From: Ben Ruekberg <bruekberg**At_Symbol_Here**CHM.URI.EDU>
Subject: Re: [DCHAS-L] Safer Diels-Alder reaction
Date: Fri, 19 Jul 2019 11:38:04 -0400
Reply-To: bruekberg**At_Symbol_Here**chm.uri.edu
Message-ID: 00e501d53e47$fb912050$f2b360f0$**At_Symbol_Here**chm.uri.edu
In-Reply-To


I don’t know what the exact procedure you are planning to use, but a simple solution comes to mind.

 

First, let me suggest that you perform the cracking using the apparatus described in DOI: 10.1021/ed064p726. (You may wish to switch the hose attached to the bottom nipple of the fractionating column to the top one.  The distillation may go faster.)  It is simpler to set up and to use.  Cyclopentadiene has an unpleasant odor and this system reduces the escape of the vapor.

 

In answer to your actual question, let me suggest that you have the maleic anhydride dissolved in ethyl acetate in the receiver flask of the distillation apparatus.  This will assure that the cyclopentadiene will be added drop-wise.  If needed, you can also cool the receiver flask in a water bath or an ice/water bath (or even an acetone/ice bath).  There is some advantage to having the condenser of the distillation apparatus above the receiver flask to act as a reflux condenser IF you add a glass tube that rises vertically above the condenser inserted immediately after the take-off adapter and then going to the filter flask.  (A short section of PVC tubing is probably preferable to rubber tubing for this purpose.)  The filter flask can be held near the end of the glass tube on a ring stand.

 

(While it is common to block the nipples of the fractionating column, DO NOT DO THAT with the recommended apparatus—it will change the system to a vacuum distillation.  You want the air flow unrestricted.)

 

If I have been unclear, please feel free to contact me privately, bruekberg**At_Symbol_Here**chm.uri.edu.

 

Thank you very much,

 

Ben  

 

From: ACS Division of Chemical Health and Safety [mailto:DCHAS-L**At_Symbol_Here**PRINCETON.EDU] On Behalf Of Denlinger, Kendra
Sent: Friday, July 19, 2019 10:41 AM
To: DCHAS-L**At_Symbol_Here**PRINCETON.EDU
Subject: [DCHAS-L] Safer Diels-Alder reaction

 

Hello everyone,

I'm teaching an organic lab right now (my first time teaching this course), and we're supposed to do a Diels-Alder reaction in a few weeks. It's a reaction between cyclopentadiene and maleic anhydride, and the students are supposed to "crack" dicyclopentadiene to cyclopentadiene using a distillation with mineral oil, and then react cyclopentadiene with maleic anhydride in ethyl acetate (which is a very exothermic reaction). Long story short, the whole thing sounds like an accident waiting to happen. 

 

I know there has got to be a safer (and maybe even greener!) Diels-Alder reaction out there for organic lab students, but I don't know exactly where to look and thought maybe it would be a good question for all of you! I don't have a long time to search and test things, so if someone has a Diels-Alder procedure you use at your university that works and is safer, I would love to hear about it!

 

Thanks for any assistance!

Kendra Denlinger

 

Kendra Leahy Denlinger, Ph.D.

Adjunct Faculty

Department of Chemistry

Xavier University

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