Sodium N-methyl-N-(1-oxo-9-octadecenyl)aminoacetate

Endpoint summary

Additional information

Physico-chemical properties – data matrix (*)

ID No.	Substance	CAS No.	Physical state; melting point/ melting range	Boiling point at atmospheric pressure	Relative Density at 20 °C	Vapour pressure at 20 °C^(f)	Octanol-water partition coefficient, log Pow	Water solubility at 20 °C	Surface tension, c= ca. 1 g/L	Flammability
# 1	N-lauroylsarcosine	97-78-9	ER: solid; 44.8 – 52.1 °C	ER: 201.7 – 317.2 °C	ER: 0.99959 g/cm³^(a, h)	QSAR: 27.5 Pa^(b)	QSAR: 4.1	ER: 0.5 g/L^(c)	ER: 25.9 mN/m	ER: Fp = 239 °C non‑flammable
# 2	Sodium N-lauroylsarcosinate	137-16-6	ER: solid; 146 °C	ER: 350 – 410 °C	ER:1.141 g/cm³	ER: 2 Pa QSAR: 0.00104 Pa	QSAR: 0.37	ER: 400 g/L	ER: 37.9 mN/m	ER: Fp = 267 °C non‑flammable
# 3	N-(1-oxotetradecyl) sarcosine	52558-73-3	ER: solid; 54 – 58.4 °C	ER: 296.4 – 328 °C	ER: 0.9856 g/cm³^(a, d)	QSAR: 0.174 Pa^(b)	QSAR: 5.08	ER: 0.9 g/L^(c)	ER: 31 mN/m	ER: Fp = 241 °C non‑flammable
# 4	Sodium N-methyl-N-(1-oxotetradecyl) aminoacetate	30364-51-3	ER: solid; 148.3 – 152.9 °C	ER: 411 – 417.8 °C	ER: 0.603 g/cm³^(a)	QSAR: 0.0000749 Pa^(b)	QSAR: 1.35	ER: 360 g/L	ER: 25.7 mN/m	ER: Fp = 282 °C non‑flammable
# 5	(Z)-N-methyl-N-(1-oxo-9-octadecenyl) glycine	110-25-8	ER: liquid; ‑6 °C	ER: 202 °C, decomposition	ER: 0.96	QSAR: 39.9 Pa	QSAR: 6.83	ER: 0.00044 g/L	ER: 60 mN/m^(e)	ER: Fp = 225 °C non‑flammable
# 6	Reaction products of oleoyl sarcosine with sodium hydroxide	--	ER: solid; 49 – 87.4 °C	ER: 146.4 °C	ER: 1.0547	ER: 0.000000092 Pa QSAR: 150 – 355 Pa	QSAR: 2.67 ‑ 3.92^(g)	ER: 300 – 400 g/L	31.91 mN/m	ER: no ignition non‑flammable

(*) substances marked in bold are registered under REACH Regulation EC 1907/2006 in 2013, the remaining substances were registered in 2010 or will be registered later.

(a) This figure represents pour density at 25 °C.

(b) Calculated at 25 °C.

(c) Measured at 25 °C.

(d) Density values were also measured in the liquid phase: 0.9658 g/cm³ at 60 °C; 0.9506 g/cm³ at 80 °C.

(e) Measured at a concentration of 1 mg/L.

(f) All vapour pressure estimations use the experimental boiling point / boiling range and, if relevant, the melting point / melting range.

For broad melting ranges, ((T_high– T_low) / T_low) > 0.25, vapour pressure is expressed as a range between the lowest and the highest estimate possible. For narrow melting ranges, vapour pressure represents the highest estimated value.

For boiling ranges, the initial boiling point had been considered.

(g) log Pow of all identified constituents had been calculated. Result is given as a range.

(h) Density values were also measured in the liquid phase: 0.9788 g/cm³ at 60 °C; 0.9671 g/cm³ at 80 °C.

Common origin

The substances within the Sarcosine category are produced from fatty acids and the amino acid N-methylglycine. The acylation reaction is usually accomplished using the Schotten-Baumann procedure. Condensation of fatty acid chloride with sodium N-methylglycinate under alkaline conditions produces the highly soluble fatty sarcosinate sodium salt which is separated cleanly from the by-product impurities or unreacted fatty acid by a simple acid-base wash. The obtained sarcosine may be neutralized with bases such as NaOH, KOH, NH3, TEA or amino alcohols to produce the correspondent salt (Hampshire Chemical Corporation 2001; CIR 2001)

Structural similarity

The substances in the Sarcosine category share the same basic structure: All of them have a long aliphatic chain attached to a polar head. They also share the same functional group, the α-[acyl(methyl)amino]acetic acid or the correspondent sodium salt.

The long aliphatic chains are linear, range between 12 and 18 carbon atoms for the most part and differ in the saturation index.

Differences in physicochemical parameters are expected due to (i) variability of the fatty chain in terms of saturation index and length and (ii) the substance being an acid or a salt.

Similar physico-chemical properties

The physico-chemical properties of sarcosines and sarcosinates are described below. The data are presented in the table above.

