Chemical Substances
Preferred Index Name in Chemical Abstracts

Finding chemical substances in Chemical Abstracts (CA) and many reference books requires identifying the preferred index name. This preferred name places a substance in the index adjacent to substances of similar structure.

Sources for Preferred Index Names
Ref RS51.M4 Merck Index
Ref QD291.H46d Dictionary of Organic Compounds
The CA preferred index name is identified by the designation "CI." CI stands for Collective Index, which is a 5-year index of Chemical Abstracts. 
For example: 9 CI = 9th Collective Index of Chemical Abstracts, which covers 1972-76. 
Ref QD411.D535 Dictionary of Organometallic Compounds
Abstract Area Chemical Abstracts Index Guide
Provides cross references to the preferred index name from former names, some chemical names, trade names, acronyms, pharmaceutical names, etc.
Abstract Area Chemical Abstracts Molecular Formula Index
Follow these steps: 
1. Convert typical molecular formula to Hill Order. 
1st: C (count number of carbon atoms) 
2nd: H (count number of hydrogen atoms 
3rd: count all other elements and arrange alphabetically
For example:  
Typical molecular formula               Formula in Hill Order
        HC[triple bond]                         CHC2H2
        CH3COCH3                                C3H6O
        ClCH2COOH                               C2H3ClO2
        NaCl                                    ClNa
        H2SO4                                   H2O4S
        (CH3)2CHCH2COCH3                        C6H12O
2. Start looking in the most recent 5-year Molecular Formula Index for the Hill Order formula.

3. Under each formula are listed all substances with that overall formula. Look through the list, keeping the chemical structure in mind, to identify the name desired. 

For example: 
C3H4(OH)2 would be found under C3H6O2. The students would know that they are 
looking for: 1) cyclopropane - a 3 member ring; and 2) an OH at certain positions 
on the ring. So, they could identify the preferred index name of: 
1,2-cyclopropanediol.
Computer Search Computerized search of a chemical dictionary of substances: Chemname (and related files) on Dialog or Registry File on STN International. Can search by:
  • * any name (trade name, acronym, etc.) 
  • * molecular formula (in Hill Order) 
  • * molecular formula alone or AND'd with a name or fragments of a name
Computer Search Computerized search specifying structure, with bonds and atoms. Registry File on STN International.
as & cs 5/93

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Last Modified: July 08, 1999
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