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This experiment tasks students with preparing triphenylphosphine sulfide, and the corresponding I2 adduct, then characterizing these products using common instrumental methods. Students are asked to consider MOs and tie this to their Lewis bonding depiction for the final product. This discussion is supported by WebMO calculations and tied to the experimental data obtained by the student.
If you would like to use this lab, please complete the feedback form (faculty files) and let me know how you adapt it. I would like to publish this procedure (eventually), and I am open to collaborative projects to get this to the best final form.
| Attachment | Size |
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| Ph3P Lab VIPEr.docx | 20.92 KB |
- Construct an MO diagram for I2, and relate this to the bonding in the Ph3PS-I2 complex
- Using MO theory as a basis, decide on the best Lewis representation for Ph3PS-I2
- Discover the wealth of bonding modes within main group species
- Identify changes in the observable spectra for P(III) and P(V) compounds
- Search and reference the primary chemical literature using correct ACS reference formatting
This experiment is run using our in house instumentation including:
- NMR spectrometer capable of acquiring 1H and 31P spectra
- IR spectrometer
- UV-vis spectrometer (we acquire data on a Spec200 that works just fine for this)
- GC-MS (optional)
These spectra are provided as faculty files. If you do not have any of these capabilities, the spectra may be given to students as a handout.
Additionally, the experiment will require use of round-bottomed flasks, condensers, beakers, scintillation vials, hot plates, and gravity filtration apparatus (stemless if hot filtration required). Solvents and reagents are typically already present in the department, or may be purchased at reasonable cost.
I use this lab as the first experiment of the semester, and begin the first week's activity after the introduction and lab safety discussion.
Prior to running the experiment, I prepare approximately one batch of each product (Ph3PS and Ph3PS-I2) in case of a laboratory mishap. The products are indefinitely stable under ambient conditions.
I do not describe the reaction as a redox process, or suggest a bond order (i.e. I try to write the formula for Ph3PS with an ambiguous bond order, as shown here).
Depending on the age of your bottle of Ph3P, you may spot a small quantity of Ph3P=O in the 31P spectrum (small peak around 30 ppm in the included spectrum). This may be an opportunity to discuss connections to biochemistry or atmospheric oxidation, or ask students to draw Lewis depictions of these species.
I teach my students how to manually run their own NMR spectra using TopSpin at this point (they have previously learned 1H and 13C using the autosampler). I typically discuss the differences between 31P{1H} and 31P (non decoupled) spectra at this time. Note that the lab handout has some instructions specific to the Bruker software that may be updated if you use a different spectrometer.
Literature articles describing the crystal structure of the final adduct (and related I2 species) are linked here. I have not typically gone into great detail about this, as the assembled I2 ribbons can confuse the students that are just putting the basic concepts together.
Evaluation
This lab report is graded using the attached rubric (see faculty files).
Over the last four iterations of this lab, the average total score was ~42/50 (n = 21). Students are generally good at recognizing that a redox process is occurring, though some struggle with this realization. Most students generate a Lewis structure with a dative bond, though some do not use the MO diagram to infer a reasonable direction for the dative interaction. I typically work through this with the students, asking them questions like "which orbitals have electrons?" and "what orbitals are interacting in your Lewis depiction?" This has been a good introduction to these synthetic and instrumental methods, and gives the lab partners an opportunity to divide up their responsibilities.
I plan to adopt this lab this semster. May I have acces to the faculty files?
Jennifer - you should have access to the faculty-only files. Please double-check and let us know if not.
Got em! Thank you.
I would like to undertake this lab. How do I get access to faculty files?
Hi Lola,
You need to request faculty privileges in order to access these files. You should be able to do that through your account settings. Once you have requested them, one of the admins will review your account. Be sure you have used an institutional email address and/or a link to your chemistry department to aid in the review process.
Let me know if you have questions!
In reply to Hi Lola, You need to… by Nicole Crowder / University of Mary Washington
Hi Nicole,
I've requested faculty privileges to access the files around a week ago. When will these files be reviewed?
Hi Lola,
Your account is under review. You should have received an email 1-2 weeks ago requesting more information. Please check your spam folder.