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Environmental fate & pathways

Phototransformation in air

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Endpoint:
phototransformation in air
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 adequate and reliable documentation / justification
Justification for type of information:
QSAR prediction: Model considered valid by OECD
Qualifier:
no guideline required
Principles of method if other than guideline:
QSAR model, EPI Suite v 4.1/Aopwin v1.92
GLP compliance:
no
Remarks:
not applicable
Estimation method (if used):
PHOTOCHEMICAL REACTION WITH OH RADICALS - assumed reaction conditions used in model:
- Concentration of OH radicals:1.5E6 per cm3
- Temperature for which rate constant was calculated: 25C
- Computer programme: AOPWIN v1.92
Light source:
sunlight
Preliminary study:
Using the AOPWIN QSAR model, the photochemical degradation rate of Sodium isobutyl xanthate in the atmosphere is 16.0392 E-12 cm3/molecule-sec, with a resultant predicted half live of 8.002 Hrs (0.667 Days (12-hr day; 1.5E6 OH/cm3)

OVERALL OH Rate Constant = 16.0392 E-12 cm3/molecule-sec
HALF-LIFE = 0.667 Days (12-hr day; 1.5E6 OH/cm3)
HALF-LIFE = 8.002 Hrs
Reaction with:
OH radicals
Rate constant:
0 cm³ molecule-1 s-1
Transformation products:
no
Results with reference substance:
OVERALL OH Rate Constant = 16.0392 E-12 cm3/molecule-sec
HALF-LIFE = 0.667 Days (12-hr day; 1.5E6 OH/cm3)
HALF-LIFE = 8.002 Hrs

Hydrogen Abstraction      = 16.0392 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   =  0.0000 E-12 cm3/molecule-sec

 

  OVERALL OH Rate Constant = 16.0392 E-12 cm3/molecule-sec

  HALF-LIFE =    0.667 Days (12-hr day; 1.5E6 OH/cm3)

  HALF-LIFE =    8.002 Hrs

Validity criteria fulfilled:
yes
Remarks:
the photochemical degradation rate of Sodium isobutyl xanthate in the atmosphere is 16.0392 E-12 cm3/molecule-sec, with a resultant predicted half live of 8.002 Hrs (0.667 Days (12-hr day; 1.5E6 OH/cm3)
Conclusions:
Using the AOPWIN QSAR model, the photochemical degradation rate of Reaction mass of SIBX in the atmosphere is 16.0392 E-12 cm3/molecule-sec, with a resultant predicted half live of 8.002 Hrs (0.667 Days (12-hr day; 1.5E6 OH/cm3)
Executive summary:

Using the AOPWIN QSAR model, the photochemical degradation rate of Reaction mass of SIBX in the atmosphere is 16.0392 E-12 cm3/molecule-sec, with a resultant predicted half live of 8.002 Hrs (0.667 Days (12-hr day; 1.5E6 OH/cm3)

Endpoint:
phototransformation in air
Data waiving:
other justification
Justification for data waiving:
other:

Description of key information

Using the AOPWIN QSAR model, the photochemical degradation rate of Reaction mass of SIBXe in the atmosphere is 16.0392 E-12 cm3/molecule-sec, with a resultant predicted half live of 8.002 Hrs (0.667 Days (12-hr day; 1.5E6 OH/cm3).
If released to air, a vapor pressure of 1.26E-009 mm Hg at 25 deg C (1.26E-009 mm Hg is equivalent to 1.68E-007 Pa ) indicates Reaction mass of SIBX will exist solely as a vapor in the atmosphere. Vapor-phase Reaction mass of SIBX will be degraded in the atmosphere by reaction with photochemically-produced hydroxyl radicals; the half-life for this reaction in air is estimated to be 0.667 days, calculated from its rate constant of 16.0392 E-12 cm3/molecule-sec at 25 deg.
Xanthates do not contain chromophores that absorb at wavelengths >290 nm and therefore Sodium isobutyl xanthate is not expected to be susceptible to direct photolysis by sunlight.

Key value for chemical safety assessment

Half-life in air:
0.667 d
Degradation rate constant with OH radicals:
0 cm³ molecule-1 s-1

Additional information

If released to air, a vapor pressure of 1.26E-009 mm Hg at 25 deg C (1.26E-009 mm Hg is equivalent to 1.68E-007 Pa ) indicatesReaction mass of SIBXwill exist solely as a vapor in the atmosphere. Vapor-phaseReaction mass of SIBXwill be degraded in the atmosphere by reaction with photochemically-produced hydroxyl radicals; the half-life for this reaction in air is estimated to be 0.667 days, calculated from its rate constant of 16.0392 E-12 cm3/molecule-sec at 25 deg. Xanthates do not contain chromophores that absorb at wavelengths >290 nm and thereforeReaction mass of SIBXis not expected to be susceptible to direct photolysis by sunlight.

Using the AOPWIN QSAR model, the photochemical degradation rate of Reaction mass of SIBX in the atmosphere is 16.0392 E-12 cm3/molecule-sec, with a resultant predicted half live of 8.002 Hrs (0.667 Days (12-hr day; 1.5E6 OH/cm3)

OVERALL OH Rate Constant = 16.0392 E-12 cm3/molecule-sec

HALF-LIFE = 0.667 Days (12-hr day; 1.5E6 OH/cm3)

HALF-LIFE = 8.002 Hrs

If released to air, a vapor pressure of1.26E-009 mm Hg at 25 deg C (1.26E-009 mm Hg is equivalent to 1.68E-007 Pa ) indicates Reaction mass of SIBX will exist solely as a vapor in the atmosphere. Vapor-phase Reaction mass of SIBX will be degraded in the atmosphere by reaction with photochemically-produced hydroxyl radicals; the half-life for this reaction in air is estimated to be0.667days, calculated from its rate constant of16.0392 E-12 cm3/molecule-secat 25 deg.

 

Xanthates do not contain chromophores that absorb at wavelengths >290 nm and therefore Sodium isobutyl xanthate is not expected to be susceptible to direct photolysis by sunlight.