Alcohols, C16-18, reaction products with D-glucose

Endpoint summary

Additional information

 Physico-chemical properties – data matrix (*)

ID No.	Substance	CAS No.	Appearance; melting point/ melting range	Boiling point	Relative Density at 20 °C	Vapour pressure at 20 °C	Octanol-water partition coefficient, log Pow (**)	Water solubility at 20 °C	Surface tension, c= ca. 1 g/L	Flammability
# 1	D-Glucopyranose, oligomeric, butyl glycoside	-	ER: solid; 225 °C (decomp.)	ER: ca. 225 °C (decomp.) at ca. 1013 hPa	ER: 1.34	ER: 1.4E-5 Pa	Calc: -0.91 QSAR: -1.03 (C4)	ER: > 1000 g/L	ER: 64.1 mN/m at 20 °C	ER: non flammable
# 2	D-Glucopyranose, oligomers, hexyl glycosides	-	ER: solid; > 300 °C (decomp. possible)	ER: > 300 °C (decomp. possible) at ca. 1013 hPa	ER: 1.18	ER: 1.5E-3 Pa	ER: 1.72-1.77 QSAR: -0.05 (C6)	ER: 750 g/L	ER: 33.9-35.5 mN/m at 24 °C	ER: non flammable
# 3	D-Glucopyranose, oligomers, decyl octyl glycosides	68515-73-1	ER: solid; RA from D-Glucopyranose, oligomers, hexyl glycosides and D-Glucopyranose, oligomeric, C10-16-alkyl glycosides : > 150 °C	RA from D-Glucopyranose, oligomers, hexyl glycosides and D-Glucopyranose, oligomeric, C10-16-alkyl glycosides : > 300 °C at ca. 1013 hPa	RA from D-Glucopyranose, oligomers, hexyl glycosides and D-Glucopyranose, oligomeric, C10-16-alkyl glycosides : 1.16-1.18	RA from D-Glucopyranose, oligomers, hexyl glycosides and D-Glucopyranose, oligomeric, C10-16-alkyl glycosides : < 1.0E-2 Pa	RA from D-Glucopyranose, oligomers, hexyl glycosides and D-Glucopyranose, oligomeric, C10-16-alkyl glycosides : < 1.77 QSAR: 1.92 (C10)	RA from D-Glucopyranose, oligomers, hexyl glycosides and D-Glucopyranose, oligomeric, C10-16-alkyl glycosides : > 200 g/L	RA from D-Glucopyranose, oligomers, hexyl glycosides and D-Glucopyranose, oligomeric, C10-16-alkyl glycosides : 29-36 mN/m	RA from D-Glucopyranose, oligomers, hexyl glycosides and D-Glucopyranose, oligomeric, C10-16-alkyl glycosides : non flammable
# 4	D-Glucopyranose, oligomers, branched and linear C9-11-alkyl glycosides	157707-87-4	ER: solid; 115 °C	ER: ca. 335 °C (boiling and/or decomp.) at 989 hPa	ER: 1.19	ER: 4E-3 Pa	Calc: -1.53 QSAR: 2.33 (C11)	ER: > 500 g/L	ER: 27.6 mN/m at 20 °C	ER: non flammable
# 5	Reaction products of D-Glucose, n-Butanol and alcohols C10-12 (even numbered)	-	ER: solid; > 200 °C (decomp. at 250 °C)	ER: 250 °C (decomp.) at ca. 1013 hPa	ER: 1.29	ER: 1E-4 Pa	RA from D-Glucopyranose, oligomeric, butyl glycosides and D-Glucopyranose, oligomeric, C10-16-alkyl glycosides : ≤ -0.07 QSAR: 2.90 (C12)	ER: > 900 g/L at 23 °C	ER: 27 mN/m at 20 °C	ER: non flammable
# 6	D-Glucopyranose, oligomeric, C10-16-alkyl glycosides	D-Glucopyranose, oligomeric, C10-16-alkyl glycosides	ER: solid; > 150 °C (decomp. possible)	ER: > 301 °C (boiling and/or decomp.) at ca. 1013 hPa	ER: 1.16	Calc: ≤ 7.7E-3 Pa	Calc: < -0.07 QSAR: 3.88 (C14)	ER: > 200 g/L	ER: 29.5 mN/m at 23 °C	ER: non flammable
# 7	D-Glucose, reaction products with alcohols C16-18 (even numbered) (excess)	-	ER: solid; 65 °C	ER: ca. 314 °C (boiling and/or decomp.) at 1004 hPa	ER: 1.03	Calc.: ≤ 4.2E-2 Pa	Calc.: > 6.03 QSAR: 7.72 (C18 alc.)	ER: < 0.05 mg/L	Too low water solubility	ER: non flammable
#8	Hexadecan-1-ol (a)	36653-82-4	ER: solid; 51 °C (pour point)	ER: 319 °C at 1013 hPa	ER: 0.89 at 16 °C	ER: 0.3 Pa at 38 °C	ER: 6.7	ER: < 1 mg/L at 23 °C	Too low water solubility	-
#9	Octadecan-1-ol (a)	112-92-5	ER: solid; 57 °C (pour point)	ER: 335 °C at ca. 1013 hPa	ER: 0.91	ER: 0.1 Pa at 38 °C	ER: 7.4	ER: < 1 mg/L at 23 °C	Too low water solubility	-

