[BrightOrange]

Hey there -- so I've got a few Chem classes this semester and I'm reviewing for them all at once before finals.  I'm trying to combine my questions into general categories, but I don't expect people to spend time helping with all of them.  Anything on any question is appreciated!

(1)  I've been having trouble with writing out reaction mechanisms properly and showing the electron movements (arrow pushing is another term I think?).  Specifically I'm looking at a 1,3-dipolar cycloaddition but really just getting it right for this one answer won't help me figure out how to do it for other reactions later.

I have trouble figuring out where to start with these most of the time, as I can never see which bonds are most likely to break or where the e- are most likely to go, but if someone could suggest a good resource for learning these techniques online I'd appreciate it (or something specific for the cycloaddition).  Or just any tips you can type out right quick about how to understand this without having to memorize each and every movement.

(2)  McLafferty Re-arrangement and how it works.  We only did one example in class (the one on wikipedia) and it doesn't look much like the ones in my study guide, nor have I found a really good guide about it online.  I think I will be expected to show this reaction on the test but, while I can reproduce the one in my notes, I don't really know how to apply it to other molecules.

I have written that it's a re-arrangement seen often in Mass Spec that involves a hydrogen (far away from something -- but what, the Oxygen?) and cleavage (but where?).  I read beta and gamma as descriptors and have only a vague idea of how to apply that here.

What causes this to happen in the first place?

(3)  Norrish II Reaction -- This was used as an example of a Photochemical reaction that is similar to McLafferty and I have no better understanding here.  From what I can see they are almost the exact same, so what is the difference?

We had a section on Photochem but this stood out as the part I really couldn't follow.  However I missed the day with the other reactions -- anyone know of a good resource for reviewing common Photochemical mechanisms in terms I could somewhat follow?  I can't get notes from anyone else easily, but I could review some of the basic known stuff for this part.

And that's all folks.  Anything you can offer is much appreciated -- I hope it's obvious that I'm at least trying.