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PubMed2005

Polarizability response in polar solvents: molecular-dynamics simulations of acetonitrile and chloroform.

The relaxation of the many-body polarizability in liquid acetonitrile and chloroform at room temperature was studied by molecular-dynamics simulations. The collective polarizability induced by intermolecular interactions was included using first- and all-orders dipole-induced-dipole models and calculated considering both molecule-centered and distributed site polarizabilities. The anisotropic response was analyzed using a separation scheme that allows a decomposition of the total response in terms of orientational and collision-induced effects. We found the method effective in approximately separating the contributions of these relaxation mechanisms, although the orientational-collision-induced interference makes a non-negligible contribution to the total response. In both liquids the main contribution to the anisotropic response is due to orientational dynamics, but intermolecular collision-induced (or translational) effects are important, especially at short times. We found that higher-order interaction-induced effects were essentially negligible for both liquids. Larger differences were found between the center-center and site-site models, with the latter showing faster polarizability relaxation and better agreement with experiment. Isotropic and anisotropic spectra were computed from the corresponding time correlation functions. The lowest-frequency contributions are largely suppressed in the isotropic spectra and their overall shape is similar to the purely collision-induced contribution to the anisotropic spectra, but with an amplitude which is smaller by a factor of approximately 5 in acetonitrile and approximately 3 in chloroform.

Journal Article↗
PubMed2006

Pulse shaping effect on two-photon excitation efficiency of alpha-perylene crystals and perylene in chloroform solution.

We demonstrated that the two-photon excitation efficiency of perylene in chloroform solution as well as that of crystalline perylene was dramatically increased by optimizing the shape of intense femtosecond laser pulses of a regenerative amplifier output. The efficiency was three times higher than for an unshaped single femtosecond pulse with the pulse width of shorter than 50 fs. The pulse shape optimized for the solution sample was a pulse train with a repetition frequency of about 340 cm(-1), and the pulse shape optimized for crystalline perylene was very similar. These results supported our previous findings on alpha-perylene crystals using weak femtosecond pulses from a mode-locked laser oscillator [T. Okada et al. J. Chem. Phys. 121, 6385 (2004)]. Furthermore, it was confirmed that the shaped pulse optimized for the liquid sample could also increase the two-photon excitation efficiency of alpha-perylene crystals and vice versa. We concluded that the mechanism for the increase in excitation efficiency of perylene in chloroform was almost the same as that for alpha-perylene crystal, and that the efficiency increased mainly through intramolecular dynamical processes. Processes involving intermolecular interactions and/or energy states delocalized over the crystal cannot play the major role.

Journal Article↗
PubMed2006

Solvation pressure in chloroform.

Molecular dynamics (MD) simulations of chloroform vapor and liquid at normal temperature and pressure and liquid under hydrostatic pressure are presented, giving bond lengths and vibrational frequencies as functions of pressure. The change in bond lengths between vapor and liquid at normal temperature and pressure is consistent with a pressure equivalent to the cohesive energy density (CED) of the liquid, supporting the solvation pressure model which predicts that solvated molecules or nanoparticles experience a pressure equal to the CED of the liquid. Experimental data for certain Raman frequencies of chloroform in the vapor phase, in the liquid, and in the liquid under pressure are presented and compared to MD. Results for C-Cl vibrational modes are in general agreement with the solvation pressure model whereas frequencies associated with the C-H bond are not. The results demonstrate that masking interactions exist in the real liquid that can be reduced or eliminated in simplified simulations.

Journal Article↗
PubMedDate not supplied

A fatal fire with "nonflammable" methyl chloroform.

A methyl chloroform fire was fatal to a welder. The widely held belief that this material is nonflammable contributed to his death. As shown here, methyl chloroform is much easier to burn than is commonly believed.

Accidents, Occupational↗
PubMed2001

(12,17-diethoxycarbonyl-2,3,6,7,11,18-hexamethylcorrphycenato-kappa4N)iodoiron(III) chloroform solvate.

