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41.
George L Sander W 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2004,60(13):3225-3232
The infrared spectra of the formic acid-water complexes isolated in argon matrices are reported. Both supersonic jet expansion and a conventional effusive source followed by trapping in solid argon at 10K are used to obtain the matrices. The experimental IR spectra are compared to the data obtained from high level ab initio (MP2) and DFT (B3LYP) calculations with 6-311++G(d,p) and aug-cc-pVTZ basis sets. The complex formation results in red shifts in the C=O and O-H stretching vibrations and a blue shift in the C-O stretching vibration of formic acid. The O-H stretching modes of water also exhibit pronounced red shifts. Both the MP2 and B3LYP calculations located three minima corresponding to cyclic HCOOH...H2O complexes with two hydrogen bond interactions. The binding energies are -10.3, -5.1, and -3.5 kcal mol(-1), respectively, for the three complexes at the MP2/ aug-cc-pVTZ level, corrected for the basis set superposition error (BSSE) using the Boys-Bernardi counterpoise scheme. Comparison of the calculated frequencies of the three complexes with the matrix IR spectrum reveals that the lowest energy complex is formed. In addition, a complex of formic acid with two water molecules is observed. 相似文献
42.
Niamh NicDaéid Saravana Jayamana William J. Kerr Wolfram Meier-Augenstein Helen F. Kemp 《Analytical and bioanalytical chemistry》2013,405(9):2931-2941
A number of methods of clandestine manufacture of methylamphetamine involve the extraction and subsequent reaction of pseudoephedrine hydrochloride with other essential chemicals. The precursor can be easily extracted from over-the-counter medication widely available in the UK and elsewhere. Essential chemicals such as iodine and red phosphorous are also readily available and can be extracted from iodine tinctures and matchboxes, respectively. This work reports the repetitive preparation of methylamphetamine using two popular routes (the Moscow and Hypophosphorous synthesis). The focus was on the extraction solvent used for isolation of the precursor chemical and any consequential isotopic variation which may arise in the final product. Six batches of methylamphetamine were prepared under precisely controlled conditions for each synthetic route and for each of three different precursor extraction solvents. Synthesis of the final product from laboratory grade precursor using the synthetic methods described was used as a template for comparison. The resultant IRMS data from all 48 prepared samples suggests some underlying trends in the identification of the synthetic route which may aid in the interpretation of IRMS data derived from clandestine samples. 相似文献
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44.
Wolfram W. Rudolph 《Journal of solution chemistry》2010,39(7):1039-1059
Measurements have been made of the Raman spectra of aqueous solutions of Be(ClO4)2, BeCl2, (NH4)2SO4 and BeSO4 to 50 cm−1. In some cases low concentrations (0.000770 mol⋅kg−1) have been used and two temperatures (23 and 40 °C) were studied. In BeSO4(aq), the ν
1-SO42-\mathrm{SO}_{4}^{2-} mode at 980 cm−1 broadens with increasing concentration and shifts to higher wavenumbers. At the same time, a band at 1014 cm−1 is detectable with this mode being assigned to [BeOSO3], an inner-sphere complex (ISC). Confirmation of this assignment is provided by the simultaneous appearance of stretching
bands for the Be2+-OSO32-\mathrm{Be}^{2+}\mbox{-}\mathrm{OSO}_{3}^{2-} bond of the complex at 240 cm−1 and for the BeO4 skeleton mode of the [(H2O)3BeOSO3] unit at 498 cm−1. The ISC concentration increases with higher temperatures. The similarity of the n1-SO42-\nu_{1}\mbox{-}\mathrm{SO}_{4}^{2-} Raman bands for BeSO4 in H2O and D2O is further strong evidence for formation of an ISC. After subtraction of the ISC component at 1014 cm−1, the n1-SO42-\nu_{1}\mbox{-}\mathrm{SO}_{4}^{2-} band in BeSO4(aq) showed systematic differences from that in (NH4)2SO4(aq). This is consistent with a n1-SO42-\nu_{1}\mbox{-}\mathrm{SO}_{4}^{2-} mode at 982.7 cm−1 that can be assigned to the occurrence of an outer-sphere complex ion (OSCs). These observations are shown to be in agreement
with results derived from previous relaxation measurements. Infrared spectroscopic data show features that are also consistent
with a beryllium sulfato complex such as the appearance of a broad and weak n1-SO42-\nu_{1}\mbox{-}\mathrm{SO}_{4}^{2-} mode at ∼1014 cm−1, normally infrared forbidden, and a broad and asymmetric n3-SO42-\nu_{3}\mbox{-}\mathrm{SO}_{4}^{2-} band contour which could be fitted with four band components (including n3-SO42-(aq)\nu_{3}\mbox{-}\mathrm{SO}_{4}^{2-}(\mathrm{aq})). The formation of ISCs in BeSO4(aq) is much more pronounced than in the similar MgSO4(aq) system studied recently. 相似文献
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46.
