Naphthylamine-sulphonic acids

In this method the order of addition of the reactants is changed. The most general application is to the diazotisation of aniline- and naphthylamine-sulphonic acids, many of which are sparingly soluble in acidic media and form sparingly soluble diazonium salts. Typically, the arylaminesulphonic acid is dissolved as its sodium salt in dilute alkali and sodium nitrite is then added to the solution. The resulting solution is run slowly into a mixture of hydrochloric acid and ice, the diazonium salt being formed almost instantaneously. 

Naphthylamine Sulphonic Acids and Naphthol Sulphonic Acids... 

The most important dyes derived from naphthylamine sulphonic acids and from naphthol sulphonic acids result from coupling them as azo compounds with other rings. This coupling is effected through a diazonium salt made by diazotizing an amine and bringing this di-... 

Congo Red.—When benzidine is diazotized a double diazo or tetrazo compound results (p. 575) from the diazotization of both of the amino groups. This diazonium or tetrazonium salt reacts with two molecules of naphthylamine sulphonic acid, naphthionic acid, forming a double azo or disazo compound. The sodium salt of this compound is Congo red. The reactions are ... 

These mercurated naphthylamine sulphonic acids react immediately with halogen halides, the mercury being freed, and in the case of potassium iodide solution mercuric iodide separates. 

Naphthylamine sulphonic acid Derivatives.— The free acid (2-4 grams) is dissolved in 25 c.c of water containing a little sodium... 

It will be of interest, before entering into the consideration of these dyestuffs, to examine the constitution of the naphthylamine-sulphonic acids. 

The sparingly soluble sodium salt yields an a-naphthylamine-sulphonic acid on reduction, which has the constitution expressed by the formula ... 

The pKa values of thirteen naphthylamine-sulphonic acids (proton lost constants only) are available to supplement the anilinesulphonic acids of Table 8.11 (Bryson, 1951). 

Reaction of a Substituted Triazine with a Substituted Naphthylamine Sulphonic Acid in Water... 

Fig. 5.19 Temporal course of signal 2F of temperature sensor after injection of triazine A in aqueous solution of naphthylamine sulphonic acid B, non-isothermal, isopeiibolic, discontinuous reaction...

Fig. 5.21 Conversion of triazine A and naphthylamine sulphonic acid B in aqueous solution A + B C + D...

Fig. 5.22 Comparison of sensor signal T2f versus time for different rate orders of conversion, triazine A and naphthylamine sulphonic acid B, in aqueous solution, non-isothermal, discontinuous reaction, isoperibolic condition, Ao = Bq...

Chapter IV. a-Chloromethylnaphthalene (IV,23) benzylamine (Gabriel synthesis) (IV,39) i r.N -dialkylanilines (from amines and trialkyl orthophosphates) (IV,42) a-naphthaldehyde (Sommelet reaction) (IV,120) a-phenyl-cinnamic acid (Perkin reaction using triethylamine) (IV,124) p-nitrostyrene (IV,129) p-bromonaphthalene and p naphthoic acid (from 2 naphthylamine-1 -sulphonic acid) (IV,62 and IV,164) diphenic acid (from phenanthrene) (IV,165). 

Ar NHi = Sulphanilic acid ArH = l-Naphthylamlne-4-sulphonic acid Aniline l-Naphthylamine-8-sulphonic acid 4-Nitroaniline Indole ... 

A kinetic study of the desulphonation of 2-naphthylamine-l-sulphonic acid by hydrochloric, sulphuric and phosphoric acids showed the rate to be proportional to the concentration of hydrogen ions and the aromatic and a mechanism involving the formation of 1-naphthylsulphamic acid was proposed702. 

P-Bromonaphthalene. The preparation from p-naphthylamine, which has carcinogenic properties, is avoided by the use of 2-naphthylamine-1-sulphonic acid ( 2-amino-1-naphthalenesulphonic acid ) the latter is obtained commercially by cautious treatment of p-naphthol with sulphuric acid—the SOjH group first enters the 1-position—followed by the Bucherer reaction. Diazotisation and reaction with cuprous bromide yields 2-bromonaphthalene-l-sulphonic acid heating with sulphuric acid eliminates the sulphonic acid group to give 2-bromonaphthalene. 

In the above reaction mechanisms it is noteworthy that the sulphonic acid group introduced has been shown to enter at the 3-position and not the 4-position as previously postulated. A consequence of this situation is that an attempted Bucherer reaction on a naphthol (or a naphthylamine) carrying a sulphonic acid group located meta to the hydroxy (or amino) group would require a second sulphonic acid group to be introduced at this position. Since it is impossible to locate two sulphonic acid groups on the same carbon atom, these compounds cannot undergo the transformation. 

In some cases where it is difficult to carry out the Bucherer reaction successfully, it is easier to prepare N-arylnaphthylamines by heating together a naphthylamine and an arylamine. In particular, this reaction is useful in the preparation (Scheme 4.24) of 1-phenylaminonaphthalene-8-sulphonic acid (4.34 N-Phenyl Peri acid) and its N-4-methylphenyl analogue (Tolyl Peri acid), both of which intermediates are valuable components for the production of navy blue dyes. 

After sulphonation to 2-naphthylamine-l,5,7-trisulphonic acid, the labile 1-sulphonic acid substituent, which has now served its purpose, is eliminated by diluting the sulphonation mixture and heating. Fusion of the resulting disulphonic acid (4.42) with sodium hydroxide replaces the more labile 5-sulphonic acid group by a hydroxy group, forming ] acid. 

Naphthylamine-5,7-disulphonic acid and 2-naphthylamine-l-sulphonic acid, which are intermediate products in Scheme 4.28, as well as 2-naphthylamine-l,5-disulphonic acid (obtained by careful low-temperature sulphonation of Tobias acid), are all used in the synthesis of azo dyes. 

Nitration of naphthalene-1-sulphonic acid produces two isomeric nitronaphthalenes that have very similar solubilities. It is convenient to reduce the mixture without separation, giving a mixture of l-naphthylamine-8-sulphonic acid (4-44 Peri acid) and 1-naphthylamine-5-sulphonic acid (4.45 Laurent s acid), as in Scheme 4-29. These two... 

In all the above sequences, single isomers are produced by careful control of the reaction conditions combined with purification by selective isolation at various points in the synthesis. Occasionally two isomers are produced which give dyestuffs that have very similar properties in these cases it is often quite acceptable and economically beneficial not to separate the individual components but to use the total mixture in dye preparation. An example is the mixture of l-naphthylamine-6- and 7-sulphonic acids (4.46 mixed Cleve s acids), which arises by nitration and reduction of naphthalene-2 Sulphonic acid (Scheme 4.30). 

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