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Safety Hazard from m-Toluidine To the Editor: For several years we have used an experiment in our introductory organic chemistry laboratory involving the synthesis of an aryl iodide by treatment of a diazo- nium salt with potassium iodide. Several inexpensive aromatic amines have been used as starting materials and over a period of time we have probably had four or five hundred students run these syntheses. On three occasions, once two years ago and once again this spring, we have experienced very violent reactions at the point in this synthesis where the solution of potas- sium iodide has just been added to the ice-cold solution of diazonium salt. The reaction mixture, contained in an open beaker, was blown to the ceiling and a sharp crack was heard. In these three cases the amine from which the diazonium salt had been prepared was m-tolu- idine. Of the other half-dozen amines we use, none has ever behaved this way and nz-toluidine has only done so three times although we have used it on perhaps fifty occasions. When it does not go wrong, the reaction with m-toluidine gives a good yield of m-iodotoluene. The two "explosions" that we experienced two years ago happened to the same student on successive runs, and we attributed them to some error in procedure although we were not able to identify any error. How- ever, since the same thing happened to one student this year, we have withdrawn m-toluidine from the list of amines to be diazotised. I send this note as a precau- tion to others who may plan to use this synthesis. We have no evidence as to whether the apparent sensitivity of m-tolyldiasonium ion is limited to reactions with io- dide ion although we suspect it is, nor can we be sure that no other diazonium salt will show a violent reaction with iodide ion. We have had no trouble with the other amines we use, namely aniline, o-and p-toluidine, o-and p-chloroaniline, m- and p-nitroaniline and p- anisidme. I would be interested to learn of any experiences of a similar nature with such reactions. ELMER R. TRUMBULL COLGATE UNIVERSITY HAMILTON, NEW YORK 13346 Dialectrical Polarity? To The Editor: Sometimes the contributions of the scientific past contain an explanation of contemporary social and political problems. Thus we owe a debt of gratitude to Larder and Kluge [J. CHEM. EDUC., 48, 287, col. 2, line 17 (1971)] for emphasizing Buterlov's dialectrical materialism. No doubt this is the source of the present polarization between East and West. 640 / Journal o f Chemical Education
