Energetics of C−Cl, C−Br, and C−I Bonds in Haloacetic Acids: Enthalpies of Formation of XCH2COOH (X=Cl, Br, I) Compounds and the Carboxymethyl Radical

Lagoa, Ana L. C.; Diogo, Hermı́nio P.; Dias, M. Pilar; Piedade, Manuel E. Minas da; Amaral, Luı́sa M.P.F.; Silva, Manuel A.V. Ribeiro da; Simões, José A. Martinho; Guedes, Rita C.; Cabral, Benedito J. Costa; Schwarz, Karsten; Epple, Matthias

doi:10.1002/1521-3765(20010119)7:2<483::aid-chem483>3.0.co;2-a

Cited by 23 publications

(19 citation statements)

References 42 publications

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“…Other reference BDEs were computed when possible from the ATcT enthalpies of formation database. − The Luo reference reports multiple BDE measurements based on a variety of experimental techniques including spectroscopy and kinetics studies. For instance, five D 298 s ranging from 93.9–98.7 kcal/mol are listed for H–CH 2 C(O)OH. − The Luo recommended value of 95.3 ± 2.9 kcal/mol from collision-induced dissociation was measured in 1994, while a value of 98.7 ± 0.8 kcal/mol from calorimetry was obtained later in 2001 . It is not obvious which of the five entries is the most accurate, so we note the full range of experimental data when validating computed energies.…”

Section: Validation and Benchmarking Of Mracpf2 Bdes For Small Acids ...mentioning

confidence: 99%

Accurate Bond Energies of Biodiesel Methyl Esters from Multireference Averaged Coupled-Pair Functional Calculations

2014

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Accurate bond dissociation energies (BDEs) are important for characterizing combustion chemistry, particularly the initial stages of pyrolysis. Here we contribute to evaluating the thermochemistry of biodiesel methyl ester molecules using ab initio BDEs derived from a multireference averaged coupled-pair functional (MRACPF2)-based scheme. Having previously validated this approach for hydrocarbons and a variety of oxygenates, herein we provide further validation for bonds within carboxylic acids and methyl esters, finding our scheme predicts BDEs within chemical accuracy (i.e., within 1 kcal/mol) for these molecules. Insights into BDE trends with ester size are then analyzed for methyl formate through methyl crotonate. We find that the carbonyl group in the ester moiety has only a local effect on BDEs. C═C double bonds in ester alkyl chains are found to increase the strengths of bonds adjacent to the double bond. An important exception are bonds beta to C═C or C═O bonds, which produce allylic-like radicals upon dissociation. The observed trends arise from different degrees of geometric relaxation and resonance stabilization in the radicals produced. We also compute BDEs in various small alkanes and alkenes as models for the long hydrocarbon chain of actual biodiesel methyl esters. We again show that allylic bonds in the alkenes are much weaker than those in the small methyl esters, indicating that hydrogen abstractions are more likely at the allylic site and even more likely at bis-allylic sites of alkyl chains due to more electrons involved in π-resonance in the latter. Lastly, we use the BDEs in small surrogates to estimate heretofore unknown BDEs in large methyl esters of biodiesel fuels.

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Section: Validation and Benchmarking Of Mracpf2 Bdes For Small Acids ...mentioning

confidence: 99%

Accurate Bond Energies of Biodiesel Methyl Esters from Multireference Averaged Coupled-Pair Functional Calculations

2014

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“…Thus, the nature of the halogenated substituents plays a key role in the reactivity toward HDH, overall if monochlorinated and monobrominated HAAs are compared. Although there is some debate about the influence factors in the HDH reactivity, particularly in the aromatic and saturated compounds, the HAAs are remarkably affected by the C-X strength bonds. , In this sense, the higher HDH activity of MBAA can be attributed to the lower C-Br strength bond according to the C-X bond dissociation energy values of the haloacetic acids (XCH 2 COOH): C–H (413 kJ mol –1 ) > C–Cl (311 kJ mol –1 ) > C–Br (257 kJ mol –1 ) > C–I (198 kJ mol –1 ) …”

Section: Resultsmentioning

confidence: 54%

Catalytic Hydrodehalogenation of Haloacetic Acids: A Kinetic Study

Nieto-Sandoval

Gomez‐Herrero

Morabet

et al. 2020

Ind. Eng. Chem. Res.

