Organic Synthesis help

I think your right in that it is pointless trying to remember what each reagent does, though you should get a basic grasp of reagents from your A-level course, if you have something like sodium sulfide, the sodium ion is not really ever going to do anything, it will most like;y simply be there as a spectator ion, the sulfide ion however can be used as a reducing agent, you could perhaps realise that because it has many oxidation states that the presence of sulfur or sulfide ions in low oxidation states are likely to be good reducing agents. SO2Cl2 is similar to thionyl chloride SOCl2 and these groups of compounds are used as chlorinating agents, they are generally mild agents and reactive cleanly. You can swap the Cl for other halogens. Good luck and don't get stressed, its meant to be fun!