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Please be aware that this old REACH registration data factsheet is no longer maintained; it remains frozen as of 19th May 2023.

The new ECHA CHEM database has been released by ECHA, and it now contains all REACH registration data. There are more details on the transition of ECHA's published data to ECHA CHEM here.

Diss Factsheets

Environmental fate & pathways

Phototransformation in air

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Link to relevant study record(s)

Reference
Endpoint:
phototransformation in air
Type of information:
calculation (if not (Q)SAR)
Adequacy of study:
supporting study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Accepted modeling approach
Qualifier:
according to guideline
Guideline:
other: estimation
GLP compliance:
no
Estimation method (if used):
AOP Program (v1.92)
Details on test conditions:
SMILES : O=C(O)C(=C)C
CHEM : 2-Propenoic acid, 2-methyl-
MOL FOR: C4 H6 O2
MOL WT : 86.09
DT50:
20.6 h
Test condition:
calculated for a 24-hr day; reaction with hydroxyl radicals at a concentration of 0.5E6 OH/cm3
DT50:
24.2 h
Test condition:
calculated for reaction with ozone at a concentration of 7E11 mol/cm3

------------------- SUMMARY (AOP v1.92): HYDROXYL RADICALS (25 deg C) --------

Hydrogen Abstraction      =  0.1360 E-12 cm3/molecule-sec

Reaction with N, S and -OH =  0.5200 E-12 cm3/molecule-sec

Addition to Triple Bonds  =  0.0000 E-12 cm3/molecule-sec

Addition to Olefinic Bonds = 17.9900 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 = 18.6460 E-12 cm3/molecule-sec

  HALF-LIFE =    0.860 Days (24-hr day; 0.5E6 OH/cm3)

  HALF-LIFE =    20.651 Hrs

------------------- SUMMARY (AOP v1.91): OZONE REACTION (25 deg C) -----------

  OVERALL OZONE Rate Constant =    1.137500 E-17 cm3/molecule-sec

  HALF-LIFE =     1.007 Days ( at 7E11 mol/cm3)

  HALF-LIFE =    24.179 Hrs

 

Experimental Database: NO Structure Matches

Conclusions:
Using a valid estimation method the OVERALL OH Rate Constant for MAA = 18.6460 E-12 cm3/molecule-sec and the HALF-LIFE was = 0.86 Days (24-hr day; 0.5E6 OH/cm3); the OVERALL OZONE Rate Constant was = 1.137500 E-17 cm3/molecule-sec and the HALF-LIFE was = 1.007 Days (at 7E11 mol/cm3).
Executive summary:

Using a valid estimation method the OVERALL OH Rate Constant for MAA = 18.6460 E-12 cm3/molecule-sec and the  HALF-LIFE was =    0.86 Days (24-hr day; 0.5E6 OH/cm3); the OVERALL OZONE Rate Constant was =    1.137500 E-17 cm3/molecule-sec and the HALF-LIFE was =  1.007 Days (at 7E11 mol/cm3).

Description of key information

Model calculation using EpiSuite 4.10 (AOP program v1.92, US-EPA, 2013):
Half-life for reaction  with hydroxyl radicals ( 0.5E6 OH/cm³) = 20.6 h
Half-life for reaction  with ozone (at 7E11 mol/cm³) =  24.2 h

Key value for chemical safety assessment

Additional information

MAA does not possess UV-absorbing structures. Therefore, direct photolysis is not expected to occur to any significant degree.

While experimental data with model atmospheres exist for MMA which are broadly consistent with model data, no experimental photodegradation data exist for MAA. A model calculation using EpiWin v4.10 AOP v1.92 showed a rate constant for the reaction of MAA with hydroxyl radicals in the atmosphere of 18.6460 E-12 cm³/molecule*sec. From this rate constant the half-life for the reaction of OH radicals with the test substance is calculated as 20.6 h.

In conclusion, after evaporation or emission to air, methacrylic acid will be rapidly degraded by photochemical processes.