2-tert-pentylcyclohexyl acetate

Adsorption / desorption

Description of key information

The potential for adsorption/desorption is assessed based on read-across from the close structural analogue Verdox (CAS# 20298-69-5) and the log Koc value determined at 3.51 (Koc = 3236 L/kg).

Key value for chemical safety assessment

Koc at 20 °C:

3 236

Additional information

For the close structural analogue Verdox a study performed in accordance with OECD Guideline 121 (HPLC Method) and in complaince with GLP criteria is available. In this study solutions of reference substances with known log Koc values based on soil adsorption data and the test substance were analysed by HPLC using a Hypersil BDS-CN column. The log k’ values of reference substances were plotted against the known log Koc values. The log Koc value for the test substance was calculated by substituting its mean log k’ in the calibration curve. Under the conditions of the test, the Koc of Verdox was determined to be 1300 L/kg (log Koc = 3.12).

 

Adsorption potential, log Koc, of Coniferan (CAS #67874-72-0) using read across from data available for Verdox (CAS #20298-69-5).

Introduction and hypothesis for the analogue approach

Coniferan is an acetate-ester attached to a cyclohexyl ring with a tert-pentyl -group attached at the ortho-position. For this substance no adsorption/desorption (Koc) information is available. In accordance with Article 13 of REACH, lacking information can be generated whenever possible by means other than experimental testing, i.e. applying alternative methods such as in vitro tests, QSARs, grouping and read-across. For assessing the log Koc of Coniferan the analogue approach is selected because for a closely related analogue, Verdox, experimental log Koc is available, which can be used for read across.

Hypothesis: Coniferan has similar sorption potential as Verdox as the twosubstances are very close structural analogues. There are no indications that sorption to sediment or soil of both substances is triggered by mechanisms other than lipophilicity, such as, for example, ionisation or surface activity. Therefore, the substances’ octanol-water partitioning coefficients (log Kow) are considered to give direct indication of their sorption potential. In view of the somewhat higher log Kow of Coniferan compared to Verdox (due to the extra methyl group), the log Koc will be corrected accordingly.

Available information: No experimental data on the sorption potential are available for the target chemical Coniferan. For the source chemical Verdox data are available from an OECD TG 121 study in compliance with the principles of GLP. In this study the log Koc was determined at 3.12 (Koc value of ca. 1300 L/kg) and it was concluded that the substance has a moderate adsorption potential to sediment/soil.

Target chemical and source chemical

Chemical structures and physico-chemical properties of the target chemical and the source chemical are shown in the data matrix.

Purity / Impurities

Coniferan is a multi-constituent containing two stereo isomers. The purity of Coniferan is close to 100%. In view of Verdox also being a multi-constituent containing two stereo isomers and having a purity close to 100%, there will be no significant impurities relevant for read across.

Analogue approach justification

According to Annex XI section 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.

Structural similarities and differences:Coniferan and Verdox show very close structural resemblance. Both are esters with acommon cyclohexyl acetate backbone.Coniferan has a 2-tert-pentyl group attached where in Verdox this is a tert-butyl group (see data matrix for chemical structures).

Comparing available experimental data to support the read-across:Coniferan has one additional methyl group attached to the tert-butyl group (i.e. tert-pentyl group) which will lead to a slightly higher log Kow value. Due to the otherwise close structural resemblance of the two substances, the octanol-water partitioning coefficients (log Kow) are considered to give direct indication of their potential for adsorption.

Comparing QSAR estimated data using KocWin:Using the log Kow method of KocWin provides log Koc values of 3.57 and 3.30 for Coniferan and Verdox, respectively. Using the MCI method, these values are 2.94 and 2.64, respectively. These values support the use of read across and the use of a conversion factor to correct for the difference in log Kow.

Deriving Log Koc for Coniferan: Based on the difference in experimental log Kow values available for both substances, the following log Koc value for Coniferan can be derived:

Log Koc Coniferan = log Koc Verdox * (log Kow Coniferan/log Kow Verdox) = 3.12 *( 5.4/4.8) = 3.51

Uncertainty of the prediction:There is no remaining uncertainty in view of the close structural resemblance, the similarity in physico-chemical properties and the application of a conversion factor to correct for the higher log Kow due to the extra methyl group of Coniferan.

Data matrix

The relevant information on physico-chemical properties and other environmental fate properties are presented in the Data Matrix below.

Conclusions for Chemical Safety Assessment

The log Koc of 3.51 (Koc = 3236 L/kg) for Coniferan, as derived from read-across from Verdox, is used directly for environmental exposure assessment. It will also be directly used for derivation of PNECs for sediments and soil by means of the equilibrium partitioning method (EPM).

Data matrix for Coniferan and the read across from Verdox

Common names	Coniferan	Verdox
Chemical name	2-tert-pentylcyclohexyl acetate	2-tert-butylcyclohexyl acetate
Chemical structures	see read across justification document	see read across justification document
Target / Source chemical	Target	Source
CAS No.	67874-72-0	20298-69-5
EC No	267-500-0 (registration in 2018)	243-718-1 (registered)
Empirical formula	C13H24O2	C12H22O2
Physico-chemical data
Molecular weight	212.3	198.3
Physical state	liquid	Liquid at 30°C
Melting point,^oC	-20	29.8
Boiling point,^oC	252	232
Vapour pressure, Pa	4.24 (at 24 °C)	9.72 (at 23 °C)
Water solubility, mg/L	7.6 (at 24 °C)	10 (at 23 °C)
log Kow experimental	5.4	4.8
log Kow KOWWIN	4.9	4.4
Environmental fate data
Adsorption-/desorption	Read across from Verdox Log Koc = 3.51 (= 3.12 * 5.4/4.8 (log Kow)) (Koc = 3236 L/kg)	Experimental data: log Koc = 3.12 (Koc = 1300 L/kg)
Adsorption-/desorption (QSAR (KOCWIN, log Kow method))	log Koc = 3.57 (Koc = 3762 L/kg)	log Koc = 3.30 (Koc = 2015 L/kg)