N-cyclohexylbenzothiazole-2-sulfenamide

Phototransformation in air

Link to relevant study record(s)

Reference

Endpoint:

phototransformation in air

Type of information:

(Q)SAR

Adequacy of study:

key study

Study period:

2021

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

accepted calculation method

Justification for type of information:

1. SOFTWARE
Individual model AOPWIN included in the Estimation Programs Interface (EPI) Suite.

2. MODEL (incl. version number)
AOPWIN v1.93 included in EPISuite v 4.11, 2000 - 2012

3. SMILES OR OTHER IDENTIFIERS USED AS INPUT FOR THE MODEL
A SMILES NOTATION was entered in the initial data entry screen. In the structure window, the molecular weight, structural formula and the structure of the input SMILES notation is shown. If available, experimental determined values of melting point and boiling point are taken for input.

4. SCIENTIFIC VALIDITY OF THE (Q)SAR MODEL
a. Defined endpoint: Rate constant for the atmospheric, gas-phase reaction between photochemically produced hydroxyl radicals and organic chemicals at 25°C. The rate constant estimated by the program is then be used to calculate the atmospheric half-life for an organic compound based upon an 24h-day average atmospheric concentration of hydroxyl radicals of 0.5E+06 molecules/cm3.

b. Dependent variable: Hydroxyl radical rate constant in units of cm3/molecule sec

c. Estimation methodology: The molecule is separated into distinct fragments. The reaction rate constant for hydroxyl radicals are the summation of the following mechanisms:
Hydrogen Abstraction = 34.3610 E-12 cm3/molecule-sec
Reaction with N, S and -OH = 0.0000 E-12 cm3/molecule-sec
Addition to Triple Bonds = 0.0000 E-12 cm3/molecule-sec
Addition to Olefinic Bonds = 0.0000 E-12 cm3/molecule-sec
Addition to Aromatic Rings = 0.0000 E-12 cm3/molecule-sec
**Addition to Fused Rings = 45.1292 E-12 cm3/molecule-sec
** Designates Estimation(s) Using ASSUMED Value(s)

As depending on the structure of the substance, OH-radicals generally react by one or more of the above mentioned pathways, the result of 0.0000 E-12 cm3/molecule¬sec for each mechanism indicate that these mechanisms are not relevant for the substance of interest.
An "assumed value" is applied, showing that a structure fragment that has not been assigned a numeric value by the developer of the estimation methods used by AOPWIN or derived explicitly from experimental values.

Overall OH Rate Constant = 79.4902 E-12 cm3/molecule-sec
Half-life = 0.202 Days (24-hr day; 0.5E6 OH/cm3)
Half-life = 4.844 Hrs

Hydrogen Abstraction Calculation:
Ktert = 1.94 F(-CH2-)F(-CH2-)F(-NH-)
= 1.94(1.230)(1.230)(9.300) = 27.296
Ksec = 0.934 F(-CH2-)F(>CH-)=0.934(1.230)(1.230)= 1.413
Ksec = 0.934 F(-CH2-)F(-CH2-)=0.934(1.230)(1.230)= 1.413
Ksec = 0.934 F(-CH2-)F(-CH2-)=0.934(1.230)(1.230)= 1.413
Ksec = 0.934 F(-CH2-)F(-CH2-)=0.934(1.230)(1.230)= 1.413
Ksec = 0.934 F(-CH2-)F(>CH-)=0.934(1.230)(1.230)= 1.413
H Abstraction TOTAL = 34.361 E-12 cm3/molecule-sec

OH-Addition to Fused Rings Calculation:
Most negative Es+ = -0.604
Log Kar = -11.1549 - 1.34(Es+) cm3/molecule-sec; where -11.1549 is the estimated parent value for Benzothiazole
Kar (Benzothiazole-derivative) = 45.1292 E-12 cm3/molecule-sec
TOTAL Kar = 45.1292 E-12 cm3/molecule-sec

OH-Addition to Aromatic Rings Calculation:
TOTAL Kar = 0.0000 E-12 cm3/molecule-sec
Note: The bimolecular rate constant karom is expressed as Kar by the program.

d. Applicability domain: Due to the fragment-based approach of AOPWIN, estimation is adequate as the fragments present in the molecule are available in the list of all fragment and reaction values provided by the program. The AOPWIN program allows the user to select 12 or 24 hour time frames and any average hydroxyl radical concentrations, but the default is originally set at 1.5 × 10^6 molecules (radicals)/cm3 per 12-h of daylight.

e. Estimation accuracy:
i. Hydroxyl radical estimation accuracy of AOPWIN: For the 667 AOPWIN estimations, 90 % are within a factor of two of the experimental value and 95 % are within a factor of three. A correlation between the experimental OH rate constants and the rate constants estimated by the AOP program shows the following statistical accuracy for APOWIN: correlation coefficient (r^2) = 0.963, standard deviation = 0.218, absolute mean error = 0.127
ii. Ozone reaction rate estimation accuracy of AOP: A correlation of experimentally determined gas-phase, ozone reaction rate constants for 112 organic chemicals at room temperature and the rate constants estimated by the APOWIN program shows the following statistical accuracy: correlation coefficient (r^2) = 0.88, standard deviation = 0.52, absolute mean error = 0.35

f. Mechanistic interpretation: The Atmospheric Oxidation Program for Microsoft Windows (AOPWIN) estimates the rate constant for the atmospheric, gas-phase reaction between photochemically produced hydroxyl radicals and organic chemicals. It also estimates the rate constant for the gas-phase reaction between ozone and olefinic/acetylenic compounds. The rate constants estimated by the program are then used to calculate atmospheric half-lives for organic compounds based upon average atmospheric concentrations of hydroxyl radicals and ozone.

g. Uncertainty of the prediction (OECD principle 4): The substance is not highly complex and the rules applied for the substance appear appropriate. An individual uncertainty for the investigated substance is not available.

h. Chemical and biological mechanisms according to the model underpinning the predicted result (OECD principle 5): No information available.

5. APPLICABILITY DOMAIN
a. Despcriptor domains:
i. Molecular weight: Not relevant
ii. Structural fragment domain: Due to the fragment-based approach of AOPWIN, estimation is adequate as the fragments present in the molecule are available in the list of all fragment and reaction values provided by the program.
iii. Mechanism domain: No information available
iv. Metabolic domain: Not relevant
b. Structural analogues: No information available
i. Considerations on structural analogues: No information available

6. ADEQUACY OF THE RESULT
a. Regulatory purpose: The data may be used under any regulatory purpose.
b. Approach for regulatory interpretation of the model result: If no experimental data are available the estimated value may be used to fill data gaps needed for hazard and risk assessment.
c. Outcome: The prediction of the rate constant for the atmospheric, gas-phase reaction between photochemically produced hydroxyl radicals and N-cyclohexylbenzothiazole-2-sulphenamide and its atmospheric half-life yields useful results for further evaluation.
d. Conclusion: The result is considered as useful for regulatory purposes.

Principles of method if other than guideline:

Estimation Program Interface EPI-Suite version 4.11: AOPWIN (v1.93) for the estimation of the atmospheric half-lives for organic compounds based upon average atmospheric concentrations of hydroxyl radicals and ozone.
The Estimation Program Interface was developed by the US Environmental Agency's Office of Pollution Prevention and Toxics, and Syracuse Research Corporation (SRC). © 2000 - 2012 U.S. Environmental Protection Agency for EPI SuiteTM (Published online in November 2012).

GLP compliance:

no

Estimation method (if used):

PHOTOCHEMICAL REACTION WITH OH RADICALS
- sensitiser for indirect photolysis: OH radicals
- Concentration of OH radicals: 0.5 E6 OH/cm³, 24 h/d

Key result

% Degr.:

50

Sampling time:

0.202 d

Key result

DT50:

0.202 d

Remarks on result:

other: OH radical reaction

1) Defined Endpoint: Rate constant for the atmospheric, gas-phase reaction between photochemically produced hydroxyl radicals and organic chemicals at 25°C.

2) Unambiguous algorithm: The molecule is separated into distinct fragments. The reaction rate constant for hydroxyl radicals are the summation of the following mechanisms:

Hydrogen Abstraction = 34.3610 E-12 cm3/molecule-sec
Reaction with N, S and -OH = 0.0000 E-12 cm3/molecule-sec
Addition to Triple Bonds = 0.0000 E-12 cm3/molecule-sec
Addition to Olefinic Bonds = 0.0000 E-12 cm3/molecule-sec
Addition to Aromatic Rings = 0.0000 E-12 cm3/molecule-sec
**Addition to Fused Rings = 45.1292 E-12 cm3/molecule-sec

As depending on the structure of the substance, OH-radicals generally react by one or more of the above mentioned pathways, the result of 0.0000 E-12 cm3/molecule-sec for each mechanism indicate that these mechanisms are not relevant for the substance of interest. An "assumed value" is applied, showing that a structure fragment that has not been assigned a numeric value by the developer of the estimation methods used by AOPWIN or derived explicitly from experimental values.

