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Full-Text Articles in Chemistry
Monte Carlo Simulation Of The Solid To Super Liquid Phase Transition Of Langmuir Monolayers Using Cross-Section Potentials, D.R. Swanson, Robert J. Hardy, Craig J. Eckhardt
Monte Carlo Simulation Of The Solid To Super Liquid Phase Transition Of Langmuir Monolayers Using Cross-Section Potentials, D.R. Swanson, Robert J. Hardy, Craig J. Eckhardt
Craig J. Eckhardt Publications
A cross-section potential which models the interaction of two planar objects of prescribed shape is developed and used to model the interactions of amphiphiles in vertical phases of Langmuir monolayers. The results of Monte Carlo simulations of an isobaric-isothermal ensemble show qualitative agreement with experiment. The model system undergoes a continuous, bound-to-free rotator transition between phases of the same symmetries as the solid (S) and super liquid (LS) phases exhibited by fatty acid films.
Piezomodulated-Raman-Spectroscopy Study Of The Phase Transition In Phenothiazine, J. Sartwell, Craig J. Eckhardt
Piezomodulated-Raman-Spectroscopy Study Of The Phase Transition In Phenothiazine, J. Sartwell, Craig J. Eckhardt
Craig J. Eckhardt Publications
Single crystals of phenothiazine undergo a displacive order-disorder phase transition near 250 K. The microscopic mechanism of this transition is not clear owing to the complexity of a disordered lattice and the lack of direct mode-anharmonicity data. Unstable optical modes have been observed in phenothiazine and are regarded as coupled, by symmetry, to an acoustic mode that becomes overdamped through the phase transition. The latter is considered to have the primary role in the phase transition. This premise is in doubt, however, based on the optical-mode anharmonicity directly observed by uniaxial-piezomodulation-Raman-spectroscopy results presented here. Anharmonic responses are observed in the …
Brillouin-Scattering Study Of The Elastic Constants Of Phenothiazine Through The Phase Transition, J. Sartwell, Craig J. Eckhardt
Brillouin-Scattering Study Of The Elastic Constants Of Phenothiazine Through The Phase Transition, J. Sartwell, Craig J. Eckhardt
Craig J. Eckhardt Publications
It has been proposed that single crystals of phenothiazine undergo a proper ferroelastic phase transition: Pnma(D2h)→P21/c (C2h). This premise is in conflict with Brillouin-scattering studies from both quasi- and high-symmetry longitudinal and transverse acoustic modes reported here. The C55 elastic constant of phenothiazine as an orthorhombic crystal at ambient conditions shows no temperature dependence. The inelastic, light-scattering spectra support an order-disorder phase transition; no significantly unstable acoustic phonons were observed through the phase transition. Laser diffraction from structural domains reveals that the crystal is polysynthetically …
Investigation Of The Β-Γ Phase Transition In Single Crystal Malononitrile By Polarized Raman Spectroscopy, S.J. Bonafede, Craig J. Eckhardt
Investigation Of The Β-Γ Phase Transition In Single Crystal Malononitrile By Polarized Raman Spectroscopy, S.J. Bonafede, Craig J. Eckhardt
Craig J. Eckhardt Publications
Temperature dependent, polarized Raman spectra in the lattice mode region for sublimed, single crystal malononitrile through the β-γ phase transition (Tc=294.7 K) are reported. Symmetry assignments and frequencies of vibrational modes are made and compared to previous studies. Nine out of 12 possible lattice modes are observed in each phase with three of the observed modes being affected by the phase transition. The temperature dependence of these three affected modes is attributed to cyano group and molecular dipole interactions between molecules in the crystal. The behavior of malononitrile through the β-γ phase transition is analogous to the …
Temporary Negative-Ion Resonances In The Nio(100) High-Resolution Electron-Energy-Loss Spectrum , K.W. Wulser, Marjorie Langell
Temporary Negative-Ion Resonances In The Nio(100) High-Resolution Electron-Energy-Loss Spectrum , K.W. Wulser, Marjorie Langell
Marjorie A. Langell Publications
The NiO(100) Fuchs-Kliewer phonon spectrum has been investigated by high-resolution electron-energy-loss spectroscopy (HREELS) at beam energies of 0.8–17 eV and the intensity distribution of the phonons relative to the dielectric properties of the NiO substrate has been considered. Over most of the range, the spectrum is well behaved, with the single-loss phonon energy at -70.5 meV and multiple excitations decreasing according to the predicted Poisson distribution. At 5.0-, 8.5-, and 13.5-eV primary beam energies, however, a substantial resonant enhancement in the phonon cross section is observed. The enhancement is accompanied by a shift from the Poisson intensity distribution to favor …
Processes For Producing Doxorubicin, Daunomycinone, And Derivatives Of Doxorubicin, Desmond M. S. Wheeler
Processes For Producing Doxorubicin, Daunomycinone, And Derivatives Of Doxorubicin, Desmond M. S. Wheeler
Chemistry Department: Faculty Publications
To produce doxorubicin and its analogues methyl 3alpha, 5alpha-dihydroxy-5beta-(trimethylsilylethynyl)- 2alpha-nitromethylcyclohexane-1beta-carboxylate acetonide is condensed with 1,4-dihydro-4,4,5-trimethoxy-1-oxonaphthalene in the presence of 1,8-diazabicyclo-5.4.0]undec-7-ene in an aprotic solvent to produce 3-(2beta-carbomethoxy-4-beta-ethynyl-4-alpha, 6alpha-(di-O-isopropylidenyl)cyclohexanyl-1-yl)-nitromethyl-4,4,5-trimethoxy-1-oxo-1,2,3,4-tetrahydronaphthalene; which is cyclized to produce 9beta ethynyl-12-hydroxy-7alpha, 9alpha-(di-O-iso propylidenyl)-6-nitro-4,5,5-trimethoxy-5,5a,6- 6a,7,8,9,10,10a,11-decahydro -11-naphthacenone. The decahydro-11-naphthacenone is converted to 7alpha 9alpha,(di-O-isopropyl-idenyl)-4,5-dimethoxy-9beta ethynyl-12-hydroxy-6-nitro-6,6a,7,8,9,10,10a, 11 octahydro-11, -naphthacenone. The octahydro-11 naphthacenone is oxidized to 7alpha-9alpha, (di-O-iso propyl-idenyl)-9beta-ethynyl-11-hydroxy-4-methoxy-6- nitro-7,8,9,10-tetrahydro-5,12-naphthacenedione which is converted to 6-desoxy-6-nitrodaunomycinone, daunomycinone and related 6-substituted analogues of daunomycinone.
