Comparison of Unimolecular Decomposition Pathways for Carboxylic Acids of Relevance to Biofuels

Clark, Jared; Nimlos, Mark R.; Robichaud, David J.

doi:10.1021/jp4095485

Cited by 36 publications

(40 citation statements)

References 69 publications

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“…19 Ketene 3 19,20 has been reported experimentally, 21 while 4 may have been detected, 19 and substituted derivatives of 4 are known. 22 The formation of 4 by the dehydration of 3-butynoic acid has also been studied computationally, 23 as has the structure of isomer 5.…”

Section: Structure Bonding and Spectroscopymentioning

confidence: 99%

“…Computations have been used to study the dehydration of unsaturated acids such as 70 forming the extended ketene 71, 67 as well as of other unsaturated acids to the corresponding ketenes. 67 In a separate investigation dehydration of the dienyl acid 72 to the vinyl extended ketene 73 was included (Scheme 36).…”

mentioning

confidence: 99%

“…67 In a separate investigation dehydration of the dienyl acid 72 to the vinyl extended ketene 73 was included (Scheme 36). Flash vacuum pyrolysis of N-(2-pyridyl)acetamides 78 generates ketenes 79 by elimination, and these are trapped by argon matrix isolation of the products, with characterization of the ketene products by IR absorption between 2106 and 2156 cm -1 (Scheme 38).…”

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confidence: 99%

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Recent advances in ketene chemistry

Allen¹,

Tidwell²

2016

Arkivoc

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Recent advances in ketene chemistry are reviewed, including synthetic, mechanistic, and computational studies. Topics include ketene structure determination by experimental and theoretical methods, computational studies of bonding in ketenes, spectroscopic properties of ketenes, preparation and formation of ketenes including photochemical and thermal methods, the discovery and observation of ketenes in space, and ketene reactions. The last category includes decarbonylation, cycloadditions with carbon-carbon, carbon-nitrogen, and carbon-oxygen multiple bonds, addition of oxygen, nitrogen, and carbon nucleophiles, and electrophilic additions.

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Section: Structure Bonding and Spectroscopymentioning

confidence: 99%

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confidence: 99%

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confidence: 99%

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Recent advances in ketene chemistry

Allen¹,

Tidwell²

2016

Arkivoc

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“…One of the most promising methods for the conversion of biomass to hydrocarbons is through deoxygenation of fatty acids [7,9,10] . In the absence of a metal catalyst, pyrolysis of fatty acids proceeds via competing decarboxylation and dehydration pathways [11] . Pioneering work by Sabatier has shown that deoxygenation of carboxylic acids proceeds via either decarboxylation, dehydration with decarbonylation, or a combination of both, [12] illustrated by Eqs.…”

Section: Introductionmentioning

confidence: 99%

Gas‐Phase Models for the Nickel‐ and Palladium‐Catalyzed Deoxygenation of Fatty Acids

et al. 2020

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Using fatty acids as renewable sources of biofuels requires deoxygenation. While a number of promising catalysts have been developed to achieve this, their operating mechanisms are poorly understood. Here, model molecular systems are studied in the gas phase using mass spectrometry experiments and DFT calculations. The coordinated metal complexes [(phen)M(O2CR)]+ (where phen=1,10‐phenanthroline; M=Ni or Pd; R=CnH2n+1, n≥2) are formed via electrospray ionization. Their collision‐induced dissociation (CID) initiates deoxygenation via loss of CO2 and [C,H2,O2]. The CID spectrum of the stearate complexes (R=C17H35) also shows a series of cations [(phen)M(R’)]+ (where R’ < C17) separated by 14 Da (CH2) corresponding to losses of C2H4‐C16H32 (cracking products). Sequential CID of [(phen)M(R’)]+ ultimately leads to [(phen)M(H)]+ and [(phen)M(CH3)]+, both of which react with volatile carboxylic acids, RCO2H, (acetic, propionic, and butyric) to reform the coordinated carboxylate complexes [(phen)M(O2CR)]+. In contrast, cracking products with longer carbon chains, [(phen)M(R)]+ (R>C2), were unreactive towards these carboxylic acids. DFT calculations are consistent with these results and reveal that the approach of the carboxylic acid to the “free” coordination site is blocked by agostic interactions for R > CH3.

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“…In a more comprehensive study of the unimolecular reaction pathways for carboxylic acids of relevance to biofuels Clark et al 45 found that α,β-unsaturated acids, of which 2,4-pentadienoic acid is a member, were more prone to decarboxylation than dehydration in comparison to the analogous saturated acids. Their results for senecioic acid, (CH 3 ) 2 CCH−COOH, very closely match ours for 2,4-pentadienoic acid.…”

Section: -Methyl-2(3h)-furanone Skorianetz and Ohloffmentioning

confidence: 99%

Thermal Decomposition of 2(3H) and 2(5H) Furanones: Theoretical Aspects

et al. 2015

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The thermal decomposition reactions of 2(3H) and 2(5H) furanones and their methyl derivatives are explored. Theoretical calculations of the barriers, reaction enthalpies, and the properties of these and intermediate species are reported using the composite model chemistry CBS-QB3 and also the functional M06-2X allied to the 6-311++G(d,p) basis set. Thus, the bond dissociation enthalpies, ionization energies, and unimolecular chemical kinetic rate constants in the high-pressure limit were computed. We show that flow reactor experiments that intimated that heating the 2(3H) furanone converts it to the isomeric 2(5H) furanone occurs via a 1 → 2 H-transfer reaction to an open ring ketenoic aldehyde. The latter can then ring close to the other isomeric structure. The final products acrolein and carbon monoxide are only formed from 2(3H), and acrolein will further decompose to ethylene and CO. Comparable channels explain the interconversion of 5-methyl-2(3H) furanone to its 2(5H) isomer and to the formation of methyl vinyl ketone and CO. The influence of the methyl group at other positions on the ring is hardly of significance except in the case of 5-methyl-2(5H) furanone where a hydrogen atom transfer from the methyl group leads to the formation of a doubly unsaturated carboxylic compound, 2,4-pentadienoic acid. Studies of the UV photolysis of the parent compounds in both low-temperature inert argon matrices and in solution are broadly in accord with the thermal findings insofar as product formation is concerned and with our theoretical calculations. The dominant features of the early decomposition chemistry of these compounds are simple hydrogen transfer and simultaneous ring opening reactions, which do however result in some quite unusual species.

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Comparison of Unimolecular Decomposition Pathways for Carboxylic Acids of Relevance to Biofuels

Cited by 36 publications

References 69 publications

Recent advances in ketene chemistry

Recent advances in ketene chemistry

Gas‐Phase Models for the Nickel‐ and Palladium‐Catalyzed Deoxygenation of Fatty Acids

Thermal Decomposition of 2(3H) and 2(5H) Furanones: Theoretical Aspects

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