Reversible tautomerization of radical cations. Photoionization of 2-methoxyethanol and 3-methoxy-1-propanol

Biermann, H. W.; Morton, Thomas Hellman

doi:10.1021/ja00353a028

Cited by 19 publications

(13 citation statements)

References 2 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…20 Their PIE spectrum matches well to our flamesampled PIE spectra as seen in Figure 7A. Further isomers are possible, and photoelectron spectra of species with known ionization energy (IE) close to the observed onset at 9.4 eV, that is, dimethoxyethane, 57 ethoxyethanol, 57 and methoxypropanol, 58 are shown in Figure 7B in comparison to the TPE spectrum of m/z 90 measured in the 2butene/H 2 flame. The first band in the photoelectron spec-tra of these species is significantly broader than our measured TPE spectrum, but dissociative photoionization cannot be excluded as discussed for the identification of the propyl hydroperoxides.…”

Section: 14supporting

confidence: 77%

See 1 more Smart Citation

Observation of low‐temperature chemistry products in laminar premixed low‐pressure flames by molecular‐beam mass spectrometry

Bierkandt

Oßwald

Gaiser

et al. 2021

Int J of Chemical Kinetics

View full text Add to dashboard Cite

The formation of typical low‐temperature oxidation products is observed in laminar premixed low‐pressure flames investigated by photoionization molecular‐beam mass spectrometry at the Swiss Light Source. The C1–C4 alkyl hydroperoxides can be identified in n‐butane‐ and 2‐butene‐doped hydrogen flames by their photoionization efficiency spectra at m/z 48, 62, 76, and 90. C1–C3 alkyl hydroperoxides are also observed in a propane‐doped hydrogen flame and in a neat propane flame. In addition, threshold photoelectron spectra reveal the presence of the alkyl hydroperoxides. In the 2‐butene/H2 flame, the photoionization spectrum at m/z 88 also enables the identification of butenyl hydroperoxides by comparison with calculated ionization energies of the alkenyl hydroperoxides and a literature spectrum. The low‐temperature species are formed close to the burner surface with maximum mole fractions at 0.25–0.75 mm above the burner. At 0.5 mm, even the methylperoxy radical (CH3OO) is measured for the first time in a laminar premixed flame. The rate of production analyses show that consumption of the hydroperoxyalkyl radicals results in the formation of cyclic ethers. In the n‐butane/H2 flame, ethylene oxide, oxetane, and methyloxirane are identified. Besides expected small oxygenated species, for example, formaldehyde or acetaldehyde, the larger C4 oxygenates butanone (C2H5COCH3) and 2,3‐butanedione (C4H6O2) are formed in the two C4 hydrocarbon‐doped hydrogen flames. Quantification of alkyl hydroperoxides with estimated photoionization cross sections based on the corresponding alcohols, which have similar photoelectron structures to the alkyl hydroperoxides, shows that mole fractions are on the order of 10−5–10−6 in the n‐butane/H2 flame. Measurements are corroborated by simulations, which also predict the presence of some peroxides in detectable concentrations, that is, mole fractions larger than 10−7, under the investigated conditions. The observation of peroxide species and cyclic ethers in the investigated laminar premixed flames give new insights into the contribution of low‐temperature combustion chemistry in a flame.

show abstract

Section: 14supporting

confidence: 77%

“…(B) Flame‐sampled TPE spectra of m/z 90 in comparison with the photoelectron spectra of dimethoxyethane and ethoxyethanol by Kimura et al 57 . and methoxypropanol by Biermann and Morton 58 …”

Section: Resultsmentioning

confidence: 99%

Observation of low‐temperature chemistry products in laminar premixed low‐pressure flames by molecular‐beam mass spectrometry

Bierkandt

Oßwald

Gaiser

et al. 2021

Int J of Chemical Kinetics

View full text Add to dashboard Cite

show abstract

“…Numerous studies have therefore been carried out to elucidate ionization-induced isomerization/dissociation mechanisms. − Ethylene glycol (HOCH 2 CH 2 OH) is one of the fundamental ethane derivatives and is the prototype of diols. Neutral ethylene glycol energetically favors the gauche form, in which the intramolecular hydrogen bond is formed between the two OH groups. − It has been reported that the protonated methanol fragment is generated upon photoionization of ethylene glycol with the photon energy higher than 10.4 eV, which is near the vertical ionization energy. − Because a double proton transfer reaction is necessary to generate protonated methanol from ionized ethylene glycol, this ionization-induced isomerization/dissociation process has attracted much interest. (Here, we should note that the reaction is, strictly speaking, proton and hydrogen transfer.…”

Section: Introductionmentioning

confidence: 99%

“…Therefore, in this paper, we use the term “double proton transfer” for simplicity.) Its mechanism has therefore undergone various investigations with mass spectrometry, photoelectron spectroscopy, collision induced dissociation (CID), threshold photoelectron–photoion coincidence spectroscopy (TPEPICO), theoretical computations, and so on. − The vertical ionization energy of ethylene glycol has been determined to be 10.55 eV by photoelectron spectroscopy. − For the isomerization process of ionized ethylene glycol to generate protonated methanol, mechanism I, shown in Figure a, has been proposed in the mass spectrometric and theoretical investigation by Burgers et al In this mechanism, the double proton transfer reaction from OH to the other O atom and from CH to the other C atom occurs between the two CH 2 OH moieties. As a result, the CH 3 OH 2 + –OCH complex is formed.…”

