Teaching Chemical Information:
Tips and Techniques

Chemical Abstracts Service was founded in 1907 as a division of the American Chemical Society. The first volume contained 15,000 abstracts and was distributed free of charge to ACS members.

Today: about 5,000,000 abstracts per year; annual subscription—over $15,000.

What CAS Does

CAS attempts to comprehensively index the chemical literature, including:

• some 8–12,000 journals; 1,300 of which are now indexed cover to cover—covering documents of chemical importance
• patents from 28 nations and two international organizations
• technical reports, conference papers, books and dissertations.

Chemical Industry Notes (CIN)

• indexes the literature of chemical business (e.g. C&E News, Chemical Week)

Chemical Abstracts Service Source Index (CASSI)

• Lists all periodicals ever indexed by CAS
• Lists many pre-1907 sources, such as those appearing in Beilstein
• Available in print or on CD-ROM
• Periodicals are listed in alphabetical order by their abbreviations—the name appears in full, with the abreviated portion in boldface.
• Listing include language information, starting dates and curent volume numbers, cross-references to changed titles or translations and holdings information.

CAS Document Detective Service

• provides copies of documents indexed by CA or CIN, generally for the past 20 year.
• Exceptions: indirectly indexed documents, like tech reports or dissertations
• If copyright is a problem, they will lend the original.

CAS Registry Service

• Started to track chemical substances for CAS internal files; now the standard method for uniquely identifying chemicals
• All substanced indexed by CAS get RN’s, plus substances submitted by outside firms or agencies
• Registry Numbers are of the form: xxxxxx-xx-x

Comprehensiveness

Chemistry as the “central science”

• high overlap with medicine, biology, physics, materials, agriculture, geology, etc.

Constant ehnhancements

• CAS has been in forefront of computerization of indexing for over 30 years

An issue each week, but subject coverage alternates, so it is effectively updated every two weeks.

Each volume covers six months; cumulative indexes arrive about two months after the volume ends.

Collective Indexes cover a ten-volume period.

For ease of browsing, abstracts are grouped by subject area

Currently there are 80 subject sections, divided into five broad groups.

Biochemistry and Organic Chemistry used to cmoe out in odd-numbered weeks

Macromolecular Chemistry, Applied Chemistry and Chemical Engineering and Physical, Inorganic and Analytical Chem. used to come in even-numbered weeks.

Cross-references are used where a given abstract might ligitimately appear in more than one section.

Note that subject sections change with time to reflect current research

Subject Coverage Manual gives a detailed definition of each section, and a table of changes over the years.

All CA records contain:

• Title of the document
• Author(s) or inventor(s) for patents
• Corporate source or patent assignee information
• Source Information, e.g. journal title, volume, issue, pages or patent numbers
• Language
• Abstracts (usually)

Author’s name appear as given in the original document

Abstracts for journal articles are usually those written by the author

Patent abstracts may be fleshed out by the indexer

Disertations and some other documents have no abstracts

Journal names are listed using CASSI abbreviations

Corporate names are heavily abbreviated

All abstracts use abbreviations for common chemical terms (see handout)

The types of indexing available in CA reflect the constraints of print.

The indexing available in the weekly issues is that which can be done most quickly

The indexing in the Volume and Collective Indexes is more systematic, but still reflects the limitations of print.

Issue Indexes

• Author
• Keyword
• Patent

Volume & Collective Indexes

• Author
• Chemical Substance
• General Subject
• Molecular Formula
• Patent

All authors are listed by last name and initials only. The index gives only the abstract number. Examples:

• Lipshutz B H 151869t
• Little R D 152780u

Patents have entries for both inventor and assignee; their abstract numbers have P before the number.

Examples:

• Genentech, Inc. P146735s
• Leong S R P146735s

Other types of corporate authors, such as societies and government agencies, also get author entries:

United States Food and Drug Administration 150996v 150997w

First authors get both the abstract number and title of the paper listed under their names

The author name is not necessarily the form used in the article, but may be a standardized form of the name

Other authors are cross-referenced to the first author of the document

Examples:

Ford, Peter Campbell

Quantitative mechanistic studies of the photoreactions of…148765a

Lange, Frederick Fouse

See Miller, Kelly T.; Sudre, Olivier
--; Lam, D.C.C.; Sudre, O.
Powder processing and densification of ceramics 144196x

Even though CA tries to pull all of an author’s works under one name, it cannot always distinguish authors with the same initials, so it alphabetizes by last name and initials, even where the full name is spelled out!

