2-Naphthalenesulfonic acid, derivative

Among the naphthalenesulfonic acid derivatives, particular note should be taken of the so-called letter acids. Table 9.6 shows some important letter acids, which are used as coupling components in the production of azo dyes. 

Sulfonation. Sulfonation of naphthalene with sulfuric acid produces mono-, di-, tri-, and tetranaphthalenesulfonic acids (see Naphthalene derivatives), ah of the naphthalenesulfonic acids form salts with most bases. Naphthalenesulfonic acids are important starting materials in the manufacture of organic dyes (15) (see Azo dyes). They also are intermediates used in reactions, eg, caustic fusion to yield naphthols, nitration to yield nitronaphthalenesulfonic acids, etc. 

By the alkaline hydrolysis of the sultone formed on boiling an aqueous solution of the diazonium salt of S-amino-l-naphthalenesulfonic acid or its appropriate derivatives. 

Direct dyes are defined as anionic dyes substantive to ceUulosic fibers (cotton, viscose, etc), when applied from an aqueous bath containing an electrolyte. Before the discovery of Congo Red in 1884, only mordanted cotton could be dyed. Congo Red [573-58-0] (62) (Cl Direct Red 28 Cl 22120) a primary symmetrical disazo dye, which is made readily from bisdiazotized benzidine and naphthionic acid [84-86-6] (4-arnino-l-naphthalenesulfonic acid), was the precursor of a most important line of dyes, including all shades, derived from benzidine and its homologues. Today, no benzidine dye is produced because benzidine is carcinogenic. 

Interesting regioselectivities have been known for more than 100 years for azo coupling reactions with aminonaphthol derivatives such as 6-amino-4-hydroxy-2-naphthalenesulfonic acid (12.136, y-acid), 7-amino-4-hydroxy-2-naphthalenesulf-onic acid (J-acid), and 4-amino-5-hydroxy-2,7-naphthalenedisulfonic acid (H-acid). They give two types of isomeric azo compounds depending on the pH-value of the... 

Extrinsic fluorescence is used whenever the natural fluorescence of a macromolecule is inadequate for accurate fluorescence measurement. In this case, one can attach a fluorescent reporter group by using the reactive isocyanate or isothiocyanate derivatives of fluorescein or rhodamine, two intensely fluorescent molecules. One can covalently also label a protein s a- and e-amino groups with dansyl chloride (/.e., A,A-dimethylaminonaphtha-lenesulfonyl chloride). Another useful reagent is 8-ani-lino-l-naphthalenesulfonic acid (abbreviated ANS). This compound is bound noncovalently by hydrophobic interactions in aqueous solutions, ANS is only very fluorescent, but upon binding within an apolar environment, the quantum yield of ANS becomes about 100 times greater. 

By alkali fusion or alkaline hydrolysis under pressure of appropriate naphthalenedisulfonic or naphthalenetrisulfonic acid or hydroxynaphthalenedisulfonic acid f By alkaline hydrolysis of sulfone formed on boiling aqueous solution of diazonjum salt of S-arnino-l-naphthalenesulfonic acid or appropriate derivatives. 

Monoazo dyes with heterocyclic coupling components, such as pyrazolone or pyridone, are yellow to greenish yellow. Other suitable coupling components include aniline and naphthylamine derivatives. Substituted anilines or amino-naphthalenesulfonic acids are employed as diazo components. Examples are C.I. Reactive Yellow4, C.I. Reactive Yellow 17 (see Section 3.1.5). 

A particularly important class of coupling components are the aminohydroxy-naphthalenesulfonic acids. Appropriate variation of the disazo component permits the development of shades ranging from orange to black. Orange and scarlet are achieved with I-acid (6-amino-l-hydroxy-naphthalene-3-sulfonic acid) and y-acid (7-amino-1-hydroxynaphthaIcne-3-sulfonic acid), whereas H-acid (8-amino-l-hydroxynaphthalene-3,6-disulfonic acid) and K-acid (8-amino-l-hydroxy-naphthalene-3,5-disulfonic acid) derivatives are useful for red to bluish-red hues. Extremely lightfast red shades are also accessible with disazo dyes ( brown dyes ). For chemical structures see Section 3.1.5). 

Naphthalenesulfonic acids are hydrolyzed to hydroxy derivatives under drastic alkaline conditions, and sulfonic acid groups in the a-position react preferentially [119],... 

Chem. Descrip. naphthalenesulfonic acid, bis(l-methylethyl)-, me derive. 50% CAS 99811-86-6 UN 3265... 

FIGURE 9.3 Structures of benzene, naphthalene, and anthracene derivatives analyzed sodium benzenesulfonate (1), 4-chloroaniline (2), 3,4-dichloroaniline (3), 2-naphthylamine (4), sodium 2-naphthalenesulfonate (5), sodium anthraquinone 2-sulfonate monohydrate (6), 1,2-diamineanthraquinone (7), 2-anthraceencarboxilic acid (8), and 2-anthramine (9). 

Primary aromatic amines and their N-mono- and N,N-dialkyl derivatives can be coupled with diazonium salts in a slightly acid medium. The reaction can be carried out using stabilized diazonium salts (which do not contain free nitrous acid), for example, with p-nitrobenzenediazonium fluoroborate (17) or with a salt with 1-naphthalenesulfonate. The reaction takes place in dilute acetic acid in the presence of sodium acetate. Recently, 4-azo-benzenediazonium fluoroborate was proposed as the reagent, and dimethyl sulfoxide or dimethylformamide (18, 19) as the reaction medium in which intensely colored di-cations of bis-azo dyes can be formed. 

---