The title complex, (diethyl 3,4,8,15,19,20-hexamethyl-21,22,23,24-tetraazopentacyclo[16.2.1.1(2,5).1(7,11).1(14,17)]tetracosa-1(20),2(22),3,5,7,9,11,13(24),14,16,18-undecaene-9,14-dicarboxylate-kappa4N)iodoiron(III) chloroform solvate, [Fe(C32H32N4O4)I].CHCl3, shows an almost planar arrangement of the corrphycene moiety with a slightly distorted trapezoid pyramidal core; the Fe(III) atom is 0.416 (1) A from the plane of the C20N4 system. The Fe-N distances are 2.049 (3), 2.044 (3), 2.079 (3) and 2.075 (3) A. The solvated chloroform forms a C-H...O hydrogen bond [C...O 3.107 (10) A] to an adjacent carbonyl O atom. This is the first X-ray structure analysis of a corrphycenatoiron(III) derivative.

Journal Article↗
PubMed2001

Hydrogen bonding in bis(triphenylphosphine-P)iminium hydrogensulfate chloroform solvate.

The title compound, C(36)H(30)NP(2)(+).HSO(4)(-).CHCl(3), consists of discrete ions and well separated chloroform solvate molecules. The central feature of the structure is O-H...O hydrogen bonding between two hydrogensulfate ions related by a crystallographic inversion centre. The chloroform solvate molecule takes part in a well defined C-H...O hydrogen bond.

Journal Article↗
PubMed2006

2,3-Dimethoxybenzaldehyde isonicotinoylhydrazone chloroform monosolvate, and the mono- and dihydrates of 3,4,5-trimethoxybenzaldehyde isonicotinoylhydrazone: hydrogen-bonded supramolecular structures in one, two and three dimensions.

In 2,3-dimethoxybenzaldehyde isonicotinoylhydrazone chloroform monosolvate, C15H15N3O3.CHCl3, the hydrazone molecules are linked by a combination of N-H...N and C-H...N hydrogen bonds into chains from which the chloroform molecules are pendent. 3,4,5-Trimethoxybenzaldehyde isonicotinoylhydrazone forms two stoichiometric hydrates. In the monohydrate, C16H17N3O4.H2O, the components are linked into sheets by a combination of O-H...O, O-H...N and N-H...N hydrogen bonds, and in the dihydrate, C16H17N3O4.2H2O, a combination of O-H...O, O-H...N and N-H...O hydrogen bonds links the components into a three-dimensional framework structure.

Journal Article↗
PubMed2000

Effect of 2-bromo-ethane sulfonate, molybdate and chloroform on acetate consumption by methanogenic and sulfate-reducing populations in freshwater sediment.

The relative importance of methanogenesis and sulfate reduction in freshwater sediment supplemented with acetate was investigated. Addition of acetate stimulated both methane formation and sulfate reduction, indicating that an active aceticlastic population of methanogens and sulfate reducers was present in the sediment. Sulfate reducers were most important in the consumption of acetate. However, when sulfate reducers were inhibited, acetate was metabolised at a similar rate by methanogens. Acetate, propionate and valerate accumulated only when both processes were inhibited by the combined addition of 2-bromo-ethane sulfonate and molybdate. The relative amounts of acetate, propionate and valerate were 93, 6 and 1 mol%, respectively. These results demonstrate the role of acetate as a key intermediate in the terminal step of organic matter mineralisation in the sediment. Addition of chloroform inhibited both methanogenesis and sulfate reduction. We studied the inhibitory effect of CHCl(3) on homoacetogenic bacteria, sulfate-reducing bacteria and methanogens. The results showed that inhibition by CHCl(3) correlates with microorganisms, which operate the acetyl-CoA cleavage pathway. We propose that chloroform can be used to elucidate the role of different metabolic types of sulfate reducers to sulfate reduction in natural environments.

Journal Article↗
PubMed1993

A chloroform extract of the herb feverfew blocks voltage-dependent potassium currents recorded from single smooth muscle cells.

