Birge–Sponer Estimation of the C–H Bond Dissociation Energy in Chloroform Using Infrared, Near-Infrared, and Visible Absorption Spectroscopy. An Experiment in Physical Chemistry

Myrick, Michael L.; Greer, Ashley; Nieuwland, Alexander A.; Priore, Ryan J.; Scaffidi, Jonathan; Andreatta, D.; Colavita, Paula E.

doi:10.1021/ed085p1276

Cited by 11 publications

(8 citation statements)

References 2 publications

(3 reference statements)

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“…The best series of calculated Δ f H values can be included in the databases needed to establish the correct identification of isomeric structures by Diff‐MS. In this way, mass spectrometry can be used as an attractive, simple and precise approach to monitor quantum‐chemical calculations, in a similar way to that demonstrated for other techniques, such as calorimetry, thermal analysis, NMR, IR, UV–VIS, and Raman spectroscopy …”

Section: Resultsmentioning

confidence: 93%

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Structural identification by differential mass spectrometry as a criterion for selecting the best quantum chemical calculation of formation enthalpy for tetrachlorinated biphenyls

Dincă

2012

Rapid Comm Mass Spectrometry

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RATIONALE The assignment of correct structures for isomers with similar mass spectra (e.g. polyhalogenated aromatic compounds) is not always successful when spectral libraries alone are employed or, even worse, when the compounds are not present in commercial spectral libraries. METHODS We present a computational method based on differential mass spectrometry (Diff‐MS) for the validation of formation enthalpy (ΔfH) series calculated using quantum chemistry for the fragments produced in electron ionization (EI)‐MS. The method simulates the chemical structure identification (CSI) of isomers with similar mass spectra using differential mass spectra and ΔfH series. The best ΔfH values were those from which the correct structures could be derived. RESULTS We have used six tetrachlorinated biphenyl isomers (TeCBs 44, 46, 52, 66, 74, 77). Their EI mass spectra were acquired at 70 eV and, for the principal ions, five series of ΔfH values were computed by the semi‐empirical methods, AM1, MINDO3, MNDO, PM3, and RM1. The generation of differential mass spectra and the correlation with the ΔfH series for the calculation of probabilities from the list of structural assignments were carried out with the ordering algorithm (ORD) of the CSI‐Diff‐MS Data Analysis 3.1.1 program. CONCLUSIONS Intelligent software, used for structural elucidation based on MS and QCC, was employed to select the best values of the formation enthalpies of TeCBs. The advantages and disadvantages of the semi‐empirical methods for the calculation of ΔfH values for different TeCB ions are critically presented. The best semi‐empirical methods were RM1, AM1 and MINDO3, which can be used to calculate the ΔfH database necessary to identify TeCB isomers. This approach allowed the correct assignment of structures for isomers with very similar mass spectra and demonstrated the reliability of the correlation between differential mass spectra and the formation enthalpies of the fragment ions. Copyright © 2012 John Wiley & Sons, Ltd.

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Section: Resultsmentioning

confidence: 93%

“…In this way, mass spectrometry can be used as an attractive, simple and precise approach to monitor quantum-chemical calculations, in a similar way to that demonstrated for other techniques, such as calorimetry, thermal analysis, NMR, IR, UV-VIS, and Raman spectroscopy. [18,19]…”

Section: Computing Performances Of δ F H For Various Tecb Congenersmentioning

confidence: 99%

Structural identification by differential mass spectrometry as a criterion for selecting the best quantum chemical calculation of formation enthalpy for tetrachlorinated biphenyls

Dincă

2012

Rapid Comm Mass Spectrometry

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“…44 As regards the C-H stretching, anharmonicity is estimated to be around 100-200 cm −1 for many organic molecules. 45,46 The very large anharmonicity of the C-H, N-H and O-H stretching modes can be estimated by taking advantage of their independence from the other normal modes. [33][34][35]39 A scheme has been implemented in the Crystal code that solves numerically the one-dimensional Schrödinger equation when the potential energy, evaluated for a set of 7 points along the C-H coordinate, is fitted with a sixth order polynomial.…”

