[R-390] [OT] Acetone [WAS: How are your knobs?]

[Charles Steinmetz]

OT now, but a very interesting sub-thread.

Robert wrote:

>>  A word on acetone: it polymerizes and leaves an organic residue.

and

>>search for 'addition co polymers from aldehydes and ketones' on
>>dogpile and you will find an ample offering of references. I have also
>>seen a bottle of 'acetone' that was quite solid. It was filled with a
>>white block of plastic (acetone co polymer).

Mike wrote:

>This is interesting.
>
>I've used it for the final cleaning on lab glass and optics, and my wife, a
>chemist, has used it to clean and dry lab glass forever. Neither one of us has
>ever heard of any problems with acetone polymerizing by itself on clean glass
>surfaces. When mixed with other reagents, though not water, it may polymerize,
>and there are articles on this in the literature, but none that I could find
>for just acetone by itself or with water.

It is interesting, indeed.  I spent several hours researching the 
literature this weekend, and that was my experience as well.

Just as an initial clarification, I assume we must be talking about 
homopolymers of acetone, since we presuppose pure, clean acetone and 
substrate materials that are not organic monomers (thus, there would 
by definition be no other monomer present to form a co-polymer).

It seems to be uncontroversial that (unlike aldehydes) ketones are 
difficult to polymerize in general, and the successful polymerization 
of acetone seems to require unusual conditions: very low 
temperatures, stong acids or alkalies, or magnesium or Ziegler 
catalysts.  Spectrometrists have reported field-induced 
polymerization in field ion microscopes.  Several researchers 
reported that the polymers resulting from these methods are very 
unstable, even at room temperature.

According to the Handbook of Polymer Synthesis, which I believe is a 
canonical reference text:

>In the 1960s acetone was claimed to have been polymerized by several 
>groups, mostly by means of anionic initiators, but the identity of 
>the products of these experiments is doubtful, and reproducibility 
>is questionable. *   *   *  While the occurrence of ketone 
>homopolymerization is doubtful, more recently copolymerization of 
>acetone with formaldehyde has been reported to take place in bulk at 
>-78C with hexafluoroacetone as initiator.  The product, a copolymer 
>containing 33% acetone and 66% formaldehyde, was obtained in 50% 
>yield and was characterized as being a poly(acetal) by elemental 
>analysis, IR, and NMR. It had a reduced viscosity of 0.39 dL/g in 
>chloroform (0.2 g per 100 mL).  Another copolymerization of acetone 
>which has been reported is that with 
>dimethylketene.  Copolymerization of these monomers was accomplished 
>at -6OC in toluene, with Li alkyls as initiators.  The product was 
>shown by x-ray analysis to be highly crystalline and to consist of 
>alternating acetone and dimethylketene units.  However, this polymer 
>is not a true polyaectal, but can be considered a polyester of a 
>[beta]-hydroxy acid.

I have not been able to find any reports in the literature of the 
polymerization of acetone at room temperatures, without the presence 
of initiators or catalysts, and/or in the short time it takes a film 
of acetone to evaporate at room temperature and pressure.  This is 
interesting in itself, given that so much research has been devoted 
to attempts to polymerize acetone with so little success.  I realize 
that, as Robert said, sometimes the received wisdom dies hard even in 
science -- it just seems odd that so many researchers have devoted so 
much effort to polymerizing acetone and nobody ever noticed that all 
they had to do was pour some out in a beaker and let it evaporate.

Best regards,

Charles