careysub - 21-9-2015 at 18:18
I am interested in setting up a demonstration of three systems that show case the Arrhenius acid definition, the Bronsted-Lowry (but not Arrhenius)
acid definition, and the Lewis (but not B-L/A) definition, but am a little stuck on the best model for the B-L system.
In Bassam Z. Shakhashiri's "Chemical Demonstrations" Vol. 3 he provides instructions for a Lewis acid demo using either AlCl3 in DCM, or HCl in DCM.
His comment about the HCl in DCM version is that although there is a proton technically available, due to the low polarity of the DCM there will
little ionization, and so the instructor can assert the demo is a Lewis acid demo.
Similarly Googling easily brings up Lewis acid demos, but not clear examples of a B-L acid demo.
Modifying the Shakhashiri demo by using a more polar aprotic solvent presents the problem of which solvent would be best. DMF and DMSO are possible,
except that HCl appears to react with them to form complexes. Acetonitrile is likely candidate, but I am concerned about whether mixing acid with it
might liberate the cyanide ion.
Any suggestions or comments?
I am a bit surprised that I did not run across someone with a demo scheme for all three acid models.
Experimentation would be needed I expect to find a good indicator for the B-L demo, that puts on a good color change.