Dr. Peter Schweyen Martin Hoffmann Jens Krumsieck Dr. Benedikt Wolfram Dr. Xiulan Xie Prof. Dr. Martin Bröring 《Angewandte Chemie (International ed. in English)》2016,55(34):10118-10121
Zinc and cadmium complexes of meso‐arylisoporphyrins carrying a pyrrolyl or dipyrrinyl substituent at the sp3 carbon atom were obtained through a simple one‐pot variation of the Alder–Longo porphyrin synthesis. Key to the formation and stabilization of isoporphyrins is the presence of metal acetates during the oxidative macrocyclization step. The characteristic Q‐bands of isoporphyrins are found in the NIR region between 750 nm and 880 nm. All of the isolated pyrrolyl‐ and dipyrrinyl‐appended isoporphyrins are stable under typical laboratory conditions and allow chemical transformations like BF2 coordination, transmetalation, and ligand exchange. 相似文献
47.
A Highly Reactive Geminal P/B Frustrated Lewis Pair: Expanding the Scope to C−X (X=Cl,Br) Bond Activation 下载免费PDF全文
Kamil Samigullin Isabelle Georg Dr. Michael Bolte Dr. Hans‐Wolfram Lerner Prof. Dr. Matthias Wagner 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(10):3478-3484
The geminal frustrated Lewis pair tBu2PCH2B(Fxyl)2 ( 1 ; Fxyl=3,5‐(CF3)2C6H3) is accessible in 65 % yield from tBu2PCH2Li and (Fxyl)2BF. According to NMR spectroscopy and X‐ray crystallography, 1 is monomeric both in solution and in the solid state. The intramolecular P ??? B distance of 2.900(5) Å and the full planarity of the borane site exclude any significant P/B interaction. Compound 1 readily activates a broad variety of substrates including H2, EtMe2SiH, CO2/CS2, Ph2CO, and H3CCN. Terminal alkynes react with heterolysis of the C?H bond. Haloboranes give cyclic adducts with strong P?BX3 and weak R3B?X bonds. Unprecedented transformations leading to zwitterionic XP/BCX3 adducts occur on treatment of 1 with CCl4 or CBr4 in Et2O. In less polar solvents (C6H6, n‐pentane), XP/BCX3 adduct formation is accompanied by the generation of significant amounts of XP/BX adducts. FLP 1 catalyzes the hydrogenation of PhCH=NtBu and the hydrosilylation of Ph2CO with EtMe2SiH. 相似文献
48.
Julia Rüger Christopher Timmermann Dr. Alexander Villinger Alexander Hinz Dr. Dirk Hollmann Prof. Dr. Wolfram W. Seidel 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(32):11191-11195
The capability of donor‐substituted alkynes to link different metal ions in a side‐on carbon donor‐chelate coordination mode is extended from the donor centers S and P to the second period element N. The complex [Tp′W(CO)2{η2‐C2(S)(NHBn)}] (Tp′=hydrido‐tris(3,5‐dimethylpyrazolyl)borate, Bn=benzyl) bearing a terminal sulfur atom and a secondary amine substituent is accessible by a metal‐template synthesis. Subsequent deprotonation allowed the formation of remarkably stable heterobimetallic complexes with the [(η5‐C5H5)Ru(PPh3)] and the [Ir(ppy)2] moiety. Electrochemical and spectroscopic investigations (cyclic voltammetry, IR, UV/Vis, luminescence, EPR), as well as DFT calculations, and X‐ray structure determinations of the W–Ru complex in two oxidation states reveal a strong metal–metal coupling but also a limited delocalization of excited states. 相似文献
49.
Werner Fuss Wolfram E Schmid Sergei A Trushin Paul S Billone William J Leigh 《Chemphyschem》2007,8(4):592-598
Photochemical pericyclic reactions are believed to proceed via a so-called pericyclic minimum on the lowest excited potential surface (S(1)), which is common to both the forward and backward reactions. Such a common intermediate has never been directly detected. The photointerconversion of 1,3-butadiene and cyclobutene is the prevailing prototype for such reactions, yet only diene ring closure proceeds with the stereospecificity that the Woodward-Hoffmann rules predict. This contrast seems to exclude a common intermediate. Using ultrafast spectroscopy, we show that the excited states of two cyclobutene/diene isomeric pairs are linked by not one, but by two common minima, p* and ct*. Starting from the diene side (cyclohepta-1,3-diene and cycloocta-1,3-diene), electrocyclic ring closure passes via the pericyclic minimum p*, whereas ct* is mainly responsible for cis-trans isomerization. Starting from the corresponding cyclobutenes (bicyclo[3.2.0]heptene-6 and bicyclo[4.2.0]octene-7), the forbidden isomer is formed from ct*. The path branches at the first (S(2)/S(1)) conical intersection towards p* and ct*. The fact that the energetically unfavorable ct* path can compete is ascribed to a dynamic effect: the momentum in C=C twist direction, acquired--such as in other olefins--in the Franck-Condon region of the cyclobutenes. 相似文献
50.