Soluble Highly Reactive Form Of Calcium And Reagents Thereof, Reuben D. Rieke
Soluble Highly Reactive Form Of Calcium And Reagents Thereof, Reuben D. Rieke
Chemistry Department: Faculty Publications
A soluble highly reactive form of calcium, prepared from Ca(II) salts and a reducing agent in ethereal, polyethereal, or hydrocarbon solvents, is presented. This form of calcium can be used in the preparation of organocalcium reagents. The organocalcium reagents resulting from the reaction of the soluble highly reactive calcium with organic compounds containing either halide, cyanide, a 1,3-diene, or a polyunsaturated functionality, are stable, useful reagents for organic synthesis. The organocalcium halide reagents undergo Grignard-type reactions. They also undergo reactions with Cu(I) salts to form organocalcium cuprate reagents. The organocalcium cuprate reagents undergo a variety of cross-coupling reactions. The soluble …
Preparation And Use Of (2-Butene-1,4-Diyl)Magnesium Complexes In Organic Synthess, Reuben D. Rieke
Preparation And Use Of (2-Butene-1,4-Diyl)Magnesium Complexes In Organic Synthess, Reuben D. Rieke
Chemistry Department: Faculty Publications
The magnesium complexes of cyclic hydrocarbons, such as 1,2-dimethylenecycloalkanes, are readily prepared in high yields using highly reactive magnesium. Reactions of these (2-butene-1,4-diyl)magnesium reagents with electrophiles such as dibromoalkanes, alkyl ditosylates, or bromoalkylnitriles serve as a convenient method for synthesizing spirocyclic systems. Significantly, spirocarbocycles prepared by this method contain functional groups such as the exocyclic double bond or a keto group in one of the rings which could be used for further elaboration of these molecules. Furthermore, fused bicyclic systems containing a substituted five-membered ring can be conveniently prepared at high temperatures by the reactions of (2-butene-1,4- diyl)magnesium complexes with …
Preparation Of Functionalized Polymers Utilizing A Soluble Highly Reactive Form Of Calcium, Reuben D. Rieke
Preparation Of Functionalized Polymers Utilizing A Soluble Highly Reactive Form Of Calcium, Reuben D. Rieke
Chemistry Department: Faculty Publications
Calcium-substituted polymeric reagents are provided. These reagents can be prepared via the oxidative addition of a soluble highly reactive calcium species to organic and inorganic polymers containing alkyl, aryl, or alkylaryl pendent groups substituted with halide atoms, cyanide molecules, 1,3-dienes, or any conjugated poly unsaturated system. Preferably, the polymer is a cross linked p-bromopolystyrene, p-chloropolystyrene, p-fluoropolystyrene, or chloromethylated polystyrene. Preferably, the soluble highly reactive calcium species is prepared from the reduction of Ca(II) salts with an alkali metal arene, such as lithium biphenylide. These calcium-substituted polymeric reagents react with a variety of electrophiles to yield functionalized polymers. Reaction with Cu(I) …
Telomere Processing In Euplotes, Joris Robert Vermeesch, Dewight Williams, Carolyn M. Price
Telomere Processing In Euplotes, Joris Robert Vermeesch, Dewight Williams, Carolyn M. Price
Chemistry Department: Faculty Publications
In Euplotes crassus millions of telomeres are synthesized during the sexual phase of the life cycle. Since these newly synthesized telomeres are longer than normal macronuclear telomeres, they must be trimmed to the mature size. We have examined the timing and mechanism of this trimming step. We have shown that a sudden decrease in telomere length takes place at a specific time during macronuclear development. The decrease in telomere length is not caused by incomplete replication of the most terminal DNA sequences; rather it is the result of an active processing event that occurs independently of DNA replication. The developmentally …
Preparation Of Functionalized Polymers Utilizng A Soluble Highly Reactive Form Of Calcium, Reuben D. Rieke
Preparation Of Functionalized Polymers Utilizng A Soluble Highly Reactive Form Of Calcium, Reuben D. Rieke
Chemistry Department: Faculty Publications
Calcium-substituted polymeric reagents are provided. These reagents can be prepared via the oxidative addition of a soluble highly reactive calcium species to organic and inorganic polymers containing alkyl, aryl, or alkylaryl pendent groups substituted with halide atoms, cyanide molecules, 1,3-dienes, or any conjugated poly unsaturated system. Preferably, the polymer is a cross linked p-bromopolystyrene, p-chloropolystyrene, p fluoropolystyrene, or chloromethylated polystyrene. Preferably, the soluble highly reactive calcium species is prepared from the reduction of Ca(II) salts with an alkali metal arene, such as lithium biphenylide. These calcium-substituted polymeric reagents react with a variety of electrophiles to yield functionalized polymers. Reaction with …