2-[(4-chloro-2-nitrophenyl)azo]-N-(4-ethoxyphenyl)-3-oxobutyramide

Endpoint summary

Description of key information

Acute oral toxicity: 

Acute oral toxicity dose (LD50) of 2-[(E)-2-(4-chloro-2-nitrophenyl)diazen-1-yl]-N-(4-ethoxyphenyl)-3-oxobutanamide (CAS no: 52320-66-8) was predicted based on OECD QSAR toolbox 3592 mg/kg bw and different studies available on structurally similar read across substances 2,2'-[(3,3'-dichloro[1,1'-biphenyl]-4,4'-diyl)bis(azo)]bis [N-(2,4-dimethylphenyl)-3-oxobutyramide] (CAS no: 5102-83-0) >5000 mg/kg bw and 2,2'-[(3,3'-dichlorobiphenyl-4,4'-diyl)didiazene-2,1-diyl]bis(3-oxo-N-phenylbutanamide) (CAS no: 6358-85-6) >10800 mg/kg bw. All these studies concluded that the LD50 value is >2000 mg/kg bw. Thus, comparing this value with the criteria of CLP regulation, 2-[(E)-2-(4-chloro-2-nitrophenyl)diazen-1-yl]-N-(4-ethoxyphenyl)-3-oxobutanamide cannot be classified for acute oral toxicity.

Acute Inhalation toxicity: 

2-[(E)-2-(4-chloro-2-nitrophenyl)diazen-1-yl]-N-(4-ethoxyphenyl)-3-oxobutanamide (CAS no: 52320-66-8) has very low vapour pressure (2.67E-10 Pa at 25°C), so the potential for the generation of inhalable vapours is very low. Also the normal conditions of use of this substance will not result in aerosols, particles or droplets of an inhalable size, so exposure to humans via the inhalatory route will be highly unlikely and therefore this end point was considered for waiver.

Acute Dermal toxicity: 

Acute Dermal toxicity dose (LD50) for 2-[(E)-2-(4-chloro-2-nitrophenyl)diazen-1-yl]-N-(4-ethoxyphenyl)-3-oxobutanamide (CAS no: 52320-66-8) was predicted based on OECD QSAR toolbox 2504 mg/kg bwand differentstudies available for the structurally similar read across substanceN-(4-chloro-2,5-dimethoxyphenyl)- 2-[[2,5-dimethoxy-4 -[(phenylamino)sulphonyl]phenyl]azo]-3-oxobutyramide (CAS no: 12225-18-2) >3000 mg/kg bw and 2,2'-[(3,3'-dichloro[1,1'-biphenyl]-4,4'-diyl)bis(azo)]bis [N-(2,4-dimethylphenyl)-3-oxobutyramide] (CAS no: 5102-83-0)>3000 mg/kg bw. All these studies concluded that the LD50 value is>2000 mg/kg bw. Thus, comparing this value with the criteria of CLP regulation, 2-[(E)-2-(4-chloro-2-nitrophenyl)diazen-1-yl]-N-(4-ethoxyphenyl)- 3-oxobutanamide cannot be classified for acute dermal toxicity.

Key value for chemical safety assessment

Acute toxicity: via oral route

Link to relevant study records

Reference

Endpoint:

acute toxicity: oral

Type of information:

(Q)SAR

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

results derived from a valid (Q)SAR model and falling into its applicability domain, with limited documentation / justification

Justification for type of information:

Data is predicted using OECD QSAR toolbox version 3.3 and the supporting QMRF report has been attached

Qualifier:

according to guideline

Guideline:

other: estimated data

Principles of method if other than guideline:

Prediction is done using QSAR Toolbox version 3.3

GLP compliance:

not specified

Test type:

other: not specified

Limit test:

no

Specific details on test material used for the study:

