Amines, C12-18-alkyldimethyl

Water solubility

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

water solubility

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:

read-across source

Reason / purpose for cross-reference:

assessment report

Type of method:

other: Determination of the critical micellization concentration -- Method by measuring surface tension with a plate

Key result

Water solubility:

0.25 g/L

Temp.:

21 °C

Remarks on result:

other: RA from C18-DMA HCl; Critical micelle conncentration

Executive summary:

The study used as source investigated the critical micelle concentration of the test substance C18-DMA HCl (hydrochloride) according to ISO 4311. 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:

water solubility

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2011-2012

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: According to OECD Guideline 105

Qualifier:

according to guideline

Guideline:

OECD Guideline 105 (Water Solubility)

Type of method:

flask method

Key result

Water solubility:

8 mg/L

Temp.:

20 °C

pH:

7.8

Details on results:

The water solubility of 8 mg/L and the pH of 7.8 represent the means from two determinations with different equilibration times (see below).

Preliminary test:

mL of water for 0.1 g soluble	0.1	0.5	1	2	10	100	150
Approx. solubility in g/L	>1000	1000 to 200	200 to 100	100 to 50	50 to 10	10 to 1	<1
Visual evaluation	not soluble	not soluble	not soluble	not soluble	not soluble	not soluble	not soluble

Solubility test:

Flask No.	Equilibration time at 20 °C [h]	pH of aqueous solution	Test substance content [mg/kg]
1 2 3	24 48 72	7.8 7.6 7.9	10 (29)* 6
mean	---	---	8

*: outlier, not evaluated

Individual titration results:

Day	Weight of aqueous phase [g]	Volume of volumetric solution [mL]	Test substance content [mg/kg]
1	9.4277	0.074	10
	9.7712	0.070	9
2	8.9742	0.212	(30)*
	8.5585	0.194	(28)*
3	10.0976	0.052	6
	9.5531	0.044	6
mean	---	---	11

*: outlier, not evaluated

Conclusions:

Interpretation of results (migrated information): slightly soluble (0.1-100 mg/L)
The water solubility of the test substance at 20 °C is 8 mg/L.

Executive summary:

The water solubility of the test substance was determined according to the OECD Guideline for the Testing of Chemicals 105. The water solubility at 20 °C is 8 mg/L.

Reference 3

Endpoint:

water solubility

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:

read-across source

Reason / purpose for cross-reference:

assessment report

Key result

Water solubility:

3.64 g/L

Temp.:

21 °C

Remarks on result:

other: Critical micelle conncentration

Details on results:

The temperature given is the one observed in the experimental studies upon which the interpolated value is based.

When the resulting CMCs (in g/L) are plotted against the number of carbon atoms in the alkyl chain (C10, C12, C14, C16 and C18), the resulting linear regression shows an acceptable fit (R²= 0.82).

Executive summary:

The study used as source investigated the critical micelle concentration of C12-DMA HCl (hydrochloride) by interpolation from experimental values determined according to ISO 4311. 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.

Description of key information

Water solubility C12-18-DMA (20 °C; pH 7.8; OECD 105): 8 mg/L
Water solubility C12-DMA hydrochloride (21 °C; CMC acc. to ISO 4311): 3.64 g/L
Water solubility C18-DMA hydrochloride (21 °C; CMC acc. to ISO 4311): 0.25 g/L
Water solubility C12-18-DMA hydrochloride (RA; 21 °C; CMC acc. to ISO 4311): 0.25 g/L - 3.64 g/L; geometric mean: 0.95 g/L

Key value for chemical safety assessment

Water solubility:

481 mg/L

at the temperature of:

20 °C

Additional information

Members of the category of dimethylalkylamines (DMAs) are medium strong bases with a pKa of 9.78 (25 °C), independent of the chain length.
In an aqueous system as well as in a physiological medium, a chemical equilibrium between the dimethylalkylamine and the dimethylalkylammonium ion is formed, depending on the prevailing pH. Due to the ionic character, the dimethylalkylammonium ion is of a pronouncedly higher solubility in water compared to the neutral amine. Accordingly, the water solubility of DMAs is strongly dependent on pH, with higher solubility in the neutral and acidic range compared to alkaline pH close or above the pKa. Consequently, the water solubility of the DMA amine is lower than the solubility of the corresponding DMA hydrochloride (DMA HCl). In water, the DMA HCl salt dissolves under slightly acidic reaction, such that the equilibrium is to nearly 100% at the side of the alkylammonium ion. Because of the pKa of 9.78 characteristic for the DMA category, already at neutral pH the equilibrium is at the side of the alkylammonium ion. To take this into account, the key value is given as the arithmetic mean of the water solubility determined with the DMA and the water solubility of the DMA HCl. Because the DMA HCl is surface-active, in lieu of the water solubility the critical micelle concentration (CMC) is given to avoid an overestimation of the water solubility due to the formation of micelles.