Absolute rates of recombination and disproportionation of dimethylaminyl radicals

Lazarou, Yannis G.; Papagiannakopoulos, Panos

doi:10.1021/j100138a012

Cited by 7 publications

(6 citation statements)

References 3 publications

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“…In the work reported here, we generated the amino(hydroxy)methyl radical ( 1 ) which is the prototypical hydrogen atom adduct to the amide bond. In addition to being a model for ECD, radical 1 belongs to the class of alkyl radicals carrying electron-donating substituents that have been of keen interest to experimental and computational chemists …”

Section: Introductionmentioning

confidence: 99%

Hydrogen Atom Adducts to the Amide Bond. Generation and Energetics of the Amino(hydroxy)methyl Radical in the Gas Phase

Syrstad

Tureček

2001

J. Phys. Chem. A

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The amino(hydroxy)methyl radical (1) represents the simplest model for hydrogen atom adducts to the amide bond. Radical 1 was generated in the gas phase by femtosecond electron transfer to protonated formamide and found to be stable on the microsecond time scale. The major unimolecular dissociation of 1 was loss of the hydrogen atom from the hydroxyl group. Losses of hydrogen atoms from the CH and NH2 groups in 1 were less abundant. RRKM calculations on the G2(MP2), G2, and CCSD(T)/aug-cc-pVTZ potential energy surfaces predicted preferential loss of the hydroxyl hydrogen atom, in qualitative agreement with experiment. Bimolecular reactions of hydrogen atoms with formamide were predicted by calculations to prefer H atom abstraction from the H−C bond forming H2 and NH2CO•. This reaction was calculated to be 43 kJ/mol exothermic and had to overcome an activation energy barrier of 28.5 kJ/mol. Hydrogen atom additions to the carbon and oxygen termini of the carbonyl group in formamide had similar activation energies, 51 and 49 kJ/mol, respectively. H atom addition to the C-terminus producing the aminomethyloxy radical (6) was calculated to be 2 kJ/mol endothermic.

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Section: Introductionmentioning

confidence: 99%

Hydrogen Atom Adducts to the Amide Bond. Generation and Energetics of the Amino(hydroxy)methyl Radical in the Gas Phase

Syrstad

Tureček

2001

J. Phys. Chem. A

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“…Since decomposition of 7 affords two equivalents of dimethylamino radical 3 (Scheme 2), the critical reactive intermediate from cleavage of either the W-N1 or N1-N2 bond of 2 (Scheme 1) will be 3. radicals can yield methylmethyleneimine (8) and dimethylamine (9) (18)(19)(20) or tetramethylhydrazine (7) by disproportionation or recombination, respectively (16,21) (Scheme 3, path a). Since bimolecular reactions of radicals have low activation energies, products of recombination and disproportion are expected to be formed in comparable quantities (22). In addition to these reactions, dimethylaminyl radical undergoes dissociation into methylnitrene and methyl radical (Scheme 3, path b).…”

Section: Dft Calculationsmentioning

confidence: 99%

Analysis of the Homogeneous Thermal Decomposition of the Tungsten Dimethylhydrazido Complex Cl₄(CH₃CN)W(NNMe₂) Using In Situ Raman Spectroscopy and DFT Calculations

Lee

Kim

et al. 2010

ECS Trans.

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The gas-phase decomposition pathways of the tungsten dimethylhydrazido complexes Cl 4 (RCN)W(NNMe 2 ) (1a: R = CH 3 ; 1b: R = Ph), precursors for single source deposition of WN x C y , were investigated using a combination of experiments and calculations. Raman scattering experiments were performed in an impinging-jet, up-flow, aerosol-assisted CVD reactor to identify reaction intermediates.Density Functional Theory calculations (B3LYP/LanL2DZ) were used to estimate Raman active frequencies and explore the reaction surface.Dimethylamine and methylmethyleneimine, products from N-N cleavage of the hydrazido ligand, were observed under deposition conditions and identified by comparison with previously reported Raman shifts and calculated frequencies.