Examples:

Ellis, A.
Ellis, Arthur Baron
Ellis, A. D.
Ellis, Anthony Ewart
Ellis, Avery K.
Ellis, Andrew Michael
Ellis, Albert T.

Be aware of special rules for handling certain names. Names with “Mc” or umlauted letters or transliteration from non-Roman alphabets can be tricky.

Example: Mossbauer is listed as Moessbauer

Chemical Abstracts only indexes patents with “new” chemical information and it only indexes the first version of each patent it receives.

However, the patent index (arranged by country code and patent number) gives cross-references from later, equivalent patents.

When searching for an equivalent patent, start at the year of issue of the known patent reference and work forward until you find the equivalent or run out of indexes.

Chemical Abstracts
Print, Part II, Subject Indexing

Weekly issues use keywork indexing assigned by the indexer. Terms are not systematically selected.

Volume and Collective Indexes use systematic indexing for both general concepts and chemical substances.

Keywords are assigned by the indexer based on the body of the document, not just the title of the abstract.

Terms are often abbreviated, following the standard Ca abbreviations

To save space, a keyword is not assigned if it’s part of the section heading for the section the abstract appears in, e.g. “Steroids”.

Additional keywords are listed beneath the main keyword heading to flesh out the concept (like the co-terms in Science Citation Index)

Chemical names are listed along with concept terms in the issue indexes. The chemical names are not systematic, but follow the author’s nomenclature.

“Facile preparations of 4-fluororesorcinol”

-Acetophenone

Methoxy fluorination regiochem

-Benzene

Fluoro dihydroxy

-Deacetylation

Demethylation fluorodimethoxyacetophenone

-Demethylation

Fluorodimethoxybenzene

-Methoxybenzene

methoxyacetophenone fluorination regiochem

Fluorodihydroxybenzene

Fluororesorcinol

Resorcinol

fluoro

The General Subject Index uses standard subject headings in order to better bring related documents together (collation).

The standard headings list does get modified and expanded to reflect new areas of research. Major changes are usually done at the beginning of a Collective Index period.

This index includes:

• classes of chemical substances
• physial and chemical phenomena
• types of reactions
• chemical technology
• industrial processes and equipment
• scientific names for living organisms
• biological and medical terminology

For extensive subjects, qualifiers are added as part of the main subject heading, such as:

• Blood, analysis
• Sulfonic acids, uses and miscellaneous

Classes of substances may also have derivative categories, such as:

• Carboxylic acids, esters

Note: the following lists of categories apply to pre-1997 indexes. Some are undergoing dramatic changes.

For ketones, aldehydes

• acetals, hydrazones, mercaptals, oximes

For acids

• anhydrides, anhydrosulfides, esters, lactones

For alcohols

• ethers

For amines

• oxides

General: compounds, derivatives, polymers

For substances and classes of substances

• analysis
• biological studies
• occurance
• preparations
• properties
• reactions
• uses and miscellaneous

For Organs and Tissues

• composition
• disease or disorder
• metabolism
• neoplasm
• toxic chemical or physical damage

For alloys

• base
• non-base

The Index Guide is the key printed tool for indentifying the correct subject heading for any topic in Chem. Abs.

Each IG lists the approved headings in use for its period of coverage.

An IG is published at the beginning of each Collective Index period, with updates every 18 months until the final comes with the Collective Index itself.

An alphabetical listing of the approved subject headings, with cross-references to related headings and descriptive notes.

Many common terms not used as headings are listed, with see references to the correct heading.

Many common and / or trade names for chemical substances are listed, giving the correct CA systematic name (and Registry #!)

There are also appendixes on the organization and use of the subject indexes; how CA indexers select headings; CA chemical nomenclature; and a hierarchical list of the headings.

Whenever you are doing a subject search, in print or online, it’s a good idea to check the Index Guide!!

Note: at this point, the first 1997 Index Guide has not appeared, since the first 1997 Volume Indexes have not. See: http://www.cas.org/terms/vocab.html for an interesting compilation of changes.

