Rapid preparation of gaseous methanediol (CH₂(OH)₂)

Abstract

The simplest geminal diol CH2(OH)2 serves as an important precursor to form atmospheric formic acid. CH2(OH)2 vapour can be generated by evaporation of the aqueous formaldehyde solution, prepared by dissolving...

Confirmation of gaseous methanediol from state-of-the-art theoretical rovibrational characterization

“…Simulated spectra from state-of-the-art, purely ab initio F12-TZ-cCR QFFs confirm the assignment of the 980–1100 cm −1 rovibrational feature reported by Chen and Chu 26 as arising from gaseous methanediol. The unadulterated F12-TZ-cCR rovibrational spectrum matches exceptionally well with the experimentally observed spectral features arising from the ν 10 and ν 11 vibrational transitions and agrees with the experimental band origins to within 3 cm −1 .…”

“…In the top portion, the black computed spectrum almost exactly matches the experimental IR data of Chen and Chu for this rovibrational feature in the 980–1100 cm −1 range. 26 This provides unambiguous confirmation of Chen and Chu's successful preparation of methanediol in the gas-phase. The F12-TZ-cCR spectrum additionally matches with the authors' previous spectrum produced with experimental band origins and B3LYP/aug-cc-pVTZ rotational constants, also shown in green in the bottom of Fig.…”

“…The simulation is performed at 298 K similar to the experimental conditions of Chen and Chu. 26 S 1 ( a ′) = H 1 –C S 2 ( a ′) = H 2 –C S 3 ( a ′) = (O 1 –C) + (O 2 –C) S 4 ( a ′) = (O 1 –H 3 ) + (O 2 –H 4 ) S 5 ( a ′) = ∠(H 1 –C–H 2 ) S 6 ( a ′) = ∠(O 1 –C–H 1 ) + ∠(O 2 –C–H 1 ) S 7 ( a ′) = ∠(C–O 1 –H 3 ) + ∠(C–O 2 –H 4 ) S 8 ( a ′) = τ (O 1 –C–H 1 –H 2 ) − τ (O 2 –C–H 1 –H 2 ) S 9 ( a ′) = τ (H 3 –O 1 –C–H 1 ) − τ (H 4 –O 2 –C–H 2 ) S 10 ( a ′′) = (C–O 1 ) + (C–O 2 ) S 11 ( a ′′) = (O 1 –H 3 ) + (O 2 –H 4 ) S 12 ( a ′′) = ∠(O1–C–H 1 ) + ∠(O 2 –C–H 1 ) S 13 ( a ′′) = ∠(C–O 1 –H 3 ) + ∠(C–O 2 –H 4 ) S 14 ( a ′′) = τ (O 1 –C–H 1 –H 2 ) − τ (O 2 –C–H 1 –H 2 ) S 15 ( a ′′) = τ (H 3 –O 1 –C–H 1 ) − τ (H 4 –O 2 –C–H 1 ) S 1 ( a ) = (C–H 1 ) + (C–H 2 ) S 2 ( a ) = (C–O 1 ) + (C–O 2 ) S 3 ( a ) = (O 1 –H 3 ) + (O 2 –H 4 ) S 4 ( a ) = ∠(H 1 − C–H 2 ) S 5 ( a ) = ∠(O 1 –C–H 1 ) + ∠(O 2 –C–H 2 ) S 6 ( a ) = ∠(C–O 1 –H 3 ) + ∠(C–O 2 –H 4 ) S 7 ( a ) = τ (O 1 –C–H 1 –H 2 ) + τ (O 2 –C–H 2 –H 1 ) S 8 ( a ) = τ (H 3 –O 1 –C–H 1 ) + τ (H 4 –O 2 –C–H 2 ) S 9 ( b ) = (C–H 1 ) − (C–H 2 ) S 10 ( b ) = (C–O 1 ) − (C–O 2 ) S 11 ( b ) = (O 1 –H 3 ) − (O 2 –H 4 ) S 12 ( b ) = ∠(O 1 –C–H 1 ) − ∠(O 2 –C–H 2 ) S 13 ( b ) = ∠(C–O 1 –H 3 ) − ∠(C–O 2 –H 4 ) S 14 ( b ) = τ (O 1 –C–H 1 –H 2 ) − τ (O 2 –C–H 2 –H 1 ) S 15 ( b ) = τ (H 3 –O 1 –C–H 1 ) − τ (H 4 –O 2 –C–H 2 )…”

“…Following this, a method for rapid preparation of gaseous methanediol was reported earlier this year by Chen and Chu. 26 An aqueous formaldehyde solution is evaporated allowing for measurement of the IR absorption spectrum of the vapour. The rovibrational feature at 980–1100 cm −1 is free from interference of water and formaldehyde, and is identified as methanediol using the computational data from Jian et al from the experimental band origins and B3LYP/aug-cc-pVTZ rotational parameters.…”

“…Fig.2Convolved F12-TZ-cCR spectra (black) from the corresponding n 10 (blue) and n 11 (orange) features overlaid with experimental spectra (purple) and B3LYP (green) from Chen and Chu 26. …”