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Haloacetic acids (HAAs) are undesired halogenated byproducts commonly generated upon oxidation treatments carried out in drinking water treatment plants. In this work, the removal of a representative group of these hazardous species (monochloroacetic acid, dichloroacetic acid, trichloroacetic acid, monobromoacetic acid, dibromoacetic acid, and bromochloroacetic acid) by catalytic hydrodehalogenation (HDH) was investigated and kinetic models were accordingly developed. Complete dehalogenation of all these pollutants (0.05 mmol L–1) was achieved using a Pd/Al2O3 catalyst (0.5 g L–1), although it was found that their reactivity depended on the nature and number of halogen substituents present in the HAA molecule. In general, bromoacetic acids showed higher reactivity than the chlorinated ones, which was attributed to the lower C-X bond dissociation energy. On the other hand, while the chloroacetic acid reactivity increased with the chlorination degree of the molecule, particularly from one to two Cl substituents, the bromoacetic acids did not show higher reaction rates with the increase in Br substituents. Based on the results obtained, different reaction pathways, via stepwise and/or concerted reactions, were proposed for the HDH of the HAAs. Consistent with those pathways, kinetic models were also developed, which allowed describing successfully the experimental data.

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“…This value, together with Δ f (H, g) = 217.998 ± 0.006 kJ·mol -1 , Δ f (Cl, g) = 121.301 ± 0.008 kJ·mol -1 , and the standard enthalpies of formation of Δ f [XCH(CH 3 )COOH, g] (X = H, Cl) indicated above, yield the bond dissociation enthalpies DH °[H−CH(CH 3 )COOH] = 380.7 ± 3.9 kJ·mol -1 and DH °[Cl−CH(CH 3 )COOH] = 298.0 ± 3.2 kJ·mol -1 . These values are compared in Table with the corresponding C−H and C−Cl bond dissociation enthalpies in XCH 2 COOH, XCH 3 , XC 2 H 5 , XCH 2 Cl, XCH(CH 3 )Cl, XCHCH 2 , and XC 6 H 5 (X = H, Cl) quoted or calculated from the literature. , The order DH °(C−H) > DH °(C−Cl) is observed for the carboxylic acids and all other RX compounds in Table (Figure ). Comparison of DH °[X−CH(CH 3 )COOH] and DH °[X−CH 2 COOH] (X = H, Cl) indicates that the replacement of a hydrogen of the CH 2 group of XCH 2 COOH by a methyl group leads to a decrease of both the C−H and C−Cl bond dissociation enthalpy.…”

Section: Resultsmentioning

confidence: 99%

“…A considerable number of applications of halocarboxylic acids in laboratory synthesis and in industry are related to reactions in which the carbon−halogen bond is cleaved. , Among the halocarboxylic acids, the chloro derivatives are by far the most widely used. Surprisingly, very little information exists on the energetics of the carbon−chlorine bond in chlorocarboxylic acids, as well as on the enthalpies of formation of the acids themselves − and of the radicals formed upon cleavage of the C−Cl bond. ,− These data are usually very helpful in the rationalization of the observed reactivity trends and in devising strategies for the synthesis of new compounds. In addition, they are important to model the pyrolysis , and the atmospheric chemistry of chlorocarboxylic acids.…”

Section: Introductionmentioning

confidence: 99%

“…These two topics have become particularly relevant in recent years in relation to the environmental problems associated with the incineration of chlorinated organic compounds and with the suggestion that industrial sources of chlorine lead to the depletion of the ozone layer . We have recently applied a combination of experimental (combustion calorimetry, differential scanning calorimetry, and vapor pressure versus temperature measurements) and computational chemistry (density functional theory, DFT) methods to study the energetics of chloro-, bromo-, and iodoacetic acids and of the carboxymethyl radical . Here, these studies are extended to chloropropionic acid and the 1-carboxyethyl radical.…”

Section: Introductionmentioning

confidence: 99%

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Energetics of the C−Cl Bond in CH₃CH(Cl)COOH. Enthalpy of Formation of (S)-(−)-2-Chloropropionic Acid and of the 1-Carboxyethyl Radical^,

