New reactions of germylenes with ketones and assessment of studio general chemistry.

Abstract

New reaction modes of germylenes with ketones are presented. The germylene, Ge[CH(SiMe₃)₂]₂ (<bold>1</bold>), will undergo reversible [4+2] addition with alkyl or aryl phenones to form a conjugated triene. Anthraquinone or 1,4-naphthylquinone will undergo a similar triene formation, but an insertion by a second molecule of <bold>1</bold> yields a product stable to reversion. In these cases, the second equivalent of germylene acts as a trap for the initially formed conjugated triene. A similar germylene, Ge[N(SiMe₃)₂]₂ (<bold> 2</bold>), reacts in analogous fashion with anthraquinone or 1,4-naphthylquinone indicating that it too engages in an equilibrium with phenones. The equilibrium for <bold>2</bold> with phenones lies heavily toward free <bold>2</bold> and phenone as no triene is detected via UV/Vis or NMR spectroscopies. Successful catalytic hydrogenation of the conjugate triene formed from the reaction of <bold> 1</bold> with benzophenone is also presented. Other non-phenone ketones react with <bold>1</bold> via either CH or OH insertion. Three acetyl-containing ketones (acetone, butanone and cyclopropyl methyl ketone) have been observed to undergo CH insertion with <bold>1</bold> in the presence of one equivalent of MgCl₂. The absence of MgCl₂ yields apparent OH insertion into the enol tautomer of the ketone. All secondary ketones examined undergo OH insertion even in the presence of MgCl₂. The development, assessment and a description of a studio version of general chemistry are presented. This new course was implemented in the Fall 2002 semester at the University of Michigan. Content-based interviews focusing on equilibrium indicated that the students from the studio course had a better understanding of the underlying principles of equilibrium than their non-studio counterparts. The students enrolled in the studio course also gave more non-prompted explanations for a chemical reaction demonstrated during the interview, suggesting that they were more capable of transferring their chemical knowledge to new systems. The Motivated Strategies for Learning Questionnaire indicated that the students from the studio course were significantly more likely to rely on their peers when seeking help for the class than their counterparts. This result, coupled with student comments from two different group interviews, indicates the course successfully accomplished its goal of building a learning community.