Reaction Mass of 2,6-dimethyloct-7-en-2-ol and 2,6-dimethyloct-7-en-2-yl formate

Endpoint summary

Description of key information

No data on aquatic toxicity is available for Dimyrcetol, however an acute algae and acute daphnia study with Dihydromyrcenol and with the structural analogue of Dihydromyrcenyl formate: Dihydromyrcenyl acetate are available. The data derived for Dimyrcetol is described below.

	Dimyrcetol (mg/L)	Dihydromyrcenol (mg/L)	Dihydromyrcenyl formate (mg/L)	Dihydromyrcenyl acetate (mg/L)
Algae (ErC50) (mg/l)	39.5 (0.426*80 + 0.528*10.2)	80 (OECD 201)	10.2 (RA corrected value)	5.4 (OECD 201)
Algae (ErC10/NOEC) (mg/l)	13.9 (0.426*25 + 0.528*6.2)	25 (OECD 201)	6.2 (RA corrected value)	2.9 (OECD 201)
Daphnia (EC50) (mg/l)	17.9 (0.426*38 + 0.528*3.2)	38 (OECD 202)	3.2 (RA corrected value)	1.3 (OECD 202)

Additional information

Dimyrcetol (EC no.: 915-335-6) and its aquatic toxicity using read acrossfrom Dihydromyrcenol (CAS no.: 18479-58-8) and Dihydromyrcenyl acetate (Cas no.: 53767-93-4)

Introduction and hypothesis for the analogue approach

Dimyrcetol is a reaction mass containing 42.6% Dihydromyrcenol (CAS no.: 18479-58-8) and 52.8% Dihydromyrcenyl formate (CAS no.: 25279-09-8). For this substance, no aquatic toxicity data are available. In accordance with Article 13 of REACH,lacking information can be generated by means of applying alternative methods such asin vitrotests, QSARs, grouping and read-across.For assessing the aquatic toxicity of Dimyrcetol, the constituent and analogue approach is selected because for one constituent, and for a related analogue of the other constituent, reliable aquatic toxicity data are present, which can be used for read-across.

Hypothesis: The aquatic toxicity of Dimyrcetol can be determined using the weighted average between the aquatic toxicity data of Dihydromyrcenol and Dihydromyrcenyl formate.

Available experimental information: For Dihydromyrcenol, the algae Er50, algae NOErC, and Daphnia EC50 values are 80, 25, and 38 mg/L, respectively. For Dihydromyrcenyl acetate, the algae Er50, algae ErC10, and Daphnia EC50 values are 5.4, 2.9, and 1.3 mg/L, respectively. The values are all derived from OECD TG 201 and 202 studies, following GLP, with Klimisch scores of 1.

Target chemical and source chemical(s)

Chemical structures of the target chemical and the source chemicals and relevant information on these substances are shown in the data matrix.

Purity / Impurities

Dimyrcetol is a reaction mass containing 42.6% Dihydromyrcenol and 52.8% Dihydromyrcenyl formate covering 95.4% of the substance.

Analogue approach justification

According to Annex XI 1.5 read across can be used to replace testing when the similarity can be based on a common backbone and a common functional group. When using read across the result derived should be applicable for C&L and/or risk assessment and it should be presented with adequate and reliable documentation, which is presented below.

Analogue selection: For Dimyrcetol the constituent Dihydromyrcenol is selected for read across because it is one of the two key constituents. For the other constituent, Dihydromyrcenyl formate, information from Dihydromyrcenyl acetate was used and converted to Dihydromyrcenyl formate.

Structural similarities and differences: Dihydromyrcenol, Dihydromyrcenyl formate and Dihydromyrcenyl acetate all have the same hydrocarbon backbone. Dihydromyrcenol is the alcohol derivative of these esters, while the other constituent and its analogue are both esters: the key constituent Dihydromyrcenyl formate has a formic ester as functional group, while the Dihydromyrcenyl acetate has an acetic ester as functional group, which is one additional -CH2- fragment which will increase the log Kow.

Bioavailability: Dihydromyrcenyl formate and Dihydromyrcenyl acetate have similar bioavailability based on the similarity in chemical structure and physico-chemical properties as presented in the data matrix.In view of the lower log Kow, the aquatic toxicity values for Dihydromyrcenyl acetate are converted using molecular weight and log Kow.

Mode of Action (MoA): Dihydromyrcenol has a neutral MoA. Both Dihydromyrcenyl formate and Dihydromyrcenyl acetate have the same ester MoA.

Acute aquatic toxicity: For Dihydromyrcenol, the algae Er50, algae NOErC, and Daphnia EC50 values are 80, 25, and 38 mg/L, respectively. For Dihydromyrcenyl formate the aquatic toxicity is derived from Dihydromyrcenyl acetate. Its algae Er50 and ErC10, and Daphnia EC50 values are 5.4, 2.9, and 1.3 mg/L, respectively. The conversion based on MW and Log Kow is presented in Table 1 below.

