The complex thiirane-trifluoromethane (C 2H 4S...HCF 3) has been observed in a supersonic expansion using Fourier-transform microwave spectroscopy. Its structure was derived from the rotational spectra of the parent and three minor 34S and 13C isotopomers observed in natural abundance. The thiirane-trifluoromethane dimer exhibits an equilibrium C s symmetry stabilized by one C-H...S and two C-H...F-C weak hydrogen bonds. The rotational spectrum shows A-E splittings due to the internal rotation of trifluoromethane in the complex around an axis close to its C-H bond, suggesting that the C-H...S linkage is the primary hydrogen bond interaction in the dimer. [All rights reserved Elsevier]

The complex thiirane-trifluoromethane (C(2)H(4)S(...)HCF(3)) has been observed in a supersonic expansion using Fourier-transform microwave spectroscopy. Its structure was derived from the rotational spectra of the parent and three minor (34)S and (13)C isotopomers observed in natural abundance. The thiirane-trifluoromethane dimer exhibits an equilibrium C, symmetry stabilized by one C-H(...)S and two C-H(...)F-C weak hydrogen bonds. The rotational spectrum shows A-E splittings due to the internal rotation of trifluoromethane in the complex around an axis close to its C-H bond, suggesting that the C-H(...)S linkage is the primary hydrogen bond interaction in the dimer. (C) 2004 Elsevier B.V. All rights reserved.

Twenty years ago, the landmark AM1 was introduced, and has since had an increasingly wide following among chemists due to its consistently good results and time-tested reliability--being presently available in countless computational quantum chemistry programs. However, semiempirical molecular orbital models still are of limited accuracy and need to be improved if the full potential of new linear scaling techniques, such as MOZYME and LocalSCF, is to be realized. Accordingly, in this article we present RM1 (Recife Model 1): a reparameterization of AM1. As before, the properties used in the parameterization procedure were: heats of formation, dipole moments, ionization potentials and geometric variables (bond lengths and angles). Considering that the vast majority of molecules of importance to life can be assembled by using only six elements: C, H, N, O, P, and S, and that by adding the halogens we can now build most molecules of importance to pharmaceutical research, our training set consisted of 1736 molecules, representative of organic and biochemistry, containing C, H, N, O, P, S, F, Cl, Br, and I atoms. Unlike AM1, and similar to PM3, all RM1 parameters have been optimized. For enthalpies of formation, dipole moments, ionization potentials, and interatomic distances, the average errors in RM1, for the 1736 molecules, are less than those for AM1, PM3, and PM5. Indeed, the average errors in kcal x mol(-1) of the enthalpies of formation for AM1, PM3, and PM5 are 11.15, 7.98, and 6.03, whereas for RM1 this value is 5.77. The errors, in Debye, of the dipole moments for AM1, PM3, PM5, and RM1 are, respectively, 0.37, 0.38, 0.50, and 0.34. Likewise, the respective errors for the ionization potentials, in eV, are 0.60, 0.55, 0.48, and 0.45, and the respective errors, in angstroms, for the interatomic distances are 0.036, 0.029, 0.037, and 0.027. The RM1 average error in bond angles of 6.82 degrees is only slightly higher than the AM1 figure of 5.88 degrees, and both are much smaller than the PM3 and PM5 figures of 6.98 degrees and 9.83 degrees, respectively. Moreover, a known error in PM3 nitrogen charges is corrected in RM1. Therefore, RM1 represents an improvement over AM1 and its similar successor PM3, and is probably very competitive with PM5, which is a somewhat different model, and not fully disclosed. RM1 possesses the same analytical construct and the same number of parameters for each atom as AM1, and, therefore, can be easily implemented in any software that already has AM1, not requiring any change in any line of code, with the sole exception of the values of the parameters themselves. 2006 Wiley Periodicals, Inc.

\0

Acute congestive heart failure (CHF) is one of the most common syndromes encountered in emergency care settings. Correct diagnosis and treatment for pulmonary edema, the most common acute manifestation of CHF, are of primary importance as misdiagnosis can result in deleterious consequences to patients. The pathogenesis of acute pulmonary edema (APE) is currently believed to arise primarily from the redistribution of intravascular fluid to the lungs secondary to acutely elevated left ventricular (LV) filling pressures. This understanding has provided a basis for the management of acute APE, which entails reduction of LV preload, reduction of LV afterload, ventilatory support, inotropic support as needed, and identification and treatment of other underlying factors contributing to elevated LV filling pressures. The agent most applicable and effective for field treatment is nitroglycerin. Diuretics and morphine should be used with caution, as they carry higher risks, especially in misdiagnosed patients. The role of angiotensin-converting enzyme (ACE) inhibitors has yet to be demonstrated in a prehospital setting. Noninvasive positive pressure ventilation methods are effective adjuncts to current treatment, but their mode of delivery presents technical challenges. The development of novel rapid diagnostic tools, currently in progress, might prove valuable for emergency medical services (EMS) personnel in the future. But for now, EMS personnel must rely on their fundamental skills of history taking and physical examination for accurate diagnosis of CHF.

A high-temperature gas is a relatively simple mixture of gas species in homogeneous equilibrium. Volcanic gases are composed of the elements C, O, H, S, Cl and F along with trace amounts of other components. We present a Microsoft EXCEL spread sheet and add-in for calculation of homogeneous equilibrium in this system. This EXCEL extension allows users to calculate equilibrium species fugacitics at 1 bar for any volcanic or laboratory gas mixture in the C-O-H-S-Cl-F system. Homogeneous equilibrium is calculated using the RAND algorithm based on the assumption of ideal mixing of 66 molecular gas species. This is implemented as a hierarchy of class objects written in C++. This computation engine is compiled into a dynamically linked EXCEL add-in which can be accessed by any EXCEL spread sheet. An easy to use spread sheet is provided which implements this add-in

For the first time the structurally characterized heavier chalcogen analogues of alkanoyl halides,[{HC(CMeNAr)(2)}Ge(S)X] (Ar = 2,6-iPr(2)C(6)H(3); X = Cl (1), F (2)) and [{HC(CMeNAr)(2)}Ge(Se)X] (X = Cl (4), F (5)) have been prepared from the starting material [{HC(CMeNAr)(2)}GeCl] (3). The nature of the germanium-chalcogen bond is best described as between the two resonance structures, Ge+-E- <-> Ge=E. The investigation of the reactivity of the germanium-halogen bond with RLi reagents (R = Me, nBu) led to the formation of [{HC(CMeNAr)(2)}Ge(E)R] (E = S, R = Me (6); E = Se, R = Me (7), nBu (8)). The solid-state structures of 1, 2, 4, 5, 6, and 8 are reported.

Theoretical calculations on r-1,c-3,c-5-trifluorocyclohexane (1), r-2,c-4,c-6-trifluoro-1,3,5-trioxane (2), and r-2,c-4,c-6-trifluoro-1,3,5-trithiane (3) confirm the importance of n(F) -> sigma*(C-Y)(gem), where Y =3D H, C, O, S, hyperconjugative interactions; that is, contrary to common wisdom, fluorine is a good lone pair electron donor toward geminal sigma bonds. This conclusion is in line with the recent observations reported by O'Hagan and co-workers, who synthesized and examined all-cis 1,2,3,4,5,6-hexafluoro-cyclohexane. (Nat. Chem. 2015, 7, 483-488).