Question # 544

544. According to the Chemical Abstract Service (CAS), the Chemical Abstracts Registry name for CAS number 26471-62-5 is 'benzene, 1,3-diisocyanatomethyl-.' The structural formula that describes this CAS number is as follows: Structural formula for 'benzene, 1,3-diisocyanatomethyl-.' This name and structure imply only that the isocyanate groups must be one/three with respect to one another and that the position of the methyl group is not known. It should be noted that neither the name nor the structure imply that there is necessarily a mixture of chemicals. The EPCRA section 313 list of toxic chemicals (40 CFR Section 372.65) includes CAS number 26471-62-5 with the name 'toluene diisocyanate (mixed isomers).' This name implies no positional relationship of the isocyanate groups with respect to each other or to the methyl group. In addition, the name seems to imply that there must necessarily be a mixture of compounds for this listing to apply. For the purposes of EPCRA section 313 reporting, what compounds are reportable under the CAS number 26471-62-5?
The chemical name 'benzene, 1,3-diisocyanatomethyl-' is listed as a synonym for 'toluene diisocyanate (mixed isomers)' under CAS number 26471-62-5 in EPA’s document Common Synonyms For Chemicals Listed Under Section 313 of the Emergency Planning and Community Right-To-Know Act, EPA 745-R-95-008, March 1995. For purposes of reporting under EPCRA section 313, 'toluene diisocyanate (mixed isomers)' includes any possible mixture of any toluene diisocyanates in which the isocyanate groups are separated by one carbon in the ring (i.e., are one/three to each other). This listing includes the 2,4-, 2,6-, and 3,5- isomers of toluene diisocyanate (TDI). TDI is commonly manufactured as a mixture of isomers (e.g., an 80:20 mixture of 2,4- and 2,6-TDI). Even if the mixture is made up of the specifically listed isomers (i.e., 2,4- and 2,6-TDI), the listing 'toluene diisocyanate (mixed isomers)' still applies. The 'mixed isomer' listing is meant to include any mixture that contains two or more of the toluene diisocyanate isomers (i.e., 2,4-, 2,6-, or 3,5-TDI). The specifically listed 2,4- and 2,6- TDI isomers should be reported individually if not present as a mixture of TDI isomers. If, however, the individual thresholds for the pure TDI isomers are exceeded, the covered facility may file a single report for TDI (mixed isomers) and include the total quantity released or otherwise managed as waste.