Physical state and melting point

The members of this category are solids at room temperature and pressure. They show generally moderate melting points (ca. 45 °C) to slightly high (ca. 150 °C), depending on if they are acids or salts. Exceptionally, (Z)-N-methyl-N-(1-oxo-9-octadecenyl) glycine (CAS 110-25-8) is a liquid (mp = -6 °C). These differences can be explained on the basis of their slight structural variability.

Variations in the aliphatic chain partially account for the differences of the melting points which follow the expected trend within the category, i.e. the melting point increases proportionally to the fatty acid chain length.

However, variations in length do not account for all differences of the melting points exclusively; the different grades of unsaturation of the acyl chain (i.e. some constituents of (Z)-N-methyl-N-(1-oxo-9-octadecenyl) glycine (CAS 110-25-8) and its corresponding salt, Reaction products of oleoyl sarcosine with sodium hydroxide) also play a role and reduce the melting point compared to their saturated counterparts. The molecular geometry of a saturated fatty acid chain is relatively linear and molecules can develop stronger interactions with each other while introduction of an unsaturation bends the molecule, breaking the linearity. Bent molecules are not able to exert intermolecular forces (Van der Waals force) to the same extent as their linear counterparts, leading to a reduction of the melting points.

Boiling point

A similar trend to that of the melting points can be seen for the boiling points within the category. The substances display moderate (ca. 150 °C) to high boiling points (ca. 417 °C), depending on being a carboxylic acid or the corresponding salt.

Density

The densities of the category members were measured to be in the range of 0.6 to 1.1 g/cm³. These values are normal for organic compounds.

Vapour pressure

Vapour pressure of all members of this category were calculated using the same software (MPBPWIN v1.43 of the EPI Suite programme, Grain-Watson method). For solid substances this approach is based on the lowest possible melting and boiling temperatures, and the calculated vapour pressures should be interpreted as the highest possible ones (worst case).

Calculated vapour pressure values range from non-volatile (ca. 7E-5 Pa) to volatile (ca. 300 Pa). They are very much dependent on the experimental boiling point and melting point of the respective substance (boiling point only in case of liquids) and, therefore, follow a similar trend within the category.

Generally, the vapour pressure decreases with increasing fatty acid chain length. The C18-acid member has an exceptionally high vapour pressure. This is due to the substance being a liquid. The algorithm for calculation of vapour pressure does not take into account the melting point of liquids.

In all cases vapour pressure values of sarcosines are higher than those of their corresponding salts.

Octanol-water partition coefficient (log Pow)

The accurate determination of log Pow is very difficult for surface-active substances. Surfactants tend to concentrate at hydrophilic/hydrophobic boundaries rather than to equilibrate between phases. Therefore, Pow is not a good descriptor of surfactant hydrophobicity and only of limited predictive value for the partitioning of these compounds in the environment (Könnecker et al, 2011).

A calculated value had been obtained following the advice in EU 440/2008, Annex, method A.8. For comparison purposes, the estimation was done in all cases using the same algorithm, KOWWIN v1.68 model of the EPI Suite software.

The values obtained show a clear trend, as expected, of salts displaying values of 3 to 4 units lower than their corresponding acid partners.

In addition, an increase of log Pow with increasing fatty acid chain length can be seen.

Acid members of the category show high log Pow values (> 4) while the salt member values range between low and moderate (all < 4).

Water solubility

Water solubility, like other physico-chemical properties, is difficult to measure for surface active substances. Micelle formation may pose difficulties to determine the saturation point and, in many cases, it is only possible to determine a threshold value.

Indeed, gel formation was observed when conducting the water solubility studies on all the ionic members of the sarcosine category (C12-salt, C14-salt and C18-salt).

Water solubility is typically high throughout the whole category. Salt members display values in the hundreds of g/L range and are typically 3 orders of magnitude more soluble compared to their protonated partners.

(Z)-N-methyl-N-(1-oxo-9-octadecenyl) glycine (CAS 110-25-8), though, displays an exceptionally low value (ca. 0.4 mg/L). Usually in chain-length based chemical categories, water solubility decreases with increasing chain-length and as expected, (Z)-N-methyl-N-(1-oxo-9-octadecenyl) glycine follows this trend. The exceptional features of this substance (high log Pow, low water solubility) can be thus predicted on the basis of the molecular structure. The substance may be regarded as category member but its different properties must be treated with special care.

Surface tension

Sarcosines are surface active substances and they lower considerably the surface tension of water (i.e. 72 mN/m at room temperature).

The measured values for the category members range between ca. 26 and 38 mN/m at a concentration of 1 g/L. (Z)-N-methyl-N-(1-oxo-9-octadecenyl) glycine (CAS 110-25-8) surface tension had to be tested at a different concentration (1 mg/L), and even under this condition the substance displayed surface tension activity (60 mN/m).

Flammability

Five out of six flash points were determined and range between 225 °C and 282 °C. The flammability of the reaction products of oleoyl sarcosine with sodium hydroxide was determined based on the EU test A.10 and UN test N.1

All substances are considered non-flammable. Flammability on contact with water and pyrophoric properties are excluded based on the molecular structure of all homologues involved.

Summary

Physico-chemical properties of the category members are provided in the table above. These were determined to be similar over the category or to follow the expected trends based on the structural similarities and dissimilarities.