Sodium hydroxide reaction with nitrous acid

While the cuprous cyanide solution is warmed gently (to 60°-70°) on the water bath, a solution of p-tolyldiazonium chloride is prepared as follows Heat 20 g. of p-toluidine with a mixture of 50 g. of concentrated hydrochloric acid and 150 c.c. of water until dissolution is complete. Immerse the solution in ice-water and stir vigorously with a glass rod so that the toluidine hydrochloride separates as far as possible in a microcrystalline form. Then cool the mixture in ice and diazotise with a solution of 16 g. of sodium nitrite in 80 c.c. of water, added until the nitrous acid test with potassium iodide-starch paper persists. The diazonium chloride solution so obtained is poured during the course of about ten minutes into the warm cuprous cyanide solution, which is meanwhile shaken frequently. After the diazo-solution has been added the reaction mixture is heated under an air condenser on the water bath fox a further quarter of an hour, and then the toluic nitrile is separated by distillation with steam (fume chamber, HCN ). The nitrile (which passes over as a yellowish oil) is extracted from the distillate with ether, the p-cresol produced as a by-product is removed by shaking the ethereal extract twice with 2 A-sodium hydroxide solution, the ether is evaporated,... 

Extract the oil obtained in the nitrous acid test with about 5 ml of ether and wash the extract successively with water, dilute sodium hydroxide and water, and evaporate off the ether. Apply Liebermann s nitroso reaction to the residual oil or solid. Place 1 drop of 0.01-0.02 g of the nitroso compound in a dry test tube, add 0.05 g of phenol and warm together for 20 seconds cool, and add 1 ml of concentrated sulphuric acid. An intense green (or greenish-blue) coloration will be developed, which changes to pale red upon pouring into 30-50 ml of cold water the colour becomes deep blue or green upon adding excess of sodium hydroxide solution. 

Not all acids are completely ionized when converting formula equations to ionic equations they are kept together as molecules because only a small fraction of their molecules actually ionize in solution. These are the weak acids which were discussed previously in this chapter. We will be concerned with these three acetic acid, HC2H302faql, nitrous acid, HN02(7q) and hydrofluoric acid, HF(aq). The formula, ionic and net-ionic equations for the reaction of acetic acid with sodium hydroxide are shown below. 

The amino group in 8-aminopyrido[2,3-b]pyrazine is hydrolyzed to give the 8-0x0 compound by treatment with sodium hydroxide. Similarly the 6-amino groups in compounds 103 and 104 have been replaced by treatment with nitrous acid." Reaction of 5-alkyl quaternary salts of pyrido[2,3-b]pyrazine with a variety of nucleophiles has been recently described " (see Section IIIl). 

An alternative method of removing the aniline is to add 30 ml. of concentrated sulphuric acid carefully to the steam distillate, cool the solution to 0-5°, and add a concentrated solution of sodium nitrite until a drop of the reaction mixture colours potassium iodide - starch paper a deep blue instantly. As the diazotisation approaches completion, the reaction becomes slow it will therefore be necessary to teat for excess of nitrous acid after an interval of 5 minutes, stirring all the whUe. About 12 g. of sodium nitrite are usually required. The diazotised solution is then heated on a boiling water bath for an hour (or until active evolution of nitrogen ceases), treated with a solution of 60 g. of sodium hydroxide in 200 ml. of water, the mixture steam-distilled, and the quinoline isolated from the distillate by extrsM-tion with ether as above. 

Synthesis. Almost without exception, azo dyes ate made by diazotization of a primary aromatic amine followed by coupling of the resultant diazonium salt with an electron-rich nucleophile. The diazotization reaction is carried out by treating the primary aromatic amine with nitrous acid, normally generated in situ with hydrochloric acid and sodium nitrite. The nitrous acid nitrosates the amine to generate the N-nitroso compound, which tautomerizes to the diazo hydroxide. 

Thienyimethanol (360a) underwent allylic rearrangement to 4-hydroxy-2//-pyran (2) with oxalic acid at 20°C for 6 days.341 2-Thienylmethylamine (360b) with nitrous acid (Demyanov reaction) gave a mixture of 360a and 2.3 An 86% yield of a mixture of 2,6-di-te/ -bu tyl-2//- and 4//-thiopyrans 362 and 363 was obtained when 2,5-dihydrothiophene ketone 361 (readily accessible by Birch reduction of 2-pivaIoyl-5-ter/-butylthiophene) was reduced with zinc and sodium hydroxide in the presence of trimethylsilyl chloride.286... 

Hydrazotc acid, HN,. ply.. = 4.72, and most of its covalent compounds (including its heavy metal salts) are explosive. It is formed (1) in 90% yield by reaction of sodium amide with nitrous oxide, (2) by reaction of hydraztntum ion with nitrous acid, (3) by oxidation of hydrazimum salts, (4) by reactio n of hydt azinium hydrate with nitrogen trichloride tin benzene solution). Hvdrazoic acid forms metal azides with the corresponding hydroxides and carbonates. It reacts with HC1 to give ammonium chlonde and nitrogen, with H2SO4 to form hydrazinium acid solfate, with benzene to form aniline, and it enters into a number of oxidation-reduction reactions. 

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