Ask A Scientist Chemistry Archive

From:       connie
Text:       I am a 7th grade science teacher in the Princeton, NJ area and my 
students are completing their science projects this year.  One of my students 
tested the strength of super glue as compared to other adhesives for the 
strongest.  It does not say on the label what is in it.  Anybody know?  Also, 
what type of chemical reaction/change occurs when it is placed on metal?

Response #:  1 of 1
Author:      Robert Topper
Text:        Great! A question I can partially answer...  Krazy Glue/Super 
Glue are commercial (brand) names for Methyl alpha-cyanoacrylate.  Here is the 
chemical structure:
H  COOCH3
 \/
  C = C
 /\ 
H  CN

My organic text tells me that if this stuff is spread in a thin film between 
two surfaces, traces of basic impurities (like rust and other metal oxides) 
can catalyze its rapid polymerization.  The polymerization happens because 
both CN and COOCH3 are powerful electron-withdrawing groups, so the anion 
precursor needed to form the first link in the polymer is very stable.  
Apparently the trace impurities leave a trace of base (OH-) on the metal 
surface (sounds right for metal oxides to do this), and this is what initiates 
the polymerization.  Try having the students clean the metal surfaces really 
well (perhaps with steel wool followed by kerosene) and then try to glue them 
together.  If all of this is right, it should be difficult for the Super Glue 
to harden.