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Quinoline is a heterocyclic aromatic organic compound with the chemical formula C9H7N. It is a colorless hygroscopic liquid with a strong odor. Aged samples, especially if exposed to light, become yellow and later brown. Quinoline is only slightly soluble in cold water but dissolves readily in hot water and most organic solvents. Quinoline itself has few applications, but many of its derivatives are useful in diverse applications. A prominent example is quinine, an alkaloid found in plants. Over 200 biologically active quinoline and quinazoline alkaloids are identified. 4-Hydroxy-2-alkylquinolines (HAQs) are involved in antibiotic resistance.
Fischer esterification or Fischer–Speier esterification is a special type of esterification by refluxing a carboxylic acid and an alcohol in the presence of an acid catalyst. The reaction was first described by Emil Fischer and Arthur Speier in 1895. Most carboxylic acids are suitable for the reaction, but the alcohol should generally be primary or secondary. Tertiary alcohols are prone to elimination. Contrary to common misconception found in organic chemistry textbooks, phenols can also be esterified to give good to near quantitative yield of products. Commonly used catalysts for a Fischer esterification include sulfuric acid, p-toluenesulfonic acid, and Lewis acids such as scandium(III) triflate. For more valuable or sensitive substrates other, milder procedures such as Steglich esterification are used. The reaction is often carried out without a solvent or in a non-polar solvent that can facilitate Dean–Stark distillation to remove the water byproduct. Typical reaction times vary from 1–10 hours at temperatures of 60–110 °C.
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Acetic acid, systematically named ethanoic acid, is an acidic, colourless liquid and organic compound with the chemical formula CH3COOH. Vinegar is at least 4% acetic acid by volume, making acetic acid the main component of vinegar apart from water. It has been used, as a component of vinegar, throughout history from at least the third century BC.
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The Dille–Koppanyi reagent is used as a simple spot-test to presumptively identify barbiturates. It is composed of a mixture of two solutions. Part A is 0.1 g of cobalt(II) acetate dihydrate dissolved in 100 ml of methanol mixed with 0.2 ml of glacial acetic acid. Part B made up of is 5% isopropylamine (v/v) in methanol. Two drops of A are dropped onto the substance followed by one drop of B and any change in colour is observed.
Dragendorff's reagent is a color reagent to detect alkaloids in a test sample or as a stain for chromatography plates. Alkaloids, if present in the solution of sample, will react with Dragendorff's reagent and produce an orange or orange-red precipitate. This reagent was invented by the German pharmacologist, Johann Georg Dragendorff (1836–1898) at the University of Dorpat.
The Chen-Kao reaction is a chemical method for determining the presence of pseudoephedrine, ephedrine, and similar phenylalkylamines. The reaction is used in spot tests and is also known as Chen-Kao test. The test is often used to distinguish ephedrine, pseudoephedrine, norephedrine, cathinone and methcathinone from amphetamine and methamphetamine, which do not react with Chen’s test reagent.
The Dische test, or Dische reaction, is used to distinguish DNA from RNA. It was invented by Zacharias Dische.
References
- 1 2 Ondetti, Miguel A.; Deulofeu, Venancio (1961), "Alkaloids from Aspidosperma australe Müll. Argov.: The structure of olivacine and u-alkaloid C (Guatambuine)", Tetrahedron, 15 (1–4): 160–166, doi:10.1016/0040-4020(61)80020-3 . An extract of heartwood reacts with the reagent to produce a yellow-brown color.
- 1 2 Svoboda, Gordon H.; Gorman, Marvin; Neuss, Norbert; Barnes, Albert J. Jr. (1961), "Alkaloids of Vinca rosea Linn. (Catharanthus roseus G. Don.) VIII. Preparation and characterization of new minor alkaloids", Journal of Pharmaceutical Sciences, 50 (5): 409–413, doi:10.1002/jps.2600500508 . Certain compounds "can be detected by means of a bright blue color formed with Keller's reagent".
- 1 2 Renner, Ulrich (1963), Hunteria Alkaloid J and the Extraction Thereof from Hunteria Eburnia, U.S. Patent 3,108,095. "With Keller's reagent there is first a pale red, later a blue violet color."
- ↑ Cohn, Alfred Isaac (1909), Tests and reagents chemical and microscopical known by their authors' names, together with an index of subjects, J. Wiley & Sons, p. 154.
- ↑ Keller, C. C. (1895), "Keller's reagent", Berichte der Deutschen Pharmazeutischen Gesellschaft, 5: 277.
- ↑ Kiliani, H. (1896), "Ueber den Nachweis der Digitalis-Glycoside und ihrer Spaltungsprodukte durch eisenhaltige Schwefelsäure", Archiv der Pharmazie (in German), 234 (3–4): 273–277, doi:10.1002/ardp.18962340310, S2CID 84449886 .
- 1 2 James, Arthur E.; Laquer, Fritz O.; McIntyre, Joseph D. (1947-01-01). "A photoelectric Colorimetric Assay for Digitoxin by Comparison with a Standard Powder*†". Journal of the American Pharmaceutical Association (Scientific Ed.). 36 (1): 1–4. doi:10.1002/jps.3030360102. ISSN 0095-9553. PMID 20285818.
- ↑ "GYLCOSIDES Presented by BAHADUR SINGH HOD - ppt download". slideplayer.com. Retrieved 2024-11-18.
- 1 2 Smith, Sydney (1930-01-01). "LXXII.—Digoxin, a new digitalis glucoside". Journal of the Chemical Society (Resumed): 508–510. doi:10.1039/JR9300000508. ISSN 0368-1769.