Scientific Publications 2004
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B
2004. "Ligand-Field Effects for the 3p Photoelectron Spectra of Cr2O3." Physical Review. B, Condensed Matter and Materials Physics 69(20):205112. Abstract A major reason for the departure of core level X-ray photoelectron spectra (XPS) of transition metal cations in oxides from the predictions of atomic models is shown to arise from ligand field splittings in the initial state of photoemission. This splitting often leads to a change in the spatial degeneracy of the initial state but the consequences of this for the XPS have not been identified in prior work. Further changes arise from ligand field splittings in the core-hole final states. Results are reported for non-empirical cluster model many body wavefunctions for the 3p XPS of Cr2O3. The agreement of the theoretical cluster model XPS with experiment is considerably improved over the pure atomic model. Furthermore, the treatment allows screening of the core hole through changes in the covalent character of the cluster orbitals. This is quite different from the usual description of screening in oxides within the framework of charge transfer configurations and it offers new insights into the role of charge transfer for satellite structure.
2004. "A New Near Degeneracy Effect for Photoemission in Transition Metals." Chemical Physics Letters 394(1-3):150-154. Abstract Abstract: An ab initio theoretical study shows that a previously neglected intra-atomic many-body effect has important consequences for the X-ray photoelectron spectra (XPS) of transition metal atoms and cations. For the Mn 3s XPS, inclusion of this effect correctly yields the multiplet splitting, properly describes the absolute binding energy, and predicts new satellite structure. It is not necessary to invoke an artificial scaling of the two electron integrals to improve agreement with experiment. This intra-atomic effect is expected to be of general importance and a proper interpretation of the XPS spectra requires that it be taken into account.
2004. "Vibrational and Electronic Absorption Spectroscopy of 2,3-Benzofluorene and its Cation. ." Journal of Physical Chemistry A 108(17):3713 -3722. Abstract Benzofluorene (C17H12) has been studied in argon matrices via Fourier transform infrared and UV-visible absorption spectroscopy and in the vapor phase by Fourier transform ion cyclotron resonance mass spectrometry. Analysis of the infrared absorption spectra of neutral and cationic 2,3-benzofluorene was supported by density functional theory calculations of the harmonic mode frequencies. Extensive time-dependent DFT calculations of the electronic vertical excitation energies at various levels of theory were performed to assign the observed electronic absorption bands of the neutral species. Although the observed low energy absorption bands are predicted well by theory, the higher energy bands have only been assigned tentatively. On the other hand, the observed electronic absorption bands for the parent, singly-dehydrogenated cationic and neutral species are in accord with the TDDFT results. The identification of certain fragmented species from electron impact/matrix optical experiments led to detailed studies of the dissociation pathways of the cation via Fourier transform-ion cyclotron mass spectrometry. Both hydrogen and acetylene loss pathways along various photodissociation routes have been identified. The possibility that the 2,3-benzofluorene cation contributes to the unidentified infrared (UIR) bands observed from interstellar space is discussed briefly.
2004. "Controlled Self-assembly of Colloidal Cobalt Nanocrystals Mediated by Magnetic Interactions." Journal of Magnetism and Magnetic Materials 272-276:E1367-E1368. Abstract We demonstrate the possibilityof obtaining a rich set of self-assembled arrays from a single component cobalt nanocrystal (NC) system by a controlled variation of size, shape and inter-particle interactions. By selecting appropriate conditions in which one of a set of weak but competing interaction forces (steric, van der Waals, depletion, or magnetostatic) dominates we can reproducibly achieve a wide range of nanocrystal arrays. This includes hexagonal and square arrays, arrays spatially segregated by size, linear chains and lyotropic crystals exhibiting increased orientation order as a function of concentration.
2004. "In Situ Grazing-Incidence Extended X-ray Absorption Fine Structure Study of Pb(II) Chemisorption on Hematite (0001) and (1-102) Surfaces." Langmuir 20(5):1667-1673. Abstract The dominant mode of binding of aqueous Pb(II) to single crystal (0001) (C-cut) and (1-102) (R-cut) surfaces of a-Fe₂O₃ has been determined using grazing-incidence x-ray absorption fine structure (GI-XAFS) spectroscopy. Oligomeric Pb(II) complexes were found to bind in inner-sphere modes on both surfaces, which is in contrast with the binding of aqueous Pb(II) on a-Al₂O₃ (0001) surfaces, where Pb(II) was found in past GI-XAFS studies to bind in a dominantly outer-sphere mode, indicating a significant difference in reactivity of these two surfaces to Pb(II). This difference in reactivity to Pb(II) is explained on the basis of recent crystal truncation rod diffraction studies of the a-Fe₂O₃ and a-Al₂O₃ C-cut surfaces in contact with bulk water, which found major structural differences between the surfaces of these two metal oxides.