We have studied the effects of a chloroform extract of fresh leaves from the herb feverfew (Tanacetum parthenium) on potassium currents in smooth muscle. The currents were recorded from single cells dissociated from the rat anococcygeus and the rabbit ear artery using the whole-cell patch-clamp technique. When applied to cells isolated from the rat anococcygeus, the extract reduced the inactivating voltage-dependent potassium current in a concentration-related manner, with an IC50 value (the concentration that reduced the current by 50%) of 56 micrograms mL-1. Complete block of the current occurred at 1 mg mL-1. In addition to reducing the peak current, feverfew decreased the time to peak of the current and increased the rate of decay of the current. These effects can be explained by the feverfew extract blocking open potassium channels. In single cells isolated from rabbit ear artery the feverfew extract again reduced the voltage-dependent potassium current, whilst at the same time having no effect on the spontaneous transient outward currents which arise as a consequence of activation of calcium-dependent potassium channels. These results suggest that chloroform extracts of feverfew leaf contain an as yet unidentified substance capable of producing a selective, open-channel block of voltage-dependent potassium channels.

Animals↗
PubMed1990

The Wood Library-Museum's 1858 edition of John Snow's On chloroform and other anaesthetics.

The original 1858 edition of John Snow's On Chloroform and Other Anaesthetics, from which came the Wood Library-Museum of Anesthesiology reprints in 1971 and 1989, was donated to the Wood Library-Museum by Ralph Waters of Madison, Wisconsin, in 1967. The book contains a message of appreciation to Waters, dated October 1937, with the signatures of J. Blomfield, Charles King, and R.R. Macintosh as representatives of anesthesiology in England. Correspondence exists in the archives of the University of Wisconsin-Madison between Macintosh, Professor of Anaesthetics in Oxford, and Waters, Associate Professor in Madison. This reveals that Waters, during his visit to England in 1936, inspired British anesthetists to discover more of Snow's early contributions to anesthesiology, even though Waters himself did not possess On Chloroform and Other Anaesthetics. King, a manufacturer of anesthetic equipment, found a copy in the hands of Blomfield, an anesthetist at St. George's Hospital, London, where John Snow had worked. It was this copy that they presented to Waters, and that was delivered to Waters by hand when Waters' resident, Ivan Taylor, returned from Oxford to Madison. Blomfield's ownership of the book, in addition to his position as president of the Association of Anaesthetists of Great Britain and Ireland, explains why the inscription is in his handwriting.

Anesthesiology↗
PubMedDate not supplied

Mechanism of radical cation formation from the excited states of zeaxanthin and astaxanthin in chloroform.

The C-40 xanthophylls zeaxanthin and astaxanthin were confirmed to form radical cations, Car.+, in the electron-accepting solvent chloroform by direct excitation using subpicosecond time-resolved absorption spectroscopy in combination with spectroelectrochemical determination of the near-infrared absorption of Car.+. For the singlets, the S2(1B(u+) state and most likely the S(x)(3A(g)-) state directly eject electrons to chloroform leading to the rapid formation of Car.+ on a timescale of approximately 100 fs; the lowest-lying S1(2A(g)-) state, however, remains inactive. Standard reduction potential for Car.+ was determined by cyclic voltametry to have the value 0.63 V for zeaxanthin and 0.75 V for astaxanthin from which excited state potentials were calculated, which confirmed the reactivity toward radical cation formation. On the other hand, Car.+ formation from the lowest triplet excited state T1 populated through anthracene sensitization is mediated by a precursor suggested to be a solute-solvent complex detected with broad near-infrared absorption to the shorter wavelength side of the characteristic Car.+ absorption. However, ground state carotenoids are able to react with a secondary solvent radical to yield Car.+, a process occurring within 16 micros for zeaxanthin and within 21 mus for astaxanthin. Among the two xanthophylls together with lycopene and beta-carotene, all having 11 conjugated double bonds, zeaxanthin ranks with the highest reactivity in forming Car.+ from either the S2(1B(u+)) or the ground state. The effects of substituent groups on the reactivity are discussed.

Journal Article↗
PubMed1992

Antifertility investigations on the crude chloroform extract of Carica papaya Linn. seeds in male albino rats.

