I'd read in an old text book that you can get a variety of nitrogen oxides, from NO2, N2O4 and even the fun N2O from copper in nitric acid. What it depended on was the concentration of the nitric acid. You may be able to find a reference to this in Pauling's Chemistry (mine isn't handy, so I can't check). I don't know what the acetone did, so I can't say what happened there. The safe (um, safer) way to get copper nitrate is to start with copper oxide or carbonate, and use dilute nitric acid.