2004. "A Model for the Phase Stability of Arbitrary Nanoparticles as a Function of Size and Shape." Journal of Chemical Physics 121(9):4276-4283 . doi:10.1063/1.1775770 Abstract the abstract for this product is not available at this time.
2004. "Effects of particle morphology and surface hydrogenation on the phase stability of TiO₂." Physical Review. B, Condensed Matter 70:235403 1-13. doi:10.1103/PhysRevB.70.235403 Abstract Titanium dioxide nanoparticles are currently receiving a lot of attention due to their inherent suitability for advanced photochemical applications. Size, phase, and morphology of the nanoparticles are the critical parameters determining their performance in particular applications. A thermodynamic model devised to describe the shape of nanoparticles as a function of size has been used to predict the phase stability of titanium dioxide nanoparticles, with particular attention given to the crossover of stability between the anatase and rutile phases. Density functional calculations were used to accurately determine surface energies and surface tensions. The effects of nanocrystal morphology on the phase transition are addressed and comparisons drawn with previously reported studies. Further, the model has been applied to titanium dioxide nanoparticles with hydrogenated surfaces, to investigate the effects of surface passivation on the equilibrium shape and the phase transition, and show that surface passivation has an important impact on nanocrystal morphology and phase stability. The results show that surface hydrogenation induces significant changes in the shape of rutile nanocrystals, but not in anatase, and that the size at which the phase transition may be expected increases dramatically when the under-coordinated surface titanium atoms are H-terminated.
2004. "Effects of Particle Morphology and Surface Hydrogenation on the Phase Stability of TiO2 at the Nanoscale." Physical Review. B, Condensed Matter and Materials Physics 70(23):Art. No. 235403. doi:10.1103/PhysRevB.70.235403 Abstract The abstact for this product is not available at this time.
2004. "Predicting the Energetics, Phase Stability and Morphology Evolution of Faceted and Spherical Anatase Nanocrystals." Journal of Physical Chemistry B 108 (48):18435 -18440. doi:10.1021/jp0472459 S1089-5647(04)07245-1 Abstract the abstract for this product is not available at this time.
2004. "Predicting the Energetics, Phase Stability, and Morphology Evolution of Faceted andSpherical Anatase Nanocrystals." Journal of Physical Chemistry B 108(48):18435-18440. doi:10.1021/jp0472459 Abstract Inconsistencies in experimental thermochemical analysis of the anatase to rutile phase transition have led to various studies in order to elucidate the physical and chemical parameters affecting the stability of TiO2 at the nanoscale. Using a thermodynamic model, we present predictions of the transition enthalpy of nanocrystalline anatase and rutile as a function of shape, size, and degree of surface passivation, showing that thermochemical results can differ for various faceted or spherical nanoparticles.
2004. "Air-Broadening Parameters in the ν3 Band of 14N16O2 Using a Multispectrum Fitting Technique." Journal of Molecular Spectroscopy 228(2):593-619. Abstract Air-broadened line widths, pressure-induced shift coefficients and their temperature dependences were retrieved for over 1000 transitions in the v3 band of 14N16O2 at 6 μm. In addition, precise line center positions and relative intensities were also determined. The results were obtained by fitting simultaneously 27 spectra recorded at high resolution (0.002 cm-1 to 0.006 cm-1) with two Fourier transform spectrometers and gas sample temperatures ranging from 206 K to 298 K. It was necessary to modify the multispectrum fitting software to accommodate constraints on the retrieved parameters of closely-spaced spin-split doublets in order to successfully determine their broadening and shift parameters. The variations of the widths, shifts and their temperature dependences on the quantum numbers were investigated. Subsets of the observed line widths were reproduced to within 3% using an exponential smoothing function.
