4-[(2,4-dimethylphenyl)azo]-2,4-dihydro-5-methyl-2-phenyl-3H-pyrazol-3-one

Endpoint summary

Description of key information

Acute oral toxicity: 

Acute oral toxicity dose (LD50) for 4-[(E)-2-(2,4-dimethylphenyl)diazen-1-yl]-3-methyl-1-phenyl-4,5-dihydro-1H-pyrazol-5-one (CAS no: 6407-78-9) was predicted based on OECD QSAR toolbox 2906 mg/kg bw and different studies available on structurally similar read across substances 4,4'-(1E,1'E)-(3,3'-dichlorobiphenyl-4,4'-diyl)bis(diazene-2,1-diyl)bis(3-methyl-1-phenyl-1H-pyrazol-5(4H)-one) (CAS no: 3520-72-7) >5000 mg/kg bw and 3-methyl-1-phenyl-5-pyrazolone (CAS no: 89-25-8) > 2000 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, 4-[(E)-2-(2,4-dimethylphenyl)diazen-1-yl]-3-methyl-1-phenyl-4,5-dihydro-1H-pyrazol-5-one cannot be classified for acute oral toxicity.

Acute Inhalation Toxicity:

4-[(E)-2-(2,4-dimethylphenyl)diazen-1-yl]-3-methyl-1-phenyl-4,5-dihydro-1H-pyrazol-5-one (CAS no: 6407-78-9) has very low vapour pressure (4.23E-07 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.

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: 4-[(E)-2-(2,4-dimethylphenyl)diazen-1-yl]-3-methyl-1-phenyl-4,5-dihydro-1H-pyrazol-5-one
SMILES:Cc1ccc(N=NC2C(C)=NN(c3ccccc3)C2=O)c(C)c1
InChI:1S/C18H18N4O/c1-12-9-10-16(13(2)11-12)19-20-17-14(3)21-22(18(17)23)15-7-5-4-6-8-15/h4-11,17H,1-3H3/b20-19+
Molecular Weight: 306.367 g/mole
Mol. formula: C18H18N4O

Species:

rat

Strain:

Sprague-Dawley

Sex:

male/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:

2906 mg/kg

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:

male/female

Dose descriptor:

LD50

Effect level:

2 906 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 8 nearest neighbours
Domain  logical expression:Result: In Domain

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

Domain logical expression index: "a"

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 >> Unsaturated heterocyclic azo by DNA binding by OECD

Domain logical expression index: "b"

Referential boundary: The target chemical should be classified as Schiff base formation AND Schiff base formation >> Pyrazolones and Pyrazolidinones derivatives AND Schiff base formation >> Pyrazolones and Pyrazolidinones derivatives >> Pyrazolones and Pyrazolidinones  by Protein binding by OASIS v1.3

Domain logical expression index: "c"

Referential boundary: The target chemical should be classified as Acylation AND Acylation >> Direct Acylation Involving a Leaving group AND Acylation >> Direct Acylation Involving a Leaving group >> Acetates AND SN2 AND SN2 >> SN2 reaction at sp3 carbon atom AND SN2 >> SN2 reaction at sp3 carbon atom >> Alkyl diazo by Protein binding by OECD

Domain logical expression index: "d"

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

Domain logical expression index: "e"

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

Domain logical expression index: "f"

Referential boundary: The target chemical should be classified as Acylation AND Acylation >> Direct Acylation Involving a Leaving group AND Acylation >> Direct Acylation Involving a Leaving group >> Acetates AND SN2 AND SN2 >> SN2 reaction at sp3 carbon atom AND SN2 >> SN2 reaction at sp3 carbon atom >> Alkyl diazo by Protein binding by OECD

Domain logical expression index: "g"

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

Domain logical expression index: "h"

Referential boundary: The target chemical should be classified as No alert found by DNA binding by OASIS v.1.3

Domain logical expression index: "i"

Referential boundary: The target chemical should be classified as Non-covalent interaction OR Non-covalent interaction >> DNA intercalation OR Non-covalent interaction >> DNA intercalation >> DNA Intercalators with Carboxamide Side Chain OR Non-specific OR Non-specific >> Incorporation into DNA/RNA, due to structural analogy with  nucleoside bases    OR Non-specific >> Incorporation into DNA/RNA, due to structural analogy with  nucleoside bases    >> Specific Imine and Thione Derivatives OR Radical OR Radical >> Radical mechanism via ROS formation (indirect) OR Radical >> Radical mechanism via ROS formation (indirect) >> Hydrazine Derivatives OR Radical >> Radical mechanism via ROS formation (indirect) >> Nitroarenes with Other Active Groups OR Radical >> Radical mechanism via ROS formation (indirect) >> Specific Imine and Thione Derivatives OR SN1 OR SN1 >> Nucleophilic attack after diazonium or carbenium ion formation OR SN1 >> Nucleophilic attack after diazonium or carbenium ion formation >> Nitroarenes with Other Active Groups OR SN1 >> Nucleophilic attack after reduction and nitrenium ion formation OR SN1 >> Nucleophilic attack after reduction and nitrenium ion formation >> Nitroarenes with Other Active Groups OR SN1 >> Nucleophilic substitution on diazonium ions OR SN1 >> Nucleophilic substitution on diazonium ions >> Specific Imine and Thione Derivatives OR SN2 OR SN2 >> SN2 attack on activated carbon Csp3 or Csp2 OR SN2 >> SN2 attack on activated carbon Csp3 or Csp2 >> Nitroarenes with Other Active Groups by DNA binding by OASIS v.1.3