Crude chloroform extract of C. papaya seeds (5 mg/animal/day, po, for 20, 40 and 60 days) was investigated for contraceptive efficacy and related side effects in male albino rats. The crude extract reduced fertility to zero per cent by 40 to 60 days of treatment. Suppression of cauda epididymal sperm motility was the most pronounced effect of the drug administration. Scanning electron microscopic observations revealed treatment induced abnormalities in sperms. Cauda epididymal and testicular sperm counts decreased following treatment. Clinical parameters did not show any alterations. Results suggest that the contraceptive effects of chloroform extract of papaya seeds are mainly post-testicular in nature without influencing toxicological profile and libido of the animals.

Animals↗
PubMedDate not supplied

Acute inhalation toxicity of neutralized chemical agent identification sets (CAIS) containing agent in chloroform.

An acute head-only inhalation study was conducted in rats exposed for 1 h to product solution (wastestream) resultant from the chemical neutralization of Chemical Agent Identification Sets (CAIS) containing agent (sulfur mustard (HD), nitrogen mustard (HN-1) or lewisite (L)) in chloroform. Groups of Sprague-Dawley rats were exposed to varying concentrations (24000, 18000, 12000 or 6000 ppm) of CAIS wastestream. An additional group was exposed to the vehicle (chloroform/t-butanol) only, at a concentration equivalent to the concentration of vehicle at the highest exposure level. Animals were evaluated for toxic effects, including assessment of toxicant-induced alterations to the ocular and respiratory systems. Mortality on exposure to 24000 ppm of test article or to vehicle alone was high. Mortality in the other exposure groups was roughly proportional to the concentration of test article (wastestream). Toxic signs were consistent with exposure to solvent system components (chloroform/t-butanol) and to agent decomposition products/by-products. Incidence and severity of ocular effects were similar in vehicle control and treatment groups. The salient respiratory effect observed was a decreased minute volume, which was also noted in vehicle and treatment groups.

Animals↗
PubMed2002

A molecular dynamics study of the stoichiometric complex formed by poly (alpha, L-glutamate) and octyltrimethylammonium ions in chloroform solution.

We present a molecular dynamics simulation at 300 K in explicit solvent environment of chloroform of the stoichiometric complex formed by poly(alpha,L-glutamate) and octyltrimethylammonium ions. We observed that the alpha-helix conformation of the polypeptide chain remains stable during a 2-ns run. The surfactant ions predominantly adopted an extended conformation that is stabilized by favorable interactions with the organic solvent. Analysis of the organization of the surfactant with respect to the polypeptide chain indicated that each octyltrimethylammonium cation was preferentially bound to more than one carboxylate group. It was found that the most populated arrangement was that with the surfactant cations interacting with two carboxylate groups simultaneously.

Cations↗
PubMed2001

Investigation of cell exudates active in carbon tetrachloride and chloroform degradation.

Contamination of groundwater by chlorinated solvents such as carbon tetrachloride (CCl4) and chloroform (CHCl3) is a widespread problem. The cell exudates from the methanogen Methanosarcina thermophila are active in the degradation of CCl4 and CHCl3. This research was performed to characterize these exudates. Examination of the influence of pH indicated that activity was greater under alkaline conditions. Rapid CCl4 degradation occurred from 35-65 degrees C, with first-order degradation rate coefficients increasing as temperature increased. It was found that proteins were not responsible for CCl4 degradation. The active agents in the cell exudates were <10 kDa in size, with degradation activity present in both 1-10 kDa and <1 kDa size ranges. Upon purification of the <10 kDa size range of the cell exudates on a C(18) chromatography column, 17 fractions (out of 100) degraded >50% of the added CCl4 in 8 h. These 17 fractions were pooled into three samples based on their elution time from the C(18) column. One of these pooled samples contained elevated levels of cobalt, zinc, and iron, at 2, 3, and 13 times the levels measured in similarly fractionated and pooled samples of medium, respectively. The UV-visible spectrum of this pooled sample had an absorption maximum at 560-580 nm, which is similar to the absorption maxima of heme (approximately 550 and 575 nm). The two other pooled samples contained elevated levels of zinc at 11 and 22 times the concentration measured in similarly fractionated and pooled samples of medium, respectively, and also contained very low levels of nickel, cobalt, and iron. This research suggests that the cell exudates from M. thermophila contain porphorinogen-type molecules capable of dechlorination, possibly excreted corrinoids, hemes, and zinc-containing molecules.

