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EC number: 481-730-0 | CAS number: 848301-65-5
Phototransformation in air
Administrative data
Link to relevant study record(s)
- Endpoint:
- phototransformation in air
- Type of information:
- (Q)SAR
- Adequacy of study:
- supporting 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
- Justification for type of information:
- QSAR prediction
- Qualifier:
- according to guideline
- Guideline:
- other: REACH guidance on QSARs Chapter R.6 , May 2008
- Deviations:
- not applicable
- Principles of method if other than guideline:
- QSAR prediction, using the Atmospheric Oxidation Program (AOPWIN v.1.92 by US EPA)
- Estimation method (if used):
- The phototransformation in air of representatives hydrocarbons was calculated using the Atmospheric Oxidation Program (AOPWIN v.1.92 by US EPA), which estimates the rate constant for the atmospheric, gas-phase reaction between photochemically produced hydroxyl radicals and organic chemicals. 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.
"Naphtha (Fischer-Tropsch), light, C4-10 - branched and linear" consists predominantly of branched and linear aliphatic hydrocarbons having carbon numbers in the range of C4 to C10, the linear alkane hydrocarbons were used for the assessment of the phototransformation rates and half lives. - Light source:
- other: calculated data
- Details on light source:
- Calculated data
- Details on test conditions:
- Theoretical conditions applied to calculations:
- 25°C
- 12 hrs day
- 1.5 x 10^6 OH/cm3 - Reference substance:
- no
- Preliminary study:
- Not applicable
- Test performance:
- Not applicable
- DT50:
- 4.064 d
- Test condition:
- QSAR calculation
- Remarks on result:
- other: Calculation for n-Butane
- DT50:
- 1.96 d
- Test condition:
- QSAR calculation
- Remarks on result:
- other: Calculation for n-Hexane
- DT50:
- 1.291 d
- Test condition:
- QSAR calculation
- Remarks on result:
- other: Calculation for n-Octane
- DT50:
- 0.963 d
- Test condition:
- QSAR calculation
- Remarks on result:
- other: Calculation for n-Decane
- Transformation products:
- not specified
- Results with reference substance:
- Not applicable
- Validity criteria fulfilled:
- not applicable
- Conclusions:
- The direct aqueous photolysis of an organic molecule occurs when it absorbs sufficient light energy to result in a structural transformation. Only light energy at wavelengths between 290 and 750 nm can result in photochemical transformations in the environment, although absorption is not always sufficient for a chemical to undergo photochemical degradation. In general, most representatives of Naphtha (Fischer-Tropsch), light, C4-10 - branched and linear will not undergo direct photolysis. Saturated hydrocarbons, which constitute the majority of the test item, do not absorb appreciable light energy above 290 nm. Therefore, this fate process will not contribute to a measurable degradative removal of chemical components in this category from the environment. Direct photodegradation is not expected to play an important role in the environmental fate of Naphtha (Fischer-Tropsch), light, C4-10 - branched and linear. Indirect photodegradation via reaction with hydroxyl radicals may be important in the gas-phase degradation of the respective hydrocarbons that volatilize to the troposphere. An overall range of half-lives expected for individual components (linear hydrocarbons C4-C10) is 0.963 to 4.064 days.
- Executive summary:
The atmospheric oxidation potential (AOP) of the respective hydrocarbon compounds was estimated using AOPWIN (atmospheric oxidation program for Microsoft Windows), a subroutine in the EPI SuiteTM (US EPA, 2000) models and used by the US EPA OPPTS (Office of Pollution Prevention and Toxic Substances). This program calculates a reaction rate constant (cm3/molecules/sec) and a chemical half-life (hour or days) of a compound based upon average atmospheric concentrations of hydroxyl radicals and a 12-h day at 25°C.
The phototransformation rate range from 2.6322 x 10-12cm3/molecule/sec to 11.1105 x 10-12cm3/molecule/sec. The calculated half-life ranges from 0.963 to 4.064 days.
- Endpoint:
- phototransformation in air
- Type of information:
- (Q)SAR
- Adequacy of study:
- supporting 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
- Justification for type of information:
- QSAR prediction
- Qualifier:
- according to guideline
- Guideline:
- other: REACH guidance on QSARs Chapter R.6 , May 2008
- Deviations:
- not applicable
- Principles of method if other than guideline:
- QSAR prediction, using the Atmospheric Oxidation Program (AOPWIN v.1.92 by US EPA)
- Estimation method (if used):
- The phototransformation in air of representatives hydrocarbons was calculated using the Atmospheric Oxidation Program (AOPWIN v.1.92 by US EPA), which estimates the rate constant for the atmospheric, gas-phase reaction between photochemically produced hydroxyl radicals and organic chemicals. 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.
