Following some other bloggers efforts in this area (started I think by ChemJobber), I will list my own list of favorites.
1. Pretty crystals. You have no soul if you cannot admire beautifully formed crystals. A particular instance is where you have precipitation in a test tube after purification and intricate feathery crystals form. Wonderful.
2. Others have mentioned their favorite smelling solvent, for me it is THF. Not sure what it is about it.
3. When the analytical data puts you right. I love it when I get an NMR or mass spec and it is not quite what I was expecting – until I check the mass or the proper structure and sure enough, that extra singlet at 3.5 ppm is there because it is supposed to be there. Forget the camera, the NMR never lies.
4. Fireworks. It is far from normal in the regular routine of chemistry, but occasionally it has been known for reactions to get a little lively. Quenching a large scale LAH reaction is just fun. Well, as long as it stays in the flask, it is. Cleaning up spills is definitely not fun.
5. Involved reaction procedures. I don’t know why exactly, but synthetic procedures that have you adjust the temperature of the reaction several times, involve multiple reagent additions and several color changes just seem more worthwhile. Sure, it is easier to just throw everything in a pot and heat, but it is too easy. More satisfying to do the intricate. Well, assuming it works after all that.
6. Easy work-ups. On the other hand, while work-ups are an important part of what we do, they aren’t exactly fun. So when a work-up comes along that says “pour into water, collect the precipitate”, I am happy.
7. I love it when a synthetic plan comes together. Misquoting the A Team aside, the feeling of working out all the wrinkles of a scheme and seeing that final NMR of clean product is a natural high. It is so energizing and makes the struggle to get there all the more worthwhile.
8. Well drawn structures. We have lots of computer assisted chemical drawing tools, but there is still something of an art to a nice clear structure. Hand-drawn ones are nice too, I like a clean crisp benzene ring and aliphatic chains where I can tell how many carbons there are.
9. Funky reactions. You know the ones, where you start with compound A, do something seemingly innocuous to it (usually involving a Lewis acid) and it is transformed to the final product in one pot.
10. Celebrating and venting with colleagues over a pint. Nothing like that.