Lagoa¹,

Diogo²,

Piedade³

et al. 2002

J. Phys. Chem. A

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The energetics of the C-Cl bond in 2-chloropropionic acid was investigated by using a combination of experimental and theoretical methods. The standard molar enthalpy of formation of liquid (S)-(-)-2chloropropionic acid, at 298.15 K, was determined as ∆ f H°m(C 3 H 5 O 2 Cl, l) ) -( 534.6 ( 1.1) kJ‚mol -1 , by rotating-bomb combustion calorimetry. The corresponding enthalpy of vaporization, ∆ vap H°m(C 3 H 5 O 2 Cl) ) (64.9 ( 0.5) kJ‚mol -1 , was also obtained from vapor pressure versus temperature measurements by the transpiration method, leading to ∆ f H°m(C 3 H 5 O 2 Cl, g) ) -(469.7 ( 1.2) kJ‚mol -1 . This value, together with the enthalpy of the isodesmic and isogyric gas-phase reaction CH 3 CH(X)COOH(g) + C 2 H 5 (g) f CH 3 CHCOOH(g) + C 2 H 5 X(g) (X ) H, Cl) predicted by density functional theory calculations and other auxiliary data, was used to derive the enthalpy of formation of the gaseous 1-carboxyethyl radical as ∆ f H°m[CH(CH 3 )COOH, g] ) -( 293( 3) kJ‚mol -1 , from which DH°[H-CH(CH 3 )COOH] ) 380.7 ( 3.9 kJ‚mol -1 and DH°[Cl-CH(CH 3 )COOH] ) 298.0 ( 3.2 kJ‚mol -1 were obtained. These values are compared with the corresponding C-H and C-Cl bond dissociation enthalpies in XCH 2 COOH, XCH 3 , XC 2 H 5 , XCH 2 -Cl, XCH(CH 3 )Cl, XCHdCH 2 , and XC 6 H 5 (X ) H, Cl). The order DH°(C-H) > DH°(C-Cl) is observed for the carboxylic acids and all other RX compounds. Comparison of DH°[X-CH(CH 3 )COOH] and DH°[X-CH 2 COOH] (X ) H, Cl) indicates that the replacement of a hydrogen of the CH 2 group of XCH 2 COOH by a methyl group leads to a decrease of both the C-H and C-Cl bond dissociation enthalpy. It is finally concluded that the major qualitative trends exhibited by the C-Cl bond dissociation enthalpies for the series of compounds addressed in this work can be predicted based on Pauling's electrostatic-covalent model. † Part of the special issue "Jack Beauchamp Festschrift". ‡ This article is dedicated to Professor Jack L. Beauchamp on the occasion of his 60th birthday.

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Energetics of C−Cl, C−Br, and C−I Bonds in Haloacetic Acids: Enthalpies of Formation of XCH2COOH (X=Cl, Br, I) Compounds and the Carboxymethyl Radical

Cited by 23 publications

References 42 publications

Accurate Bond Energies of Biodiesel Methyl Esters from Multireference Averaged Coupled-Pair Functional Calculations

Accurate Bond Energies of Biodiesel Methyl Esters from Multireference Averaged Coupled-Pair Functional Calculations

Catalytic Hydrodehalogenation of Haloacetic Acids: A Kinetic Study

Energetics of the C−Cl Bond in CH₃CH(Cl)COOH. Enthalpy of Formation of (S)-(−)-2-Chloropropionic Acid and of the 1-Carboxyethyl Radical^,

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Energetics of C−Cl, C−Br, and C−I Bonds in Haloacetic Acids: Enthalpies of Formation of XCH2COOH (X=Cl, Br, I) Compounds and the Carboxymethyl Radical

Cited by 23 publications

References 42 publications

Accurate Bond Energies of Biodiesel Methyl Esters from Multireference Averaged Coupled-Pair Functional Calculations

Accurate Bond Energies of Biodiesel Methyl Esters from Multireference Averaged Coupled-Pair Functional Calculations

Catalytic Hydrodehalogenation of Haloacetic Acids: A Kinetic Study

Energetics of the C−Cl Bond in CH3CH(Cl)COOH. Enthalpy of Formation of (S)-(−)-2-Chloropropionic Acid and of the 1-Carboxyethyl Radical,

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Energetics of the C−Cl Bond in CH₃CH(Cl)COOH. Enthalpy of Formation of (S)-(−)-2-Chloropropionic Acid and of the 1-Carboxyethyl Radical^,