On the Mechanism of the Caro Synthesis of Methylene Blue

Sánchez‐Viesca, Francisco; Gómez, Reina

doi:10.34198/ejcs.6221.209214

Cited by 9 publications

(8 citation statements)

References 6 publications

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“…In this communication we give the mechanism of the oxido degradation of uric acid that takes place during its interaction with phosphotungstic reagent (Folin test). This paper is a follow up of our studies on reaction mechanism, [2][3][4][5][6].…”

Section: Introductionmentioning

confidence: 90%

On the mechanism of the Folin test for uric aci

Sánchez-Viesca¹,

Gómez²

2023

World J. Chem. Pharm. Sci.

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The mechanism of the interaction of uric acid with sodium tungstate in phosphoric acid (Folin test) is described. This insight involves the following steps: addition of tungstic acid to the carbon-carbon double bond in uric acid. Protolysis of the organometallic ester gives rise to dihydroxyoxotungsten and an epoxide, via a concerted mechanism. Acid catalyzed ring opening of the oxirane produces a vicinal diol via reaction of the intermediate carbocation with water. Isomerization of the resulting carbinolamide groups is enhanced by the resonance of the ureido group. Breaking of the second carbinolamide gives urea and alloxan, 5-ketobarbituric acid hydrate. Uric acid oxidation in strong acidic medium like phosphoric acid produces alloxan, whereas oxidation in alkaline, neutral, or slightly acidic medium, gives allantoin.

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Section: Introductionmentioning

confidence: 90%

On the mechanism of the Folin test for uric aci

Sánchez-Viesca¹,

Gómez²

2023

World J. Chem. Pharm. Sci.

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“…Colorimetric assays offer simple visual readouts and do not require instruments for the analysis. This communication is a follow up of our studies on reaction mechanism, [5][6][7][8][9].…”

Section: Figure 1 Morphine and Codeine Structuresmentioning

confidence: 99%

The mechanism of Mecke’s test for opioids

Sánchez-Viesca¹,

Gómez²

2023

World J. Chem. Pharm. Sci.

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Mecke colour test is an official assay for opioids, either for opium or for purified compounds. It employs a solution of selenious acid in sulphuric acid. However, organoselenium chemistry was misunderstood for many years. The reaction mechanism involving selenium (IV) compounds was explained by way of electron back donation, which is a theoretical contravention. In this communication we provide the reactions that take place during this test. Each step is fully commented and the electron flow is given. The reaction proceeds by way of an enol selenite. Acidolysis gives rise to a reduced selenium (II) intermediate and an activated ketone at C-2, that is, a redox reaction with polarity inversion. Addition of selenious acid and further electron shifts affords morphine ortho-quinone and elemental selenium.

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“…In this communication we provide the reaction mechanism of Schiff test for uric acid, it is a follow up of our studies on reaction mechanism, [5][6][7][8][9].…”

Section: Introductionmentioning

confidence: 96%

The Mechanism of Schiff Test for Uric Acid in Urine

Sánchez‐Viesca

Gómez

2023

EJCS

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Uric acid in urine can be detected by reaction with silver nitrate in alkaline medium. A redox reaction occurs and black elemental silver is observed in the filter paper used in this test. However, the mechanism of the series of steps occurring in the uric acid molecule, including a second redox reaction, has not been advanced. A reaction route is provided, each step is fully commented giving also the electron flow. The mechanism involves free radicals and ionic intermediates as well. There is ring contraction with concomitant oxo-aziridine formation, imide hydrolysis, imine hydration to carbinol-amine, isomerization to ketone with concurrently ring opening, and assisted decarboxylation.

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On the Mechanism of the Caro Synthesis of Methylene Blue

Cited by 9 publications

References 6 publications

On the mechanism of the Folin test for uric aci

On the mechanism of the Folin test for uric aci

The mechanism of Mecke’s test for opioids

The Mechanism of Schiff Test for Uric Acid in Urine

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