"Naphtha (Fischer-Tropsch), light, C4-10 - branched and linear" consists predominantly of branched and linear aliphatic hydrocarbons having carbon numbers in the range of C4 to C10, the branched alkane hydrocarbons were used for the assessment of the phototransformation rates and half lives. - Light source:
- other: calculated data
- Details on light source:
- Calculated data
- Details on test conditions:
- Theoretical conditions applied to calculations:
- 25°C
- 12 hrs day
- 1.5 x 10^6 OH/cm3 - Reference substance:
- no
- Preliminary study:
- Not applicable
- Test performance:
- Not applicable
- DT50:
- 4.38 d
- Test condition:
- QSAR calculation
- Remarks on result:
- other: Calculation for 2-Methylpropane
- DT50:
- 1.963 d
- Test condition:
- QSAR calculation
- Remarks on result:
- other: Calculation for 2-Methylpentane
- DT50:
- 1.292 d
- Test condition:
- QSAR calculation
- Remarks on result:
- other: Calculation for 2-Methylheptane
- DT50:
- 0.939 d
- Test condition:
- QSAR calculation
- Remarks on result:
- other: Calculation for 3-Methylnonane
- Transformation products:
- not specified
- Results with reference substance:
- Not applicable
- Validity criteria fulfilled:
- not applicable
- Conclusions:
- The direct aqueous photolysis of an organic molecule occurs when it absorbs sufficient light energy to result in a structural transformation. Only light energy at wavelengths between 290 and 750 nm can result in photochemical transformations in the environment, although absorption is not always sufficient for a chemical to undergo photochemical degradation. In general, most representatives of Naphtha (Fischer-Tropsch), light, C4-10 - branched and linear will not undergo direct photolysis. Saturated hydrocarbons, which constitute the majority of the test item, do not absorb appreciable light energy above 290 nm. Therefore, this fate process will not contribute to a measurable degradative removal of chemical components in this category from the environment. Direct photodegradation is not expected to play an important role in the environmental fate of Naphtha (Fischer-Tropsch), light, C4-10 - branched and linear. Indirect photodegradation via reaction with hydroxyl radicals may be important in the gas-phase degradation of the respective hydrocarbons that volatilize to the troposphere. An overall range of half-lives expected for individual components (branched hydrocarbons C4-C10) is 0.939 to 4.38 days.
- Executive summary:
The atmospheric oxidation potential (AOP) of the respective hydrocarbon compounds was estimated using AOPWIN (atmospheric oxidation program for Microsoft Windows), a subroutine in the EPI SuiteTM (US EPA, 2000) models and used by the US EPA OPPTS (Office of Pollution Prevention and Toxic Substances). This program calculates a reaction rate constant (cm3/molecules/sec) and a chemical half-life (hour or days) of a compound based upon average atmospheric concentrations of hydroxyl radicals and a 12-h day at 25°C.
The phototransformation rate range from 24.418 x 10-12cm3/molecule/sec to 113.867 x 10-12cm3/molecule/sec. The calculated half-life ranges from 0.939 to 4.38 days.
