Computational Chemistry Final Project

 

One of the goals of the problems sets I have assigned has been to give you a sense of the breadth of quantum chemistry.  We can predict geometries, vibrational frequencies, NMR chemical shifts, relative stabilities of families of isomers, activation energies, and reaction energies for organic, inorganic, and organometallic systems.  With contemporary methods, we can generate reasonable predictions for literally any small molecule or complex one could imagine.  This enables us to go well beyond what is known experimentally, and it can guide future experimentation.  Moreover, if we use methods of sufficient rigor, we can predict properties as accurately, or more accurately, than experimental measurements.  This is especially true for short lived and/or dangerous species.  In short, while we have not seen all that chemists do with computation nowadays, we have nonetheless seen a lot.

 

We will spend the last half of the semester working on projects of your own choosing.  You are free to choose any subject to which the quantum chemistry you have learned can be meaningfully applied.  (So this does exclude studying systems like enzymes or polymers.)  Perhaps one of the problem sets has inspired you to explore a topic in greater detail, or the experimental research you or your classmates have done lend themselves to computational exploration.  I have some suggested topics below.

 

Here are the parameters for your project:

 

·        You must base your work on at least one article from the primary chemical literature.  The paper can be experimental or theoretical, or both (combinations are common nowadays).  You are encouraged to try to reproduce theoretical results reported in the article, but you must make new predictions as well, either by applying the same method to new systems or new methods to the same systems.  (When you write your paper and present your talk, you must use at least two other references not counting web sites.  See below for details.)

 

·        Every person must base his or her work on a different article from the literature.  (You are, of course, encouraged to help one another with all aspects of the project.)  First come, first served: the first person to submit a proposal on a particular paper lays claim to it.

 

·        At least one of your predictions must be tested against experimental data.  However, do not be cramped by this!  It is common for computational studies to validate their methodology against some experimental measurements, but then go on to make predictions that may not be verified for years to come.

 

·        Do not worry about what specific methods you should use.  I will recommend levels of theory and basis sets appropriate to the systems you wish to study.

 

·        In your talk and paper on your work, you must provide at least some qualitative discussion of your computed results.  This could take the form of discussing periodic trends, using Lewis structure, making simple molecular orbital arguments, rationalizing systematic errors in your predictions as compared to experiment, etc.  What I want you to avoid is merely tabulating numbers and calling it good!  Chemistry—even computational chemistry—is not just numbers!

 

Here are some suggested topics (admittedly biased by my personal scientific history):

 

  • Show those SN2 reaction who’s boss!  Consider tackling the project I outlined on Problem Set 4, number 4.  (A recent study of SN2 reactions is here: “Steric Retardation of SN2 Reactions in the Gas Phase and Solution.” Vayner, G.; Houk, K. N.; Jorgensen, W. L.; Brauman, J. I. Journal of the American Chemical Society 2004, 126, 9054-9058.  You are free to go back to earlier papers on SN2 reactions if you wish.)

 

  • Extend the work done by my former research students Amber Converse ‘04 and Luke Valin ’05 on isoprene ozonolysis in the atmosphere: “Quantum Chemical and Master Equation Studies of the Methyl Vinyl Carbonyl Oxides Formed in Isoprene Ozonolysis.” Kuwata, K. T.; Valin, L. C.; Converse, A. D.   Journal of Physical Chemistry A 2005, 109, 10710-10725.

 

  • Find how well quantum chemistry can predict the geometries and vibrational frequencies of the new organometallic molecules made by Prof. Fischer and his students: “(2-(Dimethylamino)ethyl)cyclopentadienyl Group VI Metal Carbonyl Anions and Divalent Tin(IV) Derivatives.” Fischer, P. J.; Krohn, K. M.; Mwenda, E. T.; Young, V. G., Jr.
    Organometallics 2005, 24, 1776-1779.  (Also see the Supporting Information.)

 

  • Extend this classic work on stratospheric ozone depletion to bromine- or iodine-containing compounds: “The Possible Role of Chlorine Trioxide Isomers in Relation to Stratospheric Ozone.” Rauk, A.; Tschuikow-Roux, E.; Chen, Y.; McGrath, M. P.; Radom, L.  Journal of Physical Chemistry 1993, 97, 7947-7954.