Name: 2-[(E)-2-(4-chloro-2-nitrophenyl)diazen-1-yl]-N-(4-ethoxyphenyl)-3-oxobutanamide
SMILES:CCOc1ccc(NC(=O)C(C(C)=O)N=Nc2ccc(Cl)cc2N(=O)=O)cc1
InChI:1S/C18H17ClN4O5/c1-3-28-14-7-5-13(6-8-14)20-18(25)17(11(2)24)22-21-15-9-4-12(19)10-16(15)23(26)27/h4-10,17H,3H2,1-2H3,(H,20,25)/b22-21+
Molecular Formula: C18H17ClN4O5
Molecular Weight: 404.808 g/mole

Species:

rat

Strain:

Wistar

Sex:

female

Details on test animals or test system and environmental conditions:

not specified

Route of administration:

oral: gavage

Vehicle:

unchanged (no vehicle)

Details on oral exposure:

not specified

Doses:

3592 mg/kg bw

No. of animals per sex per dose:

10

Control animals:

not specified

Details on study design:

not specified

Statistics:

not specified

Preliminary study:

not specified

Sex:

female

Dose descriptor:

LD50

Effect level:

3 592 mg/kg bw

Based on:

test mat.

Remarks on result:

other: 50% mortality was observed

Mortality:

not specified

Clinical signs:

other: not specified

Gross pathology:

not specified

Other findings:

not specified

The prediction was based on dataset comprised from the following descriptors: LD50
Estimation method: Takes average value from the 5 nearest neighbours
Domain  logical expression:Result: In Domain

((((((((("a" and ("b" and ( not "c") )  )  and ("d" and ( not "e") )  )  and ("f" and ( not "g") )  )  and ("h" and ( not "i") )  )  and ("j" and ( not "k") )  )  and "l" )  and "m" )  and "n" )  and ("o" and "p" )  )

Domain logical expression index: "a"

Referential boundary: The target chemical should be classified as Amides by Aquatic toxicity classification by ECOSAR

Domain logical expression index: "b"

Referential boundary: The target chemical should be classified as SN1 AND SN1 >> Nitrenium Ion formation AND SN1 >> Nitrenium Ion formation >> Aromatic azo AND SN1 >> Nitrenium Ion formation >> Aromatic nitro by DNA binding by OECD

Domain logical expression index: "c"

Referential boundary: The target chemical should be classified as Acylation OR Acylation >> Direct Addition of an Acyl Halide OR Acylation >> Direct Addition of an Acyl Halide >> Acyl halide OR Acylation >> P450 Mediated Activation to Isocyanates or Isothiocyanates OR Acylation >> P450 Mediated Activation to Isocyanates or Isothiocyanates >> Formamides OR Michael addition OR Michael addition >> P450 Mediated Activation to Quinones and Quinone-type Chemicals OR Michael addition >> P450 Mediated Activation to Quinones and Quinone-type Chemicals >> Alkyl phenols OR Michael addition >> P450 Mediated Activation to Quinones and Quinone-type Chemicals >> Arenes OR Michael addition >> P450 Mediated Activation to Quinones and Quinone-type Chemicals >> Hydroquinones OR Michael addition >> Polarised Alkenes-Michael addition OR Michael addition >> Polarised Alkenes-Michael addition >> Alpha, beta- unsaturated esters OR No alert found OR Schiff base formers OR Schiff base formers >> Chemicals Activated by P450 to Glyoxal  OR Schiff base formers >> Chemicals Activated by P450 to Glyoxal  >> Ethanolamines (including morpholine) OR Schiff base formers >> Chemicals Activated by P450 to Glyoxal  >> Ethylenediamines (including piperazine) OR SN1 >> Carbenium Ion Formation OR SN1 >> Carbenium Ion Formation >> Hydrazine OR SN1 >> Iminium Ion Formation OR SN1 >> Iminium Ion Formation >> Aliphatic tertiary amines OR SN1 >> Nitrenium Ion formation >> Primary (unsaturated) heterocyclic amine OR SN1 >> Nitrenium Ion formation >> Primary aromatic amine OR SN1 >> Nitrenium Ion formation >> Tertiary aromatic amine OR SN1 >> Nitrenium Ion formation >> Unsaturated heterocyclic azo OR SN2 OR SN2 >> SN2 at an sp3 Carbon atom OR SN2 >> SN2 at an sp3 Carbon atom >> Phosphates by DNA binding by OECD