Domain logical expression index: "j"

Referential boundary: The target chemical should be classified as (!Undefined)Group All Lipid Solubility < 0.01 g/kg AND (!Undefined)Group CN Lipid Solubility < 0.4 g/kg AND Group All Melting Point > 200 C AND Group CN Aqueous Solubility < 0.0001 g/L AND Group CN Aqueous Solubility < 0.1 g/L AND Group CN log Kow > 4.5 AND Group CN log Kow > 5.5 AND Group CN Melting Point > 180 C AND Group CN Molecular Weight > 290 g/mol AND Group CN Vapour Pressure < 0.001 Pa by Skin irritation/corrosion Exclusion rules by BfR

Domain logical expression index: "k"

Referential boundary: The target chemical should be classified as (!Undefined)Group All log Kow < -3.1 OR (!Undefined)Group All log Kow > 9 OR (!Undefined)Group All Melting Point > 200 C OR (!Undefined)Group CNHal Lipid Solubility < 4 g/kg OR (!Undefined)Group CNHal Lipid Solubility < 400 g/kg OR (!Undefined)Group CNS Surface Tension > 62 mN/m OR Group All log Kow < -3.1 OR Group All log Kow > 9 OR Group CN Molecular Weight > 540 g/mol OR Group CNHal Aqueous Solubility < 0.001 g/L OR Group CNHal Aqueous Solubility < 0.1 g/L OR Group CNHal log Kow > 3.8 OR Group CNHal Molecular Weight > 370 g/mol OR Group CNHal Molecular Weight > 380 g/mol OR Group CNS log Kow < 0.5 OR Group CNS Melting Point > 120 C OR Group CNS Melting Point > 50 C by Skin irritation/corrosion Exclusion rules by BfR

Domain logical expression index: "l"

Referential boundary: The target chemical should be classified as Inclusion rules not met by Skin irritation/corrosion Inclusion rules by BfR

Domain logical expression index: "m"

Referential boundary: The target chemical should be classified as Hydrazines,hydrazonium salts OR Ketones by Skin irritation/corrosion Inclusion rules by BfR

Domain logical expression index: "n"

Referential boundary: The target chemical should be classified as Not bioavailable by Lipinski Rule Oasis ONLY

Domain logical expression index: "o"

Parametric boundary:The target chemical should have a value of log Kow which is >= 4.21

Domain logical expression index: "p"

Parametric boundary:The target chemical should have a value of log Kow which is <= 7.37

Interpretation of results:

other: Not classified

Conclusions:

LD50 was estimated to be 2906 mg/kg bw, when 10 male and female Sprague-Dawley rats were treated with 4-[(E)-2-(2,4-dimethylphenyl)diazen-1-yl]-3-methyl-1-phenyl-4,5-dihydro-1H-pyrazol-5-one (CAS no: 6407-78-9) 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 4-[(E)-2-(2,4-dimethylphenyl)diazen-1-yl]-3-methyl-1-phenyl-4,5-dihydro-1H-pyrazol-5-one (CAS no: 6407-78-9). The LD50 was estimated to be 2906 mg/kg bw, when 10 male and female Sprague-Dawley rats were treated with 4-[(E)-2-(2,4-dimethylphenyl)diazen-1-yl]-3-methyl-1-phenyl-4,5-dihydro-1H-pyrazol-5-one via oral gavage route.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

LD50

Value:

2 906 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

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

Acute oral toxicity:

In different studies, 4-[(E)-2-(2,4-dimethylphenyl)diazen-1-yl]-3-methyl-1-phenyl-4,5-dihydro-1H-pyrazol-5-one (CAS no: 6407-78-9) 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 4-[(E)-2-(2,4-dimethylphenyl)diazen-1-yl]-3-methyl-1-phenyl-4,5-dihydro-1H-pyrazol-5-one along with the study available on structurally similar read across substances 4,4'-(1E,1'E)-(3,3'-dichlorobiphenyl-4,4'-diyl)bis(diazene-2,1-diyl)bis(3-methyl-1-phenyl-1H-pyrazol-5(4H)-one) (3520-72-7) and 3-methyl-1-phenyl-5-pyrazolone (CAS no: 89-25-8). 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 4-[(E)-2-(2,4-dimethylphenyl)diazen-1-yl]-3-methyl-1-phenyl-4,5-dihydro-1H-pyrazol-5-one (CAS no: 6407-78-9). The LD50 was estimated to be 2906 mg/kg bw, when 10 male and female Sprague-Dawley rats were treated with 4-[(E)-2-(2,4-dimethylphenyl)diazen-1-yl]-3-methyl-1-phenyl-4,5-dihydro-1H-pyrazol-5-one via oral gavage route.

