scholarly journals Quantum Chemical Calculations on CHOP Derivatives—Spanning the Chemical Space of Phosphinidenes, Phosphaketenes, Oxaphosphirenes, and COP− Isomers

Molecules ◽  
2018 ◽  
Vol 23 (12) ◽  
pp. 3341 ◽  
Author(s):  
Alicia Rey ◽  
Arturo Espinosa Ferao ◽  
Rainer Streubel
Keyword(s):  
Potential Energy Surfaces ◽  
Chemical Space ◽  
Theoretical Calculations ◽  
Kinetic Energy Density ◽  
Ring Strain ◽  
Starting Point ◽  
Time Calculation ◽  
Bonding Properties ◽  
Anionic Ring ◽  
Energy Surfaces

After many decades of intense research in low-coordinate phosphorus chemistry, the advent of Na[OCP] brought new stimuli to the field of CHOP isomers and derivatives thereof. The present theoretical study at the CCSD(T)/def2-TZVPP level describes the chemical space of CHOP isomers in terms of structures and potential energy surfaces, using oxaphosphirene as the starting point, but also covering substituted derivatives and COP− isomers. Bonding properties of the P–C, P–O, and C–O bonds in all neutral and anionic isomeric species are discussed on the basis of theoretical calculations using various bond strengths descriptors such as WBI and MBO, but also the Lagrangian kinetic energy density per electron as well as relaxed force constants. Ring strain energies of the superstrained 1H-oxaphosphirene and its barely strained oxaphosphirane-3-ylidene isomer were comparatively evaluated with homodesmotic and hyperhomodesmotic reactions. Furthermore, first time calculation of the ring strain energy of an anionic ring is described for the case of oxaphosphirenide.

scholarly journals Crystal structures of two molecules with small chemical structure difference

2014 ◽  
Vol 70 (a1) ◽  
pp. C1686-C1686
Author(s):  
Agris Berzins ◽  
Andris Actins
Keyword(s):  
Double Bond ◽  
Crystal Structures ◽  
Intermolecular Interactions ◽  
Potential Energy Surfaces ◽  
Chemical Structure ◽  
Theoretical Calculations ◽  
Torsion Angles ◽  
Structural Formation ◽  
Energy Surfaces ◽  
Molecule Conformation

Droperidol and benperidol, neuroleptic pharmaceuticals, both are used as antipsychotics. The chemical structure of these two compounds differs only by one double bond in the middle of the molecule (see Scheme). It is known that both of these substances can form several polymorphs and solvates. Crystal structures of most of these phases are known [1, 2]. Despite the molecular structure similarities, there are no known droperidol polymorph or solvate isostructural to those of benperidol. Although there has been studies characterizing the crystal structures of chemically very similar compounds, general explanation to observed structural differences was not found (e.g. [3]). In this study we analyse the crystal structures of benperidol and droperidol by comparing the molecule conformation and packing in crystal structures of both of these compounds. Molecule conformation is compared and torsion angles which differ and therefore lead to different crystal structures are identified. Theoretical calculation of potential energy surfaces of these torsion angles are performed in Gaussian09. Intermolecular interactions and molecule packing in all crystal structures are compared by trying to understand the general differences between both molecules. Analysis of structures deposited in Cambridge Structural Database is performed to find conformations and intermolecular interactions characteristic for similar molecules by therefore trying to generalize structural formation possibilities for both pharmaceuticals and understand the reasons for crystallization of only observed structures. Theoretical calculations of benperidol and droperidol crystal structures where benperidol molecules are replaced by droperidol and vice versa are performed in CASTEP to compare the energy of experimentally observed crystal structure with that of theoretically possible structure isostructural to double-bond-different molecule.

Comparison of the proton-transfer path in hydrogen bonds from theoretical potential-energy surfaces and the concept of conservation of bond order. II. (N—H...N)+ hydrogen bonds

2007 ◽  
Vol 63 (4) ◽  
pp. 650-662 ◽  
Author(s):  
Irena Majerz ◽  
Ivar Olovsson
Keyword(s):  
Hydrogen Bonds ◽  
Potential Energy ◽  
Proton Transfer ◽  
Potential Energy Surfaces ◽  
Bond Order ◽  
Theoretical Calculations ◽  
Perfect Agreement ◽  
Reaction Coordinates ◽  
Donor And Acceptor ◽  
Energy Surfaces

The quantum-mechanically derived reaction coordinates (QMRC) for the proton transfer in (N—H—N)+ hydrogen bonds have been derived from ab initio calculations of potential-energy surfaces. A comparison is made between the QMRC and the corresponding bond-order reaction coordinates (BORC) derived by applying the Pauling bond-order concept together with the principle of conservation of bond order. We find virtually perfect agreement between the QMRC and the BORC for intermolecular (N—H—N)+ hydrogen bonds. In contrast, for intramolecular (N—H—N)+ hydrogen bonds, the donor and acceptor parts of the molecule impose strong constraints on the N—N distance and the QMRC does not follow the BORC relation in the whole range. The X-ray determined hydrogen positions are not located exactly at the theoretically calculated potential-energy minima, but instead at the point where the QMRC and the BORC coincide with each other. On the other hand, the optimized hydrogen positions, with other atoms in the cation fixed as in the crystal structure, are closer to these energy minima. Inclusion of the closest neighbours in the theoretical calculations has a rather small effect on the optimized hydrogen positions. [Part I: Olovsson (2006). Z. Phys. Chem. 220, 797–810.]