Biodegradation, Environmental↗
PubMed2005

Riboflavin- and cobalamin-mediated biodegradation of chloroform in a methanogenic consortium.

Chloroform (CF) is an important priority pollutant contaminating groundwater. Reductive dechlorination by anaerobic microorganisms is a promising strategy towards the remediation of CF. The objective of this study was to evaluate the use of redox active vitamins as electron shuttles to enhance the anaerobic biodegradation of CF in an unadapted methanogenic consortium not previously exposed to chlorinated compounds. Only negligible degradation of CF was observed in control cultures lacking redox active vitamins. The addition of riboflavin (RF), cyanocobalamin (CNB12), and hydroxycobalamin (HOB12) enabled biodegradation of CF. The reactions were predominantly catalyzed biologically as evidenced by the lack of any CF conversion in heat-killed controls amended with the cobalamins or minor conversion with RF. In live cultures, significant increases in the rate of CF conversion was observed at substoichiometric molar ratios as low as 0.1 to 0.01 vitamin:CF for RF and CNB12, respectively. At the highest molar vitamin:CF ratios tested of 0.2, the first-order rate constant of CF degradation was 5.3- and 91-fold higher in RF and CNB12 amended cultures, respectively, compared to the unamended control culture. The distribution of biotransformation products was highly impacted by the type of redox active vitamin utilized. Cultures supplemented with RF provided high yields of dichloromethane (DCM). On the other hand, cobalamins promoted the near complete mineralization of organochlorine in CF to inorganic chloride and lowered the yield of DCM. In cultures where no or little CF bioconversion occurred, prolonged exposure to CF resulted in cell lysis, as evidenced by the release of intracellular chloride. The results taken as a whole suggest that the anaerobic bioremediation of CF-contaminated sites can greatly be improved with strategies aimed at increasing the concentration of redox active vitamins.

Biodegradation, Environmental↗
PubMed2007

Bio-reductive dechlorination of 1,1,1-trichloroethane and chloroform using a hydrogen-based membrane biofilm reactor.

A H(2)-based, denitrifying and sulfate-reducing membrane biofilm reactor (MBfR) was effective for removing 1,1,1-trichloroethane (TCA) and chloroform (CF) by reductive dechlorination. When either TCA or CF was first added to the MBfR, reductive dechlorination took place immediately and then increased over 3 weeks, suggesting enrichment for TCA- or CF-dechlorinating bacteria. Increasing the H(2) pressure increased the dechlorination rates of TCA or CF, and it also increased the rate of sulfate reduction. Increased sulfate loading allowed more sulfate reduction, and this competed with reductive dechlorination, particularly the second steps. The acceptor flux normalized by effluent concentration can be an efficient indicator to gauge the intrinsic kinetics of the MBfR biofilms for the different reduction reactions. The analysis of normalized rates showed that the kinetics for reductive-dechlorination reactions were slowed by reduced H(2) bio-availability caused by a low H(2) pressure or competition from sulfate reduction.

Biodegradation, Environmental↗
PubMed2005

Structure refinement of cyclosporin A in chloroform by using RDCs measured in a stretched PDMS-gel.

New developments concerning alignment media for apolar solvents like chloroform make it possible to measure anisotropic parameters such as residual dipolar couplings (RDCs) at relatively low concentrations and natural isotopic abundance. As RDCs provide structural restraints with respect to an external coordinate system, long-range structural arrangements of the time-averaged structure can be determined with high precision. The method is demonstrated on the well-studied cyclo-undecapeptide Cyclosporin A (CsA), for which crystal and conventionally derived NMR structures are available. Neither crystal nor NMR structure are consistent with heteronuclear D(CH) RDCs measured in a stretched poly(dimethylsiloxane) gel, and refinement by using the anisotropic parameter results in a highly defined structure with a slightly changed backbone conformation. The applied methods and interpretation of the structural model are discussed.

Chloroform↗