 

  • Test the ability of different quantum chemical methods to predict bond dissociation energies for oxygendated free radicals, important (and often dangerous) intermediates in atmospheric and combustion chemistry: “Bond Dissociation Energies of Organic Molecules.”   Blanksby, S. J.; Ellison, G. B.  Accounts of Chemical Research 2003, 36, 255-263.

 

Here are some key websites for searching the chemical literature (on the Macalester network):

 

http://pubs.acs.org/index.html

 

This site gives you access to every article published by the American Chemical Society since the 19th century!  (This includes the five articles listed above.)  Moreover, the entire contents of every article are fully searchable.  This is a very powerful resource.

 


http://portal.isiknowledge.com/portal.cgi/portal.cgi?DestApp=WOS&Func=Frame&Init=Yes&SID=4DdIGM1o36gI9AKld6J

 

This site lets you search all of the chemical literature published since 1985.  This includes many journals for which Macalester does not have a subscription.  However, you can request these articles via interlibrary loan.

 

Project Timetable: What you have to do, and when!

 

  • Wednesday, March 21: E-mail me a brief proposal that (1) cites the article you have chosen, (2) summarizes this article, (3) outlines what kinds of calculations you will be doing, and (4) discusses what your scientific goals are for your project.  This should require no more than one page of writing.  You are encouraged to consult with me in person or by e-mail before you turn in your proposal.  Again, if you are eager to lay claim to a particular paper, turn in your proposal before March 21.

 

  • Monday, April 9: Give a five-minute update to the class on how your calculations are progressing, and if you have modified any of your project goals.

 

  • Monday, April 23: Turn in a first draft of your paper.  I do not expect you to have completed all your calculations by this date, but your draft should resemble the final paper as much as possible.  (Actually, it is normal for scientists to start writing a paper before all the data have been collected precisely to clarify what further experiments and calculations need to be done.)  My expectations for your paper are discussed below.  The more work you do at this point, the better the feedback I can offer you before you write the final draft of your paper.

 

  • Monday, April 30: Give a 20-minute oral presentation during class.  My expectations for your talk are discussed below.

 

  • Friday, May 4: Turn in the final draft of your paper.

 

Paper Expectations

 

The general format is the same followed for Physical Chemistry I lab reports.  Here are the details: Your paper should contain each of the following sections, in the order given: Title, Abstract, Introduction, Procedure, Results and Discussion, Conclusions, Acknowledgment, References, [optional Appendix].

 

The Title should be specific and descriptive, but not overly long.

The Abstract should, in fewer than 250 words, summarize the entire work: the purpose, procedure, key results, and their significance should all be briefly addressed in this essential part of your paper.  The Abstract is not the place to introduce your calculations or describe the background in great detail.  Stated in another way, the paper really begins with the Introduction, not the Abstract.  Most scientists write the Abstract after they have written the rest of the paper, since it summarizes the work described.  Never present material in the Abstract that you have not also presented somewhere in the main body of the paper.

The Introduction should present the scientific motivation and background for your project.  At a minimum, you should discuss the article from the chemical literature that inspired your study, as well as insights gained from two other sources, not counting web sites.  In this section you must also state clearly what the goals of your project were.

The Procedure should provide a concise description of the types of calculations you performed (e.g. locating transition structures by interpolation), what level(s) of theory you used (e.g. B3LYP) and what basis set(s) you used (e.g. 6-31G(d)).  You should cite Gaussian 03 (see the raw output for citation information) and WebMO, but you do not need to cite any references for your methodology. 

The Results and Discussion section presents the key numerical results, comparison to experimental measurements whenever possible, and your interpretation of the results.  Present your results in tables or graphs as much as possible.  I also encourage you to use Chem Draw both to show molecular structures and to construct diagrams.  Three-dimensional renderings (in color) of molecules may also be appropriate, especially for your talk.  It is appropriate here to discuss any problems you had in your calculations, and what you did to (try to) fix these problems.  As I discuss above, it is essential that you provide some qualitative discussion of your numbers.  You should draw on other references to help you interpret your data.

The Conclusions section should summarize what you have accomplished in your project.  Unlike the Abstract, the conclusion need not recapitulate every part of the paper.  This section also should contain reflections on what hypothetical future calculations would be useful or interesting.

