Reactions of Methylene. 2. Ketene and Carbon Dioxide

Kistiakowsky, G. B.; Sauer, Kenneth

doi:10.1021/ja01538a013

Cited by 39 publications

(17 citation statements)

References 7 publications

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“…-Lactones were generated from the reaction of carbenes with carbon dioxide and examined by TRIR spectroscopy. (This method of -lactone generation has been used by Kistiakowsky and Sauer in the gas phase, 16 by Wheland and Bartlett in solution 12 and by both Milligan and Jacox 17 and Sander and co-workers 14,15 in lowtemperature matrices; Kovacs and Jackson reported a comprehensive computational investigation of the reaction of methylene with CO 2 . 18 ) Representative TRIR data for the reaction of phenylchlorocarbene (9), produced by laser photolysis of phenylchlorodiazirine (8), with CO 2 in dichloromethane are shown in Figs 1 and 2.…”

Section: Resultsmentioning

confidence: 99%

Time‐resolved IR studies of α‐lactones

Showalter

Toscano

2004

J of Physical Organic Chem

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epoc ABSTRACT: A series of -lactones were generated from the reaction of phenylchlorocarbene, 4-nitrophenylchlorocarbene, diphenylcarbene, bis(4-nitrophenyl)carbene and bis(4-methoxyphenyl)carbene with carbon dioxide and examined by nanosecond time-resolved infrared (TRIR) spectroscopy. Estimated second-order rate constants for the reaction of these carbenes with carbon dioxide indicate that more nucleophilic carbenes react at faster rates, in agreement with previous low-temperature matrix experiments. Spectral TRIR data confirms that the structure oflactones is dependent both on substituents at the -carbon and on solvent polarity, with electron-donating substituents and polar solvents favoring a zwitterionic ring-opened structure as opposed to the three-membered ring oxiranone form. B3LYP calculations using self-consistent reaction field (SCRF) methods also provide support for these experimental investigations.

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Section: Resultsmentioning

confidence: 99%

Time‐resolved IR studies of α‐lactones

Showalter

Toscano

2004

J of Physical Organic Chem

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“…Preliminary experiments in our laboratory, however, indicate that the reaction of )CH2 with COz is very slow even at higher temperatures and possibly proceeds exclusively via collisional activation of 'CH2 to 'CH2 [43]. From a product analysis using a GC/ MS combination as detection system it was concluded that HCHO is a product of reaction (8) in the gas phase, because the HCO fragment appeared in the mass spectrum [41]. The most detailed product analysis of reaction (8) was not carried out in the gas phase, but by IR-spectroscopic detection of the species arising after photolysis of CH2N2 in a solid C 0 2 matrix [42].…”

Section: The Reactions Of 'Ch2 With Co N 2 0 and Cosmentioning

confidence: 95%

Kinetics of the Reactions of CH₂(ã¹A¹) with CH₃C₂H, HCN, CO₂, N₂O and COS

Koch

Temps

Wagener

et al. 1990

Ber Bunsenges Phys Chem

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Carbenes / Chemical Kinetics / Elementary Reactions / RadicalsThe reactions of CH2(H'AI) with CH3C2H, HCN, C02, N 2 0 and COS are investigated at room temperature. CH2(B'AI) is generated by pulsed laser photolysis of CH2C0. Overall removal rate constants are derived from concentration profiles under first order reaction conditions using direct, time resolved LIF detection of CH2(B1A1). The second order rate constants are found in units of lot3 cm2/mol s to be 24, 18, 2.0, 3.8 and 20, respectively,-The contributions of physical quenching to the removal of CH2(B1AI) are determined by monitoring directly the formation of CH2(X3BI) with the LMR absorption technique. The branching ratios of collision induced intersystem crossing versus total consumption of 'CH2 are 0.24, 0.32, 0.67, 0.46 and 0.29 for the five reactants.Ber. Bunsenges. Phys. Chem. 94, 645-650 (1990) -0 VCH Verlagsgesellschaft mbH, D-6940 Weinheim, 1990.We consider the autocatalytic synthesis of MDV-1 RNA by Q beta replicase, which proceeds by template-instructed replication. We predict the effect of a particular point mutation in the sequence on the overall doubling time and conjecture its role on the recognition step. The mutation considered destabilizes the folding of the internal recognition site. The theoretical analysis is based on the calculation of nonequilibrium re-folding events which occur in the RNA chains as they are being synthesized. Free-energy minima are irrelevant. In order to test the theoretical findings, we incubate both the natural template and the mutant simultaneously, in the presence of the replicase. The experiment reveals that the mutation facilitates the enzyme-template interaction, thus enhancing recognition. However, examining the exponential phase of the replication kinetics, where the enzyme is in large excess with respect to the RNA species, we can conclude that the mutant presents a larger overall doubling time, in good agreement with our theoretical findings.

