The World of Synthetic Polymers. An Industrial Perspective

Synthetic polymers have become the building block in almost every aspects of our daily life. Billions of pounds of polymers are produced each year and the demand is continuously growing both in terms of volume and advanced performance. The general property of a class of polymers is often bounded by the synthetic process that produces the polymer. For example, polyolefins, are non-polar polymers due to the poor tolerance of transition metal catalysts toward polar monomers. Conversely, latices a…     

When Is a Bond Broken? The Polarizability Perspective.

The question of when a chemical bond can be said to be broken is of fundamental chemical interest but has not been widely studied. Herein we propose that the maxima of static polarizability along bond dissociation coordinates naturally define cutoff points for bond rupture, as they represent the onset of localization of shared electron density into constituent fragments. Examples of computed polarizability maxima over the course of bond cleavage in main-group and transition metal compounds are provided, across covalent, dative and charge-shift bonds. The behavior along reaction paths is also considered. Overall, the static polarizability is found to be a sensitive reporter of electronic structure reorganization associated with bond stretching, and thus can serve as a metric for describing bond cleavage (or diagnose the absence of a chemical bond).     

The measurement of derivative i.r. spectra—II. Experimental measurements

The performances of the Butler and Hopkins, and Savitzky and Golay methods, used in conjunction with the Trott and Beynon smoothing technique, for generating derivative i.r. spectra have been assessed experimentally, primarily in the context of peak finding. The test bands used were tert.-butyl benzene (761 cm-⁻¹), 1,2,3-trimethylbenzene (764.5 cm⁻¹) and m-xylene (766.5 cm⁻¹), together with doublets from two component mixtures of these hydrocarbons and a computer-generated doublet from the 1,2,3-trimethylbenzene band. Measurements were made on Perkin-Elmer 577 and 580 spectrometers, with off-line data processing; very satisfactory second and fourth derivative spectra were obtained. Conditions for the optimum compromise between signal to noise ratio and resolution, in terms of the derivatization and smoothing parameters, were established and prove to be similar to those previously deduced from a study of synthetic Lorentzian peak systems. Of the two derivatization techniques the Butler and Hopkins method gives the somewhat superior performance.     

S. P. L. Sørensen und die Kolloidchemie

Ohne Zusammenfassung     

Vapour—liquid equilibria. IV. The ternary system carbon tetrachloride—methanol—chloroform at 293.15 K

Total vapour pressure measurements made by the modified static method for the ternary system carbon tetrachloride—methanol—chloroform and constituent binaries at 293.15 K are presented. The different expressions for G^E suitable for correlation of these data are tested. The prediction of ternary VLE from constituent binaries is studied. Our results are compared to literature data.     

COMPARATIVE STUDY OF THIOPHENIC COMPOUNDS IN SUNNILAND OILS AND SOURCE ROCKS VERSUS OTHER OILS IN U. S. A.

This paper analyzed thiophenic compounds in Sunniland oils and source rock extractsfrom the South Florida Basin, USA using GC-MS, and compared them with those of oilsfrom shales. We found that oils derived from carbonates versus shales have different distribu-tions of thiophenic compounds. Used in conjunction with such other geochemical parametersas n--alkane, sterane and terpane compositions, thiophenic compounds will be a useful toolfor oil--oil and oil--source correlations.     

The secondary thioamide function—I. The vibrational analysis of NN′ dimethyl-dithiooxamide

The i.r., far i.r. and Raman spectra of CH₃HNCSCSNHCH₃ and the N and C deuterated derivatives are given. The assignments and a complete vibrational analysis has been proposed for the four isotopes.     

The binary system benzene—hexafluorobenzene studied by SSOZ theory and computer simulation. I. The charge symmetry model

The symmetry reduction of the SSOZ equation already developed for pure components is extended to binary mixtures. The general formalism is applied to the binary system C₆F₆/C₆H₆, whose “mixing interaction” is described by a simplified “charge symmetry model”. Varying the charge strength in a systematic way the predictions of SSOZ theory are verified by extensive computer simulation (molecular dynamics) studies. Thereby mixtures and pure components are treated in a unified way. Finally, extensions of the “charge symmetry model” are presented and the computed radial excess correlation functions are compared to those measured by neutron and X-ray scattering.     

Quality (r)evolution – guidelines and practical implementation of quality management: the U.S. perspective

 All clinical laboratories in the United States were required for the first time in 1992 to comply with universal minimum regulations: the Clinical Laboratory Improvement Amendments of 1988 (CLIA'88). The CLIA'88 regulations precipitated revolutionary and evolutionary changes based in both total quality management and continuous quality improvement principles. The regulations specify minimum requirements for personnel, quality control, and proficiency testing. Under quality assurance, the requirements are more individualized and allow laboratories to meet the needs of their customers while being in compliance with the regulations. Biannual inspection is integral to CLIA'88. However, laboratories can choose other federally approved, "deemed" professional organizations, with regulations equivalent to CLIA'88. Selection of one of these organizations allows for some flexibility in the application of the requirements, and eliminates having federal CLIA'88 inspectors perform the inspection. Since CLIA's inception in 1992, inspectors have noted a decline in the number of deficiencies cited. An improved level of proficiency testing performance also indicates that better quality test results are being provided to clinicians. The quality evolution and revolution will continue in the United States, and a major impetus will be health care reform's mandate to reduce cost. Received: 13 December 1995 Accepted: January 1996     

The scientific work of John G. Verkade—A retrospect

The scientific work of John G. Verkade—A retrospect

All authors

Dietrich Gudat

https://doi.org/10.1080/10426507.2017.1273643

Published online:

25 January 2017

Dr. John G. Verkade

Photo courtesy of Iowa State University     

19.

