Decyldimethylamine

Partition coefficient

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

partition coefficient

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Justification for type of information:

For details on endpoint-specific justification, please see read-across justification document (analogue approach) in section 13.

Reason / purpose for cross-reference:

assessment report

Reason / purpose for cross-reference:

read-across source

Partition coefficient type:

octanol-water

Type:

Pow

Partition coefficient:

89.5

Temp.:

20 °C

Remarks on result:

other: RA from C10-DMA HCl: mildly acidic (salt of a medium strength base and a strong acid), pH not measured

Key result

Type:

log Pow

Partition coefficient:

1.95

Temp.:

20 °C

Remarks on result:

other: RA from C10-DMA HCl: mildly acidic (salt of a medium strength base and a strong acid), pH not measured

Executive summary:

The study used as source investigated the log Pow at 20 °C for C10-DMA hydrochloride. The study results of the source substance were considered applicable to the target substance. Justification and applicability of the read-across approach (structural analogue) is outlined in the read-across report in section 13.

Reference 2

Endpoint:

partition coefficient

Type of information:

(Q)SAR

Adequacy of study:

supporting study

Study period:

2022-09-08

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 limited documentation / justification

Justification for type of information:

See attached QMRF/QPRF.

Guideline:

other: ECHA Practical guide How to use and report (Q)SARs

Version / remarks:

July 2016

Guideline:

other: ECHA Guidance on Information Requirements and Chemical Safety Assessment. Chapter R. 6: QSARs and grouping of chemicals

Version / remarks:

2018

Principles of method if other than guideline:

Five different QSAR models are used to predict the Kow for the neutral (unprotonated) DMAs. Further information can be found in the attached QMRF/QPRF.

GLP compliance:

no

Type of method:

other: Different QSAR models for the prediction of Kow from molecular structure

Partition coefficient type:

octanol-water

Analytical method:

other: Not applicable, QSAR

Type:

log Pow

Partition coefficient:

4.08

Temp.:

25 °C

pH:

> 11

Remarks on result:

other: In silico study on log Pow of the neutral DMA - based on a pKa of 9.78, a pH of ca. >11 will be required for the DMA to be in the fully neutral state

Details on results:

Consensus result (i.e., geometric mean value over single Kow results) from five applied models based on different methodologies.
Standard deviation (log values): SD = 0.48

For further details, see attached QMRF/QPRF

Conclusions:

Log Kow for the neutral C10-DMA (corresponding to pH >11): 4.08 (SD 0.48)

Executive summary:

Using US EPA CTS (Chemical Transformation Simulator) v1.2.3, the physico-chemical properties module (PCP) applied in total five different QSPR models based on different methodological approaches. For the shorter chain DMAs C10-DMA and C12-DMA, applicability domains were met for all five models. Due to the long hydrocarbon chains of C14-, C16-, and C18-DMAs, the model applicability domain was failed for the OPERA model but fulfilled for the other four models.
Overall, based on standard deviations on log-values between 0.48 and 0.67, the consensus based final values can be regarded as reliable quantitative estimates of log Kow values for the neutral (unprotonated) alkyldimethylamines (DMAs).

Reference 3

Endpoint:

partition coefficient

Type of information:

calculation (if not (Q)SAR)

Adequacy of study:

key study

Study period:

16 January 2012

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Remarks:

Acceptable, well-documented study report which meets basic scientific principles.

Principles of method if other than guideline:

Calculation of log Pow from solubility in n-octanol (see section 4.9) and water (see section 4.8). Since the test substance is miscible with n-octanol at every ratio, the maximum solubility in n-octanol corresponds to 100 % test substance and the quantitative value of the solubility is the density (see section 4.4) expressed in g/L.

Type of method:

other: Calculation

Partition coefficient type:

octanol-water

Analytical method:

other: calculated from density and water solubility

Type:

Pow

Partition coefficient:

18 983

Temp.:

20 °C

pH:

8.8

Type:

log Pow

Partition coefficient:

4.3

Temp.:

20 °C

pH:

8.8

Details on results:

The density and the water solubility were both determined at 20 °C and the same batch of the substance was used in both determinations (see sections 4.4 and 4.8).

Calculation:

log Pow = log (density/water solubility)

(see sections 4.4 and 4.8 and below).

Density [g/L]	778.3
Water solubility [g/L]	0.041

Conclusions:

The calculated log Pow of the test substance is 4.3 at 20 °C.

