Evaluation of N–H bond dissociation energies in some amides using ab initio and density functional methods

Kaur, Deepinder; Kaur, Rupinder

doi:10.1016/j.theochem.2005.07.001

Cited by 26 publications

(17 citation statements)

References 36 publications

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“…BDE is calculated as the enthalpy change of the following reaction (1) in the gas phase at 298 K and 1 atm pressure [29][30][31][32][33][34][35][36][37][38]. Calculations were also performed using restricted open (RO) shell formalism at DFT method.…”

Section: Computational Detailsmentioning

confidence: 99%

A theoretical study on NH bond dissociation enthalpies of oxo, thio and seleno carbamates and their N-protonated and N-deprotonated species

Kaur

2008

Journal of Molecular Structure: THEOCHEM

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Section: Computational Detailsmentioning

confidence: 99%

A theoretical study on NH bond dissociation enthalpies of oxo, thio and seleno carbamates and their N-protonated and N-deprotonated species

Kaur

2008

Journal of Molecular Structure: THEOCHEM

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“…The backbone amide N -H was modeled by the dipeptide Ala-Ala. In the determination of β carbon C-H BDEs, appropriate small molecules with experimentally known BDEs were chosen as references as previously described [37] In addition, (CH 3 ) 3 CN -H, C 6 H 5 -H, and HCONHCH 3 were chosen as reference molecules to accurately model the BDEs of the amine N -H, tyrosyl C -H, and amide N -H radicals respectively [33][34][35].…”

Section: Bond Dissociation Energy (Bde) Calculationsmentioning

confidence: 99%

“…However, no unmodified z 4 ion is detected, suggesting that acetylation at the Nterminus does interfere. According to Scheme 1, N-terminal acetylation would require abstraction of an amide hydrogen, which is significantly less energetically favorable than an amine hydrogen (BDEs of 453 [35] and 383 kJ/mol, respectively). This explains the absence of the z 4 ion and also provides a rationale for why z ions are not generated throughout the peptide.…”

Section: Bold Downward Arrows Indicate Precursor Ionmentioning

confidence: 99%

Dissociation Chemistry of Hydrogen-Deficient Radical Peptide Anions

Moore

Sun

Hsu

et al. 2011

J. Am. Soc. Mass Spectrom.

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The fragmentation chemistry of anionic deprotonated hydrogen-deficient radical peptides is investigated. Homolytic photodissociation of carbon-iodine bonds with 266 nm light is used to generate the radical species, which are subsequently subjected to collisional activation to induce further dissociation. The charges do not play a central role in the fragmentation chemistry; hence deprotonated peptides that fragment via radical directed dissociation do so via mechanisms which have been reported previously for protonated peptides. However, charge polarity does influence the overall fragmentation of the peptide. For example, the absence of mobile protons favors radical directed dissociation for singly deprotonated peptides. Similarly, a favorable dissociation mechanism initiated at the N-terminus is more notable for anionic peptides where the N-terminus is not protonated (which inhibits the mechanism). In addition, collisional activation of the anionic peptides containing carbon-iodine bonds leads to homolytic cleavage and generation of the radical species, which is not observed for protonated peptides presumably due to competition from lower energy dissociation channels. Finally, for multiply deprotonated radical peptides, electron detachment becomes a competitive channel both during the initial photoactivation and following subsequent collisional activation of the radical. Possible mechanisms that might account for this novel collision-induced electron detachment are discussed.

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“…Earlier studies on NOH BDEs indicate that RO formalism give better results [10]. By following the comprehensive report of Scott and Radom [16], ZPE energies are scaled by 0.9135 at HF/6-31ϩG*, and these scaled zero point vibrational energy (ZPE) values are used for applying corrections to energies evaluated at MP2/6-31ϩG* theoretical level and by 0.9806 for the energies at B3LYP level.…”

Section: Computational Detailsmentioning

confidence: 99%

“…In a previous study, we analyzed the performance of ab initio and DFT methods for the evaluation of NOH BDE of some amides like HC(AO)NH 2 , CH 3 C(AO)NH 2 , NH 2 C(AO)NH 2 , and HC(AO)NHCH 3 [10]. The aim of the present work is to extend the studies to a series of amides and analyze the substituent effect on the NOH BDE of amines and amides.…”

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confidence: 99%

Substituent effect on NH bond dissociation enthalpies of amines and amides: A theoretical study

Kaur

Kohli

2008

Int J of Quantum Chemistry

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NOH bond dissociation enthalpies for the substituted ammonia, amine, amides, and their thio-and seleno-analogs have been studied employing ab initio and density functional methods. The orbital interactions involving lone pair of electrons on nitrogen and substituent, electrostatic interactions, spin delocalization, and hydrogen bonding are the important factors affecting the stability of the molecule and the radical. The molecule stabilization effect and radical stabilization effect have been calculated using isodesmic reactions in order to analyze the effect of substituent on the stabilization of the molecule and the radical.

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Evaluation of N–H bond dissociation energies in some amides using ab initio and density functional methods

Cited by 26 publications

References 36 publications

A theoretical study on NH bond dissociation enthalpies of oxo, thio and seleno carbamates and their N-protonated and N-deprotonated species

A theoretical study on NH bond dissociation enthalpies of oxo, thio and seleno carbamates and their N-protonated and N-deprotonated species

Dissociation Chemistry of Hydrogen-Deficient Radical Peptide Anions

Substituent effect on NH bond dissociation enthalpies of amines and amides: A theoretical study

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