nitro compound to a primary amine. In a 50 ml. round-bottomed or conical flask fitted with a reflux condenser, place 1 g. of the nitro compound and 2 g. of granulated tin. Measure out 10 ml. of concentrated hydrochloric acid and add it in three equal portions to the mixtiue shake thoroughly after each addition. When the vigorous reaction subsides, heat under reflux on a water bath until the nitro compound has completely reacted (20-30 minutes). Shake the reaction mixture from time to time if the nitro compound appears to be very insoluble, add 5 ml. of alcohol. Cool the reaction mixture, and add 20-40 per cent, sodium hydroxide solution imtil the precipitate of tin hydroxide dissolves. Extract the resulting amine from the cooled solution with ether, and remove the ether by distillation. Examine the residue with regard to its solubility in 5 per cent, hydrochloric acid and its reaction with acetyl chloride or benzene-sulphonyl chloride. 

Reduction of 2.4-dimethyl-5-nitrothiazole with activated iron gives a product that after acetylation yields 25% 2.4-dimethyl-5-acetamido-thiazole (58). The reduction of 2-methyl 5-nitrothiazole is also reported (351 to give a mixture of products. The nitro group of 2-acetylhydrazino-5-nitrothiazole is reduced by TiCl in hydrochloric acid or by Zn in acetic acid (591. 

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