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

(**) QSAR calculations: EPISUITE KOWWIN v1.68, the highest obtained value – for monomer (C16-18: alcohol) and the longest chain represented.

(a) Surrogate substances: fatty alcohols. Available data on these substances are used for assessment of eco- and toxicological properties by read-across on the basis of structural similarity and/or mechanistic reasoning.

Abbreviations:

ER - experimental result

RA – read across

WoE – weight of evidence

QSAR - Quantitative Structure–Activity Relationships

ES – expert statement (based on category data)

Common origin

The synthesis of alkyl polyglycosides was discovered by the reaction of glucose and fatty alcohol in the presence of an acid catalyst. Two methods can be applied: direct synthesis and alternative transacetalization process (Geetha and Tyagi, 2012).

Direct synthesis: it is a synthesis of fatty alcohols of varying alkyl chain length and purities of either technical or natural origin with D-Glucose; the end product is obtained using the alcohol in excess with respect to the stoichiometric value (ibid).

Alternative synthesis: a transacetalization process is applied when oligo- and polyglycoses (starch or syrups) are used. Polysaccharide is depolymerised with lower alcohols (butanol or propylene glycol) in the presence of an acid catalyst. APGs are formed when oligoglucoside intermediate is treated with long chain alcohol in the presence of an acid catalyst (ibid).

Structural similarity

Alkyl polyglycosides are monomers or oligomers containing D-Glucopyranose rings (up to m = 2) and fatty alcohol chains, in the C_n range from n = 4 to 18. The structural similarity is straightforward and the properties depend on the number of rings m and the alcohol chain length n. The alcohol chains are linear; up to 10% mono-methyl branched (predominantly linear) species contribute to D-Glucopyranose, oligomers, branched and linear C9-11-alkyl glycosides. Another feature of this particular substance is that it contains odd chain lengths, while the other chains represented in the category are even-numbered. These features are not expected to cause exceptions from the overall assumption that the differences in properties of category members are related to the number of glucopyranose rings m and the alcohol chain length n.

The substance D-Glucose, reaction products with alcohols C16-18 (even numbered) (excess) is characterised with the longest alcohol chains over the category. The exceptional character of this category member is additionally revealed in the fact that this UVCB substance contains C16 and C18 alcohol homologues. They can be described as 0-mers (m = 0). Their presence is not related to any additional chemical functionality: the influence is manifested in variability in physico-chemical parameters. In particular, the octanol-water partition coefficient is considerably higher than those observed for the rest of category members, and correspondingly, the water solubility is lower.

Similar physico-chemical properties

Physical state and melting point

Substances in the Alkyl Polyglycosides Category are marketed predominantly as aqueous solutions, with an exception of the in water non-soluble D-Glucose, reaction products with alcohols C16-18 (even numbered) (excess). The tests examining their physico-chemical properties were conducted on pure dried substances after eliminating the aqueous phase. In all cases alkyl polyglycosides were determined solids under ambient conditions. Due to the nature of these substances, it is difficult to describe their melting behaviour. Experiments performed using DSC (digital scanning calorimetry) resulted mostly in estimations revealing decomposition of the substances at relatively high temperatures (> 150 °C; cf. data matrix). For two substances, D-Glucopyranose, oligomers, branched and linear C9-11-alkyl glycosides, and D-Glucose, reaction products with alcohols C16-18 (even numbered) (excess), the melting point is determined precisely (115 °C vs. 65 °C, respectively), however the methods applied are different (capillary method vs. DSC, respectively). With respect to the differences of the methods applied, any clear trends cannot be observed. The common property over the category is the solidity of all members in ambient conditions.

Boiling point

DSC diagrams of alkyl polyglycosides show that category members boil and/or decompose at high temperatures reaching ca. 300 °C (cf. data matrix). The decomposition often occurs already during melting. The data reveal that alkyl polyglycosides are non-volatile (cf. Vapour pressure).

Density

Relative densities of alkyl polyglycosides were measured in the range 1.0-1.34. This is typical for solid organic substances.

