R -acid

Direct Blue 218 had reported sales of 623 t valued at 4.4 million ia 1987. It is produced from Direct Blue 15 (76) by metallizing and elimination of methyl groups from the methoxide to form the copper complex. Direct Blue 15 (76) is prepared by coupling o-dianisidine [119-90-4] to two moles of H-acid (4-amiQO-5-hydroxy-2,7-naphthalenedisulfonic acid) under alkaline pH conditions. Other important direct blues iaclude Direct Blue 80 (74), (9-dianisidine coupled to two moles of R-acid (3-hydroxy-2,7-naphthalenedisulfonic acid [148-75-4]) followed by metallizing to form a bis copper complex, and Direct Blue 22 (77), an asymmetrical disazo dye, prepared by coupling o-dianisidine to Chicago acid [82-47-3] and 2-naphthol. Direct Blue 75 (78) is an example of a trisazo dye represented as metanilic acid — 1,6-Q.eve s acid — 1,6-Q.eve s acid — (alb) Ai-phenyl J-acid. 

A number of transition-metal complexes of RNSO ligands have been structurally characterized. Three bonding modes, r(A,5), o-(5)-trigonal and o (5 )-pyramidal, have been observed (Scheme 9.1). Side-on (N,S) coordination is favoured by electron-rich (et or j °) metal centers, while the ff(S)-trigonal mode is preferred for less electron-rich metal centres (or those with competitive strong r-acid co-ligands). As expected ti (N,S)... 

Oleum. Fuming sulfuric acid a soln of sulfur trioxide in sulfuric acid used as a sulfating and sulfonating agent. See under Acidity in Acids in Vol 1, A88-R to A90-R Acids Used in Manufacture and Analysis of Explosives in Vol 1, A93-L to A93-R and under Nitration in this Vol For analytical procedures, see under Glass Bulbs for Weighing Acids in Vol 6, G78-R to G79-R... 

A quantitative study of the azo coupling reactions of heterocyclic diazo compounds was made by Sawaguchi et al. (1971), who measured the coupling rates of seventeen heterocyclic diazonium ions with R-acid (2-naphthol-3,6-disulfonic acid) and compared them with those of the benzenediazonium ion with the same coupling component. All the heterocyclic diazonium ions investigated react faster with R-acid than does the benzenediazonium salt. More recently, Diener and Zollinger (1986) confirmed Sawaguchi s results and interpreted them in more detail. 

The hydrolysis with a (R)-specific amidase from Klebsiella oxytoca resolved 2-hydroxy- and 2-amino-3,3,3-trifluoro-2-methylpropionamide, giving the (R)-acid and the remaining (S)-amide (Figure 6.39) [104,105]. 

Rochester, C. R., Acidity Functions, John Wiley Sons, New York, 1970. 

Optically active 3-hydroxybutanoic acid and its methyl ester were first prepared by McKenzie, Magnus-Levy, and Emil Fischer.3 The biopolymer PHB and mixed polymers containing (R)-3-hydroxybutanoate and (R)-3-hydroxypentanoate were also discovered long ago,4 5 and are now produced on an industrial scale. .7 As described here, depolymerization by transesterification [H+ or Ti(OR)4 catalysis], or by hydrolysis, produces8-9 the corresponding monomeric (R)-esters and (R)-acids 1. The 3-hydroxybutanoic acid can also be prepared by hydrolysis of the ester.2-10... 

The kinetic behaviour of anionic dyes on amide fibres tends to be much more closely related to molecular size and hydrophilic-lipophilic balance. Thus within a related series of dye structures it is possible to discern more specific relationships. For example, in the series of p-substituted aniline—>R acid dyes (3.91 R = H, methyl, n-butyl or n-dodecyl) the logarithm of the rate of dyeing on wool is inversely proportional to the molecular volume [110]. 

The preparation of 2-naphthol by high-temperature sulphonation of naphthalene followed by alkali fusion of the resulting naphthalene-2-sulphonic acid has been mentioned previously. Further sulphonation of 2-naphthol yields several useful naphtholsulphonic acids and conditions can be chosen to make one or other of these compounds the main product. The initial product is the unstable 2-naphthol-l-sulphonic acid, which readily rearranges to 2-naphthol-6-sulphonic acid (4-36 Schaeffer s acid). Further sulphonation leads to 2-naphthol-6,8-disulphonic acid (4-37 G acid) at low temperature and 2-naphthol-3,6-disulphonic acid (4.38 R acid) at higher temperature. 

Condensation of a diphenylmethanol derivative, such as Michler s hydrol (6.159), with a reactive aryl component under acid conditions (the hydrol synthesis) also provides a leuco base. The dye 6.163 (Cl Acid Green 50) is made by reacting Michler s hydrol with R acid (2-naphthol-3,6-disulphonic acid) and oxidising the resulting leuco compound (Scheme 6.30). 

A sample of the reaction mixture should not become turbid when sodium acetate solution is added. But if now a few drops of a solution of an aniline salt are poured in, there is precipitated yellow diazoaminobenzene, which can be re-dissolved with concentrated hydrochloric acid after a few small pieces of ice have been added. Further, when a few particles of j8-naphthol or of R-acid are dissolved in a small excess of 2 A-sodium hydroxide solution and a sample of the diazo-solution is added, an intense red colour is produced. The development of this colour, which results from coupling , is an infallible test for a diazonium salt, and hence also for the corresponding primary aromatic amine. 

The development of the intense colour of the azo-dyes provides a delicate and distinctive test for primary aromatic amines. Since the naphthalene derivatives are more deeply coloured than those of benzene, it is customary to use not phenol but j8-naphthol or the so-called R-acid ( acid for Red ), i.e. /S-naphthol-3 6-disulphonic acid ... 

It is well known that heating of honey resrrlts in HMF, which is formed dming acid-catalysed dehydration of hexoses [6]. The presence in honey of simple sugars (glucose and fructose) and mar r acids is a favotrrable condition for the production of this substance. 

Scheme 4.26 Polystyrene-bound dicyanoketen acetal - solid with high r-acidity for the activation of acetals.

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