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Dos Santos PR, Pereira CMP, Ritter M, de Paula FR, Moura S. Relationship between Hammett's parameters and in silico density functional with tandem mass ESI-CID fragmentation: Dihydropyridines as prototypes. JOURNAL OF MASS SPECTROMETRY : JMS 2018; 53:195-202. [PMID: 29194867 DOI: 10.1002/jms.4050] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/10/2017] [Revised: 10/06/2017] [Accepted: 11/21/2017] [Indexed: 06/07/2023]
Abstract
Over the years, with the instrumental analysis evolution, the relationships between the carried-out results with the data of theoretical analysis in silico and the Hammett's parameters have been reported. They have been very useful for chemical characterization of small organic molecules. Thus, this work aims at showing the feasibility and limitations for Hammett's and density functional theory applications in electrospray ionization-collision-induced dissociation (ESI-CID) fragmentation provision. For this, 13 dihydropyrimidinones para, meta, and orto monosubstituted were studied using ESI and CID in positive mode. As a result, it was observed that the main fragmentation includes the isocyanate and ethanol loses at low energy. Nevertheless, at higher energies, radical ions formed by McLafferty rearrangement were observed. The Hammett plots were correlated fragmentation profiles, showing good linearity for the [M + H]+ , which does not occur to radical ions and carbocation's. These tendencies had demonstrated that the stability of protonate and activation energy of secondary ions changes with the pKa. The density functional theory studies indicated that, both nitrogen atoms in the dihydropyrimidinone's prototypes are capable of being protonated. However, the activation energy of fragmentation products is not changed. Therefore, this work has shown information, which can be useful to understand tandem mass spectrometry in ESI-CID conditions for small organic molecules series. This is the first step for normalization of fragmentation pathway.
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Affiliation(s)
- P R Dos Santos
- Laboratory of Natural and Synthetics Products, University of Caxias do Sul, Caxias do Sul, Brazil
| | - C M P Pereira
- Chemical Sciences, Pharmaceutical and Food Center, University of Pelotas, Brazil
| | - M Ritter
- Chemical Sciences, Pharmaceutical and Food Center, University of Pelotas, Brazil
| | - F R de Paula
- Laboratory of Drug Development and Quality Control, University Federal of Pampa, Brazil
| | - S Moura
- Laboratory of Natural and Synthetics Products, University of Caxias do Sul, Caxias do Sul, Brazil
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2
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Remya GS, Suresh CH. Assessment of the electron donor properties of substituted phenanthroline ligands in molybdenum carbonyl complexes using molecular electrostatic potentials. NEW J CHEM 2018. [DOI: 10.1039/c7nj04592a] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Molecular electrostatic potential analysis of substituent effects in phenanthroline ligands clearly suggests that the coordination strength of the ligand to a metal complex is highly predictable solely from the quantification of substituent effects.
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Affiliation(s)
- Geetha S. Remya
- Chemical Sciences and Technology Division, CSIR – National Institute for Interdisciplinary Science and Technology
- Thiruvananthapuram
- India
- Academy of Scientific & Innovative Research (AcSIR)
- India
| | - Cherumuttathu H. Suresh
- Chemical Sciences and Technology Division, CSIR – National Institute for Interdisciplinary Science and Technology
- Thiruvananthapuram
- India
- Academy of Scientific & Innovative Research (AcSIR)
- India
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3
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Böhm S, Exner O. Interaction of two functional groups through the benzene ring: Theory and experiment. J Comput Chem 2009; 30:1069-74. [DOI: 10.1002/jcc.21131] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
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Lepšík M, Srnec M, Hnyk D, Grüner B, Plešek J, Havlas Z, Rulíšek L. exo-Substituent effects in halogenated icosahedral (B12H122–) and octahedral (B6H62–) closo-borane skeletons: chemical reactivity studied by experimental and quantum chemical methods. ACTA ACUST UNITED AC 2009. [DOI: 10.1135/cccc2008189] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
The exo-substituent effects in halogenated icosahedral B12H122– (B12) and octahedral B6H62– (B6) closo-borane skeletons were studied both experimentally and theoretically. Firstly, the equilibrium geometries of exo-substituted B12 and B6 clusters were obtained using quantum chemical calculations at the MP2/def2-SVP level. A comparison with the available X-ray crystallographic data revealed a very good agreement between the theoretical and experimental values. Secondly, other descriptors of the molecular structure of these borane compounds – 11B NMR chemical shifts – were experimentally determined and compared with the calculated values obtained by the ab initio/GIAO approach at the MP2/def2-TZVP level. It was shown that the calculated data reproduced the experiment very closely. Thirdly, we investigated experimentally the halogenation reactions of B12 and attempted to explain the observed ratios between the two obtained disubstituted products (meta/ortho ~ 4:1) by calculating their thermodynamic stabilities using the DFT/B3LYP method. These calculations showed the enhanced stability of the meta disubstituted B12 but did not explain why the para product had not been observed in the experiment. We thus turned our attention to the kinetic aspects of exo-substitution reactions by exploring the possible reaction pathways and transition states. In spite of the complexity of the plausible reaction mechanisms, reasonable agreement was obtained between the calculated activation barriers and the experimental observations concerning the halogenation reactions of the B6 and B12 molecules. It also allowed to exclude from considerations certain reaction pathways leading to the mono- and dihalogenated B12 and B6 species.