Domain logical expression index: "d"

Referential boundary: The target chemical should be classified as Acylation AND Acylation >> Ester aminolysis AND Acylation >> Ester aminolysis >> Amides by Protein binding by OASIS v1.3

Domain logical expression index: "e"

Referential boundary: The target chemical should be classified as Nucleophilic addition OR Nucleophilic addition >> Addition to carbon-hetero double bonds OR Nucleophilic addition >> Addition to carbon-hetero double bonds >> Ketones OR SNAr OR SNAr >> Nucleophilic aromatic substitution on activated aryl and heteroaryl compounds OR SNAr >> Nucleophilic aromatic substitution on activated aryl and heteroaryl compounds >> Activated aryl and heteroaryl compounds by Protein binding by OASIS v1.3

Domain logical expression index: "f"

Referential boundary: The target chemical should be classified as No alert found by Protein binding alerts for Chromosomal aberration by OASIS v1.1

Domain logical expression index: "g"

Referential boundary: The target chemical should be classified as Ac-SN2 OR Ac-SN2 >> Acylation involving an activated (glucuronidated) carboxamide group OR Ac-SN2 >> Acylation involving an activated (glucuronidated) carboxamide group >> Carboxylic Acid Amines OR Ac-SN2 >> Direct acylation involving a leaving group OR Ac-SN2 >> Direct acylation involving a leaving group >> Carboxylic Acid Amines OR AN2 OR AN2 >> Michael-type addition to quinoid structures OR AN2 >> Michael-type addition to quinoid structures >> Carboxylic Acid Amines by Protein binding alerts for Chromosomal aberration by OASIS v1.1

Domain logical expression index: "h"

Referential boundary: The target chemical should be classified as No alert found by Protein binding alerts for skin sensitization by OASIS v1.3

Domain logical expression index: "i"

Referential boundary: The target chemical should be classified as Acylation OR Acylation >> Ester aminolysis OR Acylation >> Ester aminolysis >> Amides by Protein binding alerts for skin sensitization by OASIS v1.3

Domain logical expression index: "j"

Referential boundary: The target chemical should be classified as No alert found by Respiratory sensitisation

Domain logical expression index: "k"

Referential boundary: The target chemical should be classified as Pro-Michael Addition OR Pro-Michael Addition >> Pro-quinone and related OR Pro-Michael Addition >> Pro-quinone and related >> Phenylenediamines by Respiratory sensitisation

Domain logical expression index: "l"

Similarity boundary:Target: CCOc1ccc(NC(=O)C(C(C)=O)N=Nc2ccc(Cl)cc2N(=O)=O)cc1
Threshold=20%,
Dice(Atom centered fragments)
Atom type; Count H attached; Hybridization

Domain logical expression index: "m"

Similarity boundary:Target: CCOc1ccc(NC(=O)C(C(C)=O)N=Nc2ccc(Cl)cc2N(=O)=O)cc1
Threshold=40%,
Dice(Atom centered fragments)
Atom type; Count H attached; Hybridization

Domain logical expression index: "n"

Similarity boundary:Target: CCOc1ccc(NC(=O)C(C(C)=O)N=Nc2ccc(Cl)cc2N(=O)=O)cc1
Threshold=50%,
Dice(Atom centered fragments)
Atom type; Count H attached; Hybridization

Domain logical expression index: "o"

Parametric boundary:The target chemical should have a value of log Kow which is >= 2.4

Domain logical expression index: "p"

Parametric boundary:The target chemical should have a value of log Kow which is <= 7.05

Interpretation of results:

other: Not classified

Conclusions:

D50 was estimated to be 3592 mg/kg bw, when 10 female Wistar rats were treated with 2-[(E)-2-(4-chloro-2-nitrophenyl)diazen-1-yl]-N-(4-ethoxyphenyl)-3-oxobutanamide (CAS no: 52320-66-8) via oral gavage route.