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“…Substituted alkyl radicals have been of interest to both experimentalists 1,2 and computational chemists. [3][4][5] Lossing, Holmes and co-workers have measured ionization energies of a number of substituted alkyl radicals [6][7][8][9][10][11][12] and neutralization-reionization mass spectrometry has been used by John Holmes' group and others to generate and characterize various substituted methyl radicals, for example, CH 2 OH and CH 2 NH 2 , 13 CH 2 Cl, 14 CHCl 2 and CHFCl, 15 CH 2 NO 2 , 16 HO-CH-OH, 17 H 2 N-CH-OH, 18 C(OH) 3 19 and CH 3 NH-C(CH 3 )-OH.…”

Section: Introductionmentioning

confidence: 99%

Electron-Rich Radicals by Neutralization—Reionization Mass Spectrometry. Generation, Dissociations and Energetics of the Hydrogen Atom Adduct to Acetamide

Tam

Syrstad

Chen

et al. 2004

Eur J Mass Spectrom (Chichester)

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Protonated acetamide exists as two planar conformers, the more stable anti-form (anti-1(+)) and the syn-form (syn-1(+)), DeltaG(degree) (298) (anti-->syn) = 10.8 kJ mol(-1). Collisional neutralization of 1(+) produces 1-hydroxy-1-amino-1-ethyl radicals (anti-1 and syn-1) which in part survive for 3.7 micros. The major dissociation of 1 is loss of the hydroxyl hydrogen atom (approximately 95%) which is accompanied by loss of one of the methyl hydrogen atoms (approximately 3%) and loss of the methyl group (approximately 2%). The most favorable dissociation of the OH bond is calculated to be only 34 kJ mol(1) endothermic but requires 88 kJ mol(-1) in the transition state. Other dissociations of 1, e.g., loss of one of the amide hydrogens, methyl hydrogens, and loss of ammonia are calculated to proceed through higher- energy transition states and are not kinetically competitive if proceeding from the ground doublet electronic state of 1. The unimolecular dissociation of 1 following collisional electron transfer is promoted by large Franck-Condon effects that result in 8090 kJ mol(-1) vibrational excitation in the radicals. Radicals 1 are calculated to exoergically abstract hydrogen atoms from acetamide in water, but not in the gas phase. The different reactivity is due to solvent effects that favor the products, (.)CH(2)CONH(2) and CH(3)CH(OH)NH(2), over the reactants.

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Absolute rates of recombination and disproportionation of dimethylaminyl radicals

Cited by 7 publications

References 3 publications

Hydrogen Atom Adducts to the Amide Bond. Generation and Energetics of the Amino(hydroxy)methyl Radical in the Gas Phase

Hydrogen Atom Adducts to the Amide Bond. Generation and Energetics of the Amino(hydroxy)methyl Radical in the Gas Phase

Analysis of the Homogeneous Thermal Decomposition of the Tungsten Dimethylhydrazido Complex Cl₄(CH₃CN)W(NNMe₂) Using In Situ Raman Spectroscopy and DFT Calculations

Electron-Rich Radicals by Neutralization—Reionization Mass Spectrometry. Generation, Dissociations and Energetics of the Hydrogen Atom Adduct to Acetamide

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Absolute rates of recombination and disproportionation of dimethylaminyl radicals

Cited by 7 publications

References 3 publications

Hydrogen Atom Adducts to the Amide Bond. Generation and Energetics of the Amino(hydroxy)methyl Radical in the Gas Phase

Hydrogen Atom Adducts to the Amide Bond. Generation and Energetics of the Amino(hydroxy)methyl Radical in the Gas Phase

Analysis of the Homogeneous Thermal Decomposition of the Tungsten Dimethylhydrazido Complex Cl4(CH3CN)W(NNMe2) Using In Situ Raman Spectroscopy and DFT Calculations

Electron-Rich Radicals by Neutralization—Reionization Mass Spectrometry. Generation, Dissociations and Energetics of the Hydrogen Atom Adduct to Acetamide

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Analysis of the Homogeneous Thermal Decomposition of the Tungsten Dimethylhydrazido Complex Cl₄(CH₃CN)W(NNMe₂) Using In Situ Raman Spectroscopy and DFT Calculations