Theoretical Investigation of the Reactivity of Organosulfur Compounds with OH Radical

ABSTRACT

Organosulfur compounds (OSs), including organosulfates (R–OSO₃⁻) and sulfonates (R–SO₃⁻), are important constituents of atmospheric aerosols and cloud droplets, playing a significant role in Earth’s energy balance and climate dynamics. OSs are considered dominant contributors to particulate-phase organosulfur, accounting for approximately 5–30% of the organic mass in PM10, and are formed through complex chemical pathways involving biogenic volatile organic compounds and sulfate under acidic conditions. Inspired by recent experimental studies using LP-LPA [1], LC–MS [2,3], and DART [4] techniques, this work presents a comprehensive theoretical investigation of the conformational preferences, chemical reactivity, and atmospheric transformation pathways of methyltetrol sulfates (2-MTS and 3-MTS), together with several smaller organosulfates and sulfonates.

In particular, the reaction of these OSs with hydroxyl radical OH was examined by means of computational chemistry methods. DFT optimization of all stationary points at the M06-2X/6-311++G(d,p) level was used, followed by single-point calculations using CBS/DLPNO-CCSD(T1) with implicit solvation through the SMD model [5]. Rate constants at 298 K were obtained from transition-state theory, enabling direct comparison with experiments [1-4]. We also explored reaction channels leading to fragmentation, functionalization, conversion to non-organosulfate products, and degradation to inorganic sulfate.

 

Keywords: Organosulfur, atmospheric chemistry, quantum chemistry, hydroxyl radicals, kinetics.

 

References

 

[1] Lai, D.; Schaefer, T.; Zhang, Y.; Li, Y. J.; Xing, S.; Herrmann, H.; Chan, M. N. ACS ES&T Air, 2024.

[2] Gweme, D. T.; Styler, S. A. J. Phys. Chem. A, 2024, 128, 9462–9475.

[3] Lam, H. K.; Kwong, K. C.; Poon, H. Y.; Davies, J. F.; Zhang, Z.; Gold, A.; Surratt, J. D.; Chan, M. N. Atmos. Chem. Phys., 2019, 19, 2433–2440.

[4] Chen, Y.; Zhang, Y.; Lambe, A. T.; Xu, R.; Lei, Z.; Olson, N. E.; Zhang, Z.; Szalkowski, T.; Cui, T.; Vizuete, W. Environ. Sci. Technol. Lett., 2020, 7, 460–468

[5] Marenich, A. V.; Cramer, C. J.; Truhlar, D. G. J. Phys. Chem. B, 2009.