LINEAR ALKYLBENZENE SULFONATE (LAS) - UNEP Chemicals

OECD SIDS LINEAR ALKYLBENZENE SULFONATE (LAS)
II. Substance information
(1) Category name
Linear Alkylbenzene Sulfonate (LAS)
(2) Substance Name(s) and CAS RN
1322-98-1 Decylbenzene sulfonic acid, sodium salt
25155-30-0 Dodecylbenzene sulfonic acid, sodium salt
26248-24-8 Tridecylbenzene sulfonic acid, sodium salt
27636-75-5 Tridecylbenzene sulfonic acid, sodium salt
68081-81-2 C10-16 Monoalkylbenzene sulfonic acid, sodium salt
68411-30-3 C10-13 Alkylbenzene sulfonic acid, sodium salt
69669-44-9 C10-14 Alkylbenzene sulfonic acid, sodium salt
85117-50-6 C10-14 Monoalkylbenzene sulfonic acid, sodium salt
90194-45-9 C10-13 Alkyl derivatives benzene sulfonic acid, sodium salt
127184-52-5 4-C10-13-sec Alkyl derivatives benzene sulfonic acid, sodium salt
CH 3 (CH 2 ) 5 CH(CH 2 ) 4 CH 3
S0 - Na +
3
(3) Substance Formula and Structure
The LAS molecule contains an aromatic ring sulfonated at the para position and attached to a linear alkyl
chain at any position except the terminal carbons (Valtorta et al., 2000). The alkyl carbon chain typically has
10 to 14 carbon atoms. The linearity of the alkyl chains ranges from 87-98%. While commercial LAS
consists of more than 20 individual components, the ratio of the various homologues and isomers,
representing different alkyl chain lengths and aromatic ring positions along the linear alkyl chain, is relatively
constant across the various detergent and cleaning applications, with the average carbon number of the alkyl
chain varying between 11.7-11.8. Because of the close consistency of the mixtures, their commercial uses,
fate and effects, LAS is discussed as a category rather than as individual CAS numbers in this assessment.
The structure of a C12-LAS, representative of the category, is shown in the figure.
(4) Physical Form
All members of the category are solid at room temperature; melting point >198.5°C.
(5) Other Constituents
Some methyl-substituted (i.e., iso-branched) LAS may be present in the mixtures (Nielsen et al. 1997). The
amount of the iso-LAS component is small (1-6%) and was shown not to limit biodegradation relative to pure
linear component (Nielsen et al. 1997; Cavalli et al. 1999). Non-linear components such as dialkyltetralin
sulfonates (DATS) can be present at levels of less than 1 to 8% depending on the manufacturing process
(Nielsen et al 1997). The presence of these amounts of DATS does not significantly affect the biodegradation
of LAS (Nielsen et al 1997). Improvements in processing techniques in the US, Europe and Japan incorporated
to increase LAS yields also reduce the amount of DATS present in LAS.
UNEP PUBLICATIONS 67