Executive summary:

In a prediction done by SSS (2017) using the OECD QSAR toolbox with log kow as the primary descriptor, the acute oral toxicity was estimated for 2-[(E)-2-(4-chloro-2-nitrophenyl)diazen-1-yl]-N-(4-ethoxyphenyl)-3-oxobutanamide (CAS no: 52320-66-8). The LD50 was estimated to be 3592 mg/kg bw, when 10 female Wistar rats were treated with 2-[(E)-2-(4-chloro-2-nitrophenyl)diazen-1-yl]-N-(4-ethoxyphenyl)-3-oxobutanamide via oral gavage route.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

LD50

Value:

3 592 mg/kg bw

Quality of whole database:

Data is Klimisch 2 and from QSAR toolbox 3.3.

Acute toxicity: via inhalation route

Link to relevant study records

Reference

Endpoint:

acute toxicity: inhalation

Data waiving:

other justification

Justification for data waiving:

other:

Endpoint conclusion

Quality of whole database:

Waiver

Acute toxicity: via dermal route

Link to relevant study records

Reference

Endpoint:

acute toxicity: dermal

Type of information:

(Q)SAR

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

results derived from a valid (Q)SAR model and falling into its applicability domain, with limited documentation / justification

Justification for type of information:

Data is predicted using OECD QSAR toolbox version 3.3 and the supporting QMRF report has been attached

Qualifier:

according to guideline

Guideline:

other: estimated data

Principles of method if other than guideline:

Prediction is done using QSAR Toolbox version 3.3.

GLP compliance:

not specified

Test type:

other: not specified

Limit test:

no

Specific details on test material used for the study:

Name: 2-[(E)-2-(4-chloro-2-nitrophenyl)diazen-1-yl]-N-(4-ethoxyphenyl)-3-oxobutanamide
SMILES:CCOc1ccc(NC(=O)C(C(C)=O)N=Nc2ccc(Cl)cc2N(=O)=O)cc1
InChI:1S/C18H17ClN4O5/c1-3-28-14-7-5-13(6-8-14)20-18(25)17(11(2)24)22-21-15-9-4-12(19)10-16(15)23(26)27/h4-10,17H,3H2,1-2H3,(H,20,25)/b22-21+
Molecular Formula: C18H17ClN4O5
Molecular Weight: 404.808 g/mole

Species:

rabbit

Strain:

New Zealand White

Sex:

male/female

Details on test animals or test system and environmental conditions:

not specified

Type of coverage:

occlusive

Vehicle:

unchanged (no vehicle)

Details on dermal exposure:

not specified

Duration of exposure:

24 hours

Doses:

2504 mg/kg bw

No. of animals per sex per dose:

6

Control animals:

not specified

Details on study design:

not specified

Statistics:

not specified

Preliminary study:

not specified

Sex:

male/female

Dose descriptor:

LD50

Effect level:

2 504 mg/kg bw

Based on:

test mat.

Remarks on result:

other: 50% mortality was observed

Mortality:

not specified

Clinical signs:

other: not specified

Gross pathology:

not specified

Other findings:

not specified

The prediction was based on dataset comprised from the following descriptors: LD50
Estimation method: Takes average value from the 5 nearest neighbours
Domain  logical expression:Result: In Domain

((((("a" and ("b" and ( not "c") )  )  and ("d" and ( not "e") )  )  and ("f" and ( not "g") )  )  and ("h" and ( not "i") )  )  and ("j" and "k" )  )

Domain logical expression index: "a"

Referential boundary: The target chemical should be classified as Amides by Aquatic toxicity classification by ECOSAR

Domain logical expression index: "b"

Referential boundary: The target chemical should be classified as Not possible to classify according to these rules by DPRA Cysteine peptide depletion

Domain logical expression index: "c"

Referential boundary: The target chemical should be classified as High reactive OR High reactive >> Organic disulfides OR Low reactive OR Low reactive >> N-substituted aromatic amides by DPRA Cysteine peptide depletion

Domain logical expression index: "d"

Referential boundary: The target chemical should be classified as Non binder, without OH or NH2 group by Estrogen Receptor Binding

Domain logical expression index: "e"

Referential boundary: The target chemical should be classified as Non binder, MW>500 OR Non binder, non cyclic structure by Estrogen Receptor Binding

