Reactivo de Mayer

El reactivo de Mayer se emplea para la caracterízación no específica de alcaloides. La mayoría de los alcaloides reaccionan dando un precipitado blanco o amarillo claro, amorfo o cristalino.[1]​ El precipitado (una sal compleja) puede disolverse posteriormente en algún solvente menos polar para su identificación.[2]​

Preparación

Se prepara disolviendo 1,358 g de cloruro mercúrico y 5,000 g de yoduro de potasio por cada 100,0 ml de agua destilada.[3]​[4]​[1]​ De acuerdo a la siguiente fórmula, pero con un exceso de KI:[5]​

HgCl2 + 4 KI → K2[HgI4] + 2 KCl

Referencias

  1. ↑ a b Krishnaswamy, N. R. (2003). «p. 87». Chemistry of Natural Products: A Laboratory Handbook. Orient Blackswan. p. 87. ISBN 8173714525, 9788173714528. «This reagent which gives a white or pale yellow precipitate with solution of an alkaloid is prepared as follows. A solution of mercuri chloride (2.72 g) in distilled water (120 ml) is mixed with a solution of potassium iodide (10 g) in distilled water (40 ml) and the mixture made up to 200 ml with the addition of distilled water.» 
  2. ↑ Houghton, Peter J.; Raman, Amala (1998). «p. 180». Laboratory handbook for the fractionation of natural extracts (illustrated edición). Springer. p. 180. ISBN 0412749106, 9780412749100. «The complex is not soluble in water but is soluble in less-polar solvents. [...] The eluate containing alkaloids can be concentrated and other preparative methods used to isolate individual alkaloids.» 
  3. ↑ Lide, David R. (2004). «8». CRC Handbook of Chemistry and Physics: A Ready-reference Book of Chemical and Physical Data (85 edición). CRC Press. p. 8-2. ISBN 0849304857, 9780849304859. «Mayer's reagent (white precipitate with most alkaloids in slightly acid solutions). Dissolve 1.358 g of HgCl2 in 60 mL of water and pour into a solution of 5 g of KI in 10 ml of H2O. Add sufficient water to make 100 mL.» 
  4. ↑ * Institute of Medicine (U.S.). Committee on Food Chemicals Codex (2003). «p. 967». Food chemicals codex (5ª, ilustrada edición). National Academies Press. p. 967. ISBN 0309088666, 9780309088664. «Mercuric-Potassium Iodide TS (Mayer's Reagent) Dissolve 1.358 g of mercuric chloride (HgCl2) in 60 mL of water. Dissolve 5 g of potassium iodide (KI) in 10 ml of water. Mix the two solutions, and add water to make 100 mL.» 
  5. ↑ Bourne, Geoffrey H.; Danielli, J. F. (1987). «p. 299». International Review of Cytology. Academic Press. p. 299. ISBN 0123643104, 9780123643100.