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Please be aware that this old REACH registration data factsheet is no longer maintained; it remains frozen as of 19th May 2023.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

Administrative data

Link to relevant study record(s)

Description of key information

The calculated half-lives are in the range of 23.24 hours for hexanoic acid (C6) to 4.56 hours for docosanoic acid (C22).

Key value for chemical safety assessment

Additional information

No experimental data on photolysis in air are available for fatty acids. However comprehensive modeled data are provided in the OECD SIDS (2009) for aliphatic fatty acids of C6-C22 carbon chain length. In the EPISuite model a hydroxyl radical reaction of 1.5 * 106cm3hydroxyl radical concentration at 25 °C is assumed. The data show a decreasing photodegradation half-life with increasing chain length. Unsaturated fatty acids undergo photolysis faster than saturated. The half-life declines with the number of double bonds. The calculated half-lives of saturated fatty acids are in the range of 23.24 hours for hexanoic acid (C6) to 4.56 hours for docosanoic acid (C22).


Aliphatic Acid

CAS Name
CAS Number

Photodegradation in air [half-life]
(EPISuite modelled data)


Hexanoic acid

CAS 142-62-1

23.236 hrs


Octanoic acid
CAS 124-07-2 

15.372 hrs


Nonanoic acid

CAS 112-05-0

13.15 hrs


Decanoic acid
 CAS 334-48-5

11.485 hrs


Dodecanoic acid
CAS 143-07-7 

9.167 hrs


Tetradecanoic acid
 CAS 544-63-8

7.627 hrs


Hexadecanoic acid
CAS 57-10-3

6.530 hrs


Octadecanoic acid
CAS 57-11-4

5.710 hrs

C18, 1 double bond

9-Octadecenoic acid, (Z)
CAS 112-80-1

1.544 - 1.699 hrs

C18, 2 double

 dienoic acid, (Z,Z)
CAS 60-33-3

0.892 - 0.998 hrs


Docosanoic acid
CAS 112-85-6

4.562 hrs

C22, 1 double

13-Docosenoic acid, (Z)-
CAS 112-86-7

1.446 - 1.581 hrs

Data are cited from OECD SIDS Dossier “Aliphatic Acids Category”, 2009