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“…[23,74] They have also been proposed as intermediates in atmospheric oxidation reactions [75,76] in mass spectrometry, [77][78][79][80] and as products of the reaction of carbenes with CO 2 . [81][82][83][84][85] Despite being highly reactive, α-lactones have been investigated spectroscopically by using matrix isolation, [82][83][84] gas phase, [86] and solution-phase time-resolved IR. [85] There has long been a discussion regarding the electronic structure of α-lactones, and whether they are best considered to be cyclic, canonical structures [56,[58][59][60] or zwitterionic, [55] although those discussions generally relate to the structure in solution.…”

Section: Dissociation Of the α-Lactonementioning

confidence: 99%

Mass spectrometric study of the decomposition pathways of canonical amino acids and α‐lactones in the gas phase

Koirala

Kodithuwakkuge

Wenthold

2015

J of Physical Organic Chem

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The dissociation pathways of a gas‐phase amino acid with a canonical (non‐zwitterionic) α‐amino acid moiety are studied by using mass spectrometry. Investigation of the canonical amino acid moiety is possible because the ionized amino acid, a sulfonated phenylalanine, has a charge center that is separated from the amino acid, and dissociation occurs by charge‐remote fragmentation. The amino acid is found to dissociate only by loss of NH3 upon collision‐induced dissociation to form a substituted α‐lactone. The dissociation is consistent with what has been observed previously upon pyrolysis of other α‐substituted carboxylic acids. Decarboxylation, which has also been reported previously for amino acid pyrolysis, is not observed, likely because the product would be a high‐energy, ammonium ylide. The resulting α‐lactone is found to undergo dissociation by decarbonylation to give an aldehyde, and by loss of CO2. Decarboxylation is calculated to occur through a transition state involving hydride shift coupled with lactone ring‐opening. The transition state is found to be stabilized by the negative charge, and therefore, decarboxylation is more favorable for anions. The results show that remote ionic groups can be used as mostly inert charge carriers to enable mass spectrometry to be used to investigate the gas‐phase physical and chemical properties of different types of functional groups, including amino acids. Copyright © 2015 John Wiley & Sons, Ltd.

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Reactions of Methylene. 2. Ketene and Carbon Dioxide

Cited by 39 publications

References 7 publications

Time‐resolved IR studies of α‐lactones

Time‐resolved IR studies of α‐lactones

Kinetics of the Reactions of CH₂(ã¹A¹) with CH₃C₂H, HCN, CO₂, N₂O and COS

Mass spectrometric study of the decomposition pathways of canonical amino acids and α‐lactones in the gas phase

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Reactions of Methylene. 2. Ketene and Carbon Dioxide

Cited by 39 publications

References 7 publications

Time‐resolved IR studies of α‐lactones

Time‐resolved IR studies of α‐lactones

Kinetics of the Reactions of CH2(ã1A1) with CH3C2H, HCN, CO2, N2O and COS

Mass spectrometric study of the decomposition pathways of canonical amino acids and α‐lactones in the gas phase

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Kinetics of the Reactions of CH₂(ã¹A¹) with CH₃C₂H, HCN, CO₂, N₂O and COS