The i.r. spectroscopy of some highly conjugated systems—I. Rationale of the investigation     

《Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy》1976,32(8):1471-1476

The solvent shift method of BELLAMY is re-examined, particularly as a tool for the identification of vibrations that include and are coupled to carbonyl, all of which show solvent sensitivity. For α,β-unsaturated ketones, it is shown that s-cis and s-trans conformers are readily distinguished by plots of νCC vs. νCO. The nature of this coupling is discussed and it is concluded that, in so far as coupling occurs, νCO and νCC take on the character of out-of-phase and in-phase modes respectively. In either conformer, the in-phase (νCC) mode gains in relative intensity as the frequencies converge. While s-cis conformers couple more, conjugation is unaffected by this; the true index of conjugation is neither νCO nor νCC but mean frequency ν_m. The whole of the solvent effect appears to be relayed by carbonyl: even a highly polar carbon double bond is insensitive to solvent unless so coupled.     

20.

Perspective on “An extended Hückel theory. I. Hydrocarbons”     

Myung-Hwan Whangbo 《Theoretical chemistry accounts》2000,104(3-4):252-256

 The size-consistent self-consistent matrix dressing method has been applied on an open-shell single-configuration reference state. Once the reference state is converged, several low-lying roots can be obtained for the dressed configuration interaction (CI) matrices of appropriate symmetry. The CI matrices were built with a complete-active-space singles and doubles CI method in order to deal properly with multiconfiguration excited states. The vertical ionization and ionization–excitation transitions are obtained from the difference to the closed shell ground-state energy of the neutral molecule. The method has been applied to NH⁺ ₃ and N⁺ ₂ using atomic natural orbital basis sets and state-average adapted molecular orbitals. Two ²A₁ states, very similar and showing great mixing of the (2a _l ⁻¹) and (3a _l ⁻²5a _l ¹) determinants, can be assigned to the broad asymmetric band at 27.6 ± 2 eV in the photoelectron spectrum of NH₃. The possible contribution of a ²Π _g (3σ _g ⁻²1π _g ¹) state to the A shake-up peak of N₂ at 24.6 eV is also discussed. Other states, doublets and quadruplets, are reported for both systems up to 30 eV for NH₃ and 37 eV for N₂. Received: 16 September 1999 / Accepted: 3 February 2000 / Published online: 2 May 2000     

The i.r. spectroscopy of some highly conjugated systems—I. Rationale of the investigation

The solvent shift method of BELLAMY is re-examined, particularly as a tool for the identification of vibrations that include and are coupled to carbonyl, all of which show solvent sensitivity. For α,β-unsaturated ketones, it is shown that s-cis and s-trans conformers are readily distinguished by plots of νCC vs. νCO. The nature of this coupling is discussed and it is concluded that, in so far as coupling occurs, νCO and νCC take on the character of out-of-phase and in-phase modes respectively. In either conformer, the in-phase (νCC) mode gains in relative intensity as the frequencies converge. While s-cis conformers couple more, conjugation is unaffected by this; the true index of conjugation is neither νCO nor νCC but mean frequency ν_m. The whole of the solvent effect appears to be relayed by carbonyl: even a highly polar carbon double bond is insensitive to solvent unless so coupled.     

Perspective on “An extended Hückel theory. I. Hydrocarbons”

 The size-consistent self-consistent matrix dressing method has been applied on an open-shell single-configuration reference state. Once the reference state is converged, several low-lying roots can be obtained for the dressed configuration interaction (CI) matrices of appropriate symmetry. The CI matrices were built with a complete-active-space singles and doubles CI method in order to deal properly with multiconfiguration excited states. The vertical ionization and ionization–excitation transitions are obtained from the difference to the closed shell ground-state energy of the neutral molecule. The method has been applied to NH⁺ ₃ and N⁺ ₂ using atomic natural orbital basis sets and state-average adapted molecular orbitals. Two ²A₁ states, very similar and showing great mixing of the (2a _l ⁻¹) and (3a _l ⁻²5a _l ¹) determinants, can be assigned to the broad asymmetric band at 27.6 ± 2 eV in the photoelectron spectrum of NH₃. The possible contribution of a ²Π _g (3σ _g ⁻²1π _g ¹) state to the A shake-up peak of N₂ at 24.6 eV is also discussed. Other states, doublets and quadruplets, are reported for both systems up to 30 eV for NH₃ and 37 eV for N₂. Received: 16 September 1999 / Accepted: 3 February 2000 / Published online: 2 May 2000