SciFinder and Reaxys are go to sources for substance information, but information about chemical substances may be found in a wide variety of publications and on many kinds of websites. These sources of information vary in quality, reliability, depth, and level of technicality.
You should always check the information you find at an informational website against one or more reliable sources, such as handbooks or desk references or curated databases. Here are some suggestions for starting points when looking for data and other information about chemical substances.