Methyl violet

Methyl violet is a family of organic compounds that are mainly used as dyes. Depending on the number of attached methyl groups, the color of the dye can be altered. Its main use is as a purple dye for textiles and to give deep violet colors in paint and ink. It is also used as a hydration indicator for silica gel. Methyl violet 10B is also known as crystal violet (and many other names) and has medical uses.[1]

Structure

The term methyl violet encompasses three compounds that differ in the number of methyl groups attached to the amine functional group. Methyl violets are mixtures of tetramethyl (2B), pentamethyl (6B) and hexamethyl (10B) pararosanilins.[2]

They are all soluble in water, ethanol, diethylene glycol and dipropylene glycol.

Name Methyl violet 2B Methyl violet 6B Methyl violet 10B (Crystal violet)
Structure
Methyl violet 10B
Methyl violet 10B
Formula (salt) C23H26ClN3 C24H28ClN3 C25H30ClN3
CAS no 84215-49-6 8004-87-3 548-62-9
C.I. 42536 42535 42555
ChemSpider ID 21164086 170606 10588
PubChem ID 91997555 164877 11057
Formula (cation) C23H26N3+ C24H28N3+ C25H30N3+
ChemSpider ID 2006225 3349, 9080056, 10354393
PubChem ID 2724053 3468

Methyl violet 2B

Methyl violet 2B (IUPAC name: '4,4'-((4-Iminocyclohexa-2,5-dien-1-ylidene)methylene)bis(N,N-dimethylaniline) monohydrochloride) is a green powder which is soluble in water and ethanol but not in xylene. It appears yellow in solution of low pH (~0.15) and changes to violet with pH increasing toward 3.2.[3]

Methyl violet 10B

Main article: Crystal violet

Methyl violet 10B has six methyl groups. It is known in medicine as Gentian violet (or crystal violet or pyoctanin(e)[1]) and is the active ingredient in a Gram stain, used to classify bacteria. It is used as a pH indicator, with a range between 0 and 1.6. The protonated form (found in acidic conditions) is yellow, turning blue-violet above pH levels of 1.6.[4]

Methyl violet 10B inhibits the growth of many Gram positive bacteria, except streptococci.[citation needed] When used in conjunction with nalidixic acid (which destroys gram-negative bacteria), it can be used to isolate the streptococci bacteria for the diagnosis of an infection.[citation needed]

Degradation

Methyl violet is a mutagen and mitotic poison, therefore concerns exist regarding the ecological impact of the release of methyl violet into the environment. Methyl violet has been used in vast quantities for textile and paper dyeing, and 15% of such dyes produced worldwide are released to environment in wastewater. Numerous methods have been developed to treat methyl violet pollution. The three most prominent are chemical bleaching, biodegradation, and photodegradation.

Chemical bleaching

Chemical bleaching is achieved by oxidation or reduction. Oxidation can destroy the dye completely, e.g. through the use of sodium hypochlorite (NaClO, common bleach) or hydrogen peroxide.[5][6] Reduction of methyl violet occurs in microorganisms but can be attained chemically using sodium dithionite.

Biodegradation

Biodegradation has been well investigated because of its relevance to sewage plants with specialized microorganisms. Two microorganisms that have been studied in depth are the white rot fungus and the bacterium Nocardia Corallina.[7][8]

Photodegradation

Light alone does not rapidly degrade methyl violet,[9] but the process is accelerated upon the addition of large band-gap semiconductors, TiO2 or ZnO.[10][11]

Other methods

Many other methods have been developed to treat the contamination of dyes in a solution, including electrochemical degradation,[12] ion exchange,[13] laser degradation, and absorption onto various solids such as activated charcoal.

See also

References

  1. ^ a b Gorgas, Ferdinand J. S. (1901). "Pyoctanin – Methyl-Violet – Pyoctanine". chestofbooks.com. Archived from the original on 2011-07-08. Retrieved 2011-03-15. {{cite journal}}: Cite journal requires |journal= (help)
  2. ^ C. Bouasla, M. E. H. Samar, F, Ismail: Degradation of methyl violet 6B dye by the Fenton process. In: Desalination. 254.1–3, 2010, S. 35–41, doi:10.1016/j.desal.2009.12.017.
  3. ^ R. W. Sabnis (29 March 2010). Handbook of Biological Dyes and Stains: Synthesis and Industrial Applications. John Wiley and Sons. pp. 309–. ISBN 978-0-470-40753-0. Retrieved 27 June 2011.
  4. ^ Kristallviolett – ein pH-Indikator Archived June 9, 2011, at the Wayback Machine
  5. ^ Pizzolato, T (2002). "Colour removal with NaClO of dye wastewater from an agate-processing plant in Rio Grande do Sul, Brazil". International Journal of Mineral Processing. 65 (3–4): 203–211. Bibcode:2002IJMP...65..203P. doi:10.1016/S0301-7516(01)00082-5.
  6. ^ XP-Chloro Degradation Malachite green U.S. patent 2,755,202
  7. ^ Bumpus, JA; Brock, BJ (1988). "Biodegradation of crystal violet by the white rot fungus Phanerochaete chrysosporium". Applied and Environmental Microbiology. 54 (5): 1143–50. Bibcode:1988ApEnM..54.1143B. doi:10.1128/AEM.54.5.1143-1150.1988. PMC 202618. PMID 3389809.
  8. ^ Yatome, Chizuko; Yamada, Shigeyuki; Ogawa, Toshihiko; Matsui, Masaki (1993). "Degradation of Crystal violet by Nocardia corallina". Applied Microbiology and Biotechnology. 38 (4). doi:10.1007/BF00242956. S2CID 43686541.
  9. ^ Bhasikuttan, A; Sapre, A.V.; Shastri, L.V. (1995). "Oxidation of crystal violet and malachite green in aqueous solutions — a kinetic spectrophotometric study". Journal of Photochemistry and Photobiology A: Chemistry. 90 (2–3): 177–182. Bibcode:2018JPPA..364...59D. doi:10.1016/1010-6030(95)04094-V.
  10. ^ Senthilkumaar, S; Porkodi, K (2005). "Heterogeneous photocatalytic decomposition of Crystal Violet in UV-illuminated sol-gel derived nanocrystalline TiO2 suspensions". Journal of Colloid and Interface Science. 288 (1): 184–9. Bibcode:2005JCIS..288..184S. doi:10.1016/j.jcis.2005.02.066. PMID 15927578.
  11. ^ Sahoo, C; Gupta, A; Pal, A (2005). "Photocatalytic degradation of Crystal Violet (C.I. Basic Violet 3) on silver ion doped TiO". Dyes and Pigments. 66 (3): 189–196. doi:10.1016/j.dyepig.2004.09.003.
  12. ^ Sanroman, M; Pazos, M; Ricart, M; Cameselle, C (2004). "Electrochemical decolourisation of structurally different dyes". Chemosphere. 57 (3): 233–9. Bibcode:2004Chmsp..57..233S. doi:10.1016/j.chemosphere.2004.06.019. PMID 15312740.
  13. ^ Wu, J; Liu, C; Chu, K; Suen, S (2008). "Removal of cationic dye methyl violet 2B from water by cation exchange membranes". Journal of Membrane Science. 309 (1–2): 239–245. doi:10.1016/j.memsci.2007.10.035.