Is there any database or book that has an index of organic reactions where the mechanisms are written out, complete with curly arrows? It would really help if I could look up a reaction and see a proposed mechanism with curly arrows.
As far as free online resources go, I've found the following useful:
- Organic Reactions (organic-chemistry.org)
- List of organic reactions (en.wikipedia.org)
I would also strongly recommend acquiring a copy of March's Advanced Organic Chemistry at some point. I think it's fair to say that it's widely regarded as one of the most essential reference works in the field of organic chemistry. It's concise, more comprehensive than one would've thought possible, beautifully organized, and contains thousands of primary literature references. While not every reaction is presented with an accompanying mechanism, many are, and useful exposition is typically provided.
Another book you might find useful is Strategic Applications of Named Reactions in Organic Synthesis. More than a mere reference text, it includes an overview describing important applications for the reactions it covers, examples of uses in practical syntheses, as well as comprehensive stepwise mechanisms.
This is the closest I've seen to what you're asking for; some of the reactions have curly arrows. The Chemical Thesaurus
The answer to your question depends on what type of reactions you are looking for. If you are looking for simple 'name reactions' such as aldol condensation reaction, or Grignard reaction, then the links suggested by Greg would suffice. On the other hand, if you are looking for very specific reactions or reactions published in recent literature, then you must search in a dedicated chemistry database such as Scifinder. You may check the website here: http://www.cas.org/products/scifinder/what-s-new-in-scifinder
However, scifinder is a paid database, and your academic institution will need to have an active subscribtion to this service. Most universities in the US and the Europe have subscription to Scifinder. You will not be access this service from your home, as it is IP restricted.