Referenceopen allclose all
Table 1. AOPWIN v.1.92 results for alkanes
C nr. |
Name Smiles |
Formula |
Overall OH rate constant (10-12cm3/molecule sec) |
Half life |
Days |
||||
4 |
n-Butane |
C4H10 |
2.6322 |
4.064 |
| 5 | n-Pentane | C5H12 | 4.0452 | 2.664 |
| 6 | n-Hexane | C6H14 | 5.4583 | 1.960 |
| 7 | n-Heptane | C7H16 | 6.8713 | 1.557 |
| 8 | n-Octane | C8H18 | 8.2844 | 1.291 |
| 9 | n-Nonane | C9H20 | 9.6974 | 1.103 |
| 10 | n-Decane | C10H22 | 11.1105 | 0.963 |
SMILES : C(CC)C CHEM : Butane
MOL FOR: C4 H10
MOL WT : 58.12
------------------- SUMMARY (AOP v1.92): HYDROXYL RADICALS (25 deg C) --------
Hydrogen Abstraction = 2.6322 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 = 2.6322 E-12 cm3/molecule-sec
HALF-LIFE = 4.064 Days (12-hr day; 1.5E6 OH/cm3)
HALF-LIFE = 48.762 Hrs
------------------- SUMMARY (AOP v1.91): OZONE REACTION (25 deg C) -----------
****** NO OZONE REACTION ESTIMATION ******
(ONLY Olefins and Acetylenes are Estimated)
Experimental Database Structure Match: Chem Name : n-Butane CAS Number: 000106-97-8
Exper OH rate constant : 2.54 E-12 cm3/molecule-sec
Exper OH Reference: ATKINSON,R (1989)
Exper Ozone rate constant: 9.8 E-24 cm3/molecule-sec
Exper NO3 rate constant : 4.3 E-17 cm3/molecule-sec
SMILES : C(CCC)C
CHEM : Pentane
MOL FOR: C5 H12
MOL WT : 72.15
------------------- SUMMARY (AOP v1.92): HYDROXYL RADICALS (25 deg C) --------
Hydrogen Abstraction = 4.0452 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 = 4.0452 E-12 cm3/molecule-sec
HALF-LIFE = 2.644 Days (12-hr day; 1.5E6 OH/cm3)
HALF-LIFE = 31.729 Hrs
------------------- SUMMARY (AOP v1.91): OZONE REACTION (25 deg C) -----------
****** NO OZONE REACTION ESTIMATION ******
(ONLY Olefins and Acetylenes are Estimated)
Experimental Database Structure Match: Chem Name : n-Pentane CAS Number: 000109-66-0
Exper OH rate constant : 3.94 E-12 cm3/molecule-sec
Exper OH Reference: ATKINSON,R (1989)
Exper Ozone rate constant: --- cm3/molecule-sec
Exper NO3 rate constant : 8.2 E-17 cm3/molecule-sec
SMILES : C(CCCC)C
CHEM : Hexane
MOL FOR: C6 H14
MOL WT : 86.18
------------------- SUMMARY (AOP v1.92): HYDROXYL RADICALS (25 deg C) --------
Hydrogen Abstraction = 5.4583 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 = 5.4583 E-12 cm3/molecule-sec
HALF-LIFE = 1.960 Days (12-hr day; 1.5E6 OH/cm3)
HALF-LIFE = 23.515 Hrs
------------------- SUMMARY (AOP v1.91): OZONE REACTION (25 deg C) -----------
****** NO OZONE REACTION ESTIMATION ******
(ONLY Olefins and Acetylenes are Estimated)
Experimental Database Structure Match: Chem Name : n-Hexane CAS Number: 000110-54-3
Exper OH rate constant : 5.61 E-12 cm3/molecule-sec
Exper OH Reference: ATKINSON,R (1989)
Exper Ozone rate constant: --- cm3/molecule-sec
Exper NO3 rate constant : 1.05 E-16 cm3/molecule-sec
SMILES : C(CCCCC)C
CHEM : Heptane
MOL FOR: C7 H16
MOL WT : 100.21
------------------- SUMMARY (AOP v1.92): HYDROXYL RADICALS (25 deg C) --------
Hydrogen Abstraction = 6.8713 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 = 6.8713 E-12 cm3/molecule-sec
HALF-LIFE = 1.557 Days (12-hr day; 1.5E6 OH/cm3)
HALF-LIFE = 18.679 Hrs
------------------- SUMMARY (AOP v1.91): OZONE REACTION (25 deg C) -----------
****** NO OZONE REACTION ESTIMATION ******
(ONLY Olefins and Acetylenes are Estimated)
Experimental Database Structure Match: Chem Name : n-Heptane CAS Number: 000142-82-5
Exper OH rate constant : 7.15 E-12 cm3/molecule-sec
Exper OH Reference: ATKINSON,R (1989)
Exper Ozone rate constant: --- cm3/molecule-sec
Exper NO3 rate constant : 1.37 E-16 cm3/molecule-sec
SMILES : C(CCCCCC)C
CHEM : Octane
MOL FOR: C8 H18
MOL WT : 114.23
------------------- SUMMARY (AOP v1.92): HYDROXYL RADICALS (25 deg C) --------
Hydrogen Abstraction = 8.2844 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 = 8.2844 E-12 cm3/molecule-sec
HALF-LIFE = 1.291 Days (12-hr day; 1.5E6 OH/cm3)
HALF-LIFE = 15.493 Hrs
------------------- SUMMARY (AOP v1.91): OZONE REACTION (25 deg C) -----------