Domain logical expression index: "f"

Referential boundary: The target chemical should be classified as Aliphatic Carbon [CH] AND Aliphatic Carbon [-CH2-] AND Aliphatic Carbon [-CH3] AND Aliphatic Nitrogen, one aromatic attach [-N] AND Alpha-oxoamide [C(C(=O))C(=O)N] AND Amide, aliphatic attach [-C(=O)N] AND Amino, aliphatic attach [-N<] AND Amino-carbonyl compound [NCC(=O)-C] AND Aromatic Carbon [C] AND Azo [-N=N-] AND Carbonyl, aliphatic attach [-C(=O)-] AND Chlorine, aromatic attach [-Cl] AND Chlorine, olefinic attach [-Cl] AND Miscellaneous sulfide (=S) or oxide (=O) AND Nitro, aromatic attach [-NO2] AND Nitrogen, two or tree olefinic attach [>N-] AND Olefinic carbon [=CH- or =C<] AND Oxygen, one aromatic attach [-O-] by Organic functional groups (US EPA)

Domain logical expression index: "g"

Referential boundary: The target chemical should be classified as Aldehyde, aliphatic attach [-N-CHO] by Organic functional groups (US EPA)

Domain logical expression index: "h"

Referential boundary: The target chemical should be classified as Amide   [-C(=O)-N  or -C(=S)-N] AND Aromatic chloride   [-CL] AND Aromatic ether  [-O-aromatic carbon] AND Aromatic nitro  [-NO2] AND Aromatic-H AND Azo group   [-N=N-] AND Benzene AND -CH-   [linear] AND -CH2-  [linear] AND Ketone   [-C-C(=O)-C-] AND Methyl  [-CH3] by Bioaccumulation - metabolism alerts

Domain logical expression index: "i"

Referential boundary: The target chemical should be classified as Pyridine ring by Bioaccumulation - metabolism alerts

Domain logical expression index: "j"

Parametric boundary:The target chemical should have a value of log Kow which is >= 1.23

Domain logical expression index: "k"

Parametric boundary:The target chemical should have a value of log Kow which is <= 5.3

Interpretation of results:

other: Not classified

Conclusions:

LD50 was estimated to be 2504 mg/kg bw, when 6 male and female New Zealand White rabbits were treated with 2-[(E)-2-(4-chloro-2-nitrophenyl)diazen-1-yl]-N-(4-ethoxyphenyl)-3-oxobutanamide (CAS no: 52320-66-8) for 24 hours by dermal application occlusively.

Executive summary:

In a prediction done by SSS (2017) using the OECD QSAR toolbox with log kow as the primary descriptor, the acute dermal toxicity was estimated for 2-[(E)-2-(4-chloro-2-nitrophenyl)diazen-1-yl]-N-(4-ethoxyphenyl)-3-oxobutanamide (CAS no: 52320-66-8). The LD50 was estimated to be 2504 mg/kg bw, when 6 male and female New Zealand White rabbits were treated with 2-[(E)-2-(4-chloro-2-nitrophenyl)diazen-1-yl]-N-(4-ethoxyphenyl)-3-oxobutanamide for 24 hours by dermal application occlusively.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

LD50

Value:

2 504 mg/kg bw

Quality of whole database:

Data is Klimisch 2 and from QSAR toolbox 3.3.

Additional information

Acute oral toxicity:

In different studies, 2-[(E)-2-(4-chloro-2-nitrophenyl)diazen-1-yl]-N-(4-ethoxyphenyl)-3-oxobutanamide (CAS no: 52320-66-8) has been investigated for acute oral toxicity to a greater or lesser extent. Often are the studies based on in-vivo experiments in rodents, i.e. most commonly in rats for 2-[(E)-2-(4-chloro-2-nitrophenyl)diazen-1-yl]-N-(4-ethoxyphenyl)-3-oxobutanamide along with the study available on structurally similar read across substances 2,2'-[(3,3'-dichloro[1,1'-biphenyl]-4,4'-diyl)bis(azo)]bis[N-(2,4-dimethylphenyl)-3-oxobutyramide] (CAS no: 5102-83-0) and 2,2'-[(3,3'-dichlorobiphenyl-4,4'-diyl)didiazene-2,1-diyl]bis(3-oxo-N-phenylbutanamide) (CAS no: 6358-85-6). The predicted data using the OECD QSAR toolbox has also been compared with the experimental studies. The studies are summarized as below –

