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Exploring the C4H7+ Energy Surface: A Computational Discovery Process for Students

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Roger S. Macomber

Natural Science Division, Pepperdine University, Malibu, CA 90263

J. Chem. Educ., 1998, 75 (10), p 1346

DOI: 10.1021/ed075p1346

Publication Date (Web): October 1, 1998

Section:

History, Education, and Documentation

Abstract

This article poses a seven part exercise to students interested in honing their skills with molecular modeling and computational chemistry. All the exercises explore different aspects of the C₄H₇⁺ carbocation manifold: cyclopropylcarbinyl, homoallyl, cyclobutyl, and bicyclobutonium ions. The student is first asked to generate structures for all possible isomers of C₄H₆ and all isomeric C₄H₇⁺ ions where the charge resides (formally) on an sp² carbon. Next, the conformational mobility of each ion is explored qualitatively. Then the student carries out semi-empirical MO calculations (e.g., AM1 or PM3) to provide the gas phase heat of formation of each C₄H₆ and C₄H₇⁺ isomer. With this information, the student predicts the most stable carbocation accessible from each hydrocarbon, and determines which carbocation rearrangements are likely to occur. Finally, the student is asked to explain why solvolyses of homoallyl, cyclobutyl, or cyclopropylcarbinyl substrates often yield comparable mixtures of products. An appendix with a complete analysis of each exercise is included.

Keywords (Audience):

Second-Year Undergraduate

Keywords (Domain):

Organic Chemistry

Keywords (Feature):

Teaching with Technology

Keywords (Pedagogy):

Testing / Assessment

Keywords (Subject):

Computational Chemistry

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This article has been cited by 2 ACS Journal articles (2 most recent appear below).

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  E. Goldstein , Andrew G. Leach
  Journal of Chemical Education2006 83 (3), 451
  Plotting how the computed energy changes as one or two internal coordinates are varied while retaining a similar atomic arrangement simplifies the potential energy surface. This simplification makes it possible for students to reliably apply theoretical ...
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Insights into Regioselective Oxy (−O−) and Imino (−NH−) Group Insertions of 3-Nortricyclanone
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The Journal of Organic Chemistry2002 67 (2), 450-456
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  Lactam 4-azatricyclo[3.2.1.02,7]octan-3-one (16a) was proven to be formed in a previously reported reaction that claimed production of lactam 3-azatricyclo[3.2.1.02,7]octan-4-one (17a). In a related reaction, bicyclo[3.1.0]hex-2-ene-endo-6-carbonitrile (...
  Abstract | Full Text HTML | Hi-Res PDF