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Grisenti DL, Thomas WW, Turlington CR, Newsom MD, Priedemann CJ, VanDerveer DG, Wagenknecht PS. Emissive Chromium(III) Complexes with Substituted Arylethynyl Ligands. Inorg Chem 2008; 47:11452-4. [DOI: 10.1021/ic801376p] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- David L. Grisenti
- Department of Chemistry, Furman University, Greenville, South Carolina 29613, and Department of Chemistry, Clemson University, Clemson, South Carolina 29634-0973
| | - W. Walsh Thomas
- Department of Chemistry, Furman University, Greenville, South Carolina 29613, and Department of Chemistry, Clemson University, Clemson, South Carolina 29634-0973
| | - Christopher R. Turlington
- Department of Chemistry, Furman University, Greenville, South Carolina 29613, and Department of Chemistry, Clemson University, Clemson, South Carolina 29634-0973
| | - Matthew D. Newsom
- Department of Chemistry, Furman University, Greenville, South Carolina 29613, and Department of Chemistry, Clemson University, Clemson, South Carolina 29634-0973
| | - Christopher J. Priedemann
- Department of Chemistry, Furman University, Greenville, South Carolina 29613, and Department of Chemistry, Clemson University, Clemson, South Carolina 29634-0973
| | - Donald G. VanDerveer
- Department of Chemistry, Furman University, Greenville, South Carolina 29613, and Department of Chemistry, Clemson University, Clemson, South Carolina 29634-0973
| | - Paul S. Wagenknecht
- Department of Chemistry, Furman University, Greenville, South Carolina 29613, and Department of Chemistry, Clemson University, Clemson, South Carolina 29634-0973
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Sreeruttun RK, Ramasami P, Wannere CS, Simmonett AC, Schaefer HF. Pi and sigma-phenylethynyl radicals and their isomers o-, m-, and p-ethynylphenyl: structures, energetics, and electron affinities. J Phys Chem A 2008; 112:2838-45. [PMID: 18335906 DOI: 10.1021/jp0763329] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Molecular structures, energetics, vibrational frequencies, and electron affinities are predicted for the phenylethynyl radical and its isomers. Electron affinities are computed using density functional theory, -namely, the BHLYP, BLYP, B3LYP, BP86, BPW91, and B3PW91 functionals-, employing the double-zeta plus polarization DZP++ basis set; this level of theory is known to perform well for the computation of electron affinities. Furthermore, ab initio computations employing perturbation theory, coupled cluster with single and double excitations [CCSD], and the inclusion of perturbative triples [CCSD(T)] are performed to determine the relative energies of the isomers. These higher level computations are performed with the correlation consistent family of basis sets cc-pVXZ (X = D, T, Q, 5). Three electronic states are probed for the phenylethynyl radical. In C2v symmetry, the out-of-plane (2B1) radical is predicted to lie about 10 kcal/mol below the in-plane (2B2) radical by DFT methods, which becomes 9.4 kcal/mol with the consideration of the CCSD(T) method. The energy difference between the lowest pi and sigma electronic states of the phenylethynyl radical is also about 10 kcal/mol according to DFT; however, CCSD(T) with the cc-pVQZ basis set shows this energy separation to be just 1.8 kcal/mol. The theoretical electron affinities of the phenylethynyl radical are predicted to be 3.00 eV (B3LYP/DZP++) and 3.03 eV (CCSD(T)/DZP++//MP2/DZP++). The adiabatic electron affinities (EAad) of the three isomers of phenylethynyl, that is, the ortho-, meta-, and para-ethynylphenyl, are predicted to be 1.45, 1.40, and 1.43 eV, respectively. Hence, the phenylethynyl radical binds an electron far more effectively than the three other radicals studied. Thermochemical predictions, such as the bond dissociation energies of the aromatic and ethynyl C-H bonds and the proton affinities of the phenylethynyl and ethynylphenyl anions, are also reported.
