Use of this information is subject to copyright laws and may require the permission of the owner of the information, as described in the ECHA Legal Notice.
EC number: 220-020-5
CAS number: 2605-79-0
Coefficient of Amine Oxide: Determined
by Ratio of Solubility in Octanol
CMC in Water (study
Alkyl chain length
Octanol Solubility (g/L)
CMC = critical micelle concentration in
DMAO = dimethyl amine oxide.
CMC’s from literature. Octanol
solubility measured in lab (of the test material, C12-14 DMAO).
The Partition Coefficient of C12/14
alkyl dimethyl amine oxide in octanol/water was determined by four
different methods: (1) HPLC according to OECD 117; (2) computational
models; (3) solubility in octanol divided by solubility in water; and
(4) solubility in octanol divided by the aqueous critical micelle
The HPLC method was unsuitable for
determining the partition coefficient of amine oxide, due to poor peak
shape and poor elution. The computational models had difficulty
estimating a reliable partition coefficient since the amine oxide
structural unit is not well parameterized in these models. The
partition coefficient by solubility in octanol divided by solubility in
water is unreliable because a large portion of the test material is
present as micelles in water, and not as a true solution.
Calculating the partition coefficient
of amine oxide by the ratio of solubility in octanol to the aqueous CMC
was superior to these other approaches, because the CMC is the
concentration at which the test material is a saturated solution, and
begins to form micelles. The CMC is the aqueous solubility limit of the
partition coefficient (n-octanol/water) of C12/14 alkyl dimethyl amine
oxide, determined by the ratio of solubility in octanol to the CMC in
water, was below 2.7 (log Pow).
The log Kow is estimated conservatively to be 0.95.
The log Pow of C10 AO has been estimated on
the basis of experimental data for the solubility of C12-14 AO in
n-octanol and literature data for the critical micelle concentration of
the C10 AO. The result was log Pow = 0.95. This is considered to be a
worse case value for the following reasons:
Surfactants can form different types of
solutions in water (e.g. mono-molecular-, micellar-, hexagonal or
lamellar solutions) depending on concentration and temperature. The
mono-molecular solubility of a surfactant is defined by the critical
micelle concentration (cmc). If cmc data are available, they may be used
as a worst-case approach in cases where the resulting log Pow is not
critical. However, from a physico-chemical point of view, the cmc is not
a good descriptor for the water solubility, as the micelles themselves
completely dissolve in water. The rationale behind using the
octanol/water solubility ratio as a measure for the octanol/water
partitioning coefficient is that material insoluble in octanol would be
“pushed” into the water phase while material insoluble in water would be
“pushed” into the octanol phase. With micelles, this is definitely not
true. Micelles form an isotropic, homogeneous solution in water and
cannot partition into an organic phase due to their hydrophilic nature.
Further, the typical lifetime of surfactant micelles is only a few
milliseconds, and the lifetime of micelle/bulk exchange of surfactant
molecules is only a few microseconds, i.e. there is a very rapid
exchange between mono-molecular dissolved and micellar dissolved
surfactant molecules. This is in stark contrast to classical undissolved
material, which has molecular lifetimes of several seconds or longer.
Thus, the cmc underestimates the total solubility of a surfactant and
hence overestimates the partition coefficient.
Taking all the available evidence together it
has been concluded that it is valid to use the value
of log Pow = 0.95 for C10 AO, as this is still likely to overestimate
the partition coefficient.
Information on Registered Substances comes from registration dossiers which have been assigned a registration number. The assignment of a registration number does however not guarantee that the information in the dossier is correct or that the dossier is compliant with Regulation (EC) No 1907/2006 (the REACH Regulation). This information has not been reviewed or verified by the Agency or any other authority. The content is subject to change without prior notice.Reproduction or further distribution of this information may be subject to copyright protection. Use of the information without obtaining the permission from the owner(s) of the respective information might violate the rights of the owner.
Tato webová stránka používá cookies, aby se vám naše stránky používaly co nejlépe.
Welcome to the ECHA website. This site is not fully supported in Internet Explorer 7 (and earlier versions). Please upgrade your Internet Explorer to a newer version.
Do not show this message again