1,2-dichloro-4-nitrobenzene

Oxidising properties

Link to relevant study record(s)

Reference

Endpoint:

oxidising solids

Type of information:

calculation (if not (Q)SAR)

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

accepted calculation method

Principles of method if other than guideline:

For nitro compounds, the net atomic charge on the Nitrogen atom of the NO2 group should be a simple indicator of oxidising properties as redox reaction means the transfer of electrons from the reducing to the oxidising agent. Therefore, semiempirical SCF-MO calculations were performed using the MOPAC program package with the PM3 Hamiltonian.

GLP compliance:

no

Sample tested:

other: test substance atomic charge claculation

Parameter:

other: theoretical consideration based on net atomic charges

Result:

1.307 other: dimensionless

In report 2009/01371, m-Nitrotoluene (liquid at room temperature) was found to have no oxidising properties in the EC A.21 test. Similarly 2, 4-Dichloronitrobenzene (solid at room temperature) did not exhibit any oxidising behaviour in the UN O.2 test (report 2009/01427).
A redox reaction means the transfer of electrons from the reducing to the oxidising agent. Therefore, electron- withdrawing substituents should increase a molecule’s oxidation potential. For nitro compounds, the net atomic charge on the Nitrogen atom of the NO2 group should be a simple indicator of this effect.
Therefore, a series of semiempirical SCF-MO calculations was performed using the MOPAC program package with the PM3 Hamiltonian. The results are shown in the table below:

 

Compound	Net atomic charge (calculated)	Rank
2, 4-Dichloronitrobenezene	1,3104	1
o-Chloronitrobenzene	1,3089	2
2,3-Dichloronitrobenzene	1,3083	3
3, 4-Dichloronitrobenzene	1,3066	4
m-Nitrotoluene	1,3060	5

 

The rank describes the relative oxidation potential which is totally in agreement with chemical intuition. Since m-Nitrotoluene (rank 5) as well as 2, 4-Dichloronitrobenzene (rank 1) have been found to be not an oxidizer in testing, the substances with intermediate ranks should not be classified as such either.

Therefore, 3, 4-Dichloronitrobenzene is not to be classified as an oxidising solid.

Interpretation of results:

GHS criteria not met

Remarks:

EU GHS criteria not met

Conclusions:

3, 4-Dichloronitrobenzene expected to be not an oxidizer.

Executive summary:

A series of semiempirical SCF-MO calculations was performed using the MOPAC program package with the PM3 Hamiltonian. Test item and it's structural isomers' net atomic charges were calculaed. The rank describes the relative oxidation potential which is totally in agreement with chemical intuition. Since m- Nitrotoluene (rank 5) as well as 2, 4-Dichloronitrobenzene (rank 1) have been found to be not an oxidizer in testing, the substances with intermediate ranks should not be classified as such either.

Description of key information

A series of semiempirical SCF-MO calculations was performed using the MOPAC program package with the PM3 Hamiltonian. Test item and it's structural isomers' net atomic charges were calculaed. The rank describes the relative oxidation potential which is totally in agreement with chemical intuition. Since m- Nitrotoluene (rank 5) as well as 2, 4-Dichloronitrobenzene (rank 1) have been found to be not an oxidizer in testing, the substances with intermediate ranks should not be classified as such either.

Key value for chemical safety assessment

Oxidising properties:

no

Additional information

The experimental study was performed with 1,3 -dichloro-4 -nitrobenzene which is a structural analogue to 1,2 -dichloro-4 -nitrobenzene. Both substances consist of one benzene ring, one NO2 -group and two chlorine-substituents which are directly linked with the respective aromatic carbon atoms. The difference between these two substances is merely the position of the chlorine-substituents compared to the NO2 -group. It is assumed that oxidzing properties are caused by the presence of certain chemical moieties (for example electron-withdrawing substituents ) rather than their position within the molecule.

This decision is in accordance with the grouping of substances and read-across approach in Annex XI, 1.5 of the REACH Regulation. The results of the test accoring to the UN-method O.2 showed no oxidizing properties of 1,3 -dichloro-4 -nitrobenzene (Currenta, 2009b).

Furthermore, for nitro compounds, the net atomic charge on the Nitrogen atom of the NO2 group should be a simple indicator of oxidizing properties. These theoretical consideration included the comparison of the calculated net atomic charge of 1,2 -dichloro-4 -nitrobenzene with that of structural analogue having no oxidizing properties. As the substances with the highest and lowest net atomic charge does not have oxidizing properties, the test item with an intermediate value should not have oxidizing properties as well (Currenta, 2009a)

Justification for classification or non-classification

Based on theoretical considerations (Currenta, 2009a) and the non-oxidizing properties of the structural analogue 1,3-dichloro-4-nitrobenzene (Currenta, 2009b) 1,2-Dichloro-4-nitrobenzene does not need to be classified as oxidizing solid.