In a prediction done by SSS (2017) using the OECD QSAR toolbox with log kow as the primary descriptor, the acute oral toxicity was estimated for 2-[(E)-2-(4-chloro-2-nitrophenyl)diazen-1-yl]-N-(4-ethoxyphenyl)-3-oxobutanamide (CAS no: 52320-66-8). The LD50 was estimated to be 3592 mg/kg bw, when 10 female Wistar rats were treated with 2-[(E)-2-(4-chloro-2-nitrophenyl)diazen-1-yl]-N-(4-ethoxyphenyl)-3-oxobutanamide via oral gavage route.

The above study is supported by U.S. National Library of Medicine (ChemIDplus, 2017), for the structurally similar read across substance 2,2'-[(3,3'-dichloro[1,1'-biphenyl]-4,4'-diyl)bis(azo)]bis[N-(2,4-dimethylphenyl)-3-oxobutyramide] (CAS no: 5102-83-0) in rats at the concentration of 5000 mg/kg bw. No mortality was observed in treated rats at 5000 mg/kg bw. Therefore, LD50 was considered to be >5000 mg/kg bw, when rats were treated with 2,2'-[(3,3'-dichloro[1,1'-biphenyl]-4,4'-diyl)bis(azo)]bis[N-(2,4-dimethylphenyl)-3-oxobutyramide] via oral route.

This study is further supported by U.S. National Library of Medicine (ChemIDplus, 2017), for the structurally similar read across substance 2,2'-[(3,3'-dichlorobiphenyl-4,4'-diyl)didiazene-2,1-diyl]bis(3-oxo-N-phenylbutanamide) (CAS no: 6358-85-6) in rats at the concentration of 10800 mg/kg bw. No mortality was observed in treated rats at 10800 mg/kg bw. Therefore, LD50 was considered to be >10800 mg/kg bw, when rats were treated with 2,2'-[(3,3'-dichlorobiphenyl-4,4'-diyl)didiazene-2,1-diyl]bis(3-oxo-N-phenylbutanamide) via oral route.

Thus, based on the above studies on 2-[(E)-2-(4-chloro-2-nitrophenyl)diazen-1-yl]-N-(4-ethoxyphenyl)-3-oxobutanamide (CAS no: 52320-66-8) and it’s read across substances, it can be concluded that LD50 value is >2000 mg/kg bw. Thus, comparing this value with the criteria of CLP regulation, 2-[(E)-2-(4-chloro-2-nitrophenyl)diazen-1-yl]-N-(4-ethoxyphenyl)-3-oxobutanamide cannot be classified for acute oral toxicity.

Acute Inhalation toxicity: 

2-[(E)-2-(4-chloro-2-nitrophenyl)diazen-1-yl]-N-(4-ethoxyphenyl)-3-oxobutanamide (CAS no: 52320-66-8) has very low vapour pressure (2.67E-10 Pa at 25°C), so the potential for the generation of inhalable vapours is very low. Also the normal conditions of use of this substance will not result in aerosols, particles or droplets of an inhalable size, so exposure to humans via the inhalatory route will be highly unlikely and therefore this end point was considered for waiver.

