Dinitrobenzenes

The dinitrobenzenes (according to the IUPAC nomenclature dinitrobenzen , also DNB ) consist of a benzene ring with two nitro groups  (-NO ₂ ) as substituents. The different arrangement of the nitro groups results in three constitutional isomers with the empirical formula C ₆ H ₄ N ₂ O ₄ . The m -Dinitrobenzene falls u. a. in the manufacture of explosives.

Representative

Dinitrobenzenes
Surname	o -Dinitrobenzene	m- Dinitrobenzene	p -Dinitrobenzene
other names	1,2-dinitrobenzene	1,3-dinitrobenzene	1,4-dinitrobenzene
Structural formula
CAS number	528-29-0	99-65-0	100-25-4
	25154-54-5 (mixture of isomers)
PubChem	10707	7452	7492
Molecular formula	C 6 H 4 N 2 O 4
Molar mass	168.11 g mol −1
Physical state	firmly
Brief description	colorless crystals	yellowish crystals	colorless crystals
Melting point	118 ° C	89 ° C	174 ° C
boiling point	318 ° C	291 ° C	299 ° C
density	1.565 (17 ° C)	1.575 (18 ° C)	1.625 (18 ° C)
Vapor pressure	0.08 Pa (30 ° C)		0.07 Pa (30 ° C)
	0.34 Pa (50 ° C)		0.23 Pa (50 ° C)
solubility	insoluble in water
GHS labeling	from  Regulation (EC) No. 1272/2008 (CLP) , expanded if necessary danger
H and P phrases	300 + 310 + 330-373-410	330-310-300-373-410	300-310-330-373-410
	no EUH phrases
	260-280-284-301 + 310 + 330-302 + 352 + 310-361 + 364-304 + 340 + 310	260-264-273-280-284-301 + 310	260-264-273-280-284-301 + 310
MAK value	Switzerland: 0.15 ml m −3 or 1 mg m −3

properties

The dinitrobenzenes are all crystalline solids. The boiling points of the three isomers are relatively close to one another, while their melting points differ more clearly. The p- dinitrobenzene, which has the highest symmetry, has the highest melting point.

presentation

The m- dinitrobenzene can be obtained by renewed nitration of nitrobenzene ; the reaction is acid-catalyzed with sulfuric acid. The −I effect and the −M effect of the nitro group of nitrobenzene lead to 93% direction into the meta position. The ortho and para products are only 6 and 1%, respectively.

A green marked nitro group as a second substituent on the benzene ring.

use

A reduction of m- dinitrobenzene with sodium sulfide in aqueous solution leads to m-nitroaniline , the complete reduction (Fe / HCl) to m-phenylenediamine .

Web links

Commons : Dinitrobenzole  - Collection of images, videos and audio files

Individual evidence

1. ↑ ^{a b} Entry on dinitrobenzene, isomers in the GESTIS substance database of the IFA , accessed on March 12, 2017(JavaScript required) .
2. ↑ ^{a b c d} Entry on 1,2-dinitrobenzene in the GESTIS substance database of the IFA , accessed on March 4, 2020(JavaScript required) .
3. ↑ ^{a b c d} Entry on 1,3-dinitrobenzene in the GESTIS substance database of the IFA , accessed on March 4, 2020(JavaScript required) .
4. ↑ ^{a b c d} Entry on 1,4-dinitrobenzene in the GESTIS substance database of the IFA , accessed on March 4, 2020(JavaScript required) .
5. ↑ ^{a b c} Brockhaus ABC Chemie , VEB FA Brockhaus Verlag, Leipzig 1971.
6. ↑ ^{a b c d} H: Félix-Rivera, ML Ramírez-Cedeño, RA Sánchez-Cuprill, SP Hernández-Rivera: Triacetone triperoxide thermogravimetric study of vapor pressure and enthalpy of sublimation in 303-338 K temperature range ; in: Thermochim. Acta , 2011 , 514 , pp. 37-43 ( doi: 10.1016 / j.tca.2010.11.034 ).
7. ↑ Entry on Dinitrobenzene in the Classification and Labeling Inventory of the European Chemicals Agency (ECHA), accessed on August 11, 2016. Manufacturers or distributors can expand the harmonized classification and labeling .
8. ↑ Swiss Accident Insurance Fund (Suva): Limits - Current MAK and BAT values (search for dinitrobenzene (all isomers) ), accessed on March 4, 2020.
9. ↑ Joachim Buddrus : Fundamentals of organic chemistry , 3rd edition, de Gruyter, Berlin 2003, ISBN 3-11-014683-5 , p. 360.
10. ↑ Beyer / Walter : Textbook of Organic Chemistry , 19th edition, S. Hirzel Verlag, Stuttgart 1981, ISBN 3-7776-0356-2 , S. 536, 542nd