****** NO OZONE REACTION ESTIMATION ****** (ONLY Olefins and Acetylenes are Estimated)
Experimental Database Structure Match: Chem Name : n-Octane CAS Number: 000111-65-9
Exper OH rate constant : 8.68 E-12 cm3/molecule-sec
Exper OH Reference: ATKINSON,R (1989)
Exper Ozone rate constant: --- cm3/molecule-sec
Exper NO3 rate constant : 1.84 E-16 cm3/molecule-sec
SMILES : C(CCCCCCC)C
CHEM : Nonane
MOL FOR: C9 H20
MOL WT : 128.26
------------------- SUMMARY (AOP v1.92): HYDROXYL RADICALS (25 deg C) --------
Hydrogen Abstraction = 9.6974 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 = 9.6974 E-12 cm3/molecule-sec
HALF-LIFE = 1.103 Days (12-hr day; 1.5E6 OH/cm3)
HALF-LIFE = 13.236 Hrs
------------------- SUMMARY (AOP v1.91): OZONE REACTION (25 deg C) -----------
****** NO OZONE REACTION ESTIMATION ******
(ONLY Olefins and Acetylenes are Estimated)
Experimental Database Structure Match: Chem Name : n-Nonane CAS Number: 000111-84-2
Exper OH rate constant : 10.2 E-12 cm3/molecule-sec
Exper OH Reference: ATKINSON,R (1989)
Exper Ozone rate constant: --- cm3/molecule-sec
Exper NO3 rate constant : 1.92 E-16 cm3/molecule-sec
SMILES : C(CCCCCCCC)C
CHEM : Decane
MOL FOR: C10 H22
MOL WT : 142.29
------------------- SUMMARY (AOP v1.92): HYDROXYL RADICALS (25 deg C) --------
Hydrogen Abstraction = 11.1105 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 = 11.1105 E-12 cm3/molecule-sec
HALF-LIFE = 0.963 Days (12-hr day; 1.5E6 OH/cm3)
HALF-LIFE = 11.552 Hrs
------------------- SUMMARY (AOP v1.91): OZONE REACTION (25 deg C) -----------
****** NO OZONE REACTION ESTIMATION ******
(ONLY Olefins and Acetylenes are Estimated)
Experimental Database Structure Match: Chem Name : n-Decane CAS Number: 000124-18-5
Exper OH rate constant : 11.6 E-12 cm3/molecule-sec Exper OH Reference: ATKINSON,R (1989)
Exper Ozone rate constant: --- cm3/molecule-sec
Exper NO3 rate constant : 2.59 E-16 cm3/molecule-sec
Table 1. AOPWIN v.1.92 results for respective, branched hydrocarbons
| C No. | Names | Formula | Overall OH rate constant (10-12cm3/molecule sec) |
Half-lives Days |
| 4 | 2-Methylpropane |
C4H10 | 24.418 | 4.380 |
| 5 | 2-methylbutane | C5H12 | 40.369 | 2.650 |
| 6 | 2-methylpentane | C6H14 | 54.499 | 1.963 |
| 7 | 2-methylhexane | C7H16 | 68.630 | 1.559 |
| 8 | 2-methylheptane | C8H18 | 82.760 | 1.292 |
| 9 | 3-methyloctane | C9H20 | 99.737 | 1.072 |
| 10 | 3-methylnonane | C10H22 | 113.867 | 0.939 |
Description of key information
-AOPWIN calculations show that typical atmospheric hydroxyl radical reaction half-lives for the respective, linear hydrocarbons (C4 -C10) may range from 0.963 to 4.064 days.
-AOPWIN calculations show that typical atmospheric hydroxyl radical reaction half-lives for the respective, branched hydrocarbons (C4 -C10) may range from 0.939 to 4.38 days.
Key value for chemical safety assessment
Additional information
Indirect photodegradation via reaction with hydroxyl radicals may be important in the gas-phase degradation of the respective hydrocarbons that volatilize to the troposphere. An overall range of half-lives expected for individual, linear components is from 0.963 to 4.064 days and for respective, branched components is from 0.939 to 4.38 days, respectively. Finally, residence times in the atmosphere are relatively short.
The SRC AOPWIN program was used to obtain values of the rate constant kOH for reaction of each constituent of GTL Naphtha with hydroxyl radicals. The program outputs are used to calculate a weighted average value for each block based on the modelled composition of GTL Naphtha (Section 1.2). EUSES 2.1.2 calculates an overall half-life in air under default conditions of hydroxyl radical concentration, using the following expressions:
kdegair (d-1) = kOH(cm3/molecule-sec) x OHConcair (molec/cm3) x 24 x 3600
Half-life is then calculated as:
DT50(d) = ln 2/ kdegair (d-1)
Where:
kdegair= total rate constant for degradation in air
kOH= rate constant for reaction with hydroxyl radicals
OHConcair= concentration of hydroxyl radicals in air
DT50= half-life
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