2-Nitrobenzaldehyde

2-Nitrobenzaldehyde is an organic aromatic compound containing a nitro group ortho to formyl. 2-Nitrobenzaldehyde once was produced as an intermediate in the synthesis of the popular dye Indigo.

2-Nitrobenzaldehyde[1][2]
Skeletal formula of 2-nitrobenzaldehyde
Ball-and-stick model of the 2-nitrobenzaldehyde molecule
Names
Preferred IUPAC name
2-Nitrobenzaldehyde
Other names
Nitrobenzaldehyde
ortho-Nitrobenzaldehyde
o-Nitrobenzaldehyde
Identifiers
3D model (JSmol)
ChEMBL
ChemSpider
ECHA InfoCard 100.008.206
UNII
Properties
C7H5NO3
Molar mass 151.12 g/mol
Appearance Pale yellow crystalline powder
Melting point 43 °C (109 °F; 316 K)
Boiling point 152 °C (306 °F; 425 K)
Insoluble
-68.23·10−6 cm3/mol
Hazards
Main hazards Harmful, Potentially mutagenic
R-phrases (outdated) R36 R37 R38 R41
S-phrases (outdated) S26 S28
NFPA 704 (fire diamond)
Flammability code 1: Must be pre-heated before ignition can occur. Flash point over 93 °C (200 °F). E.g. canola oilHealth code 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g. chloroformReactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
1
2
0
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Y verify (what is YN ?)
Infobox references

Synthesis

The main routes to nitrobenzaldehyde begin with the nitration of styrene and cinnamic acid followed by the conversions of the resulting 2-nitrostyrene and 2-nitrocinnamic acids. Cinnamaldehyde can also be nitrated, e.g., in a solution of acetic anhydride in acetic acid, 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]

In one synthetic process, toluene is mono-nitrated at cold temperatures to 2-nitrotoluene, with about 58% being converted to the ortho- isomer, the remaining forming meta- and para- isomers.[5] The 2-nitrotoluene can then be oxidized to yield 2-nitrobenzaldehyde.[6][7]

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.[8]

The nitration of benzaldehyde produces mostly 3-nitrobenzaldehyde, with yields being about 19% for the ortho-, 72% for the meta- and 9% for the para isomer.[9] For this reason, the nitration of benzaldehyde to yield 2-nitrobenzaldehyde is not cost-effective.

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.[10][11][12][13] The method was abandoned in the early part of the 20th century, being replaced by routes from aniline.[14]

Baeyer-Drewson Indigo Synthesis

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.[15][16]

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References
  1. 2-Nitrobenzaldehyde
  2. "2-Nitrobenzaldehyde MSDS". Archived from the original on 2011-07-07. Retrieved 2009-07-18.
  3. o-NITROCINNAMALDEHYDE, nitration of cinnamaldehyde, organic-synthesis
  4. Selective aerobic oxidation of styrene to benzaldehyde catalyzed by water-soluble palladium(II) complex in water, Bo Feng, Zhenshan Hou, Xiangrui Wang, Yu Hu, Huan Li and Yunxiang Qiao
  5. http://www.thecatalyst.org/experiments/AndersonS/AndersonS.html Product Distribution in the Nitration of Toluene, Steven W. Anderson, January 7, 1999
  6. Synthesis of 2-Nitrobenzaldehyde from 2-Nitrotoluene, Alexander Popkov
  7. "o-Nitrobenzaldehyde". Archived from the original on 2009-07-23. Retrieved 2009-07-21.
  8. "Process for the Preparation of 2-Nitrobenzaldehyde". Retrieved 2010-10-18.
  9. Structure of Benzene, California State University Dominguez Hills
  10. See Baeyer-Drewson indigo synthesis
  11. Synthesis of Indigo Archived 2010-06-20 at the Wayback Machine
  12. "Indigo Synthesis". Archived from the original on 2011-07-20. Retrieved 2009-07-18.
  13. "Synthesis of Indigo and Vat Dyeing" (PDF). Archived from the original (PDF) on 2011-07-20. Retrieved 2009-07-18.
  14. Elmar Steingruber "Indigo and Indigo Colorants" Ullmann's Encyclopedia of Industrial Chemistry 2004, Wiley-VCH, Weinheim. doi: 10.1002/14356007.a14_149.pub2
  15. Šebej, Peter; Šolomek, Tomáš; Hroudná, Ľubica; Brancová, Pavla; Klán, Petr (2009). "Photochemistry of 2-Nitrobenzylidene Acetals". J. Org. Chem. 74: 8647–8658. doi:10.1021/jo901756r.
  16. Kristine L. Willett; Ronald A. Hites (2000). "Chemical Actinometry: Using o-Nitrobenzaldehyde to Measure Lamp Intensity in Photochemical Experiments". J. Chem. Educ. 77: 900. doi:10.1021/ed077p900.
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