Reactions

21. When acetophenone oxime was allowed to rearrange in 18O-enriched solvent, the amide product contained the same percent of 18O as the solvent. Explain this
observation.

22. Oximes are usually crystalline materials and have been prepared as a means of identifying liquid ketones or aldehydes. It has been found in the preparation of
these derivatives that if the concentration is too high (low pH), that the oxime
does not form. Explain.

23. Reaction of (CH3)3SiCl with alcohols produces a trimethylsilyl ether. The trimethylsilyl ether is more volatile than the corresponding alcohol, and is often used to facilitate GC analysis. Explain.

25. There are two reasons why the enols of beta-dicarbonyl compounds, such as
pentane-2,4-dione are relatively stable. One is that they are conjugated and the pi-
electron overlap due to the conjugation provides additional stability. What is the
other reason that these species are relatively stable? Would you expect the enol of
cyclohexane-1,3-dione to be as stable as the enol of pentane-2,4-dione?