2004. "Dynamic High-Resolution H-1 and P-31 NMR Spectroscopy and H-1 T-2 Measurements in Postmortem Rabbit Muscles Using Slow Magic Angle Spinning." Journal of Agricultural and Food Chemistry 52(9):2681-2688. Abstract Postmortem changes in rabbit muscle tissue with different glycogen status (normal vs low) were followed continuously from 13 min postmortem until 8 h postmortem and again 20 h postmortem using simultaneous magic angle spinning 1H and 31P NMR spectroscopy together with measurement of the transverse relaxation time, T2, of the muscle water. The 1H metabolite spectra were measured using the phase-altered spinning sidebands (PASS) technique at a spinning rate of 40 Hz. pH values calculated from the 31P NMR spectra using the chemical shifts of the C-6 line of histidine in the 1H spectra and the chemical shifts of inorganic phosphate in the 31P spectra confirmed the different muscle glycogen status in the tissues. High-resolution 1H spectra obtained from the PASS technique revealed the presence of a new resonance line at 6.8 ppm during the postmortem period, which were absent in muscles with low muscle glycogen content. This new resonance line may originate from the aminoprotons in creatine, and its appearance may be a result of a pH effect on the exchange rate between the amino and the water protons and thereby the NMR visibility. Alternatively, the new resonance line may originate from the aromatic protons in tyrosine, and its appearance may be a result of a pH-induced protein unfolding exposing hydrophobic amino acid residues to the aqueous environment. Further studies are needed to evaluate these hypotheses. Finally, distributed analysis of the water T2 relaxation data revealed three relaxation populations and an increase in the population believed to reflect extramyofibrillar water through the postmortem period. This increase was significantly reduced ( p< 0.0001) in samples from animals with low muscle glycogen content, indicating that the pH is controlling the extent of postmortem expulsion of water from myofibrillar structures. The significance of the postmortem increase in the amount extramyofibrillar water on the water-holding capacity was verified by centrifugation, which showed a reduced centrifugation loss in muscles with low preslaughter glycogen status (0.9 vs 1.9%, p) 0.07).
2004. "Uranium Immobilization by Sulfate-reducing Biofilms." Environmental Science and Technology 38(7):2067-2074 . Abstract Hexavalent uranium [U(VI)] was immobilized using biofilms of the sulfate-reducing bacterium (SRB) Desulfovibrio desulfuricans G20. The biofilms were grown in flat-plate continuous-flow reactors using lactate as the electron donor and sulfate as the electron acceptor. U(VI) was continuously fed into the reactor for 32 weeks at a concentration of 126 íM. During this time, the soluble U(VI) was removed (between 88 and 96% of feed) from solution and immobilized in the biofilms. The dynamics of U immobilization in the sulfate-reducing biofilms were quantified by estimating: (1) microbial activity in the SRB biofilm, defined as the hydrogen sulfide (H2S) production rate and estimated from the H2S concentration profiles measured using microelectrodes across the biofilms; (2) concentration of dissolved U in the solution; and (3) the mass of U precipitated in the biofilm. Results suggest that U was immobilized in the biofilms as a result of two processes: (1) enzymatically and (2) chemically, by reacting with microbially generated H2S. Visual inspection showed that the dissolved sulfide species reacted with U(VI) to produce a black precipitate. Synchrotron-based U L3-edge X-ray absorption near edge structure (XANES) spectroscopy analysis of U precipitated abiotically by sodium sulfide indicated that U(VI) had been reduced to U(IV). Selected-area electron diffraction pattern and crystallographic analysis of transmission electron microscope lattice-fringe images confirmed the structure of precipitated U as being that of uraninite.
2004. "A Theoretical Study of the H₂S0₄ + H₂0 -> HS0₄-+ H₃0₊ Reaction at the Surface of Aqueous Aerosols. ." Theoretical Chemistry Accounts 111(2-6):182-187. Abstract No description or abstract is available at this time.
2004. "Bond-Valence Methods for pK(a) Prediction: Critical Re-Analysis and a New Approach." Geochimica et Cosmochimica Acta 68(9):2025-2042. Abstract Bond-valence methods for pKa prediction: Critical re-analysis and a new approach
2004. "Intermittent Single-Molecule Interfacial Electron Transfer Dynamics." Journal of the American Chemical Society 126(30):9374-9381. Abstract We report on single molecule studies of photosensitized interfacial electron transfer (ET) processes in Coumarin 343 (C343)-TiO2 nanoparticle (NP) and Cresyl Violet (CV+)-TiO2 NP systems, using time-correlated single photon counting coupled with scanning confocal fluorescence microscopy. Fluorescence intensity trajectories of individual dye molecules adsorbed on a semiconductor NP surface showed fluorescence fluctuations and blinking, with time constrants distributed from sub-milliseconds to several seconds.
