VICTOR SUSSMAN:  Molecular Radical Synthesis

  
     
 

Objective:  Synthesize a stable radical organic molecule at ambient temperatures.

  
     
 

Lab: Dr. Andrzej Rajca

  
     

 

RESEARCH RATIONALE Radical  molecules are typically intermediates in many organic reactions and due to their reactivity they are seldom found in nature as stable molecules.  Synthesizing stable radicals will give researchers the ability to utilize certain properties of radicals, like magnetism, to produce useful plastics and polymers.
RESEARCH BACKGROUND Radicals are defined as molecules that contain unpaired electrons.  Although Lewis theory (see tutorial) states that atoms/molecules strive for stability by gaining or losing electrons to fill the valence shell with 8 electrons, in certain situations this is not the case. There are some molecules that exist without filling the valence shell, like the diatomic molecule oxygen. Due to the lone electron(s) in bonding (or anti-bonding) orbitals the radical molecules typically have magnetic properties, called paramagnetism.
  The instability of most radicals is typically of that with intermediates in free radical chain reactions.  Most reactions that utilize radicals are required by synthesizing an initiator radical during the Initiation phase. The difficulty is being able to isolate these radicals for study for other synthetic processes.  Studies that incorporate the formation of radical ions are beginning to find their way into application and show promise in industrial synthetic processes.
  So why study radicals...... Dr. James Tanko put some perspective on his research by creating his Top Ten List.
   

 

RESEARCH PROCEDURES Victor's stable radical synthesis requires creating several radical intermediates.  These intermediates are very air/water sensitive and unstable, therefore most of his reactions are performed under nitrogen gas and sealed in tubes called Schlenk Tubes.

An essential component of Victor's work is to ensure that the glassware is cleaned and dried prior to placing any reactants in the apparatus.  Victor has one of the schlenk tubes in which he will be placing his initiator molecule and other reactants.  The second picture shows one reaction in a schlenk tube that is sealed under nitrogen gas.

The initiation reaction is very sensitive to air and water.  The nitrogen system here that Victor is regulating will allow only nitrogen gas into the schlenk tubes that prevents any mixing of air or water in the reaction vessels.

Isolating a product can be performed by using a column chromatography appartus.  This separates substances based on molecular properties such as mass, charge or chemical affinity.  The column that Victor is using contains silica gel, (microscopic sand beads) which separates his sample based on the molecules affinity to this gel. The greater the affinity to the gel a molecule (mobile phase) possesses the longer it takes to travel through the gel (stationary phase). Victor is hoping to obtain a relatively pure sample which he will evaluate by performing an NMR on the separated fractions.

Victor is placing his product sample into the NMR magnet and then has to evaluate the data obtained.
 

 

 

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