The Acknowledgment section should thank every person who helped you with this project.

References:  You must cite all sources you have used except for course handouts.  Insert a superscript number the first time you cite a particular reference, and always use the same superscript number whenever you cite the same source in your report.  Instead of using footnotes, collect all citations in this final section.  Follow the American Chemical Society’s conventions:

 

Books without Editors: Author 1; Author 2; Author 3; Author 4.  Book Title, number of ed.; Publisher: Place of Publication, Year; Number of Chapter(s) Cited.  For example,

Masterton, W. L.; Slowinski, E. J.; Stanitski, C. L.  Chemical Principles, 5th ed.; Saunders: Philadelphia, 1980; Chapter 23.

 

Books with Editors: Author 1; Author 2; Author 3; Author 4.  Chapter Title.  In Book Title, number of ed.; Editor 1; Editor 2, Eds.; Publisher: Place of Publication, Year; Number of Any Specific Chapter(s) Cited.  For example,

Montgomery, M.; Norman, J.  RNAi and Cosuppression: Double-stranded RNA as an Agent of Sequence-Specific Genetic Silencing in Animal and Plants.  In Molecular Biology of Double-stranded RNA: Concepts and Applications in Agriculture, Forestry, and Medicine.  Tavantzis, S., Ed.; CRC Press: New York, 2001; Chapters 3-5.

 

Articles: Author 1; Author 2; Author 3.  “Title of Article.”  Name of Journal Year, Volume, Beginning – Ending Page.  For example,

Kuwata, K. T.; Erickson, R. I.; Doyle, J. R. “Improved Interatomic Potentials for Copper and Aluminum Sputter Atom Transport Simulations.”  Nuclear Instruments and Methods in Physics Research B 2003, 201, 566-570.

 

Software: Author 1; Author 2; Author 3.  Name of Program; Publisher: City, Year.  For example,

Corchado, J. C.; Chuang, Y.-Y.; Coitiño, E. L.; Truhlar, D. G. GAUSSRATE 9.1; Department of Chemistry and Supercomputer Institute, University of Minnesota: Minneapolis, MN, 2003.

 

Web Sites: Cite their URL.  Also note the last day you accessed the site.  For example,

http://bcs.whfreeman.com/qca/ (accessed 2/17/2005).

 

           An Appendix is not required, but it is a good place to place extra data that you should feel should be presented, but is too unwieldy to fit into the Results and Discussion section.

 

Finally, I have no absolute minimum or maximum length, but somewhere between 1500 and 2500 words should make the paper sufficiently detailed without being tedious.

 

Talk Expectations

 

Prepare a formal presentation using PowerPoint or transparencies.  Follow the same structure that you use for your paper, except that you would not have an abstract.  Be prepared to answer questions from me and from your classmates after the talk.

 

For your talk, I do have absolute time limits.  It must be between 15 and 20 minutes, not counting time for questions.  Practicing the talk will enable you to fit it into the required length.

 

Grading

 

Your work on this project will be graded out of 100 points, earned in the following ways:

 

Max Points

Task

10

Proposal

5

Five-Minute Update

20

First Draft of Paper

25

Oral Presentation

40

Final Paper

 

As stated in the course syllabus, the final project is worth 30% of your overall grade.

 

 


REVISED COURSE SCHEDULE (including final project deadlines)

 

Day

Date

What’s Due

What’s Happening in Class

M

3/5

PS 5

Lecture on basis sets, introduction to final projects, start searching the literature

3/12 – 3/16           Spring Break (no classes)

M

3/19

 

Lecture on levels of theory and highly accurate methods, hand out and introduce Problem Set 6

W

3/21

Proposal

Please e-mail to me; note that this is not due on a Monday!

M

3/26

PS 6

Brief lecture on solvation, introduce and discuss your proposals, start working on final project calculations!

M

4/2

 

Continue final project calculations

M

4/9

Update

Listen to and discuss updates, continue final project calculations

M

4/16

 

Continue final project calculations

M

4/23

First Draft

Continue final project calculations

M

4/30

Talk

Come ready to listen and ask questions of your colleagues!

F

5/4

Paper

This is when your final exam is scheduled; deadline is not negotiable!