# First Order Degradation Constant (λ)(d^-1)

Can you please tell me the First Order Degradation Constant (λ)($d^{-1}$) for 1,3,5-Trimethylbenzene (mesitylene)?

If you don't have this value, can you please tell me which VOC in 35 Illinois Administrative Code 740. Appendix A. Table A. is "most similar" to 1,3,5-TMB that I may use its First Order Degradation Constant? Please provide an explanation. Thank you!

• Hello and welcome to Chemistry.SE! At this point I recommend taking the short tour to better familiarize yourself with how this site works. Regarding your question, any additional information and context that you can give will help others to lead you to the answer you need. – airhuff Mar 7 '17 at 22:39
• For anyone trying to help with this, there is an online copy of this code with the "Table A" referred to in the OP available here. – airhuff Mar 7 '17 at 22:56
• By far the most similar compound(s) to 1,3,5-trimethylbenzene listed in Table A is "Total Xylenes", which is a mixture of "1,2-dimethylbenzene", "1,3-dimethylbenzene" and "1,4-dimethylbenzene". I don't really know what your end goal is, but I would not necessarily expect these to have the same first order degradation constants (how close do you need?) as 1,3,5-Trimethylbenzene. As far as a single (not a mixture) compound listed in Table A, toluene ("1-methylbenzene") would be the most similar, but not very similar. – airhuff Mar 7 '17 at 23:10

Based on a bit more than a cursory search, there doesn't seem to be a first order degradation constant readily available for 1,3,5-trimethylbenzene (mesitylene) in the open literature. This leaves us with your second option, the Title 35 Illinois Administrative Code 740$^{[1]}$, Table A (herein referred to as Table A).

By far the most similar compound to 1,3,5-trimethylbenzene that can be found in Table A, based on both chemical structure and physical properties, is the total xylenes (CAS # 1330-20-7). This is actually a mixture of the three possible isomers of xylene.

Both the images below and all physical and chemical properties given for the total xylenes were taken from this Wikipedia page unless otherwise stated. The 1,3,5-trimethylbenzene image and all of its chemical and physical properties were taken from here.

1,3,5-trimethylbenzene (mesitylene)

In order: o-xylene, m-xylene, p-xylene

Selected properties:
Mesitylene: density = 0.86 ($\mathrm{20^oC}$), B.P. = $\mathrm{165^oC}$, M.P. = $\mathrm{-45^oC}$, and water solbility = 50 mg/L at $\mathrm{25^oC}^{[2]}$
Xylenes : density = 0.86 ($\mathrm{20^oC}$), B.P. = $\mathrm{138^oC}$, M.P. = $\mathrm{-47^oC}$, and water solbility = 110 mg/L at $\mathrm{25^oC}^{[2]}$

2) Yalkowsky, S.H., He, Yan., Handbook of Aqueous Solubility Data: An Extensive Compilation of Aqueous Solubility Data for Organic Compounds Extracted from the AQUASOL dATAbASE. CRC Press LLC, Boca Raton, FL. 2003