Nitrotoluenes
The nitrotoluenes form a group of substances in chemistry and are aromatic compounds with a methyl group (–CH 3 ) and a nitro group (–NO 2 ) as substituents on the benzene ring . The different arrangement of the substituents ( ortho , meta or para ) results in three constitutional isomers with the empirical formula C 7 H 7 NO 2 . The mixture of substances is formed during the nitration of toluene , with 2- and 4-nitrotoluene being the main products. Nitrotoluenes occur as intermediate products in TNT production and can therefore often be detected as old armaments in the soil and groundwater.
Representative
| Nitrotoluenes | ||||||||||||
| Surname | 2-nitrotoluene | 3-nitrotoluene | 4-nitrotoluene | |||||||||
| other names |
o -nitrotoluene, 2-nitro-1-methylbenzene, ONT, 2-NT |
m -nitrotoluene, 3-nitro-1-methylbenzene |
p -Nitrotoluene, 4-nitro-1-methylbenzene |
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| Structural formula |
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| CAS number | 88-72-2 | 99-08-1 | 99-99-0 | |||||||||
| PubChem | 6944 | 7422 | 7473 | |||||||||
| Molecular formula | C 7 H 7 NO 2 | |||||||||||
| Molar mass | 137.14 g mol −1 | |||||||||||
| Physical state | liquid | firmly | ||||||||||
| Brief description | yellow oily liquid with an aromatic odor |
yellow liquid with a characteristic odor |
yellowish crystals |
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| Melting point | −4 ° C | 16 ° C | 52 ° C | |||||||||
| boiling point | 222 ° C | 232 ° C | 238 ° C | |||||||||
| solubility | practically insoluble in water, soluble in acetone, benzene, ethanol, ether and chloroform |
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GHS labeling |
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| H and P phrases | 302-340-350-361f-411 | 302-311-332-373-411 | 301 + 311 + 331-373-411 | |||||||||
| no EUH phrases | no EUH phrases | no EUH phrases | ||||||||||
| 201-273-281-308 + 313 |
280-273-309 + 310 302 + 352 |
261-273-280-301 + 310-311 | ||||||||||
| MAK value | Switzerland: 2 ml m −3 or 11 mg m −3 | |||||||||||
presentation
In the electrophilic aromatic substitution of toluene with nitric acid , the + I effect of the methyl group is decisive for the position of the second substituent. The main products are 2-nitrotoluene ( ortho ) with 65% and 4-nitrotoluene ( para ) with 30%, 3-nitrotoluene ( meta ), however, only 5%.
The 3-nitrotoluene can be obtained from 3-nitro-4-aminotoluene by diazotizing the amino group and reductively reacting the diazonium salt with ethanol ( dediazonation ).
properties
The boiling points of the three isomers are close to one another, while the melting points differ significantly. The 4-nitrotoluene, which has the highest symmetry, has the highest melting point.
use
The nitrotoluenes are intermediate products in the production of toluidines , in the organic synthesis of pesticides , pharmaceuticals, dyes and plastics .
2- and 4-nitrotoluene are intermediate products in TNT production; they are first nitrated further to 2,4-dinitrotoluene . 2- and 4-nitrotoluene are also added to plastic explosives as a marker.
In general, the nitrobenzoic acids are accessible from the nitrotoluenes by oxidation of the methyl group . So z. B. 4-nitrotoluene oxidized by sodium dichromate in the presence of concentrated sulfuric acid to 4-nitrobenzoic acid.
safety instructions
The nitrotoluenes can form explosive vapors, attack rubber and plastics and are carcinogenic.
Web links
- seilnacht.com: Toluene .
- Test specification: Nitration of toluene to 2-nitrotoluene, 4-nitrotoluene and 2,4-dinitrotoluene (PDF) from the Integrated Organic Chemistry Practical Collection at the University of Regensburg, accessed on March 12, 2017.
Individual evidence
- ↑ a b c d Entry on 2-nitrotoluene in the GESTIS substance database of the IFA , accessed on June 21, 2018(JavaScript required) .
- ↑ a b c d Entry on 3-nitrotoluene in the GESTIS substance database of the IFA , accessed on June 21, 2018(JavaScript required) .
- ↑ a b c d Entry on 4-nitrotoluene in the GESTIS substance database of the IFA , accessed on June 21, 2018(JavaScript required) .
- ↑ Swiss Accident Insurance Fund (Suva): Limit values - current MAK and BAT values (search for nitrotoluene (3- and 4-isomer) ), accessed on March 4, 2020.
- ↑ Beyer / Walter : Textbook of Organic Chemistry ; 19th edition; S. Hirzel Verlag; Stuttgart 1981; ISBN 3-7776-0356-2 ; P. 456.
- ↑ HT Clarke, ER Taylor: m-Nitrotoluene In: Organic Syntheses . 3, 1923, p. 91, doi : 10.15227 / orgsyn.003.0091 ; Coll. Vol. 1, 1941, p. 415 ( PDF ).
- ↑ Jehuda Yinon: Forensic and Environmental Detection of Explosives . John Wiley & Sons, 1999, ISBN 978-0-471-98371-2 , pp. 167 ( limited preview in Google Book search).
- ^ O. Kamm, AO Matthews: p-Nitrobenzoic acid In: Organic Syntheses . 2, 1922, p. 53, doi : 10.15227 / orgsyn.002.0053 ; Coll. Vol. 1, 1941, p. 392 ( PDF ).