2-Chloro-2,2-difluoracetamide (ClF2CC(O)NH2). Thermal Decomposition, Vapour Infrared, Mass Spectrometry, Low-temperature NMR, and Theoretical Studies. Solvent Effects on Conformational Preferences

2011 ◽  
Vol 64 (10) ◽  
pp. 1366 ◽  
Author(s):  
Ana G. Iriarte ◽  
Edgardo H. Cutin ◽  
Gustavo A. Argüello
Keyword(s):  
Mass Spectrometry ◽  
Thermal Decomposition ◽  
Potential Energy Surfaces ◽  
Density Functional ◽  
Theoretical Calculations ◽  
Vapour Phase ◽  
Basis Sets ◽  
Conformational Preferences ◽  
Ft Ir ◽  
Energy Surfaces

Gas-phase thermal decomposition of 2-chloro-2,2-difluoracetamide (CDFA) was studied at temperatures between 270 and 290°C. The rate constant for the decomposition follows the Arrhenius equation. Mass spectrometry was used to analyze the decomposition pattern of the title compound. The FT-IR spectrum of the vapour phase and the infrared spectra of CDFA in protic and aprotic solvents were recorded. Potential energy surfaces were studied by theoretical calculations performed at the density functional theory level (PBEPBE and B3LYP methods) using the 6-31G*, 6-31+G*, 6-311+G**, aug-cc-pVDZ, and aug-cc-pVTZ basis sets.

scholarly journals Experimental and DFT studies of Mtpnm

2014 ◽  
Vol 70 (a1) ◽  
pp. C1694-C1694
Author(s):  
Tufan Akbal ◽  
Erbil Agˇar ◽  
Sümeyye Gümüş ◽  
Ahmet Erdönmez
Keyword(s):  
Density Functional Theory ◽  
Potential Energy Surfaces ◽  
Density Functional ◽  
Theoretical Calculations ◽  
Dipole Moments ◽  
Dft Studies ◽  
Acta Cryst ◽  
Functional Theory ◽  
Structure Density ◽  
Energy Surfaces

Experimental and DFT studies of (Z)-N-[3- Methoxy -5-(trifluormethyl) phenyl]-1-(5- nitrothiophene -2- yl)methanamine Tufan Akbala, , Erbil Agˇarb, Sümeyye Gümüşb and Ahmet Erdönmeza aDepartment of Physics, Ondokuz Mayıs University, Samsun, Turkey . b Department of Chemistry Ondokuz Mayıs University, Samsun, Turkey E-mail: [email protected] The title molecule, C13H12N2O3F3S, is nonplanar with an interplanar angle of 23.94(23)0 between the benzene and thiophene rings. In the crystal there exist only weak intermolecular C–H...O interactions and π...π interactions between the benzene rings and thiophene rings [centroid–centroid distance= 4.892(3) A0]. The length of the C9=N2 double bond is 1.2534 A0. This value agrees well with the analogous bond reported elsewhere. [1,2]. The theoretical calculations were performed with Gaussian03W software. In calculations, the stable structure geometries of the isolated molecules in the gas phase was investigated under the framework of Density Functional Theory (DFT). In order to find the stable molecular geometries, the global minimum scanning were performed on the potential energy surfaces and some properties of molecules such as charge densities, dipole moments and frontier orbitals (HOMO and LUMO) from B3LYP/6-31G(d) calculations. REFERENCES: [1] Akbal T., Agˇar E., Erdönmez A., 2012. Acta Cryst. E68, 2673. [2] Aygün M., Işık Ş., Öcal N., Nawaz T.M., Kaban Ş. & Büyükgüngör O., 1998. Acta Cryst. C54, 527-529. Keywords: tautomerism, crystal and molecular structure, density functional theory(DFT) studies

Theoretical calculations of the quartet potential energy surfaces in the NH+ + H2 system

1993 ◽  
Vol 178 (1-3) ◽  
pp. 245-253 ◽  
Author(s):  
Rudolf Polák ◽  
Ivana Paidarová ◽  
Philip J. Kuntz
Keyword(s):  
Potential Energy ◽  
Potential Energy Surfaces ◽  
Theoretical Calculations ◽  
Energy Surfaces
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