Quinoline-8-sulfonic acid

Treatment of quinoline with fuming sulfuric acid (30% S03) at 90 °C gives quinoline-8-sulfonic acid (17) in 54% yield with the 5- and 7-isomers as minor products. The quantity of 5-sulfonic acid (18) increases with reaction temperature and use of mercury or one of its salts as a catalyst in fuming sulfuric acid at 170 °C gives (18) as exclusive product. However, the thermodynamically favoured quinoline-6-sulfonic acid (19) is obtained when heating at 300 °C either the 8- or 5-sulfonic acid or quinoline itself with fuming sulfuric acid (Scheme 13). 

Sulfonation of quinoline gives largely the 8-sulfonic acid, whereas isoquinoUne affords the 5-acid. Reactions at higher temperatures produce other isomers, under thermodynamic control, for example both quinoline 8-sulfonic acid and quinoline 5-sulfonic acid are isomerised to the 6-acid. ... 

With fuming sulfuric acid quinoline gives quinoline-8-sulfonic acid, from which... 

The main application for quinoline is the production of 8-hydroxyquinoline (oxine), which is obtained by alkali fusion of quinoline-8-sulfonic acid. 

Sulfonation of quinoline to produce quinoline-8-sulfonic acid is carried out at 180 to 200 °C. Alkali fusion is performed at 250 °C and 45 bar final purification of the crude 8-hydroxyquinoline is effected by distillation. 

When the sulfonation was carried out in the presence of mercury(ii) sulfate catalyst, quinoline-8-sulfonic acid 33 was the only isolated product. "... 

QUINOLINES AND ISOQUINOLINES] (Vol 20) -ofapigment [PIGBffiNTS - ORGANIC] (Vol 19) -lignosulfates as [SULFONIC ACIDS] (Vol 23)... 

The 8-hydroxy-7-aminoquinoline-5-sulfonic acid was used to clarify the role of intramolecular hydrogen bonding on the cyclization rate of hydroxy Schiff bases in the preparation of 2-aryloxazolo[4,5-/i]quinoline-5-sulfonic acids 13. Irradiation... 

Quinoline-5-sulfonic acid, 8-hydroxy-7-iodo-metal complexes absorptiometry, 1,549 Quinolinium salts in gravimetry, 1, 535 Quinolinol metal complexes color photography, 6,107 8-Quinolinol biological activity, 6, 771 gallium and indium complexes radiopharmacology, 6, 971 radionuclide complexes radiopharmacology, 6,994 8-Quinolyl sulfate hydrolysis metal catalysis, 6,465 Quinones... 

Isoquinoline, like quinoline, is protonated and alkylated at the nitrogen atom, but electrophilic substitution in the benzene ring is also easily achieved (Scheme 3.14). Sulfonation with oleum gives mainly the 5-sulfonic acid, but fuming nitric acid and concentrated sulfuric acid at 0 C produce a 1 1 mixture of 5- and 8-nitroisoquinolines. Bromination in the presence of aluminium trichloride at 75 °C gives a 78% yield of 5-bromoisoquinoline. 

Oxine-copper heterocyclic nitrogen, quinoline Oxolinic acid heterocyclic nitrogen, quinoline Oxycarboxin oxathiin, amide, sulfone Oxydemeton-methyl phosphoro organic, phosphoro thioate... 

Fast Green FCF and Quinoline Yellow are colours permitted to be used in foods and cosmetics and have the structures shown here. Quinoline Yellow is a mixture of isomeric sulfonic acids in the two rings shown. 

Substituent effects follow the general pattern of substituted benzene derivatives in that nitro, sulfonic acid, and carboxyalkyl groups deactivate the ring to further substitution, whereas amino and methoxy groups strongly activate, and methyl and chloro groups have little effect. Ridd383 has recently reviewed electrophilic substitutions on quinoline, pyridine, and imidazole. 

Tu and co-workers [112, 115] elaborated a green protocol for the synthesis of polysubstituted indeno[ 1,2-6]-quinolines 69 via condensation of an aldehyde, 1,3-indanedione and an enaminone using p-toluene sulfonic acid as the catalyst in water under microwave irradiation. A series of 23 indeno[l,2-6]quinolines 69 was generated in excellent yields. The same authors have also described the microwave-assisted synthesis of these compounds in acetic acid as solvent (Scheme 53). 

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