In general, CA indexers will assign the most specific subject heading that applies to the document.

For example, if a dicument deals with the synthesis of a specific ester, the indexer will assign that substance to the index, not the general term “esters”.

Cancer of the lungs will appear as Lung, neoplasm not Lung, disease (pre-1997). 1997 and later, the geneal term in Lung Tumors, with more specific types, e.g. Lung adrenocarcinomas.

In order to ensure that each substance has a unique possible name, and to group “like” compounds together, CA has devised their own system of nomenclature (not necessarily IUPAC) and scheme for arranging them in the Chemical Substance Index.

Unfortunately, this system can be hideously complex.

Dodecahedrane (C20H20) is listed as:

5,2,1,6,3,4-(2,3)Butanylidenedipentaleno (2,1,6-cde:2',1',6'-gha)pentalene, hexadecahydro

It is important to remember that the CAS nomenclature has changed over time, if you are using the older literature.

The most important change took place in 1972; nomenclature has been fairly stable since then.

CAS indexers select the “main” part of the compound to act as the heading parent.

Substituents to the parent are listed after it is inverted order

What constitutes a parent compound and how it would be named are not always obvious, even to a chemist.

Toluene is

Bezene, methyl-

ortho-Xylene is

Benzene, 1,2-dimethyl-

Benzyl alcohol is

Benzenemethanol

Teflon is

Ethene, tetrafuoro-, homopolymer

When there are multiple substituents, they are listed in alphabetical order, including the prefixes.

Carbon tetrachloride is

Methane, tetrachloro-

CCl2F2 is

Methane, dichlorodifluoro-

CCl3F is

Methane, fluorotrichloro-

Compounds are listed first by parent compound, with the parent compound itself first (with and qualifiers and categories), then by substituted forms in alphabetical order.

Substituents are read from left to right, ignoring numbers and punctuation.

Benzene

Benzene, analysis

Benzene, uses and miscellaneous

Benzene, compounds

Benzene, polymers

Benzene, azido-

Benzene, chloro-

Benzene, 1,2-dibutyl

Salts of organic acids, or inorganic oxyacids are named as derivatives of the parent acid.

Potassium Chloride is

-Potassium chloride

Potassium Sulfate is

-Sulfuric acid, potassium salt (2:1)

In general, it can be very tricky to look at the structure of a complex compound and decide what the CA name will be.

However, in many cases, you can use a variety of resources to help find the CA name.

If the compound has a common or trade name, check the Index Guide

The Index Guide is especially good fro drugs, natural preducts, dyes, etc.

For other common chemicals, even if you can’t find the specific chemical you want, you may be able to find a similar one and get a clue to follow.

CAS publishes a “handbook” which lists Registry Numbers and gives the CAS systematic name for the substance.

Remember that there are many sources you can use to find Registry Numbers which have good synonym indexes: Merck, HODOC, Aldrich, Kirk-Othmer.

Shelved just after Chem Abs. itself.

While most molecular formulas have a large number of possible compounds, it is far easier to look at a possible name and decide whether it matches your compound than to guess at a name.

Note that the Molecular Formula Index just gives a list of abstract numbers, not a breakdown by subheadings.

Molecular formulas are listed in Hill order.

If carbon is present, it comes first, followed by hydrogen, then all other elements in alphabetical order.

If not, then all (including H) in alphabetical order.

Note that the rules for salts apply to molecular formulas, too.

Molecular Formula Examples

Benzene is C6H6

Teflon is (C2F4)x

Ferrocene is C10H10Fe

Hydrochloric acid is C1H

Benzoic acid is C7H6O2

Sodium benzoate is C7H6O2, sodium salt…NOT C7H5NaO2

Most compounds with a polycyclic ring system use the name of the ring system as the parent compound.

The Handbook lists ring systems in order of:

• Increasing number of rings
• Increasing number of atoms in the ring
• Increasing Hill order formula of the ring

Gives structure diagram, name, Reg. #

Even with all of the above, sometimes none of the tools will help you find the correct name.

And if you don’t find something, does it mean that you haven’t guessed the right name, or that it hasn’t been reported?

Enter the power of computer searching — structure searching can give a definitive answer to most questions.