Discussion For:

Gas-Phase Synthesis, Column Chromatography and Visible Spectroscopy of 5,10,15,20-Tetraphenylporphyrin

Start a New Thread [Show All Threads] [Hide All Threads] Discussion Tips

Participants of GCEW

Educators

University of Oregon

Interesting to Students!

[Read more...][Read less...]      Posted: 2010-03-31 15:11:58

Extensively student tested, this experiment is often a student favorite, especially given the colorful column chromatography.


Submitted by Dana R. Garves, University of Oregon, on behalf of past participants of the Green Chemistry in Education Workshop (GCEW).

Comment on this item

Participants of GCEW

Educators

University of Oregon

Keeping Pyrrole Pure

[Read more...][Read less...]      Posted: 2010-03-31 15:13:48

While pure pyrrole is colorless, pyrrole that has been allowed to stand in air and light is often brown due to the presence of polypyrrolic species formed under these conditions. Use of impure pyrrole is the most common cause of failure of this experiment. The chromatography is often particularly problematic when impure pyrrole has been used. Distill, or more simply, pass the pyrrole through a column of basic alumina, then store under nitrogen in a dark bottle before use. Pyrrole oxidizes to oligopyrrole, and you must distill or run through basic alumina before using in the reaction.


Submitted by Dana R. Garves, University of Oregon, on behalf of past participants of the Green Chemistry in Education Workshop (GCEW).

Comment on this item

Irv Levy

Professor of Chemistry

Gordon College

Other adsorbents

[Read more...][Read less...]      Posted: 2010-10-15 12:53:16

Neutral alumina works fine, too.

Comment on this item

Participants of GCEW

Educators

University of Oregon

Tips regarding Teflon

[Read more...][Read less...]      Posted: 2010-03-31 15:15:15

Ensure that students have the Teflon side of the septum in contact with the contents of the vial. If the Teflon is on the wrong side, the septum can deform and pop off when pressure builds up during the reaction. In addition to the potential for chemical exposure and mess, the sound of the popping septum can be quite startling.


Submitted by Dana R. Garves, University of Oregon, on behalf of past participants of the Green Chemistry in Education Workshop (GCEW).

Comment on this item

Participants of GCEW

Educators

University of Oregon

Characterization Idea

[Read more...][Read less...]      Posted: 2010-03-31 15:16:52

A UV/visible spectrum of the crude reaction product should clearly display the absorption bands due to the tetraphenylporphyrin. Students may wish to semi-quantitatively determine their yield at this point, before chromatography, both to gain information about the extent of recovery of the porphyrin in the chromatography step and to backstop against the inadvertent loss of all their material during chromatography.


Submitted by Dana R. Garves, University of Oregon, on behalf of past participants of the Green Chemistry in Education Workshop (GCEW).

Comment on this item

Participants of GCEW

Educators

University of Oregon

Eluent for the Column

[Read more...][Read less...]      Posted: 2010-03-31 15:18:03

Students may want to try reducing the polarity of the eluent for the column chromatography to improve the separation – e.g., 9:1 hexanes/ethyl acetate seems to give better separation. They should note that it will take a larger volume of solvent, and more time, to elute the product if a less polar mixture is used.


Submitted by Dana R. Garves, University of Oregon, on behalf of past participants of the Green Chemistry in Education Workshop (GCEW).

Comment on this item

Participants of GCEW

Educators

University of Oregon

Flashlight Tip

[Read more...][Read less...]      Posted: 2010-03-31 15:20:01

Holding a flashlight behind the column makes the various bands that develop much easier to see.


Submitted by Dana R. Garves, University of Oregon, on behalf of past participants of the Green Chemistry in Education Workshop (GCEW).

Comment on this item

Participants of GCEW

Educators

University of Oregon

General Suggestions

[Read more...][Read less...]      Posted: 2010-03-31 15:21:38

Finely grinding the solid up prior to the reaction will improve the yield. It is also possible to use half quantities of the reaction mix and use in a pipette column for microscale.

When heating the cap can melt and stick to the glass; stop about half an inch below the cap.


Submitted by Dana R. Garves, University of Oregon, on behalf of past participants of the Green Chemistry in Education Workshop (GCEW).

Comment on this item

Sarah Cummings

Lecturer

University of Nevada, Reno

Column chromatography idea

[Read more...][Read less...]      Posted: 2010-07-21 12:08:01

A pipette column also works well to separate the porphyrin product and is a good alternative to a burette column. 

Comment on this item