Acute Dermal toxicity:

In different studies, 2-[(E)-2-(4-chloro-2-nitrophenyl)diazen-1-yl]-N-(4-ethoxyphenyl)-3-oxobutanamide (CAS no: 52320-66-8) has been investigated for acute dermal toxicity to a greater or lesser extent. Often are the studies based on in vivo experiments in rodents, i.e. most commonly in rabbits and rats for 2-[(E)-2-(4-chloro-2-nitrophenyl)diazen-1-yl]-N-(4-ethoxyphenyl)-3-oxobutanamide along with the study available on the structurally similar read across substances N-(4-chloro-2,5-dimethoxyphenyl)-2-[[2,5-dimethoxy-4-[(phenylamino)sulphonyl]phenyl]azo]-3-oxobutyramide (CAS no: 12225-18-2) and 2,2'-[(3,3'-dichloro[1,1'-biphenyl]-4,4'-diyl)bis(azo)]bis[N-(2,4-dimethylphenyl)-3-oxobutyramide] (CAS no: 5102-83-0). The predicted data using the OECD QSAR toolbox has also been compared with the experimental studies. The studies are summarized as below –

In a prediction done by SSS (2017) using the OECD QSAR toolbox with log kow as the primary descriptor, the acute dermal toxicity was estimated for 2-[(E)-2-(4-chloro-2-nitrophenyl)diazen-1-yl]-N-(4-ethoxyphenyl)-3-oxobutanamide (CAS no: 52320-66-8). The LD50 was estimated to be 2504 mg/kg bw, when 6 male and female New Zealand White rabbits were treated with 2-[(E)-2-(4-chloro-2-nitrophenyl)diazen-1-yl]-N-(4-ethoxyphenyl)-3-oxobutanamide for 24 hours by dermal application occlusively.

This study is supported by U.S. National Library of Medicine (ChemIDplus, 2017), for the structurally similar read across substanceN-(4-chloro-2,5-dimethoxyphenyl)-2-[[2,5-dimethoxy-4-[(phenylamino)sulphonyl]phenyl]azo]-3-oxobutyramide (CAS no: 12225-18-2) was conducted in rabbits at the concentration of 3000 mg/kg bw. No mortality was observed in treated rabbits at 3000 mg/kg bw. Therefore, LD50 was considered to be >3000 mg/kg bw, when rabbits were treated with N-(4-chloro-2,5-dimethoxyphenyl)-2-[[2,5-dimethoxy-4-[(phenylamino)sulphonyl]phenyl]azo]-3-oxobutyramide by dermal application to the skin.

The above study is further supported by SIDS Initial Assessment Profile, United Nations Environmental Programme (UNEP, 2003), for the structurally similar read across substance 2,2'-[(3,3'-dichloro[1,1'-biphenyl]-4,4'-diyl)bis(azo)]bis[N-(2,4-dimethylphenyl)-3-oxobutyramide] (CAS no: 5102-83-0) in rats at the concentration of 3000 mg/kg bw. No mortality was observed in treated rats at 3000 mg/kg bw. Therefore, LD50 was considered to be >3000 mg/kg bw, when rats were treated with 2,2'-[(3,3'-dichloro[1,1'-biphenyl]-4,4'-diyl)bis(azo)]bis[N-(2,4-dimethylphenyl)-3-oxobutyramide] by dermal application to the skin.

Thus, based on the above studies on 2-[(E)-2-(4-chloro-2-nitrophenyl)diazen-1-yl]-N-(4-ethoxyphenyl)-3-oxobutanamide (CAS no: 52320-66-8) and it’s read across substances, it can be concluded that LD50 value is >2000 mg/kg bw. Thus, comparing this value with the criteria of CLP regulation, 2-[(E)-2-(4-chloro-2-nitrophenyl)diazen-1-yl]-N-(4-ethoxyphenyl)-3-oxobutanamide cannot be classified for acute dermal toxicity.

Justification for classification or non-classification

Based on the above studies and prediction on 2-[(E)-2-(4-chloro-2-nitrophenyl)diazen-1-yl]-N-(4-ethoxyphenyl)-3-oxobutanamide (CAS no: 52320-66-8) and it’s read across substances, it can be concluded that LD50 value is >2000 mg/kg bw for acute oral and dermal toxicity. Thus, comparing this value with the criteria of CLP regulation, 2-[(E)-2-(4-chloro-2-nitrophenyl)diazen-1-yl]-N-(4-ethoxyphenyl)-3-oxobutanamide cannot be classified for acute oral and dermal toxicity. For Acute Inhalation toxicity wavier was added so, not possible to classify.