Chemistry-specific databases can search for substances and property data in many different ways, including:

• Chemical Structure or Substructure
• Molecular Formula​
• Registry Numbers and Chemical Identifiers
• Substance Name (common name, trade name, chemical name)

Molecular Formula (Hill Order)

Hill Order is a system of writing chemical formulae. Like atoms are grouped together following the order below: 

1. The number of carbon atoms
2. The number of hydrogen atoms
3. Every other element is listed subsequently in alphabetical order.

In the absence of carbon, all atom groups (including hydrogen) should be listed in alphabetical order

The CAS Registry Number Database, CRC Handbook of Chemistry and Physics, and the Merck Index require that Hill Order is used when searching by molecular formula.

Registry Numbers and Chemical Identifiers

Registry numbers and chemical identifiers are codes that are assigned to each substance. These allow us to avoid searching many name variations for the same substance or struggling to correctly type out complicated substance names. These unique identifiers allow for easy searching online, helping you to find the same structure in different databases and search engines.

Three common identifiers in chemistry are:

• CAS Registry Number: A unique identifying number assigned to a chemical compound, commercial mixture, or an entire class of molecules.  A CAS registry number is assigned by the Chemical Abstracts Service (CAS) when a substance is registered with them.
• Reaxys ID: A unique identifying number similar to CAS Registry numbers, however Reaxys IDs do not refer to biomolecules like enzymes or commercial mixtures. Note: these numbers as assigned by Reaxys, but can be used in both Reaxys and SciFinder-n.
• InChI Key: A unique string of characters used to identify chemical substances (an abbreviation of the longer InChI developed by IUPAC).

Below are resources where you can search for physical and chemical property data, and spectral data. Remember, you can also find this type of information by searching for the substance in SciFinder-n or Reaxys.

Remember, it's good practice to search multiple sources and cross-check your data!

Online Handbooks

Spectral Data

You can find spectra in many of the same places you look for properties, as well as in databases like SciFinder-n and Reaxys. Still having trouble finding what you're looking for? Try the resources below: