thiamethoxam (ISO); 3-(2-chloro-thiazol-5-ylmethyl)-5-methyl[1,3,5]oxadiazinan-4-ylidene-N-nitroamine

Phototransformation in air

Link to relevant study record(s)

Reference

Endpoint:

phototransformation in air

Type of information:

(Q)SAR

Adequacy of study:

key study

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 adequate and reliable documentation / justification

Qualifier:

no guideline followed

GLP compliance:

no

Estimation method (if used):

PHOTOCHEMICAL REACTION WITH OH RADICALS
- Concentration of OH radicals: 1.5E+06 OH/cm3
- Degradation rate constant: 248.9383 E-12 cm3/molecule-sec (12-hours day)
- Temperature for which rate constant was calculated: Not reported
- Computer programme: Atmospheric Oxidation program (AOP) v1.82 (1996)
- SMILES used: CN1C(=NN(=O) (=O))N(Cc2cnc(s2)CL)COC1
- Molecular weight: 291.71 g/mol

Key result

DT50:

2.37 h

Test condition:

calculated with 1.5E6 OH-Radicals/cm3 and a 12 hours day

Reaction with:

OH radicals

Rate constant:

0 m³ molecule-1 s-1

Transformation products:

not specified

RESTRICTIVE RATE ESTIMATION

In the case of unknown structural elements, the estimation accuracy decreases in the same way as the chemical similarity of the used fragments in comparison with the real structure decreases. For the chemical class of Nitro-guanidines, where the test substance belongs to, so far no measured rate values are known. Based on the well experienced chemical reactivity in the sequence amine - amide - urea it is supposed, that the fragments taken to represent the nitro-guanidine group overestimate the reactivity against an OH radical reaction. With respect to the lack of experimental data, the oxidation rate was recalculated restrictively.

DETAILS OF ESTIMATION PROCEDURE

AOPbased Hydrogen Abstraction Calculation:

Kprim = 0.136 F(-N<) = 0.136(9.300) = 1.265

Ksec = 0.934 F(-Aromatic)F(-N<) = 0.934(1.000)(9.300) = 8.686

Ksec = 0.934 F(-O-)F(-N<) = 0.934(6.100)(9.300) = 52.986

Kse6 = 0.934 F(-N<)F(-O-) = 0.934(9.300)(6.100) = 52.986

H Abstraction TOTAL (E-12cm3/molecule-sec) = 115.923

 

AOPbased Reaction Rates With Nitrogen, Sulfur and -OH:

K(>N-)(E-12 cm3/molecule-sec) = 66.000

K(>N-)(E-12 cm3/molecule-sec) = 66.000

 

AOPbased OH Addition to Aromatic Rings Calculation:

Es+ = sp+(-CH2-**)+ sm+(-CL) + = 0.104

Most negative Es+ = 0.104

Log Kar = -11.8539 - l.34(Es+)cm3/molecule-sec

where -11.8539 is the measured parent value for thiazole

Ring #1 Kar = 1.016 E-12 cm3/molecule-sec

TOTAL Kar (E-12 cm3/molecule-sec) = 1.016

**ASSUMED Values designatedby:

 

ModifiedHydrogen Abstraction Calculation:

(restrictive: for the nitro-guanidine group is taken the group rate constant and the substituent factor of an urea):

Kprirn = 0.136 F(-NC(=O)) = 0.136(4.100) = 0.558

Ksec = 0.93( F(-NC(=O))F(-O-) = 0.934(4.100)(6.100) = 23.359

Ksec = 0.934 F(-O-)F(-NC(=O)) = 0.934(6.100) (4.100) = 23.359

Ksec = 0.934 F(-Arornatic)F(-N-C(=O)) = 0.934(1.000)(4.100) = 3.829

H Abstraction TOTAL (E-12cm3/rnolecule-sec) = 51.106

 

ModifiedReaction Rates With Nitrogen. Sulfur and -OH:

K(-NC(=O)N**)(E-12 cm3/rnolecule-sec) = 1.000

K(-NC(=O)N**)(E-12 cm3/rnolecule-sec) = 1.000

OVERALL OH Rate Constant mod. (E-12 cm3/rnolecule-sec) = 54.121

Validity criteria fulfilled:

not specified

Conclusions:

The atmospheric oxidation half-life of the test substance was estimated to be 2.37 hours (calculated with 1.5E6 OH-Radicals/cm3 and a 12 hours day), with a degradation rate of 54.1214 E-12 cm3/molecule-sec.

Description of key information

Atmospheric oxidation half-life = 2.37h, AOP QSAR, Stamm 1998

Key value for chemical safety assessment

Half-life in air:

2.37 h

Degradation rate constant with OH radicals:

0 m³ molecule-1 s-1