Nitrous acid reaction with water

These reactions involve a diazonium ion (see 12-47) and are much faster than ordinary hydrolysis for benzamide the nitrous acid reaction took place 2.5 x lo times faster than ordinary hydrolysis. Another procedure for difficult cases involves treatment with aqueous sodium peroxide. In still another method, the amide is treated with water and f-BuOK at room temperature. " The strong base removes the proton from 107, thus preventing the reaction marked k j. A kinetic study has been done on the alkaline hydrolyses of A-trifluoroacetyl aniline derivatives. Amide hydrolysis can also be catalyzed by nucleophiles (see p. 427). 

This means that the ionization and rearrangement need not be concerted and that symmetrical protonated ethylene can not be a major intermediate in the reaction. A similar experiment with isobutylamine and nitrous acid in heavy water gave products that contained no carbon-deuterium bonds. Since it is known that the -complex formed from isobutylene and acid is in rapid equilibrium with protons from the solvent, none of this can be formed in the nitrous acid induced deamination. This in turn makes it probable that the transition state for the hydrogen migration is of the sigma rather than the -bonded type.261... 

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,... 

Fast dimerization of NO2 followed by reaction with water to give nitrous acid and nitric acid (this chemistry is well known from nitric add plants) ... 

The OH (X2n) can be generated from the photolysis of water, hydrogen peroxide, and nitric and nitrous acid. Reactions of OH(A2n) with various hydrocarbons arc important in understanding photochemical smog formation (see Section VIII—2). 

STRATEGY The solution contains N02 , a base, so we expect the pH to be i higher than that of nitrous acid alone. The K+ ion has no protons to donate j and cannot accept a proton, so it has no measurable effect on the pH of the ] solution. Identify the proton transfer equilibrium and use it to find the pH by means of an equilibrium table. Consider the initial molarity of HN02 (before reaction with water) to be 0.500 mol-L1. Because nitrite ions have also been added to the solution, set their initial molarity equal to the molar-5 ity of added salt (each KN02 formula unit supplies one N02 anion). Then proceed as described in Toolbox 10.1. Because the concentrations of the 1 added ions are much higher than 10-7 mol-L 1, we assume that we can S ignore the contribution to the pH from the autoprotolysis of water. 

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. 

Aromatic amines react with nitrous acid (sodium nitrite and hydrochloric acid) to form diazonium compounds. In the diazotization reaction the amine behaves as a nucleophile, adding to the nitroso group of the nitrous acid. Loss of water then yields the diazonium compound (4.8). 

The reaction of 2- and 6-amino groups with nitrous acid is similar to that of 2-amino-pyridines, in that diazonium salts are produced but, relative to phenyldiazonium salts, these are unstable. Despite this, they can be utilised for the introduction of groups such as halide or, oxygen by reaction with water, with loss of nitrogen. 8-Diazonium salts are considerably more stable. In 2-aminoadenosine, selective diazotisation occurs at the 2-amino group. ... 

Reaction of 1,2,4-triazinamines with nitrous acid yields, via the diazonium salts, cither the 1,2,4-triazinones by reaction with water or the chloro-l,2,4-triazines by reaction with chloride ions.350a,b... 

An amino group can also be acylated <84JHC697, 86JHC935) it reacts with sulfonyl chlorides and aryl isocyanates <86JHC935>, and also with nitrous acid to give, via the diazonium salt (281), either the triazinone by reaction with water or the chloro-triazine by reaction with chloride ions (Scheme 50). Nitrosation of 3-amino-1,2,4-triazine 2-oxides (282) and subsequent thermolysis of the diazonium tetrafluoroborate salts (283) afforded 3-fluoro-1,2,4-triazine 2-oxides (284) (Scheme 51). In one instance the diazonium tetrafluoroborate was isolated <85H(23)1969>. 

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