L- naphthol

Another line of analytical use is exemplified by the properties of l-(2-thiazolylazoi-2-naphthol (305), whose complexes with metals may be used for their spectrophotometric and titrimetric determination, as wel] as for their separation by solvent extraction (564, 568, 953-957, 1040). 

Naphthalenol. 1-Naphthol, a-naphthol, or l-hydroxynaphthalene/P(9-/j5 -iJ forms colorless needles, mp 96°C, bp 288°C, which tend to become colored on exposure to air or light. It is almost insoluble in water, but readily soluble in alcohol, ether, and benzene. 1-Naphthol and 2-naphthol are found in coal tar (56). 

The most important process to produce 1-naphthalenol was developed by Union Carbide and subsequently sold to Rhc ne-Poulenc. It is the oxidation of tetralin, l,2,3,4-tetrahydronaphthalene/719-64-2] in the presence of a transition-metal catalyst, presumably to l-tetralol—1-tetralone by way of the 1-hydroperoxide, and dehydrogenation of the intermediate ie, l-tetralol to 1-tetralone and aromatization of 1-tetralone to 1-naphthalenol, using a noble-metal catalyst (58). 1-Naphthol production in the Western world is around 15 x 10 t/yr, with the United States as the largest producer (52). 

The principal uses for 2-naphthalenol are in the dyes and pigments industries, eg, as a coupling component for azo dyes, and to make important intermediates, such as 3-hydroxy-2-naphthalenecarboxyhc acid (BON) (28) and its anilide (naphthol AS), 2-naphtholsulfonic acids, aminonaphtholsulfonic acids, and l-nitroso-2-naphthol/77/-5 /-5(/ (29). 

Llthol Reds. Lithol Red or Pigment Red 49 1/7103-38-4] is one of the most important of the precipitated salt pigments. They comprise a family of sodium (PR 49), barium (PR 49 1), calcium (PR 49 2), and strontium (PR 49 3) salts of dia2oti2ed Tobias acid or 2-naphthylamine-l-sulfonic acid coupled with 2-naphthol. The most popular are the barium and calcium salts, the former being yellower in shade. These reds are used where brightness, bleed resistance, and low cost ate of primary importance. They are neither resistant to heat nor chemicals, and are used primarily in printing inks and some inexpensive air-dried industrial paints where good durabiUty is not requited. 

Sodium Bisulfite. Sodium bisulfite [7631-90-5] NaHSO, is occasionally used to perform simultaneous reduction of a nitro group to an amine and the addition of a sulfonic acid group. For example, 4-amino-3-hydroxyl-l-naphthalenesulfonic acid [116-63-2] C qH NO S, is manufactured from 2-naphthol in a process which uses sodium bisulfite (59). The process involves nitrosation of 2-naphthol in aqueous medium, followed by addition of sodium bisulfite and acidification with sulfuric acid. 

Silica. The siUca content of natural waters is usually 10 to (5 x lO " ) M. Its presence is considered undesirable for some industrial purposes because of the formation of siUca and siUcate scales. The heteropoly-blue method is used for the measurement of siUca. The sample reacts with ammonium molybdate at pH 1.2, and oxaUc acid is added to reduce any molybdophosphoric acid produced. The yellow molybdosiUcic acid is then reduced with l-amino-2-naphthol-4-sulfoiiic acid and sodium sulfite to heteropoly blue. Color, turbidity, sulfide, and large amounts of iron are possible interferences. A digestion step involving NaHCO can be used to convert any molybdate-unreactive siUca to the reactive form. SiUca can also be deterrnined by atomic... 

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). 

Diazophenols, ie, o-hydroxyaryldiazonium salts, couple to 1-naphthol in weaMy basic solution primarily in the para position, but as the hydroxyl ion concentration is increased, formation of the ortho isomer is favored and is frequentiy the sole product. Pyridine and pyridine derivatives, urea, and acetate, etc, used as buffers can also catalyze azo coupling reactions (28). l-amino-2-naphthol-4-sulfonic acid [116-63-2] (1,2,4-acid) and 1-naphthol yield the important Eriochrome Black A [3564-14-5] (18a, R = H) (Cl Mordant Black 3 Cl 14640) which is reportedly (20) a mixture of ortho and para isomers. 

