11 documents found, page 1 of 2

Polymorphism in 1-methylhydantoin: Investigation by periodic DFT calculations a...

In previous studies [Puszyńska-Tuszkanow et al. Polyhedron, 2011, 30(12), 2016; Nogueira et al. J. Phys. Chem. A, 2014, 118(31), 5994; Nogueira et al., J. Mol. Struct., 2017, 1148, 111], two different polymorphs of 1-methylhydantoin (1-MH, C4H6N2O2) were identified (forms I and II) and characterized using infrared and Raman spectroscopies, as well as by X-ray diffraction. In this work, a new polymorph of the co...

Bjurböle L/LL4 ordinary chondrite properties studied by Raman spectroscopy, X-r...

Bjurböle L/LL4 ordinary chondrite was studied using scanning electron microscopy with energy dispersive spectroscopy, Raman spectroscopy, X-ray diffraction, magnetization measurements and Mössbauer spectroscopy. The phase composition and the relative iron fractions in the iron-bearing phases were determined. The unit cell parameters for olivine, orthopyroxene and clinopyroxene are similar to those observed in t...

Enhanced solid-state stability of amorphous ibrutinib formulations prepared by ...

One of the applications of Hot-Melt Extrusion (HME) is the stabilization of amorphous drugs through its incorporation into polymeric blends in the form of Amorphous Solid Dispersions (ASDs). In this study, HME was applied to solve a real problem in the development of an ibrutinib product, stabilizing the amorphous form. A systematic approach was followed by combining theoretical calculations, high-throughput sc...

Photoinduced Reactivity in a Dispiro-1,2,4-trioxolane: Adamantane Ring Expansio...

Dispiro-1,2,4-trioxolane, 1, an ozonide with efficient and broad antiparasitic activity, was synthesized and investigated using matrix isolation FTIR and EPR spectroscopies together with both B3LYP/6-311++G(3df,3dp) and M06-2X/6-311++G(3df,3dp) theoretical methods. Irradiations (λ ≥ 290 nm) of the matrix isolated 1 (Ar or N2) afforded exclusively 4-oxahomoadamantan-5-one, 4, and 1,4-cyclohexanedione, 5. These r...

Matrix isolation study of methyl propiolate in argon and nitrogen matrices

Methyl propiolate (HCtriple bondCCOOCH3, MP) isolated in argon and nitrogen matrices was experimentally studied by infrared spectroscopy and by quantum chemical calculations. The calculations, carried out at the DFT(B3LYP) and MP2 levels of theory, predict the existence of two conformers with a planar skeleton. In situ broadband UV light (λ > 200 nm) irradiation of matrix-isolated MP led to the production of ne...

A comparative multi‐reference configuration interaction study of the low‐lying ...

Multi-reference configuration interaction, MR-CI (including extensivity corrections, named +Q) calculations have been performed on S0 to S3 states of cyclohexa-2,4- diene-1-thione (thione 24) and cyclohexa-2,5-diene-1-thione (thione 25), which are thione isomers of thiophenol. Several types of uncontracted MR-CIS and MR-CISD wavefunctions have been employed, comprising MR-CI expansions as large as ~ 365 x 106 c...

Amorphous and crystalline thioacetamide ice: Infrared spectra as a probe for te...

In this work we report the effect of intermolecular interactions on the structure of thioacetamide (CH3CSNH2) as a function of temperature, monitored by IR spectroscopy. Thin films of amorphous thioacetamide ice were deposited at 10 K and gradually warmed up to 260 K. Irreversible spectral changes between 180 and 200 K provide evidence for crystallization of the ice. Quantum chemical computations on a dodecamer...

Structural, spectroscopic, and photochemical study of ethyl propiolate isolated...

Ethyl propiolate (HC ≡ CCOOCH2CH3, EP) was studied experimentally by infrared spectroscopy in argon and nitrogen cryomatrices (15 K) and by quantum chemical calculations (at the DFT(B3LYP) and MP2 levels of theory). Calculations predict the existence of four conformers: two low-energy conformers (I and II) possessing the carboxylic moiety in the cis configuration (O=C-O-C dihedral equal to ~0°) and two higher-e...

Heavy-Atom Tunneling Through Crossing Potential Energy Surfaces: Cyclization of...

Not long ago, the occurrence of quantum mechanical tunneling (QMT) chemistry involving atoms heavier than hydrogen was considered unreasonable. Contributing to the shift of this paradigm, we present here the discovery of a new and distinct heavy-atom QMT reaction. Triplet syn-2-formyl-3-fluorophenylnitrene, generated in argon matrices by UV-irradiation of an azide precursor, was found to spontaneously cyclize t...

Structural, Morphological, Raman, and Mössbauer Studies on (La<inf>0.8</inf>Ca<...