P946: Integration of computational chemistry in the organic chemistry laboratory [WITHDRAWN]

Author: Brian J. Esselman, University of Wisconsin, USA

Co-Author: Nicholas J. Hill, University of Wisconsin, USA

Date: 8/6/14

Time: 5:15 PM6:30 PM

Room: LIB

Related Symposium: S33

Computational chemistry has become fully and authentically integrated into the introductory organic chemistry laboratory curriculum at the University of Wisconsin-Madison. In a laboratory course that instructs over 500 laboratory students per term, the use of the Gaussian 09 suite of programs within the WebMO interface has become almost as common-place as NMR spectroscopy. Students begin with a set of introductory exercises designed to develop proficiency with WebMO and reinforce their understanding of key concepts related to computational chemistry, molecular orbitals, and chemical reactivity. Students build on these exercises during the semester to use computational chemistry to obtain and visualize molecular structures and conjugated systems, predict NMR and IR spectra and NBO atomic charges, and explain the regio- and stereochemical outcomes of reactions that they perform in the lab.

P843: Proper resonance depiction of Acylium cation – high level and student computational investigations


Author: Brian J. Esselman, University of Wisconsin, USA

Co-Author: Nicholas J. Hill, University of Wisconsin, USA

Date: 8/6/14

Time: 2:05 PM2:25 PM

Room: LMH 176

Related Symposium: S55

The electronic and molecular structure of the acylium cation ([CH3CO]+) receives varied treatment in undergraduate textbooks and online resources. The structure of acylium is typically represented as a combination of resonance structures containing C-O triple and double bonds, the latter structure occasionally being shown with a bent C-C-O bond. Such a treatment is inconsistent with the experimental and theoretical data, which indicate that acylium is a linear molecule of C3v geometry containing a C≡O bond, and can lead students to an incomplete understanding of structure, conjugation, and charge distribution. We present a set of simple computational chemistry exercises that allow students to calculate and rationalize the most accurate resonance representation of the acylium cation via WebMO/Gaussian09.

P263: Visible light photocatalysis – shining light on organic chemistry [WITHDRAWN]

Author: Nicholas J. Hill, University of Wisconsin-Madison, USA

Co-Author: Tehshik P. Yoon, University of Wisconsin-Madison, Madison, USA

Date: 8/4/14

Time: 2:25 PM2:45 PM

Room: LMH 114

Related Symposium: S7

Visible light is the ideal green reagent for chemical synthesis in that it is highly abundant, non-toxic, and does not generate waste products. Until recently, however, few practical methods existed to harness visible light for use in organic synthesis. This paper describes an operationally simple yet pedagogically rich undergraduate lab project designed to introduce upper-level students to the concept of visible light photocatalysis – in essence, the use of visible light to promote organic reactions that do not proceed under standard conditions. The project was adapted from the current research literature and focused on the use of readily accessible Ru(II)-polypyridyl coordination complexes as photocatalyst precursors. In the lab, students screened various complexes and conditions for their ability to promote Diels-Alder cycloadditions between a range of electronically mismatched substrates. Such reactions typically require harsh conditions and specialized apparatus yet proceed rapidly under photocatalysis. Students shared their experimental results with the class in order to critically analyze the scope and limitations of the catalyst system. The project exposed students to cutting-edge ideas in green organic synthesis and contemporary catalysis within the context of a familiar, sophomore-level reaction.