Executive summary:

The log Pow of the test substance was calculated from the solubility in n-octanol (a maximum solubility in n-octanol corresponding to 100 % test substance was assumed, with the density reported in section 4.4 taken as the quantitative value) and the solubility in water (section 4.8). The log Pow of the test substance is 4.3 at 20 °C.

Description of key information

Calculated theoretical partition coefficient for the neutral amine (QSPR): log Pow 4.08 (SD: 0.48)

Partition coefficient for the free amine (DMA): log Pow 4.3 (20 °C; pH 8.8);

Partition coefficient for the DMA hydrochloride (environmentally most relevant): log Pow 1.95 (20 °C).

 

Key value for chemical safety assessment

Log Kow (Log Pow):

1.95

at the temperature of:

20 °C

Additional information

Partition coefficient values (n-octanol/water) are difficult to measure for substances that exhibit surface-active properties under environmental conditions, such as the members of the DMA category (N,N-dimethyl-alkyl-1-amines, carbon chain lengths: C10 to C18). In fact, both the HPLC method and the flask method for the determination of log Pow are not applicable to these substances according to ECHA guidance document R.7a (2017) and test method A.8 of Regulation (EC) No 440/2008.
Therefore, Pow values were calculated on the basis of the measured solubility in water and the measured solubility in n-octanol as suggested according to ECHA guidance document R.7a and test method A.8 for surface-active substances.
Two approaches were followed:
1) Calculation of log Pow for the hydrochlorides of DMAs (DMA HCl), i.e. from the solubility of the free (neutral) amine in n-octanol and the solubility of the protonated hydrochloride (surface-active) in water. The hydrochloride is the environmentally more relevant form at pH values ≤ 7 (pKa 9.78, independent of the chain length).
2) Calculation of log Pow for the free amine from the solubility of the free amines (neutral amines; registered substances) in n-octanol and water. The solubility of the free amine in water depends on the prevailing pH value. Solubility in water decreases pronouncedly at pH values > 7.
The calculation approach was applied in both cases, in order to allow comparisons to be made.

For the surface-active (protonated) form of the DMA category members (hydrochlorides, DMA HCl), the critical micelle concentration (CMC) rather than the water solubility was used to avoid artificially low log Pow values. This approach is in agreement with the one proposed in ECHA guidance document R.7a (2017).

In water - for both, the DMA hydrochlorides and the free DMAs - there will be an equilibrium between the dimethyl-alkyl-ammonium cation (salt with chloride in case of DMA HCl) and the free amine plus a proton (HCl in case of the hydrochlorides). The position of the equilibrium is determined by the pKa of the base (i.e. 9.78, independent of the chain length) and the pH of the solution according to the Henderson-Hasselbach equation. Because at pH 7 and a pKa of 9.78, 99.8% are protonated, the log Kow value determined for the DMA HCl is regarded to be environmentally most relevant and given as the key value.

Further, a supporting QSAR study is available for determining the log Kow for the neutral DMA, which is (based on a pKa of 9.78) experimentally barely accessible. The log Kow for the neutral DMA is needed as an input value for the calculation of the organic carbon / water adsorption coefficient (Koc) based on the model by Franco and Trapp (2008; see IUCLIUD section 5.4.1).
Five QSAR models based on different methodologies are used to predict the Kow for the neutral (unprotonated) DMAs. The consensus result (i.e., geometric mean value over single Kow results) considering all applicable models is given together with the standard deviation (SD, log values).

 

Summary of log Kow values of DMAs and DMA hydrochlorides

Substance	log Kow_Hydrochloride	log Kow_Hydrochloride	log Kow_Amine	log Kow QSAR_neutral
C10-DMA	1.95	--	4.3	4.08
C12-DMA	2.33	--	4.3	4.92
C14-DMA	2.72	--	4.5	6.08
C16-DMA	3.11	--	4.6	6.99
C18-DMA	3.51	--	5.1	7.90
	Range (RA)	AM mean
C12-14-DMA	2.33 - 2.72	2.53	4.7	--
C12-16-DMA	2.33 - 3.11	2.72	4.9	--
C12-18-DMA	2.33 - 3.51	2.92	5.0	--
C16-18u-DMA	3.11 - 3.51	3.31	5.1	--
C16-18-DMA	3.11 - 3.51	3.31	5.3	--