Observation of Two Conformers of Acrylic Sulfuric Anhydride by Microwave Spectroscopy

Abstract

The rotational spectrum of acrylic sulfuric anhydride (CH═CHCOOSOOH, AcrSA) has been observed using pulsed-nozzle Fourier transform microwave spectroscopy. The species was produced from the reaction between acrylic acid and sulfur trioxide in a supersonic jet. Spectroscopic constants are reported for both the s-cis- and s-trans-AcrSA conformers of the parent and monodeuterated (OD) isotopologues. Geometries were optimized for both conformers using M06-2X/6-311++G(3df,3pd) methods. Single-point energy calculations at the M06-2X geometries were calculated using the CCSD(T)/complete basis set method with double and triple extrapolation [CBS(D-T)]. Further calculations indicate that the anhydride results from a π + π + σ cycloaddition reaction within the acrylic acid-SO complex. Because the C═O double bond of the acrylic acid migrates from one of the COOH oxygens to the other during the reaction, the s-cis form of acrylic acid leads to the s-trans form of the anhydride and vice versa. With zero-point energy corrections applied to the CCSD(T) energies, the s-cis and s-trans forms of CH═CHCOOSOOH are 19.0 and 18.8 kcal/mol lower in energy than that of SO + their corresponding CH═CHCOOH precursor conformation. The zero-point-corrected transition state energies for formation of the s-trans and s-cis anhydrides are 0.22 and 0.33 kcal/mol lower than those of the complexes of SO with s-cis and s-trans acrylic acid, respectively, indicating that the reaction is essentially barrierless. This system adds to a growing body of examples demonstrating that carboxylic acids readily add to SO in the gas phase to produce the corresponding carboxylic sulfuric anhydride.

Glyoxylic Sulfuric Anhydride from the Gas-Phase Reaction between Glyoxylic Acid and SO3: A Potential Nucleation Precursor

“…In TS1 and TS2, −COOH and −SO form a six-membered ring, analogous to the transition state structures of the reactions between SO 3 and some carboxylic acids. [29][30][31]48 The Gibbs free energies of TS1 and TS2 relative to their corresponding prereaction complexes, i.e., Gibbs free energy barriers, are 3.12 and 2.56 kcal/mol, respectively, meaning that these reactions can rapidly occur once GA collides with SO 3 in the atmosphere. The Gibbs free energy barriers also indicate that this kind of reaction seems general for carboxylic acids and is almost not affected by the adjacent aldehyde group.…”

“…Mackenzie et al have observed the gas-phase barrierless reaction between formic acid and SO 3 to form formic sulfuric anhydrides . In addition, acetic acid and acrylic acid were also found to react with SO 3 to form corresponding carboxylic sulfuric anhydrides through barrierless reactions, indicating that some hydrocarbon substituent groups, such as −CH 3 and −CHCH 2 , have little effect on the reaction between the carboxyl group and SO 3 . , These products all have stronger acidities and lower vapor pressures compared with those of their corresponding carboxylic acids, and therefore, they are much more likely to participate in nucleation. Thus, it might be an underlying way for RCOOH (R indicates hydrocarbon group) to participate in nucleation by transferring itself to the corresponding carboxylic sulfuric anhydride with a greater nucleation potential by reacting with SO 3 .…”

Mechanistic Insight into the Reaction of Organic Acids with SO3 at the Air–Water Interface

“…This reaction also involves a low free‐energy barrier of activation (2.5 kcal mol −1 for FA, Figure S1). It provides a mechanism for incorporating organic matter into aerosol particles …”

Molecular-Scale Mechanism of Sequential Reaction of Oxalic Acid with SO3: Potential Participator in Atmospheric Aerosol Nucleation

“…It seems that the nucleation ability of carboxylic acid could be improved by the reaction with SO 3 , and the corresponding product carboxylic sulfuric anhydride is speculated to participate in NPF . The subsequent theoretical calculation on monocarboxylic acids suggested that different types of substituents such as −CHCH 2 , −CCH, −CF 3 , and the aldehyde group have little effect on the reaction energy barrier, ,, while for polycarboxylic acids, the energy barriers of reactions between one SO 3 and −COOH at different sites are all low enough for these reactions to take place in the gas phase . However, the kinetics of the sequential reaction of multiple −COOH with multiple SO 3 and their influence on NPF are still unclear.…”