1-isopropyl-2,2-dimethyltrimethylene diisobutyrate

Water solubility

Description of key information

Two GLP slow stir water solubility studies.  
Two QSAR calculations for water solubility.
Summary of company supplied data.

Key value for chemical safety assessment

Water solubility:

13 mg/L

at the temperature of:

25 °C

Additional information

Determining the aqueous solubility of a test substance that is a hydrophobic chemical is inherently difficult. This test substance is a liquid at room temperature and has a density similar to that of water. Using a standard OECD 105 shake flask water solubility method promotes the formation of micelles and suspensions, which can be stable and difficult to discern from dissolved chemical. Also, trace amounts of particulate matter can serve as adsorptive sites for the test substance effectively increasing its apparent solubility. The presences of undissolved or adsorbed test substance in these forms can bias the results high, an effect that has been evident in much of the earlier solubility data on chemicals with these characteristics. There are methods that can be used to avoid these complications. Researchers have sucessfully demonstrated the use of a slow-stirring technique to measure the aqueous solubility of substances of this type. The slow-stir technique has been incorporated into OECD Method 123 for determining octanol-water partitioning coefficient. OECD 105 column elution and nephelometric methods can also be utilized.

For this substance two GLP slow-stir water solubility studies have been performed and summaries of those studies are provided. These studies determined the solubility to be 12.7 mg/L @ 27 + or - 0.5C and 13.3 mg/L @ 23.65 + or - 4.15C in distilled deionized water. In dilution water utilized for aquatic toxicity testing with fish and daphnia the solubility was determined to be 13.2 mg/L @ 23.65 + or - 4.15C.

Modeled estimations of water solubility were also detemined using WSKOW (version 1.41) and WATERNT (version 1.01) from within EPIWIN (version 4.0). WSKOW estimates the water solubility as 0.9422 mg/L @ 25C based upon an experimental log Kow value of 4.91. WATERNT estimates the solubility to be 11.457 mg/L @ 25C based upon the QSAR.

A summary of company data water solubility studies is also contained within a company document entitled "Review of Aqueous Solubility Studies of TXIB", however the studies themselves cannot be located. The summary indicates that the shake flask test procedure modeled after OECD Test Guideline 105, provided water solubilty values for TXIB of 11.9 mg/L in distilled water and 14.7 mg/L for aquatic toxicity test diluent water. However, experimental difficulties were encountered in separating undissolved TXIB from dissolved TXIB. A nephelometric test method resulted in a value of 13.4 mg/L. A column-elution method similar to OECD 105 was used for the 7 species aquatic toxicity tests and resulted in a steady state concentration of 1-2 mg/L after 96 hours and a mean measured concentration over 192 hours of 1.55 mg/L @ 20 + or - 1C. While there is some varibility among all of the experimental and modeled data, the data support a water solubility value in the range of ~0.9 to 13 mg/L at temperatures near 25C.