Cationic Coupling Components With

If the coupling component is not ionic, however, more dramatic effects occur, as found by Hashida et al. (1979) and by Tentorio et al. (1985). Hashida used N,N-bis(2-hydroxyethyl)aniline, while Tentorio and coworkers took 1-naphthylamine and l-amino-2-methylnaphthalene as coupling components. With cationic arenediazo-nium salts and addition of sodium dodecyl sulfate (SDS), rate increases up to 1100-fold were measured in cases where the surfactant concentration was higher than the critical micelle concentration (cmc). Under the same conditions the reaction... 

Coupling Components With Condensed Cyclic Ammo nium Residues. Heterocyclic compounds in which the condensed benzene ring is substituted by a hydroxyl or an amino group can be coupled with diazonium compounds and may also be quatemized, either prior or subsequent to the coupling reaction, to yield cationic azo dyes. l,2-Dialkyl-6-nitroindazolium salts are reduced to the 6-amino compounds and then coupled with diazonium salts of aromatic amines. These dyes (e g., 21) color polyacrylonitrile in bright yellow to orange shades [64],... 

The azo coupling reaction proceeds by the electrophilic aromatic substitution mechanism. In the case of 4-chlorobenzenediazonium compound with l-naphthol-4-sulfonic acid [84-87-7] the reaction is not base-catalyzed, but that with l-naphthol-3-sulfonic acid and 2-naphthol-8-sulfonic acid [92-40-0] is moderately and strongly base-catalyzed, respectively. The different rates of reaction agree with kinetic studies of hydrogen isotope effects in coupling components. The magnitude of the isotope effect increases with increased steric hindrance at the coupler reaction site. The addition of bases, even if pH is not changed, can affect the reaction rate. In polar aprotic media, reaction rate is different with alkyl-ammonium ions. Cationic, anionic, and nonionic surfactants can also influence the reaction rate (27). 

Reaction of a similar triazine component with I acid (1-hydroxy-6-amino-naphthalene-3-sulfonic acid), followed by coupling with diazotized 4-aminoazo-benzene gives the cationic substantive azo dye 4 [71032-95-6], which colors paper in red hues. 

Dialkylanilines that bear a cationic substituent at one of the alkyl groups are among the most important coupling components of cationic azo dyes. By reaction of iV-ethyl-iV-(2-chloroethyl)aniline or of N-ethyl- N-(2-chlo roethy 1)- w-toluidine with trimethylamine, ammonium salts are obtained that, upon coupling with dia-zotized aromatic amines, yield a large number of valuable dyes for coloring polyacrylonitrile. Red shades with a blue cast are obtained with 2-cyano-4-nitroani-line as the diazo component. 

Diazo Components With Amino alkyl Groups. Yellow dyes are prepared by ami-nomethylation of 2-(4 -aminophenyl)-5-methylbenzothiazole followed by diazoti-zation and coupling with acetoacetarylides. Red cationic dyes are obtained with naphthols or hydroxynaphthoic acid arylides. All are suitable for dyeing paper. The bleachability of these dyes is important for the recycling of waste paper [84], The aminomethylation of aromatic amines is carried out by reaction with formal-... 

The Friedel-Crafts acylation of acetanilide with chloroacetyl chloride yields l-acetamido-4-chloroacetylbenzene. The trimethylammonium group is introduced by reaction with trimethylamine, followed by hydrolysis of the acetamide group. This diazo component is a constituent of numerous yellow, orange, and red cationic azo dyes. Using diethyl- m-toluidine as the coupling component, the lightfast red dye 35 [67905-12-8] is obtained [99],... 

The pK values for azolediazonium ions (Scheme 12-4) refer to the heterolysis of the NH bond, not to the addition of a hydroxy group. Therefore, these heteroaromatic diazo components may react either as a cation (as shown in Scheme 12-4) or as the zwitterion (after loss of the NH proton). Diener and Zollinger (1986) investigated the relative reactivities of these two equilibrium forms (Scheme 12-5) in the azo coupling reaction of l,3,4-triazole-2-diazonium ion with the tri-basic anion of 2-naphthol-3,6-disulfonic acid. 

The EPR spectrum of 7 (R=CF3) AsFr, salt in S02, consisted of a central binomial septet due to coupling of 6 equivalent F atoms with one set of weak 33S satellites. Although trithiolylium cations contain two inequivalent sets of sulfur nuclei, only one set of 33S satellites were observed. Further studies with 7 (R=C02Me) however managed to resolve the 33S satellite into two components in 1 2 intensity ratio, consistent with the structure of a 1,2,3-trithiolylium radical cation.92... 

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