- Aniline is a specific compound, anilines is a group of compounds based on aniline (try search for anilines at google). Btw, we do have a category:anilines. Its a problem for chemical classes that they are singular at wikipedia. A lot of compounds are named as the parent compund, like cyclopropane and cyclopropanes   
 About Serotonin syndrome - I just saw it (by accident), and I have not really any opinion about the infobox.