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Silene Stereochemistry

Description: The reaction of tert-butyllithium with chloromethylphenylvinylsilane at low temperatures in hexane gave a 48% yield of a mixture of the five isomers of 1,3-dimethyl-1,3-diphenyl-2,4-dineopentyl-1,3-disilacyclobutane, formed by the head-to-tail dimerization of both E- and Z-1-methyl-1-phenyl-2-neopentylsilenes, along with an acyclic dimer. These were separated and their stereochemistry was established by ('1)H- and ('13)C-NMR spectroscopy. The E- and Z-silenes were also trapped as their {4 + 2} cycloadducts with cyclopentadiene, 2,3-dimethyl-1,3-butadiene and anthracene, which also were separated and stereochemically characterized. A consistent mole ratio of 70:30 for the E- and Z-silene adducts is interpreted as evidence for stereochemical induction in the silene generation reaction. It is also suggested that the dimerization of the silenes to give the 1,3-disilacyclobutanes occurs by a nonstereospecific stepwise pathway. When E- or Z-1-methyl-1-phenyl-2-neopentylsilene was generated by the retro-Diels-Alder flow vacuum thermolysis of its corresponding cyclopentadiene or anthracene adduct at temperatures between 400 and 600(DEGREES)C and then trapped with 2,3-dimethyl-1,3-butadiene, the stereochemical distribution of the products is independent of the stereochemistry of the silene precursor, indicating that the silene is not configurationally stable towards cis-trans isomerization at these temperatures. Evidence that the intermolecular ene reaction and the {4 + 2} cycloaddition which occur with 2,3-dimethyl-1,3-butadiene are concerted is presented. When either the E- or Z-silene, generated by the sealed tube thermolysis of its anthracene adduct by 300(DEGREES)C, was trapped with trimethylmethoxysilene, the diastereomer obtained depended on the stereochemistry of the silene precursor, showing that the silene is configurationally stable towards cis-trans isomerization up to 300(DEGREES)C. The temperature dependence of the ratio of the two diastereomers obtained when the silene formed from the pure E- or Z-anthracene adduct was trapped at higher temperatures permitted the determination of an activation energy for the silene isomerization. The activation energies for the E- and Z- and Z- to E-silene isomerization are 45 (+OR-) ...
Date: August 1984
Creator: Lee, Myong Euy

Aesthetic Justifications for Music Education: a Theoretical Examination of Their Usefulness

Description: Justifications for music education have been studied only by examining historical trends in statements of aesthetic versus utilitarian values, and not from the perspective of evaluating the justifications' usefulness. A number of prominent writers in the music education field, while supporting aesthetic values as important for music education, have expressed doubts about the effectiveness of aesthetic justifications when used for convincing outsiders of the importance of music in the public school curriculum. These doubts, along with a preponderance of aesthetic justifications in the recent music education literature, led to the present study, which conducted a theoretical examination of the usefulness of aesthetic justifications for music education. The study addressed three research problems, namely: (1) the attitudes of the clientele groups of the public schools in terms of their values toward music as a subject in the schools; (2) the attitudes of the groups within the music education profession in terms of their values for music in the public schools and for the profession itself; and 3) the likelihood that justifications based upon "aesthetics" as a system of values would be accepted by the groups both inside arid outside the music education profession. A philosophical-sociological perspective was chosen for the theoretical analysis because the problems of the study concern the manner in which values are accepted or rejected by groups of people. The particular sociological theory chosen combined the symbolic interaction theory of George Herbert Mead and the sociology of knowledge as described by Peter Berger and Thomas Luckmann. Conclusions: Problems arise in justifying music education using aesthetic theory because (1) the symbolic universe of aesthetic theory is complex and is not well-understood by music educators or the clientele of the public schools; and (2) aesthetic theory represents gestures of a reference group with norms and values not usually found in ...
Date: December 1988
Creator: Paul, Stephen John