2004. "Global Analysis of the Membrane Subproteome of Pseudomonas aeruginosa using Liquid Chromatography-Tandem Mass Spectrometry." Journal of Proteome Research 3(3):434-444. Abstract Pseudomonas aeruginosa is one of the most significant opportunistic bacterial pathogens in humans causing infections and premature death in patients with cystic fibrosis, AIDS, severe burns, organ transplants or cancer. Liquid chromatography coupled online with tandem mass spectrometry (LC-MS/MS) was used for the large-scale proteomic analysis of the P. aeruginosa membrane subproteome. Concomitantly, an affinity labeling technique, using iodoacetyl-PEO biotin to tag cysteinyl-containing proteins, permitted the enrichment and detection of lower abundance membrane proteins. The application of these approaches resulted in the identification of 786 proteins. A total of 333 proteins (42%) had a minimum of one transmembrane domain (TMD; ranging from 1 to 14) and 195 proteins were classified as hydrophobic based on their positive GRAVY values (ranging from 0.01 to 1.32). Key integral inner and outer membrane proteins involved in adaptation and antibiotic resistance were conclusively identified, including the detection of 53% of all predicted opr-type porins (outer integral membrane proteins) and all the components of the mexA-mexB-oprM transmembrane protein complex. This work represents the most comprehensive qualitative proteomic analysis of the membrane subproteome of P. aeruginosa and for prokaryotes in general to date.
2004. "Investigation of Fundamental Physical Properties of a Polydimethylsiloxane (PDMS) Membrane using a Proton Transfer Reaction-Mass Spectrometry (PRTMS)." International Journal of Mass Spectrometry 239(2-3):179-186. Abstract A membrane introduction proton transfer reaction mass spectrometry (MI-PTRMS) has been employed for the characterisation of a polydimethylsiloxane (PDMS) membrane. For this purpose the diffusion and partition coefficients (which serves as a measure for solubility) have been determined experimentally for different classes of chemical compounds both non-polar and polar species, i.e. aromatics, alcohols, ketones. It turned out that not only polar compounds exhibit strong interaction with a hydrophobic membrane such as the PDMS, but also non polar compounds as trimethylbenzene or propylbenzene which bear a relevant number of methyl groups or an alkyl chain show strong interaction with a PDMS membrane. Stronger interaction analyte-membrane leads to a slower diffusion coefficient and larger partition coefficient. The effect of the temperature on the diffusion coefficient and partition coefficient is also investigated. At higher temperature diffusion becomes faster and solubility lower. Permeability is calculated from diffusion and partition coefficients and activation energy are derived from corresponding Arrhenius plots. The MI-PTRMS system shows detection limits in the order of tens of pptv and it’s linear over five orders of magnitude.
2004. "Membrane Inlet Proton Transfer Reaction Mass Spectrometry (MI-PTRMS) for direct measurements of VOCs in water." International Journal of Mass Spectrometry 239(2-3):171-177. Abstract The use of a membrane inlet proton transfer reaction mass spectrometry (MI-PTRMS) system was investigated for the quantitative analysis of VOCs directly from water. Compounds playing an important role in environmental, biological and health issues such as methanol, acetonitrile, acetone, dimethylsulfide (DMS), isoprene, benzene, and toluene have been analyzed both in fresh and salty water. The system shows very good sensitivity, reproducibility, and a linear response of up to five orders of magnitude. The detection limit for DMS is about 100 ppt and for methanol is about 10 ppb both in fresh and salty water. The response time of the various compounds across the membrane is on the order of a few minutes. This fast response and the fact that the PTRMS can perform absolute measurements without the necessity of calibration make the system suitable for on-line and on-site measurements of VOCs directly from water.
2004. "Visualization of Distance Distribution from Pulsed Double Electron-Electron Resonance Data ." Applied Magnetic Resonance 26(1-2):23-39. Abstract Double electron-electron resonance (DEER), also known as pulsed electron-electron double resonance (PELDOR), is a time-domain electron paramagnetic resonance method that can measure the weak dipole-dipole interactions between unpaired electrons. DEER has been applied to discrete pairs of free radicals in biological macromolecules and to clusters containing small numbers of free radicals in polymers and irradiated materials. The goal of such work is to determine the distance or distribution of distances between radicals, which is an underdetermined problem. That is, the spectrum of dipolar interactions can be readily calculated for any distribution of free radicals, but there are many, quite different distributions of radicals that could produce the same experimental dipolar spectrum. This paper describes two methods that are useful for approximating the distance distributions for the large subset of cases in which the mutual orientations of the free radicals are uncorrelated and the width of the distribution is more than a few percent of its mean. The first method relies on a coordinate transformation and is parameter free, while the second is based on iterative least-squares with Tikhonov regularization. Both methods are useful in DEER studies of spin labeled biomolecules containing more than two labels.
