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Molecular formulas are often written using the Hill System. Some databases like Reaxys also use this system (NaCl becomes ClNa).
- Start with carbon, then hydrogen, then the rest of the in alphabetical order (C2H5AlCl2)
- If there's no carbon, write all of the elements in alphabetical order (ClHN4)
Find Basic Information About Your Compound
Excellent databases to find basic information about chemical compounds: molecular weight, CAS Registry numbers and common physical property data.
Extensive database of chemical and physical property data for 13 million organic, inorganic and organometallic substances. Bring up the chemical's substance record, and view the entire record or use the filter to focus on specific data fields. In many cases, you'll get the numeric data and conditions, always with a corresponding reference and link to a journal article.
Combined Chemical Dictionary
Core data (including derivatives) for 540K compounds, including organic compounds and natural products. Includes Dictionary of Organic Compounds, Dictionary of Natural Products, Dictionary of Drugs, and Dictionary of Inorganic and Organometallic Compounds.
CRC Handbook of Chemistry & Physics
Key data for thousands of organic and inorganic compounds.
Searchable property data extracted from handbooks and databases. You can search by compound and property (enthalpy AND bromobenzene).
Basic property data and key literature references for 11,500 significant chemical compounds. From here, you can also link over to your compound's record in ChemSpider to find more property data.
Chemical structure database of over 28 million compounds. Search to find property data and spectra, with sources included.
Properties of Organic Compounds
Database of 29K organic compounds found in Dictionary of Organic Compounds, but with more property data.
CAS Registry Numbers?
CAS Numbers are unique identifiers assigned to substances by Chemical Abstracts Service and maintained in their CAS Registry. You can use the CAS-RNs to locate information for a chemical in numerous print and online sources. CAS assigned ~15,000 new numbers every day.
- 58-08-2 (caffeine)
- 1411769-41-9 (CAS' 70 millionth substance, registered November 14, 2012)
- 1458220-76-2 (added October 15, 2013)