Hydrolysis of Ketene Catalyzed by Formic Acid: Modification of Reaction Mechanism, Energetics, and Kinetics with Organic Acid Catalysis

Abstract

The hydrolysis of ketene (H2C═C═O) to form acetic acid involving two water molecules and also separately in the presence of one to two water molecules and formic acid (FA) was investigated. Our results show that, while the currently accepted indirect mechanism, involving addition of water across the carbonyl C═O bond of ketene to form an ene-diol followed by tautomerization of the ene-diol to form acetic acid, is the preferred pathway when water alone is present, with formic acid as catalyst, addition of water across the ketene C═C double bond to directly produce acetic acid becomes the kinetically favored pathway for temperatures below 400 K. We find not only that the overall barrier for ketene hydrolysis involving one water molecule and formic acid (H2C2O + H2O + FA) is significantly lower than that involving two water molecules (H2C2O + 2H2O) but also that FA is able to reduce the barrier height for the direct path, involving addition of water across the C═C double bond, so that it is essentially identical with (6.4 kcal/mol) that for the indirect ene-diol formation path involving addition of water across the C═O bond. For the case of ketene hydrolysis involving two water molecules and formic acid (H2C2O + 2H2O + FA), the barrier for the direct addition of water across the C═C double bond is reduced even further and is 2.5 kcal/mol lower relative to the ene-diol path involving addition of water across the C═O bond. In fact, the hydrolysis barrier for the H2C2O + 2H2O + FA reaction through the direct path is sufficiently low (2.5 kcal/mol) for it to be an energetically accessible pathway for acetic acid formation under atmospheric conditions. Given the structural similarity between acetic and formic acid, our results also have potential implications for aqueous-phase chemistry. Thus, in an aqueous environment, even in the absence of formic acid, though the initial mechanism for ketene hydrolysis is expected to involve addition of water across the carbonyl bond as is currently accepted, the production and accumulation of acetic acid will likely alter the preferred pathway to one involving addition of water across the ketene C═C double bond as the reaction proceeds.

Computational studies on the gas phase reaction of methylenimine (CH2NH) with water molecules

“…The two-water reaction significantly reduced the activation barrier by 25.0 kcal/mol. This result is also consistent with the previous studies on similar reaction system 28,30 . Similar to the one-water reaction, aminomethanol can react catalytically with a single water molecule to either regenerate methylenimine or to form formaldehyde.…”

“…The calculated binding energies of two body complex i.e., CH 2 NH⋯H 2 O (− 4.4 kcal/mol) are in very good agreement with previously reported (− 3.8, − 4.7 kcal/mol) 15,23,24 value . The value for H 2 O⋯H 2 O (− 2.9 kcal/mol) are also in very good agreement with Louie et al 30 (− 3.1 kcal/mol) value. As shown in Fig.…”

“…The role of the water molecule as a catalyst in the hydrogen transfer reaction of simple atmospheric and combustion product i.e., ketene (H 2 C=C=O) has been studied by various research groups [28][29][30] . Nguyen et al 28 calculated gas phase pseudo-first-order reaction rate constants for ketene with water molecules at room temperature.…”

Hydrogen Sulfide Induced Carbon Dioxide Activation by Metal‐Free Dual Catalysis

“…[16] However, there are other speciest hat can catalyzet he HATr eactions in atmosphere.I nf act, it is now increasingly becomingly clear that organic acids, which are present in significant amountsi n the Earth's atmosphere, [17][18][19] can catalyzes uch reactions much more efficiently. [20][21][22][23][24][25] For example, the role of acid catalysis in influencingt he energetics of variousa tmospheric processes such as sulfuric acid (H 2 SO 4 )f orming hydrolysis of SO 3 , [20,21] hydrolysis of ketene, [23] and tautomerization of the Criegee intermediate [24,25] has been recently reported. In the Venusiana tmosphere, the inorganic acid, H 2 SO 4 is expected to be present in appreciable amounts [26] and may play ar olei nC O 2 activation.…”

Evidence of ketene emissions from petrochemical industries and implications for ozone production potential

“…Yokelson et al, 2009). A recent theoretical study proposed that hydrolysis of ketene produces acetic acid at a much faster rate in the atmosphere in presence of formic acid (Louie et al, 2015). This mechanism pathway can facilitate hydrolysis of ketene if it is adsorbed into the interface of SOA, and therefore can contribute to rapid growth of aerosols even in the absence of a proper aqueous environment.…”