The enol of propionic acid

Abstract

We demonstrate the gas-phase synthesis of prop-1-ene-1,1-diol, the hitherto unreported higher energy tautomer of propionic acid. The enol was trapped in an argon matrix and characterized by IR and UV/Vis...

The enol of isobutyric acid

“…While the existence of dimethylketene 4 in ISM has not been proven to date, the presence of related molecules including parent ketene 32 and methylketene, 33 and their role as potential intermediates in the generation of prebiotic molecules has been suggested. 25,28 That is, demonstrating the feasibility of 2 and 4 under conditions akin to the ISM ( T ∼ 3 K and high dilution) would encourage their identification via radioastronomy; our methods of preparation can readily be transferred to complementary experimental setups including microwave emission experiments. Following the approach adopted in prior studies, 25 we report here the generation of 2 alongside 4 via pyrolysis of dimethylmalonic acid ( 1 ) as the precursor.…”

“…23 The gas phase stability of enols has also been validated through laboratory experiments, including those involving the enols of acetamide, 24 acetic acid, 25 glycolic acid, 26 glycolaldehyde, 27 and propionic acid. 28 In solution, enols display high reactivity and isomerize rapidly into the more thermodynamically more stable keto tautomers through bimolecular acid–base reactions. 29 In the gas phase, however, enols are considerably more stable 30 due to significant energy barriers (ranging from 40 to 45 kcal mol −1 ) 30,31 for [1,3]H-shifts.…”

“…As previously mentioned, pyrolysis led to the formation of 4 through the elimination of water from the enol in the gas phase. Unlike the enol tautomer of propionic acid, 28 the generation of the enol from the precursor requires high activation energy ( E a = 31.1 kcal mol −1 computed at B3LYP/def2-TZVP), contributing to the formation of 4 . Subsequent irradiation ( λ = 254 nm) revealed the formation of propene ( 5 ).…”