Hydrogen Abstraction Calculation:
Ktert = 1.94 F(-CH2-)F(-CH2-)F(-NH-)
= 1.94(1.230)(1.230)(9.300) = 27.296
Ksec = 0.934 F(-CH2-)F(>CH-)=0.934(1.230)(1.230)= 1.413
Ksec = 0.934 F(-CH2-)F(-CH2-)=0.934(1.230)(1.230)= 1.413
Ksec = 0.934 F(-CH2-)F(-CH2-)=0.934(1.230)(1.230)= 1.413
Ksec = 0.934 F(-CH2-)F(-CH2-)=0.934(1.230)(1.230)= 1.413
Ksec = 0.934 F(-CH2-)F(>CH-)=0.934(1.230)(1.230)= 1.413
H Abstraction TOTAL = 34.361 E-12 cm3/molecule-sec

OH-Addition to Fused Rings Calculation:
Most negative Es+ = -0.604
Log Kar = -11.1549 - 1.34(Es+) cm3/molecule-sec; where -11.1549 is the estimated parent value for Benzothiazole
Kar (Benzothiazole-derivative) = 45.1292 E-12 cm3/molecule-sec
TOTAL Kar = 45.1292 E-12 cm3/molecule-sec

OH-Addition to Aromatic Rings Calculation:
TOTAL Kar = 0.0000 E-12 cm3/molecule-sec
Note: The bimolecular rate constant karom is expressed as Kar by the program.

3) Applicability domain:

Currently there is no universally accepted definition of model domain.

Due to the fragment-based approach of AOPWIN, estimation is adequate as the fragments present in the molecule are available in the list of all fragment and reaction values provided by the program.

4) Statistical characteristics:

The correlation includes 667 compounds; most experimental values containing a "less than" sign (<) were excluded.

correlation coefficient (r²) 0.963; standard deviation (sd in log units) 0.218; absolute mean error (me) 0.127

5) Mechanistic interpretation:

The reaction values and fragments for the reaction with OH-radicals used as descriptors reflect the most important mechanisms of indirect phototransformation processes possible in the troposphere.

Adequacy of prediction:

The estimation rules applied for the substance appears appropriate.

The predicted result for N-cyclohexylbenzothiazole-2-sulphenamide can be considered reliable yielding a useful result for further assessment.

Validity criteria fulfilled:

not applicable

Conclusions:

The calculated half-life of N-cyclohexylbenzothiazole-2-sulphenamide by photodegradation in air was 0.202 days with an Overall OH rate constant of 79.4902E-12 cm³/molecule-sec.The estimation rules applied for the substance appears appropriate.
The predicted result for N-cyclohexylbenzothiazole-2-sulphenamide can be considered reliable yielding a useful result for further assessment.

Executive summary:

The indirect photodegradation in air was calculated with the Estimation Program Interface EPI-Suite version 4.11.The estimated half-life of N-cyclohexylbenzothiazole-2-sulphenamide was 0.202 days with an Overall OH rate constant of 79.4902E-12 cm³/molecule-sec.

The estimation rules applied for the substance appears appropriate.

The predicted result for N-cyclohexylbenzothiazole-2-sulphenamide can be considered reliable yielding a useful result for further assessment.

The calculated value refers to the unaffected molecule. Any decomposition (e.g. hydrolysis) of the substance is not taken into account by the program.

Description of key information

In the atmosphere a half-life of 4.8 hours (0.202 days) for N-cyclohexylbenzothiazole-2-sulphenamide due to reaction with photochemically produced hydroxyl radicals is estimated by AOPWIN v1.93 with a rate constant of 79.4902*10-12 cm3/molecule-sec, considering an OH-concentration of 500,000 radicals/cm³ as a 24-h average (Currenta, 2021). The estimated half-life in air of N-cyclohexylbenzothiazole-2-sulphenamide is much shorter than 48 hours and hence no potential for long-range transport of N-cyclohexylbenzothiazole-2-sulphenamide in air is expected.

Key value for chemical safety assessment

Half-life in air:

0.202 d

Degradation rate constant with OH radicals:

0 cm³ molecule-1 s-1