Table 1: Aquatic effect values for Dihydromyrcenyl formate (Target) based on read across from Dihydromyrcenyl acetate (Source)

	Source					Target
Species	Effect (mg/l)	MW	mmol/L	Log mmol/l	Log Kow	Log Kow	Log mmol/l	Convert to 10^	MW	Effect (mg/l)
Algae EC50	5.4	196	0.028	-1.56	4.9	3.95	-1.26	0.055	184	10.2
Algae EC10	2.9	196	0.015	-1.83	4.9	3.95	-1.48	0.033	184	6.2
Daphnia	1.3	196	0.007	-2.18	4.9	3.95	-1.76	0.018	184	3.2

For Dimyrcetol the aquatic toxicity is based on its constituents using a weighted average of the toxicity values and the concentration of the constituents in Dimyrcetol, which are presented in the data matrix. This results inalgae Er50, ErC10/NOEC, and Daphnia EC50 values of 39.5, 13.9, and 17.9 mg/L, respectively.

Uncertainty of the prediction: There are no other uncertainties than those which have been addressed above.

Data matrix

The relevant information on physico-chemical properties and toxicological characteristics are presented in the data matrix below.

Conclusions for aquatic toxicity

For Dimyrcetol no aquatic toxicity information is available, but for one of the constituents, Dihydromyrcenol, such information is present, which can be used for read-across. In addition, data on aquatic toxicity is available for Dihydromyrcenyl acetate; a structural analogue of Dihydromyrcenyl formate. For Dihydromyrcenol the algae EC50 and EC10 values are 80 and 25 mg/l, for Dihydromyrcenyl formate these values are 10.2 and 6.2 mg/l. The latter values are derived from Dihydromyrcenyl acetate which have values of 5.4 and 2.9 mg/l. For Dihydromyrcenol the Daphna EC50 is 38 mg/l and for Dihydromyrcenyl formate it is 3.2 mg/l. The latter values are derived from Dihydromyrcenyl acetate and converted using difference in molecular weight and log Kow.

Final conclusion on hazard: For Dimyrcetol the aquatic toxicity is based on its constituents using a weighted average of the toxicity values and the concentration of the constituents in Dimyrcetol, using the values of Dihydromyrcenol present at 42.6%and Dihydromyrcenyl formate present at 52.8%. This results inalgae Er50, ErC10/NOEC, and Daphnia EC50 values of 39.5, 13.9, and 17.9 mg/L, respectively.

 

Data matrix: Information on Dimyrcetol, Dihydromyrcenol, Dihydromyrcenyl formate and Dihydromyrcenyl acetate.

Common names	Dimyrcetol   Target	Dihydromyrcenol Source	Dihydromyrcenyl formate Source	Dihydromyrcenyl acetate Source
Chemical structures
Chemical name	2,6-dimethyloct-7-en-2-ol, and 2,6-dimethyloct-7-en-2-yl formate	2,6-dimethyloct-7-en-2-ol	2,6-dimethyloct-7-en-2-yl formate	2,6-Dimethyloct-7-en-2-yl acetate
CAS no.	NA	18479-58-8	25279-09-8	53767-93-4
EC no.	915-335-	242-362-4	246-788-1	258-751-7
Empirical formula	C10H20O and C11H20O2	C10H20O	C11H20O2	C12H20O2
Molecular weight	156 and 184	156	184	196
Phys-Chem
Physical state	Liquid	Liquid	Liquid	Liquid
Water solubility (mg/L) (OECD 105)	21.5 (formate) 491 (alcohol) 221 (weighted average) at 20°C	939 at 20°C (ECHA dossier Dihydromyrcenol)	21.5 (Value from study Dimyrcetol)	6.1 at 24°C (ECHA dossier Dihydromyrcenyl acetate)
Log Kow (OECD 117)	3.95 (formate) 3.15 (alcohol) 3.43 (weighted average)	3.25 (ECHA dossier Dihydromyrcenol)	3.95 (Value from study Dimyrcetol)	4.9 (ECHA dossier Dihydromyrcenyl acetate)
Aquatic toxicity
Algae (ErC50) (mg/l)	39.5 (weighted average)	80	10.2 RA from Dihydromyrcenyl acetate including conversion	5.4
Algae (ErC10/NOEC) (mg/l)	13.9 (weighted average)	25	6.2 RA from Dihydromyrcenyl acetate including conversion	2.9
Daphnia (EC50) (mg/l)	17.9 (weighted average)	38	3.2 RA from Dihydromyrcenyl acetate including conversion	1.3