2-Nitrobenzaldehyde Explained

2-Nitrobenzaldehyde is an organic compound with the formula . It is one of three isomers of nitrobenzaldehyde. It contains a nitro group adjacent to the formyl group.^[1]

Synthesis

The nitration of benzaldehyde produces mostly 3-nitrobenzaldehyde. Partly for this reason, 2-nitrobenzaldehyde is prepared by indirect routes.^[2] The main routes to nitrobenzaldehyde begin with the nitration of styrene or cinnamic acid followed by the conversions of the resulting 2-nitrostyrene and 2-nitrocinnamic acids, respectively. Cinnamaldehyde can also be nitrated in high-yield to 2-nitrocinnamaldehyde.^[3] This compound is then oxidized to 2-nitrocinnamic acid, which is decarboxylated to the 2-nitrostyrene. The vinyl group can be oxidized in a number of different ways to yield 2-nitrobenzaldehyde.^[4]

2-Nitrotoluene can be oxidized to yield 2-nitrobenzaldehyde.^{[5] [6]}

Alternatively, 2-nitrotoluene as formed above can be halogenated to a 2-nitrobenzyl halide followed by oxidation with DMSO and sodium bicarbonate to yield 2-nitrobenzaldehyde, which is subsequently purified with the creation of a bisulfite adduct.^[7]

Uses

2-Nitrobenzaldehyde is an intermediate in an early route to indigo, a water-insoluble dye commonly used to dye jeans and other fabrics. In the Baeyer-Drewson indigo synthesis, 2-nitrobenzaldehyde condenses with acetone in basic aqueous solution to yield indigo in a one-pot synthesis^{[8] [9]} The method was abandoned in the early part of the 20th century, being replaced by routes from aniline.^[10]

Given its two relatively reactive groups, 2-nitrobenzaldehyde is a potential starting material for other compounds. Substituted 2-nitrobenzaldehydes can also be used to yield other important compounds based on indigo, such as indigo carmine.

2-Nitrobenzaldehyde has been shown to be a useful photoremovable protecting group for various functions.^{[11] [12]}

References

1. Book: 10.1002/14356007.a03_463.pub2 . Benzaldehyde . Ullmann's Encyclopedia of Industrial Chemistry . 2011 . Brühne . Friedrich . Wright . Elaine . 978-3-527-30385-4 .
2. Book: 10.1002/14356007.a03_463.pub2 . Benzaldehyde . Ullmann's Encyclopedia of Industrial Chemistry . 2011 . Brühne . Friedrich . Wright . Elaine . 978-3-527-30385-4 .
3. Org. Synth.. 1953. 33. 60. 10.15227/orgsyn.033.0060. o-Nitrocinnamaldehyde. Robert E. Buckles, M. Peter Bellis.
4. Feng . Bo . Hou . Zhenshan . Wang . Xiangrui . Hu . Yu . Li . Huan . Qiao . Yunxiang . 2009-09-01 . Selective aerobic oxidation of styrene to benzaldehyde catalyzed by water-soluble palladium(II) complex in water . Green Chemistry . en . 11 . 9 . 1446–1452 . 10.1039/B900807A . 1463-9270.
5. Acta Chim. Slov.. 2005. 52. 460–462. Synthesis of 2-Nitrobenzaldehyde from 2-Nitrotoluene. Alexander Popkov., Alexander Popkov
6. Org. Synth.. 1944. 24. 75. 10.15227/orgsyn.024.0075. o-Nitrobenzaldehyde. S. M. Tsang . Ernest H. Wood . John R. Johnson.
7. Web site: Process for the Preparation of 2-Nitrobenzaldehyde. 2010-10-18.
8. Web site: Indigo Synthesis . 2009-07-18 . https://web.archive.org/web/20110720000154/http://www.chem.missouri.edu/chem1100/Indigo%20synthesis.doc . 2011-07-20 . dead .
9. Web site: Synthesis of Indigo and Vat Dyeing . 2009-07-18 . https://web.archive.org/web/20110720032713/http://courses.chem.psu.edu/chem36/Chem36H/IndivExpt1/863%20Indigo.pdf . 2011-07-20 . dead .
10. Book: Ullmann's Encyclopedia of Industrial Chemistry . 2003-03-11 . Wiley . 978-3-527-30385-4 . Wiley-VCH . 1 . en . 10.1002/14356007.a14_149.pub2. Indigo and Indigo Colorants.
11. Photochemistry of 2-Nitrobenzylidene Acetals. Peter. Šebej. Tomáš. Šolomek. Ľubica. Hroudná. Pavla. Brancová. Petr. Klán. J. Org. Chem.. 2009. 74. 22. 8647–8658. 10.1021/jo901756r. 19824651.
12. Chemical Actinometry: Using o-Nitrobenzaldehyde to Measure Lamp Intensity in Photochemical Experiments. Kristine L. Willett . Ronald A. Hites. J. Chem. Educ.. 2000. 77. 7 . 900. 10.1021/ed077p900. 2000JChEd..77..900W .