2004. "Orientation of the g-Tensor Axes of the Rieske Subunit in Cytochrome bc1 Complex." Biochemistry 43(2):430-436. Abstract The orientation of the g-factors of the Rieske iron-sulfur protein subunit was determined in a single crystal of bovine mitochondrial cytochrome bc1 complex with stigmatellin in the Qo quinol binding site. The g-factor principal axes are skewed with respect to the Fe-Fe and S-S atom direction in the 2Fe2S cluster, which is allowed by the lack of rigorous symmetry of the cluster. The asymmetric unit in the crystal is the active dimer and the g-factor axes have slightly but noticeably different orientations relative to the iron-sulfur cluster in the two halves of the dimmer. The g~1.79 axis makes an angle of 19.8 or 40.0° with respect to the Fe-Fe direction while the g~2.024 axis is 17.6° or 35.5° from the S-S direction. These results indicate that the spectroscopic properties of the Rieske protein depend on the environment of the Rieske ‘head’ domain during the catalytic cycle of cytochrome bc1 complex. This assignment of the g-factor axis directions indicates that conformations of the Rieske protein are likely the same in the cytochrome bc1 and b6f complexes and that the extent of motion of the Rieske head domain during the catalytic cycle has been highly conserved during evolution of these distantly related complexes.
2004. "The C₃H₇⁺ Appearance Energy from 2-Iodopropane and 2-Chloropropane Studied by Threshold Photoelectron Photoion Coincidence. ." European Journal of Mass Spectrometry 10(6):819-827. doi:10.1255/ejms.685 Abstract The abstract for this product is not available at this time.
2004. "Line Intensities of CH3D in the Triad Region: 6-10 mu m." Journal of Molecular Structure 695(Sp. Iss. SI):181-188. Abstract Line intensities of the three fundamentals of the 12CH3D Triad are modeled with an RMS of 3.2% using over 2100 observed values retrieved by multispectrum fitting of enriched sample spectra recorded with two Fourier transform spectrometers. The band strengths of the Triad in units of 10-18 cm-1/(molecule cm-2) at 296 K are, respectively, 2.33 for v6 (E) at 1161 cm-1, 1.75 for v3 (A1) at 1307 cm-1 and 0.571 for v5 (E) at 1472 cm-1. The total calculated absorption arising from 12CH3D Triad fundamentals is 4.65x10-18 cm-1/molecule cm-2) at 296K. In addition, some 740 intensities of nine hotbands are fitted to 8.1%; most of the hotband measurements belong to 2v6-v6 and v3+v6-v3 near 1160 cm-1, 2v3-v3 near 1304 cm-1. The other observed hotbands are v5 + v6-v6 2v5-v5, v5+v6-v5, v3+v5-v3, and v3+v5-v5.
2004. "Strong Room-Temperature Ferromagnetism in Co2+-Doped TiO2 Made from Colloidal Nanocrystals." Journal of the American Chemical Society 126(37):11640-11647. Abstract Colloidal cobalt-doped TiO2 (anatase) nanocrystals were synthesized and studied by electronic absorption, magnetic circular dichroism, transmission electron microscopy, magnetic susceptibility, cobalt K-shell X-ray absorption spectroscopy, and extended X-ray absorption fine structure measurements. The nanocrystals were paramagnetic when isolated by surface-passivating ligands, weakly ferromagnetic (Ms * 1.5 * 10-3 íB/Co2+ at 300 K) when aggregated, and strongly ferromagnetic (up to Ms ) 1.9 íB/Co2+ at 300 K) when spin-coated into nanocrystalline films. X-ray absorption data reveal that cobalt is in the Co2+ oxidation state in all samples. In addition to providing strong experimental support for the existence of intrinsic ferromagnetism in cobalt-doped TiO2, these results demonstrate the possibility of using colloidal TiO2 diluted magnetic semiconductor nanocrystals as building blocks for assembly of ferromagnetic semiconductor nanostructures with potential spintronics applications.