Section: The Anharmonicity Of the C-h Stretching Modementioning

confidence: 99%

The characterization of the VN H defects in diamond through the infrared vibrational spectrum. A quantum mechanical investigation

Salustro

Gentile

Erba

et al. 2018

Carbon

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The six possible VNxHy defects in diamond (a vacancy surrounded by x = 1 to 3 a vacancy surrounded by x=1 to 3 nitrogens and y=1 to 4-x hydrogens) are investigated at the quantum mechanical level by using the periodic supercell approach (64 atoms), an all electron Gaussian-type basis set, and hybrid functionals. It turns out that steric hindrance and short range repulsion is not such to prevent hydrogen atoms (up to 3 in VNH3) from fitting in the V cavity and saturating the dangling bonds of the carbon atoms first neighbors of the vacancy. All the investigated systems present specific IR spectra, with bending and stretching peaks above the nearly continuous band (from 400 to about 1340 cm −1 ) resulting from the perturbation of the perfect diamond spectrum by the vacancy and the nitrogen substitutions. These peaks, ranging from 1340 to 1700 cm −1 (bending; data refer to the harmonic approximation) and from 3100 to nearly 4000 cm −1 (stretching), might be considered fingerprints of the various defects. The C-H anharmonicity, evaluated numerically, turns out to be very sensitive to the N and H load, ranging from -202 cm −1 (red shift of the triplet state of VNH) to +57 cm −1 (blue shift of the symmetric stretching in VNH3).

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“…For the O-H stretching, the anharmonicity can reach 200 cm −1 , or even more when O-H is involved in strong hydrogen bonds 29,32 . As regards the C-H stretching, anharmonicity is estimated to be around 120-140 cm −1 for many organic molecules 43,44 .…”

Section: A Harmonic Frequencies and The Ir And Raman Spectramentioning

confidence: 99%

Vibrational spectroscopy of hydrogens in diamond: a quantum mechanical treatment

Gentile

Salustro

Desmarais

et al. 2018

Phys. Chem. Chem. Phys.

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The electronic and vibrational features of the VH (n = 1 to 4) family of defects in diamond (hydrogen atoms saturating the dangling bonds of the atoms surrounding a vacancy) are investigated at the quantum mechanical level by using the periodic supercell approach, an all electron Gaussian type basis set, hybrid functionals, and the Crystal code. Most of the results have been collected for supercells containing 64 atoms; however, in order to explore the effect of the defect concentration on both the IR and Raman spectra, supercells containing 216, 512 and 1000 atoms have also been considered in the VH case. For each system, all the possible spin states are considered; their relative stability, band structure, charge and spin density distributions are thoroughly described. All the investigated systems present specific IR and Raman spectra, with vibrational spectroscopic features that can in principle be used as fingerprints for their characterization. This is particularly true for the C-H stretching, that ranges between 2500 and 4400 cm. The stretching modes are strongly affected by anharmonicity that has been evaluated in this work; it turns out to be extremely sensitive to the H load and spin state of the system, and ranges from -335 cm for VH to +85 cm for VH. All of the investigated defects have very low C-H stretching IR intensity, so that they essentially appear as silent, the exception being VH. The situation is different for the Raman spectra: the stretching modes of all defects do have similar large intensity; unfortunately here it is the experimental evidence that is lacking.

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Birge–Sponer Estimation of the C–H Bond Dissociation Energy in Chloroform Using Infrared, Near-Infrared, and Visible Absorption Spectroscopy. An Experiment in Physical Chemistry

Cited by 11 publications

References 2 publications

Structural identification by differential mass spectrometry as a criterion for selecting the best quantum chemical calculation of formation enthalpy for tetrachlorinated biphenyls

Structural identification by differential mass spectrometry as a criterion for selecting the best quantum chemical calculation of formation enthalpy for tetrachlorinated biphenyls

The characterization of the VN H defects in diamond through the infrared vibrational spectrum. A quantum mechanical investigation

Vibrational spectroscopy of hydrogens in diamond: a quantum mechanical treatment

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