Vapour pressure

Alkyl polyglycosides are non-volatile and they do not partition into the air. The vapour pressures were determined experimentally in the range ca. 1E-5 – 1E-3 Pa. For two substances, D-Glucopyranose, oligomeric, C10-16-alkyl glycosides, and D-Glucose, reaction products with alcohols C16-18 (even numbered) (excess), it was difficult to determine the vapour pressures experimentally and the calculation approach (Grain-Watson method) was applied. For solid substances this approach is based on the lowest possible melting and boiling temperatures. The calculated values up to ca. 1E-2 Pa (cf. data matrix) should be interpreted as the highest possible ones.

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).

The determinations of partition coefficients for the category substances were performed using different methods resulting in low values < 3 (exception: D-Glucose, reaction products with alcohols C16-18 (even numbered) (excess)), but hardly showing a trend. While the HPLC method with D-Glucopyranose, oligomers, hexyl glycosides results in log Pow > 1.7, the calculations employing solubilities in n-octanol and water lead to negative values of -1.53 (D-Glucopyranose, oligomers, branched and linear C9-11-alkyl glycosides) and -0.07 (D-Glucopyranose, oligomeric, C10-16-alkyl glycosides). In addition to these determinations, calculations were performed with KOWWIN v1.68. The calculated partition coefficient of homologues depends on the number of rings m and the alcohol chain length n. While each CH₂-group added to the chain increases log Pow of ca. 1 logarithmic unit, each glucopyranose ring decreases the coefficient of ca. 2.5 logarithmic units. In data matrix the highest calculated values are given (m = 1 or 0 for C16-18; n = maximal length present in the substance). The calculated values appear to describe the partition coefficient in a more satisfactory way with respect to the ones reported from different experiments. In particular, the high value obtained for D-Glucose, reaction products with alcohols C16-18 (even numbered) (excess) is in agreement with the measured low water solubility of this substance. Each of the experimental methods used has its limitations and the results should be viewed and interpreted with caution, also because the proportions of homologues with different ring numbers and chain lengths (m and n values, respectively) may vary, what influences the overall result.

Water solubility

As in the case of other physico-chemical properties, also water solubility is difficult for experimental determination in the case of surface active substances. In particular, such phenomenon as micelle formation is observed (Könnecker et al, 2011). Experimental determinations employing flask method lead in most cases to the observation that the substance is miscible in any proportions with water and only the estimated value (“not less than…”) can be given as a quantitative measure of water solubility. Typical orders of magnitude are hundreds of g/L. The exceptional case is again D-Glucose, reaction products with alcohols C16-18 (even numbered) (excess), exhibiting water solubility lower than 0.05 mg/L. This is related to the fact that the alcohol chains in this case are the longest (n = 16, 18; usually in chain-length based chemical categories water solubility decreases with the chain length), but even to more extent that alcohols C16 and C18, non-soluble in water (m = 0) contribute significantly to the composition. The exceptional features of this substance (high log Pow, low water solubility) can be thus predicted on the basis of the molecular structure and trends observed in the category: the substance can be viewed as category member, but its different properties must be treated with special care. All category substances do not dissociate in water, because of a lack of dissociable groups.

Surface tension

Alkyl polyglycosides are surfactants and their surface tension is considerably lower than the one of water at room temperature – 72 mN/m. The measured values for the category members are between 27 and 64 mN/m – cf. data matrix. Since 6 of 7 substances are well soluble in water, in all cases the concentration of 1 g/L was submitted to experiment. Only compound D-Glucopyranose, oligomers, butyl glycosides fails to fulfil the criterion: surface tension < 60 mN/m, for a substance to be characterized as surface active. The substance D-glucose, reaction products with alcohols C16-18 (even numbered) (excess), as the one insoluble in water, is exempted from the surface tension testing.

Flammability

6 of 7 substances are experimentally determined non-flammable (EU test A.10 – flammability solids). Data for D-glucopyranose, oligomers, decyl octyl glycosides is not available, so the category read-across is applied in this case. Flammability on contact with water and pyrophoric properties are excluded based on the molecular structure of all homologues involved.

Summary

A summary of physico-chemical properties is provided in Table 3, data matrix 1, Sec.3. As UVCB substances derived from natural sources with highly variable compositions, some measures of physico-chemical properties are inapplicable or not accurate enough for a trend analysis.

The physico-chemical properties of the category members were determined similar over the category at least for shorter chain (n < 16) and not alcohol-containing (m > 0) members. Properties of D-Glucose, reaction products with alcohols C16-18 (even numbered) (excess) are different especially in regard to partition coefficient and water solubility, what is in line with the trend observed with respectto the alkyl chain lengthnand the number of glucopyranose rings m (m = 0-3). For a number of endpoints the experimental values for surface active substances could be only estimated and wherever possible were supported by valid QSAR calculations.