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Conformational analysis of (S)-(+)-1-bromo-2-methylbutane and the influence of bromine on conformational stability
No full text(S)-(+)-1-bromo-2-methylbutane was investigated using vibrational circular dichroism (VCD). Experimental
absorption and VCD spectra of (+)-1-bromo-2-methylbutane in CDCl3 solution were recorded in the 2000-
900 cm-1 region, and they were compared with the ab initio predictions of absorption and VCD spectra
obtained with density functional theory using the B3LYP/6-31G* basis set for (S)-1-bromo-2-methylbutane.
This comparison indicates that (+)-1-bromo-2-methylbutane is of the (S) configuration and exists in several
conformations. The results obtained for (S)-(+)-1-bromo-2-methylbutane are also compared to those for (S)-
(+)-3-(2-methylbutyl)thiophene, which indicates that the predominant conformations are influenced by the
substitution of bromine with thiophene ring
Vibrational circular dichroism spectra of chirally substituted polythiophenes
No full textPoly-3-[5-(mentholate)-pentyl]thiophenes in both enantiomeric forms and with a high degree of regioregularity have been synthesized. Circular Dichroism spectra have been taken in the UV and in the IR ranges in chloroform solutions. While the UV-CD spectra are quite weak, the IR-CD spectra have shown many signals, most of them mirror images for the two enantiomer
Absolute configuration and conformational stability of (S)-(+)-3-(2-methylbuthyl)thiophene and (+)-3,4-di[(S)-2-methylbutyl)]thiophene and their polymers
No full textEnantiopure (+)-3-(2-methylbutyl)thiophene I and (+)-3,4-di(2-methylbutyl)thiophene II and their polymers
were prepared using literature procedures and investigated using vibrational circular dichroism (VCD).
Experimental absorption and VCD spectra of (+)-3-(2-methylbutyl)thiophene, (+)-3,4-di(2-methylbutyl)-
thiophene, and their polymers in CDCl3 solution were recorded in the 2000-900 cm-1 region, and the
experimental absorption and VCD spectra of (+)-3-(2-methylbutyl)thiophene were compared with the ab
initio predictions of absorption and VCD spectra obtained with density functional theory using B3LYP/6-
31G* basis set for (S)-3-(2-methylbutyl)thiophene. This comparison indicates that (+)-3-(2-methylbutyl)-
thiophene is of the (S) configuration and has six predominant conformations in CDCl3 solution and allows to
securely distinguish the vibrational motions of the thiophene ring from those of the substituent moiety
Circular Dichroism Spectra of Regioregular Poly[3[(S)-2-methylbutyl]-thiophene] and of Poly[3,4-di[(S)-2-methylbutyl]-thiophene]
No full textUltraviolet absorption and Circular Dichroism spectra in the region 300-700 nm for highly regioregular samples of Poly{3[(S)-2-methylbutyl]-thiophene} are reported for solutions in good and bad solvents, at variable temperature, and for films in various conditions. In the latter case novel CD data up to the melting temperature provide some hints for the self-assembling process towards supramolecular organization. UV and CD data are also reported on the related polymer Poly{3,4-di[(S)-2-methylbutyl]-thiophene}
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
EQUIVALENCE OF THE SEMICLASSICAL MODELS FOR VIBRATIONAL CIRCULAR DICHROISM
No full textAuthor Institution: Department of Chemistry, Vanderbilt UniversityThe bond moment model for VCD is reformulated to eliminate an existing inconsistancy and it is shown that the reformulated bond moment model, charge flow model and bond current model are all equivalent in the final expression for VCD intensity
NEW DEVELOPMENTS IN RAMAN OPTICAL ACTIVITY
No full textAuthor Institution: Department of Chemistry, Vanderbilt UniversityRaman optical activity (ROA) is conventionally measured by modulating the incident laser polarisation between right and left circular polarisation states and measuring the difference in the scattered Raman intensities with a dispersive spectrograph. In this presentation a new procedure for measuring ROA using a Fourier transform technique based on Martin-Puplett interferometer will be explained. Two experimental quantities, namely the Stokes parameters S1 and S3 can be simulataneously measured
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