The above study is further supported by U.S. National Library of Medicine (ChemIDplus, 2017), for the structurally similar read across substance 4,4'-(1E,1'E)-(3,3'-dichlorobiphenyl-4,4'-diyl)bis(diazene-2,1-diyl)bis(3-methyl-1-phenyl-1H-pyrazol-5(4H)-one) (3520-72-7).Acute oral toxicity study was conducted in rats at the concentration of 5000 mg/kg bw. No Mortality was observed at dose5000 mg/kg bw. Hence, LD50 value was considered to be>5000 mg/kg bw, when rats were treated with4,4'-(1E,1'E)-(3,3'-dichlorobiphenyl-4,4'-diyl)bis(diazene-2,1-diyl)bis(3-methyl-1-phenyl-1H-pyrazol-5(4H)-one) via oral route.

This study is also supported by Scientific Committee on Consumer Products (SCCP, Opinion on phenyl methyl pyrazolone COLIPA N° A39; SCCP/1033/06, 19 December 2006),for the structurally similar read across substance 3-methyl-1-phenyl-5-pyrazolone (CAS no: 89-25-8). In a acute oral toxicity study, Sprague-Dawley male and female rat were treated at the concentration of 2000 mg/kg bw using three vehicles i.e.0.5% methylcellulose; 0.5% carboxymethylcellulose; propylene glycol orally by gavage. In Group 1 (vehicle: 0.5% methylcellulose), one female on day 1 and one male on day 2 was died. Group 2 (vehicle: 0.5% carboxymethylcellulose), One male died 4 hours after treatment, and 2 females died 4 hours or 6 hours after treatment, respectively. In Group 3 (vehicle: propylene glycol), No mortality was observed in treated male and female rat at 2000 mg/kg bw. In Group 1 (vehicle: 0.5% methylcellulose), hypoactivity or sedation, piloerection, ptosis of the eyelids, reddish colouration of the extremites, dyspnoea and rhinorrhea were observed in all animals on day 1. Lateral recumbence was noted in one female and Tremors were also observed in one male. Recovery was mentioned to be complete in the other animals. Group 2 (vehicle: 0.5% carboxymethylcellulose), hypoactivity or sedation, piloerection, ptosis of the eyelids, reddish colouration of the extremities, dyspnoea and rhinorrhea were observed in all animals on day 1. Recovery was mentioned to be complete in the other animals. In Group 3 (vehicle: propylene glycol), hypoactivity or sedation, piloerection, ptosis of the eyelids, reddish colouration of the extremities, dyspnoea and rhinorrhea were observed in all animals on day 1. Recovery was complete in all animals 6 hours after dosing. No effect on body weight gain observed in treated male and female rats during the 14 days observation period. No apparent macroscopic abnormalities were observed in treated male and female rats. Therefore, LD50 was considered to be > 2000 mg/kg bw, when Sprague-Dawley male and female rat were treated with didodecyl 3,3'-sulfanediyldipropanoate orally by gavage. 

Thus, based on the above studies on 4-[(E)-2-(2,4-dimethylphenyl)diazen-1-yl]-3-methyl-1-phenyl-4,5-dihydro-1H-pyrazol-5-one (CAS no: 6407-78-9) 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, 4-[(E)-2-(2,4-dimethylphenyl)diazen-1-yl]-3-methyl-1-phenyl-4,5-dihydro-1H-pyrazol-5-one cannot be classified for acute oral toxicity.

Acute Inhalation Toxicity:

4-[(E)-2-(2,4-dimethylphenyl)diazen-1-yl]-3-methyl-1-phenyl-4,5-dihydro-1H-pyrazol-5-one (CAS no: 6407-78-9) has very low vapour pressure (4.23E-07 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.

Justification for classification or non-classification

Based on the above studies and prediction on 4-[(E)-2-(2,4-dimethylphenyl)diazen-1-yl]-3-methyl-1-phenyl-4,5-dihydro-1H-pyrazol-5-one (CAS no: 6407-78-9) and it’s read across substances, it can be concluded that LD50 value is >2000 mg/kg bw for acute oral toxicity. Thus, comparing this value with the criteria of CLP regulation, 4-[(E)-2-(2,4-dimethylphenyl)diazen-1-yl]-3-methyl-1-phenyl-4,5-dihydro-1H-pyrazol-5-one cannot be classified for acute oral toxicity.For Acute Inhalation toxicity wavier were added so, not possible to classify.