Section: Introductionmentioning

confidence: 99%

IR Spectroscopic Investigation on Isomerization of Ionized Ethylene Glycol

et al. 2019

View full text Add to dashboard Cite

It has been known that photoionization of ethylene glycol generates protonated methanol when the ionization energy is in the vicinity of the vertical ionization energy. Although two different isomerization paths have been proposed for the protonated methanol production, the isomerization path has not yet been identified. To investigate the isomerization of ionized ethylene glycol, infrared (IR) predissociation spectroscopy based on vacuum ultraviolet photoionization is carried out for neutral and cationic ethylene glycol and partially deuterated isotopomer (HOCD2CD2OH). The IR spectroscopic results indicate that ionized ethylene glycol isomerizes to the protonated methanol–HCO complex, and the isomerization path involving the double proton transfer is identified. This isomerization path is also supported by the theoretical isomerization path search, which demonstrates that several reaction pathways are mutually intercommunicated.

show abstract

“…The 2-methoxyethanol radical cation CH 3 OCH 2 CH 2 OH •+ ( 1 ) undergoes interesting unimolecular dissociation reactions, − some of which have been proposed to involve hydrogen-bridged and/or distonic radical cation intermediates. The strong intramolecular hydrogen bond 18 in the neutral CH 3 OCH 2 CH 2 OH was initially thought to remain after ionization ( 1 , Scheme ) and to lead to isomerization of the initially formed radical cation to a hydrogen-bridged complex of formaldehyde and the methoxymethyl radical, CH 3 O(CH 2 )···H···OCH 2 •+ ( 2 , Scheme ) . This ion was suggested to undergo a hydrogen atom shift to yield another hydrogen-bridged intermediate, (CH 3 ) 2 O···H···OCH •+ ( 3 ), which decomposes by expulsion of CHO • .…”

Section: Introductionmentioning

confidence: 99%

An Experimental and Theoretical Study of the Long-Lived Radical Cation of CH₃OCH₂CH₂OH

Pakarinen¹,

Smith²,

Vainiotalo³

et al. 1996

J. Am. Chem. Soc.

View full text Add to dashboard Cite

The long-lived radical cation of 2-methoxyethanol, CH3OCH2CH2OH•+, is stable toward isomerization in the gas phase. This radical cation reacts with neutral reagents via three main channels in a Fourier-transform ion cyclotron resonance mass spectrometer. CH3OCH2CH2OH•+ abstracts an electron from reagents with ionization energies less than that of CH3OCH2CH2OH. Neutral reagents with higher ionization energies replace CH3OCH2 • or CH2O in the ion. Both replacement reactions are probably driven by the formation of a hydrogen bond between the entering nucleophile and the hydroxyl group in CH3OCH2CH2OH•+, which breaks the C−C bond in CH3OCH2CH2OH•+. For strong nucleophiles, this process is so exothermic that the resulting ion/molecule complex dissociates by loss of CH3OCH2 •. However, weak nucleophiles yield a longer-lived ion−molecule complex. Within this complex, CH3OCH2 • can react with the initially produced ion by replacement of CH2O (a weaker nucleophile) to yield the hydrogen-bridged complex of CH3OCH2 • and the nucleophile. This reaction provides a general approach for the gas-phase synthesis of different hydrogen-bridged radical cations. Ab initio molecular orbital calculations suggest that the most stable geometry of CH3OCH2CH2OH•+ is characterized by an unusually long C−C bond (1.775 Å at the UMP2/6-31G** level of theory). This finding is in agreement with the observed facile cleavage of the C−C bond in CH3OCH2CH2OH•+. The isomeric ions •CH2O+(CH3)CH2OH, (CH3)2O+CH2O•, •CH2OCH2CH2OH2 +, •CH2O(CH3)−H+···OCH2, and CH3OC(H)H···O(H)CH2 •+ were calculated to be less stable than CH3OCH2CH2OH•+ (at the UMP2/6-31G**//UHF/6-31G**+ZPE level of theory). Only the ion (CH3)2O-H···OCH•+ was found to lie lower in energy than CH3OCH2CH2OH•+ (by 7.2 kcal/mol at the UMP2/6-31G**+ZPVE level of theory). However, experimental evidence does not support the formation of this hydrogen-bridged ion upon ionization of 2-methoxyethanol.

show abstract

Reversible tautomerization of radical cations. Photoionization of 2-methoxyethanol and 3-methoxy-1-propanol

Cited by 19 publications

References 2 publications

Observation of low‐temperature chemistry products in laminar premixed low‐pressure flames by molecular‐beam mass spectrometry

Observation of low‐temperature chemistry products in laminar premixed low‐pressure flames by molecular‐beam mass spectrometry

IR Spectroscopic Investigation on Isomerization of Ionized Ethylene Glycol

An Experimental and Theoretical Study of the Long-Lived Radical Cation of CH₃OCH₂CH₂OH

Contact Info

Product

Resources

About

Reversible tautomerization of radical cations. Photoionization of 2-methoxyethanol and 3-methoxy-1-propanol

Cited by 19 publications

References 2 publications

Observation of low‐temperature chemistry products in laminar premixed low‐pressure flames by molecular‐beam mass spectrometry

Observation of low‐temperature chemistry products in laminar premixed low‐pressure flames by molecular‐beam mass spectrometry

IR Spectroscopic Investigation on Isomerization of Ionized Ethylene Glycol

An Experimental and Theoretical Study of the Long-Lived Radical Cation of CH3OCH2CH2OH

Contact Info

Product

Resources

About

An Experimental and Theoretical Study of the Long-Lived Radical Cation of CH₃OCH₂CH₂OH