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

Biodegradation in water: screening tests

Description of key information

Dimyrcetol is ready biodegradable using read-across with Dihydromyrcenol and the structural analogue of Dihydromyrcenyl formate: Dihydromyrcenyl acetate, which showed 72% and 87.7% biodegradation within 28 days, respectively.

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Type of water:

freshwater

Additional information

No data on biodegradation is available for Dimyrcetol, however a biodegradation study with Dihydromyrcenol and with the structural analogue of Dihydromyrcenyl formate: Dihydromyrcenyl acetate, is available. The summaries of the experimental information is presented first and thereafter the read across rationale.

Dihydromyrcenol

The ready biodegradability of Dihydromyrcenol was determined in an OECD 301B guideline test following GLP. The concentration tested was 10 mg carbon/l with a non-adapted activated sludge concentration of 30 mg/l. Degradation was followed over a period of 28 days. Sodium benzoate was used as positive control and a toxicity control was included. 72% biodegradation was achieved after 28 days based on carbon dioxide production (60% being surpassed within 10 days after reaching 10%). Sodium benzoate achieved 78% and 79% degradation after 14 and 28 days, respectively, confirming that the inoculum and test conditions used were suitable for this test. The toxicity control achieved 80% degradation after 14 days, which confirmed that the test material was not toxic to sewage treatment micro-organisms used in the test. In conclusion, Dihydromyrcenol can be considered readily biodegradable under the conditions in this test.

Dihydromyrcenyl acetate

The ready biodegradability of Dihydromyrcenyl Acetate was examined in a study according to OECD TG 301B and in compliance with GLP criteria. The concentration tested was 10 mg carbon/l with Secondary effluent from an unacclimatised activated sludge plant. Degradation was followed over a period of 28 days. The test substance achieved 87.7% biodegradation in 28 days and passed the 10-d window criterion (11.9% day 4, 67.2% day 14). Thus, it can be concluded that Dihydromyrcenyl Acetate is readily biodegradable according to this test.

Dimyrcetol (EC no.: 915-335-6) and its ready biodegradability using read across information from Dihydromyrcenol (CAS no.: 18479-58-8) and Dihydromyrcenyl acetate (Cas no.: 53767-93-4)

Introduction

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 data on biodegradation are not available. In accordance with Article 13 of REACH, lacking information can be generated by means of applying alternative methods such as QSARs, grouping and read-across. For assessing the ready biodegradation of Dimyrcetol, the constituent and analogue approach is selected because for one constituent, Dihydromyrcenol and for a related analogue of the other constituent, Dihydromyrcenyl formate, reliable ready biodegradation data are present, which can be used for read-across.

Hypothesis: Dimyrcetol is readily biodegradable based on the ready biodegradability of its constituents.

Available information: Dihydromyrcenol and Dihydromyrcenyl acetate biodegraded after 28 days 72 and 87.7%, respectively, in CO2 Evolution tests performed according to OECD TG 301B (Rel. 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 justification: For Dimyrcetol, the constituent Dihydromyrcenol is selected for read across because for this constituent experimental ready biodegradability data was available. To cover the ready biodegradation of the other constituent, Dihydromyrcenyl formate, the readily biodegradation data of the structural analogue Dihydromyrcenyl acetate was used.

Structural similarities and differences: The Dimyrcetol constituents, Dihydromyrcenol and Dihydromyrcenyl formate have the same hydrocarbon backbone to which a tertiary alcohol or tertiary formate is attached, respectively. Dihydromyrcenyl acetate has the same backbone and has a tertiary acetic ester attached to this backbone. The formate ester has one CH2-group less compared to the acetic ester.

Bioavailability: Dimyrcetol has the same bioavailability towards micro-organisms as its two constituents and as Dihydromyrcenyl acetate, based on sufficient similar physico-chemical properties. The one additional CH2-group in the acetic ester is not expected to have a significant impact on bioavailability despite a slightly higher log Kow (3.95, and 4.9, for the formate and acetate, respectively).

Biodegradable fragments: Biowin predictions show that formate and acetic esters are easily biodegraded by bacteria. The esters show somewhat higher probabilities compared to the alcohol because the small alkyl acids are easily consumed (as presented in the Data matrix).

Uncertainty of the prediction: There or no remaining uncertainties other than those already addressed above.

Data matrix

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

Conclusions on the ready biodegradability of Dimyrcetol

For Dimyrcetol no ready biodegradation information is available. For one of the constituents, Dihydromyrcenol, such information is present, which can be used for read-across. For the other key constituent, Dihydromyrcenyl formate no biodegradation information is available but for its analogue containing an acetic ester instead of a formate ester biodegradation information is available. Dihydromyrcenol and Dihydromyrcenyl acetate are readily biodegradable (72 and 87.7%, respectively, in an OECD TG 301B test, Kl. 1) and therefore, Dimyrcetol is also readily biodegradable based on similarities in structure, physic-chemical properties and breakdown pathways.

Final conclusion: Dimyrcetol is readily biodegradable.

Data matrix: Information on Dimyrcetol to assess its biodegradability based on ready biodegradability of Dihydromyrcenol, and Dihydromyrcenyl acetate

Common names	Dimyrcetol   Target	Dihydromyrcenol   Source	Dihydromyrcenyl formate Source	Dihydromyrcenyl acetate Source
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.	915-335-6	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)
Log Kow (estimated)	-	3.47 (KOWWIN)	3.92 (KOWWIN)	4.47 (KOWWIN)
Fate
Ready biodegradation (%)	Read across	72		87.7
BIOWIN 5		0.4322	0.6926	0.6513*
BIOWIN 6		0.4368	0.7995	0.7306*

*The slightly lower probability of the acetate is due to the higher molecular weight