Gas Phase Reactions between Acetylene Radical Cation and Water. Energies, Structures and Formation Mechanism of C ₂H ₃O ⁺ and C ₂H ₄O ^+• Ions

Abstract

Reactions of the acetylene radical cation (C2H2(+*)) with H2O were investigated using ion mobility mass spectrometry. The primary products are the C2H3O(+) and C2H4O(+*) ions, produced with an overall rate coefficient k(300 K) = 2(+/-0.6) x 10(-11) cm(3) s(-1) that increases with decreasing temperature. The C2H4O(+*) (adduct) vs C2H3O(+) (H loss) ratio also increases with decreasing temperature, and with increasing third-body pressure. Ab initio calculations on the products showed seven stable C2H3O(+) isomers and eleven stable C2H4O(+*) isomers. In the C2H4O(+*) adduct channel, the reactivity and energetics suggest that the adduct is the H2C=CHOH(+*) (vinyl alcohol) ion. In the C2H3O(+) channel, the H loss occurs exclusively from water. The C2H3O(+) product ion undergoes slow deprotonation by water to form H(+)(H2O)n clusters. The reactivity, combined with energetics, suggests that the protonated ketene CH2COH(+) is the most likely observed C2H3O(+) ion probably with some contribution from the cyclic c-CH2CHO(+) ion.

Infrared spectroscopy of the acetyl cation and its protonated ketene isomer

“…Because previous mass spectrometry found acetyl from other precursors, 2, [47][48][49][50][51] we investigated its production from acetone. Previous reaction studies had suggested that acetone produces more than one ion structure at this mass.…”

“…1, 2, [47][48][49][50][51] Ion/molecule reactions, collisional dissociation, and computational studies indicate that the acetyl cation (CH 3 CO + ) is the most stable structure, with less-stable configurations identified for protonated ketene (CH 2 COH + ) and the oxiranyl cation (H 2 COCH + ). The infrared spectrum and crystal structure of the acetyl cation have been measured previously in superacid matrices, [52][53][54] but no spectroscopy has been reported for other isomers.…”

Stepwise Association of Hydrogen Cyanide and Acetonitrile with the Benzene Radical Cation: Structures and Binding Energies of (C6H6•+)(HCN)n, n = 1–6, and (C6H6•+)(CH3CN)n, n = 1–4, Clusters

“…11 Hydration of the acetylene radical cation (C 2 H 2 •+ ) results in the formation of the covalent ions C 2 H 3 O + and C 2 H 4 O •+ produced with an overall rate coefficient that increases with decreasing temperature. 12 The reactivity, combined with energetics, suggest that the C 2 H 4 O •+ adduct is vinyl alcohol (H 2 CCHOH •+ ), while the protonated ketene CH 2 COH + is the most likely observed C 2 H 3 O + ion. 12 The measured hydration energy can confirm the covalent nature of the ions as in the case of the acetylene trimer ion (C 2 H 2 ) 3 •+ where its sequential hydration energies with 1−6 water molecules are found to be identical to those of the benzene ion, thus confirming the formation of benzene cations in ionized acetylene clusters.…”

“…12 The reactivity, combined with energetics, suggest that the C 2 H 4 O •+ adduct is vinyl alcohol (H 2 CCHOH •+ ), while the protonated ketene CH 2 COH + is the most likely observed C 2 H 3 O + ion. 12 The measured hydration energy can confirm the covalent nature of the ions as in the case of the acetylene trimer ion (C 2 H 2 ) 3 •+ where its sequential hydration energies with 1−6 water molecules are found to be identical to those of the benzene ion, thus confirming the formation of benzene cations in ionized acetylene clusters. 13,17 Similarly, the measured hydration energy combined with structural calculations of the acetylene dimer ion (C 4 H 4…”

Protonen‐induzierte Umlagerung eines Oxaphosphirankomplexes

“…Geburtstag gewidmet Epoxide I (Oxirane) sind wichtige Bausteine der Synthesechemie, insbesondere der Naturstoff-und Polymerchemie. [1,2] Oxiraniumkationen II sind bislang, trotz vieler experimenteller [3][4][5][6] und theoretischer Untersuchungen, [7][8][9] schwer fassbare reaktive Intermediate säurekatalysierter Epoxidöff-nungsreaktionen geblieben. Im Unterschied dazu könnte [15] die Protonierung von s 3 l 3 -Oxaphosphiranen [10][11][12][13][14] bisher unbekannte P-protonierte Oxaphosphiraniumderivate III liefern.…”