I am an A-level student going into university and I am looking for a source of organic synthesis problems and answers that is freely available on the internet. The difficulty level I am looking for is something like first year undergraduate level. Any links would be greatly appreciated.
Search for the latest IChO tests and preparatory problems. You can find quite a few interesting problems.
Janice G. Smith's textbook "Organic Chemistry", while unfortunately expensive, has a good interactive workbook online which is useful even without the companion text.
You can find it here.