Methyl yellow explained

Methyl yellow, or C.I. 11020, is an organic compound with the formula C₆H₅N₂C₆H₄N(CH₃)₂. It is an azo dye derived from dimethylaniline. It is a yellow solid. According to X-ray crystallography, the C₁₄N₃ core of the molecule is planar.^[1]

It is used as a dye for plastics and may be used as a pH indicator. In aqueous solution at low pH, methyl yellow appears red. Between pH 2.9 and 4.0, methyl yellow undergoes a transition, to become yellow above pH 4.0.

Safety

It is a possible carcinogen. As "butter yellow", the agent had been used as a food additive in butter and margarine before its toxicity was recognized.^[2]

History

Butter yellow was synthesized by Peter Griess in the 1860s at the Royal College of Chemistry in London.^[3] The dye was used to dye butter in Germany^[4] and other parts of the world during the latter half of the 19th century and the beginning of the 20th before being phased out in the 1930s and 40s. It was in the 1930s that research led by Riojun Kinosita showed the link between several azo dyes and cancer, linking butter yellow to liver cancer in rats after two to three months exposure.^[5] In 1939, the International Congress for Cancer Research issued a recommendation for the banning of cancer-causing food dyes (including butter yellow) from food production.

In 2014, dried tofu products (a.k.a. dougan 豆乾) from Taiwan were found to have been adulterated with methyl yellow, used as a coloring agent.^[6]

See also

Structurally similar compounds:

• Methyl red
• Solvent Yellow 56
• Methyl orange

Further reading

• Chung KT, Fulk GE, Andrews AW . Mutagenicity testing of some commonly used dyes . Applied and Environmental Microbiology . 42 . 4 . 641–8 . October 1981 . 10.1128/AEM.42.4.641-648.1981 . 7039509 . 244076 . 1981ApEnM..42..641C .

External links

• • Web site: para-dimethylaminoazobenzene . Inchem .
• CDC - NIOSH Pocket Guide to Chemical Hazards

Notes and References

1. Crystal and molecular structure of C.I. Solvent Yellow 2, 1-Phenylazo-4 (N,N-dimethylamine)-phenyl . Journal of Crystallographic and Spectroscopic Research . 1992 . 22 . 151–155. Whitaker A . 2 . 10.1007/BF01186250 . 93052691 .
2. Opie EL . The Pathogenesis of Tumors of the Liver Produced by Butter Yellow . The Journal of Experimental Medicine . 80 . 3 . 231–46 . September 1944 . 19871411 . 2135460 . 10.1084/jem.80.3.231 .
3. Book: Gendered Drugs and Medicine: Historical and Socio-Cultural Perspectives . Ortiz-Gómez. Teresa. Santesmases. María Jesús . vanc . 2016-04-22. Routledge . 978-1-317-12981-3 .
4. Book: Robert, Proctor. The Nazi War on Cancer. vanc. Princeton University Press. 1999. 978-0-691-00196-8. Princeton, N.J. 165-170. registration.
5. Kinosita R . Studies on the Cancerogenic Azo and Related Compounds . The Yale Journal of Biology and Medicine . 12 . 3 . 287–300 . January 1940 . 21433884 . 2602186 .
6. Web site: Taiwan recalls tainted dried tofu in fresh food scare . Channel NewsAsia . 17 December 2014 . 13 July 2016 . https://web.archive.org/web/20141219111820/http://www.channelnewsasia.com/news/asiapacific/taiwan-recalls-tainted/1535406.html . 19 December 2014 . dead.