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Affiliation(s)
- Raj K Sreeruttun
- Department of Chemistry, Faculty of Science, University of Mauritius, Republic of Mauritius, and Center for Computational Chemistry, University of Georgia, Athens, Georgia 30602, USA
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Exner O, Böhm S. Revision of the dual substituent parameter treatment using the DFT-calculated reaction energies. J PHYS ORG CHEM 2007. [DOI: 10.1002/poc.1177] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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Hoge B, Bader J. A qualitative scale for the electron withdrawing effect of substituted phenyl groups and heterocycles. J Fluor Chem 2007. [DOI: 10.1016/j.jfluchem.2007.04.007] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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9
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Exner O, Böhm S. Substituent Effects of the Alkyl Groups: Polarity vs. Polarizability. European J Org Chem 2007. [DOI: 10.1002/ejoc.200700004] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Böhm S, Exner O. Inductive effects in radicals calculated from DFT energies; substituted bicyclo[2.2.2]octan-1-yloxy radicals. J Comput Chem 2007; 28:1783-9. [PMID: 17405123 DOI: 10.1002/jcc.20694] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Energies of a series of 4-substituted 1-oxybicyclo[2.2.2]octan-1-yloxy radicals with 18 various substituents were calculated within the framework of the DFT theory at the levels UB3LYP/6-311+G(d,p)//UB3LYP/6-311+G(d,p) and UB3LYP/6-311++G(2df,p)//UB3LYP/6-311+G(d,p) and compared with similar series of the parent alcohols, their deprotonated and protonated forms calculated at the levels B3LYP/6-311+G(d,p)//B3LYP/6-311+G(d,p) and B3LYP/6-311++G(2df,p)//B3LYP/6-311+G(d,p). The two levels are of the same performance and both are sufficient for molecules of this type according to comparison with scarce experimental gas-phase acidities and basicities. The substituent effects were analyzed in terms of isodesmic equations. In addition to strong dependence on the substituent inductive effect, a slight dependence on the electronegativity of the first atom of the substituent was proven in certain cases. In all aspects, there is no qualitative difference between the effects on radicals and on similar closed shell species. Radicals behave as slightly electron deficient; the substituent effect is weaker than that on the ions but stronger than on neutral molecules.
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Affiliation(s)
- Stanislav Böhm
- Department of Organic Chemistry, Prague Institute of Chemical Technology, 16628 Praha 6, Czech Republic
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Zácek P, Dransfeld A, Exner O, Schraml J. 15N NMR chemical shifts of ring substituted benzonitriles. MAGNETIC RESONANCE IN CHEMISTRY : MRC 2006; 44:1073-80. [PMID: 16991110 DOI: 10.1002/mrc.1900] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
15N chemical shifts in an extensive series of para (15) and meta (15) as well as ortho (8) substituted benzonitriles, X-C6H4-CN, were measured in deuteriochloroform solutions, using three different methods of referencing. The standard error of the average chemical shift was less than 0.03 ppm in most cases. The results are discussed for both empirical correlations with substituent parameters and quantum chemical calculations. The 15N chemical shifts calculated at the GIAO/B3LYP/6-31 + G*//B3LYP/6-31 + G* level reproduce the experimental values well, and include nitrogen atoms in the substituent groups (range of 300 ppm with slope 0.98 and R = 0.998, n = 43). The 15N shifts in hydroxybenzonitriles are affected by interaction with the OH group. Therefore, these derivatives are excluded from the correlation analysis. The resultant 15N chemical shift correlates well with substituent constants, both in the simple Hammett or DSP relationships and the 13C substituent-induced chemical shifts of the CN carbon.
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Affiliation(s)
- Petr Zácek
- Institute of Chemical Process Fundamentals, Academy of Sciences of the Czech Republic, 16502, Prague 6, Czech Republic
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Fiedler P, Böhm S, Kulhánek J, Exner O. Acidity of ortho-substituted benzoic acids: an infrared and theoretical study of the intramolecular hydrogen bonds. Org Biomol Chem 2006; 4:2003-11. [PMID: 16688344 DOI: 10.1039/b601875k] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The structures of ortho-substituted benzoic acids with substituents bearing hydrogen atoms (OH, NH2, COOH and SO2NH2) were investigated by means of IR spectroscopy and of density functional theory at the B3LYP/6-311 + G(d,p) level. All possible conformations, hydrogen bonds, tautomeric forms and zwitterions were taken into consideration and particular attention was given to intramolecular H-bonds and their effect on acidity. Strong H-bonds in the anions of all four acids, were revealed by calculations. In three cases they were confirmed by the IR spectra of the tetrabutylammonium salts in tetrachloromethane solution, while the salt of 1,2-benzenedicarboxylic acid was not sufficiently soluble. The H-bonds are of different strengths but in all cases they are the main cause of the strengthened acidity of these acids in the gas phase and also in solution, although their effect is opposed by weaker H-bonds present in the undissociated acid molecules. The substituent effect on the acidity was evaluated in terms of isodesmic reactions, separately in the acid molecules and in the anions. While the acidity of the 2-OH and 2-NH2 acids is determined essentially by the H-bonds, that of the 2-COOH and 2-SO2NH2 acids is strengthened by the polar effect operating in the undissociated molecule in addition to the H-bond in the anion. The steric inhibition of resonance (SIR), estimated from model conformations with fixed torsional angles, is of little importance. This analysis goes significantly beyond the classical explanation obtained from the acidities in solution but essentially conforms with it.
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Affiliation(s)
- Pavel Fiedler
- Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, 166 10, Praha 6, Czech Republic
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Shorter J. Compilation and critical evaluation of structure-reactivity parameters and equations: Part 2. Extension of the Hammett σ scale through data for the ionization of substituted benzoic acids in aqueous solvents at 25 C (Technical Report). PURE APPL CHEM 1997. [DOI: 10.1351/pac199769122497] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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