Nitro-l-diazo-2-naphthol-4-sulfonic acid prefers the 2-position in spite of the nitro group, and increasing alkalinity favors ortho coupling with diazophenols. 1-Naphthalenesulfamic acid [24344-19-2] (ArNHSO H) and N-nitro-1-naphthylamine [4323-69-7] (ArNHNO ) couple exclusively in the para position. The substitution of resorcinol [108-46-3] and y -phenylenediamine [108-45-2] is compHcated and has been discussed (29,30). The first azo dyes from aniline, eg. Aniline Yellow [60-09-3] (19) (Cl Solvent Yellow 1 Cl 11000) were manufactured in 1861 and Bismark Brown [10114-58-6] (20) (Cl Basic Brown 1 Cl 21000) appeared in 1863. The reaction is as follows ... 

In mordant dyes, phenols, naphthols, and enolizable carbonyl compounds, such as pyrazolones, are generally the couplers. As a rule, 2 1 metal complexes are formed ia the afterchroming process. A typical example of a mordant dye is Eriochrome Black T (18b) which is made from the important dyestuff iatermediate nitro-l,2,4-acid, 4-amiQO-3-hydroxy-7-nitro-l-naphthalenesulfonic acid [6259-63-8]. Eriochrome Red B [3618-63-1] (49) (Cl Mordant Red 7 Cl 18760) (1, 2,4-acid — l-phenyl-3-methyl-5-pyrazolone) is another example. The equiUbrium of the two tautomeric forms depends on the nature of the solvent. 

For colorimetric or gravimetric determination l-nitroso-2-naphthol can be used. For chromatographic ion exchange (qv), cobalt is isolated as the nitroso-(R)-salt complex. The cyanate complex is used for photometric determination and the thiocyanate for colorimetry. A rapid chemical analysis of... 

Many compounds capable of chelation have been tested for antimicrobial properties. Those showing positive results include saHcylaldoxime [94-67-7] l-nitroso-2-naphthol [131-91-9] mercaptobenzothiazol [149-30-4], dimethylglyoxime [95-45-4], saHcylaldehyde [90-02-8], cupferron [135-20-6], phenanthroline [66-71-7], isoniazid [54-85-3], thiosemicarbazones, the sulfur analogue of oxine, and numerous antibiotics (qv) including tetracyclines. Whether these compounds function exclusively, partially, or at all by virtue of their abiHty to chelate is open to debate. 

The isomeric 2-phenyla2o-l-naphthols (12) [1602-36 ] and l-phenyla2o-2-naphthols (13) [1602-30-8] exist more ia the hydra2one form than the a2o form as shown bv thek uv spectra. Then X values are each about 500 nm. 

The only nitroso dyes important commercially are the iron complexes of sulfonated l-nitroso-2-naphthol, eg. Cl Acid Green 1 [57813-94-2] (78) (Cl 10020) these inexpensive colorants are used mainly for coloring paper. 

Naphtho[2,3-h]indolizine-6,l 1-dione, 1, 337 Naphthoisocoumarin synthesis, 3, 831, 832 Naphtho[l,2-c]isothiazole, 3-amino-synthesis, 5, 136 2-Naphthol, l-(2-thiazolylazo)-analytical uses, 6, 328 Naphtholactam, 1, 326 Naphtholactone dyes, 1, 326... 

M. A. IT insky and G. Knorre proposed l-nitroso-2-naphthol as a reagent for cobalt and Zh.I. lotsich - magnesium diiodine acetylene as a reagent for carbonyl group. F.M. Flavitsky developed a method for qualitative analysis based on solid substances as well as a portable laboratory for qualitative analysis. G.V. Khlopin proposed a method for determining oxygen dissolved in water. 

The measurment in twophase systems is discussed by the example of dithizonate of zinc, in pseudomonophase systems - by the example of zinc and cadmium complexes with l-(2-pyridylazo)-2-naphthol, lanthanoid ion complexes with l-(2-pyridylazo)-resorcin. 

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