What is the enthalpy of formation of acrylic acid?

Abstract

Acrylic acid is a key industrial compound with numerous uses. Despite its importance, its enthalpy of formation is still contentious-even ignoring ''ancient'' determinations, there is a 12 kJ mol -1 range of values reported for the gas phase quantity, -320 to -332 kJ mol -1 . Our quantum chemical calculations using current methodology suggest the value of -321 ± 3 kJ mol -1 .Keywords Acrylic acid Á Chemical industry Á Enthalpy of formation Á Entropy Á Gibbs energy of formation Á G2 and G3 quantum chemical calculations Á Polymers Á Propenoic acid Á Rotamers Acrylic acid (propenoic acid) is a key industrial compound. Historically, the polymerizable monomer has been manufactured by the hydrolysis of ethylene cyanohydrin (b-hydroxypropionitrile), by a Reppe process involving carbon monoxide addition to acetylene, by the reaction of formaldehyde with ketene, and by the hydrolysis of acrylonitrile. Today, acrylic acid is produced commercially by gas phase oxidation of propylene over heterogeneous catalysts [1]. Acrylic acid is used [2] in the production of superabsorbent polymers, detergents, and water treatments. The various esters of acrylic acid are converted into acrylic polymers and copolymers that are used in a wide variety of products including architectural and industrial paints, coatings, floor polishes, adhesives, caulks, sealants, plastics additives, and dispersants. As evidence of its commercial importance, in 2004, global production capacity of acrylic acid [3] was about 9 billion lbs (ca. 4 · 10 6 tons or 4 · 10 9 kg) of which about three-quarters was for captive (i.e., intra-company, as opposed to merchant, inter-company) uses. Demand growth has been averaging slightly better than GDP and selling prices has averaged ca. $0.85 per pound (1.4 e/kg) on the American market, and somewhat higher on the European and Asian markets.Acrylic acid is also the simplest unsaturated carboxylic acid and as such, is both an archetype of functionalized olefins and of carboxylic acids alike. Acrylic acid is additionally a conceptually simple example of a conjugated bifunctional species.Despite the considerable economic and conceptual importance of acrylic acid, its enthalpy of formation is still contentious-even ignoring ''ancient'' determinations, there is a 12 kJ mol -1 range of values for the gas phase quantity. Presenting chronologically and without bias, there is an earlier seemingly reliable determination of -383.8 ± 0.9 kJ mol -1 [4] arising from the analysis of liquid phase hydrogenation calorimetry measurements. We also find recent values for the enthalpy of formation in the liquid phase: -377.8 ± 9.3 [5] and -383.8 ± 2.0 [6] kJ mol -1 , arising from the combustion of a freshly distilled sample of unstated purity and of one contaminated by acetic acid and an added polymerization inhibitor. Much R. Notario (&) Á M. V. Roux

Interplay of thermochemistry and Structural Chemistry, the journal (volume 21, 2010) and the discipline

“…Using defining reactions, G2 and G3 quantum chemical calculations, and using literature sources, values between 185 and 191 kJ mol -1 were suggested with a recommended average of (188 ± 7) kJ mol -1 . A delocalization stabilization energy of but 4 kJ mol -1 has been suggested, a small value in accord with the value for acrylic acid earlier discussed by these authors [135].…”

What is the enthalpy of formation of acrylonitrile?

“…13 kJ mol -1 spread of values quite disconcerting as it resembles the situation for experimental thermochemical measurements of the likewise industrially important acrylic acid (associated with its own Chemical Heritage Landmark status [8]), the parent carboxylic acid associated with the nitrile of interest. We follow in this brief note the quantum chemical approach we recently used [9] to understand the enthalpy of formation of this last species.…”

“…Only three measurements were reported by these authors, compared to just the mean value by the other sets of authors. We recall our earlier discussion [9] of the presence of contamination of the acrylic acid by the ''invisible'' presence of polymer, or more plausibly some low-molecular-weight oligomer. Why would not this problem arise here as well?…”

Paradigms and paradoxes: organic thermochemistry without hydrogen: carbon oxides and nitrides

“…Again, the reaction is nearly thermoneutral for chlorine. We merely note our concern about the enthalpy of formation of the monocyano species acrylonitrile based on our recent thermochemical experience [27] with the related acrylic acid (X = COOH).…”