There are many ways you can describe a compound in order to search for it within a database. Consider your options and what types of descriptions the particular database will accept. If you get zero results, try another way before moving on to another resource.
Chemical name/synonyms
Common/trivial name
Molecular formula
Empirical formula
Structure
CAS Registry Number
For example, consider ethanol:
ethanol
ethyl alcohol
ethyl hydroxide
C2H6O
H3C-CH2-OH
CAS# 64-17-15
Information is from Purdue University's Chemistry Lab Resources Guide
Both Wikipedia and Wolfram Alpha can be quick and easy to seach when it come to chemical and physical properties. But before you use these resources, please consider the following when searching each source.
WA contains a wide variety of data on many chemical compounds. However, WA's major flaw is that it DOES NOT tell you the specific source of the data presented. WA claims to have a proprietary database of data gathered from various sources. While these sources are often listed, you can not be certain where a particular boiling point or heat capacity came from. When you need to cite an exact source or justify your data from a reliable & credible source, try one of the other resource above instead
Information is from Purdue University's Chemistry Lab Resources Guide