2004. "Solution Structure of Hypothetical Nudix Hydrolase DR0079 from Extremely Radiation-Resistant Deinococcus radiodurans Bacterium." Proteins. Structure, Function, and Bioinformatics 56(1):28-39. Abstract Using nuclear magnetic resonance (NMR) based methods including residual dipolar coupling restraints, we have determined the solution structure of the hypothetical Deinococcus radiodurans Nudix protein DR0079 (171 residues, MW = 19.3 kDa). The protein contains eight b-strands and three a-helices organized into three subdomains; an N-terminal b-sheet (1-34), a central Nudix core (35-140), and a C-terminal helix-turn-helix (141-171). The Nudix core and C-terminal helix-turn-helix form the fundamental fold common to the Nudix family, a large mixed b-sheet sandwiched between a-helices. The residues that compose the signature Nudix sequence, GX5EX7REUXEEXGU (where U = I, L, or V and X = any amino acid), are contained in a turn-helix-turn motif on the face of the mixed b-sheet. Chemical shift mapping experiments suggest that DR0079 binds Mg2+, but, precipitates out of solution in the presence of excess Mn2+. Experiments designed to determine the biological function of the protein indicate that it is not a type I isopentenyl-diphosphate d-isomerase and it does not bind a,b-methyleneadenosine 5’-triphosphate (AMPCPP) and guanosine 5’-[b,g-imido]triphosphate (GMPPNP). The structure of DR0079 is compared to other known Nudix protein structures, a potential substrate binding surface is proposed, and its possible biological function discussed.
2004. "Electron Energy-loss Spectroscopy of Anomalous Plutonium Behavior in Nuclear Waste Materials." Micron 35:235-243. Abstract Plutonium-enriched layer has been observed in corroded spent uranium oxide fuel (CSNF). These Pu-enriched regions were examined with analytical transmission electron microscopy combined with electron energy-loss spectroscopy. The enriched region also contained U, Am, Ru, Zr, but only minor enrichment of rare earth elements. The Pu, possibly as Pu(V) according to EELS measurements, was dispersed within re-precipitated uranium oxide (identified as U3O8) nano-crystals between U(VI) secondary phases and the CSNF surface. The U, Pu, and Am enrichment was observed in the corrosion products with tests on different nuclear fuels. This may have implications for the long-term behavior of CSNF under storage in a geologic waste repository. Furthermore, there may be an increased potential for the generation of Pu-bearing colloids from this type of weathered CSNF.
2004. "The Energetics of the Hydrogenolysis, Dehydrohalogenation, and Hydrolysis of 4,4'-Dichloro-diphenyl-trichloroethane from Ab Initio Electronic Structure Theory." Journal of Physical Chemistry A 108(27):5883-5893. Abstract Electronic structure methods were used to calculate the aqueous reaction energies for hydrogenolysis, dehydrochlorination, and nucleophilic substitution by OH- of 4,4¢-DDT. Thermochemical properties ¢Hf° (298.15 K), S° (298.15 K, 1 bar), ¢GS (298.15 K, 1 bar) were calculated by using ab initio electronic structure calculations, isodesmic reactions schemes, gas-phase entropy estimates, and continuum solvation models for a series of DDT type structures (p-C6H4Cl)2-CH-CCl3, (p-C6H4Cl)2-CH-CCl2¥, (p-C6H4Cl)2-CHCHCl2, (p-C6H4Cl)2-CdCCl2, (p-C6H4Cl)2-CH-CCl2OH, (p-C6H4Cl)2-CH-CCl(dO), and (p-C6H4-Cl)2-CH-COOH. On the basis of these thermochemical estimates, the overall aqueous reaction energetics of hydrogenolysis, dehydrochlorination, and hydrolysis of 4,4¢-DDT were estimated. The results of this investigation showed that the dehydrochlorination and hydrolysis reactions have strongly favorable thermodynamics in the standard state, as well as under a wide range of pH conditions. For hydrogenolysis with the reductant aqueous Fe(II), the thermodynamics are strongly dependent on pH, and the stability region of the (p-C6H4Cl)2-CH-CCl2¥(aq) species is a key to controlling the reactivity in hydrogenolysis. These results illustrate the use of ab initio electronic structure methods to identify the potentially important environmental degradation reactions by calculation of the reaction energetics of a potentially large number of organic compounds with aqueous species in natural waters.
