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The sample is dissolved in water, or a mixture of water and ethanol, and a few drops of neutral ferric chloride (FeCl 3) solution, which is prepared by adding de-ionised water. Add sodium hydroxide to the mixture until a permanent brown precipitate is formed. The formation of a red, blue, green, or purple coloration indicates the presence of ...
Aqueous ferric chloride was added to a urine sample, and the formation of the iron complex turned the solution purple. [citation needed] This test was not specific to acetylsalicylic acid but would occur in the presence of any phenol or enol. The downfall of this test occurs in the presence of hyperbilirubinemia or elevated bilirubin.
The affinity of iron(III) for oxygen ligands was the basis of qualitative tests for phenols. Although superseded by spectroscopic methods, the ferric chloride test is a traditional colorimetric test. [26] The affinity of iron(III) for phenols is exploited in the Trinder spot test. [27]
Total phenols (or antioxidant effect) can be measured using the Folin-Ciocalteu reaction. Results are typically expressed as gallic acid equivalents (GAE). Ferric chloride (FeCl 3) test is also a colorimetric assay. Lamaison and Carnet have designed a test for the determination of the total flavonoid content of a sample (AlCI 3 method). After ...
The Kolbe–Schmitt reaction or Kolbe process (named after Hermann Kolbe and Rudolf Schmitt) is a carboxylation chemical reaction that proceeds by treating phenol with sodium hydroxide to form sodium phenoxide, [1] then heating sodium phenoxide with carbon dioxide under pressure (100 atm, 125 °C), then treating the product with sulfuric acid.
Samples and phenolic standards are given acidic ferric chloride and ferricyanide, which is reduced to ferrocyanide by the phenols. The ferric chloride and ferrocyanide react to form Prussian blue. Comparing the absorbance at 700 nm of the samples to the standards allows for the determination of total phenols or polyphenols. [53] [54]
The first example of an oxidative phenol coupling in synthetic chemistry can be traced to Julius Löwe’s 1868 synthesis of ellagic acid, accomplished by heating gallic acid with arsenic acid. [8] In the synthesis of complex organic compounds, oxidative phenol couplings are sometimes employed.
Substrates containing two phenols (or an aniline and a phenol; see equation (8) below for a related example), undergo oxidative coupling in the presence of hypervalent iodine(III) reagents. Coupling of both the ortho and para positions is possible; however, the use of bulky silyl-protected phenols provides complete selectivity for para coupling ...