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Substance Hierarchy

Description

The Substance Hierarchy consists of a series of levels of substance names organized by chemical structure. Each level of the hierarchy adds more chemical name information.

The hierarchy begins at simply named compounds. It leads, through subsequent levels, to compounds with detailed chemical names.

Each substance cited in a reference on CA on CD is listed in the Substance Hierarchy.

Diagram

The following diagram shows 3 levels in the Substance Hierarchy for butanoic acid.

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Path History

The path that is followed through the hierarchy is shown at the top of the window. It is represented as a sequential list of indented substance names, preceded by minus signs. Each name in the path history indicates a previously visited level in the current path.

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Level 1

Level 1 lists substance parent names, with locants removed, in alphabetic order. Numeric entries, if present, are listed first.

The substance parent name at this level may be:

A molecular skeleton name, e.g., Butane, to which a principal function may be suffixed, e.g., -sulfonic acid
A functional parent compound in which no skeleton is expressed, e.g., Carbonic acid
A trivial name, e.g., Urea

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Level 2

Substance names in Level 2 have locants added (if any).

Subdivision Headings indicate how substances are grouped in the next level of the hierarchy:

QUALIFIED
SUBSTITUTED
MODIFIED
STEREO

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Subdivision Headings

Subdivision Headings are used to organize substance information.

Subdivision Heading	This heading is used	Explore this subdivision to find
QUALIFIED	With commonly occurring substances that historically have many references	Links to references about the substance grouped by "type of study" "type of modification"
SUBSTITUTED	When there are substituted forms of the substance	A form of the substance in which a hydrogen is replaced by another atom
MODIFIED	When a nonQUALIFIED substance has a modified form	A modified form of the substance such as a Derivative Isotope Ion
STEREO	When the structure has stereochemical specificity	A particular stereochemical isomer such as R or S D or L Cis or trans

Other Levels

The content of the hierarchy, beyond Level 2, varies with the substance and the path that is followed.

The types of entries contained in a level depend on which Subdivision Heading is followed.

If the Subdivision Heading followed is	Then, nested entries are for
QUALIFIED	The "type of study" in which the substance was used, or for modified forms of the substance
SUBSTITUTED MODIFIED STEREO	Substance names with additional chemical specificity

Example: QUALIFIED Entries

The bottom window in this example shows the entries nested within Butanoic acid (QUALIFIED).

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Example: SUBSTITUTED Entries

The bottom window in this example shows the entries nested within Butanoic acid (SUBSTITUTED).

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Navigation Order

When a chemical substance fits under more than one Subdivision Heading, navigate the Substance Hierarchy in the following order:

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QUALIFIED substances may occur at any level in the hierarchy. This is because a substance is QUALIFIED based on the commonness of the substance, and not on a particular structural feature.

If, as you proceed through the hierarchy, a substance of interest is QUALIFIED, then follow these guidelines:

If you are interested in	Then, follow	Example
The substance	The QUALIFIED heading to find links to references grouped by "type of study"	Follow Butanoic acid (QUALIFIED)[107-92-6] analysis to locate studies on the analysis of butanoic acid
A specifically modified form of the substance	1. The QUALIFIED heading 2. The "type of modification" heading	Follow Butanoic acid (QUALIFIED)anhydrides (MODIFIED) to locate the name of a specific anhydride of butanoic acid
A nonspecifically modified form of the substance	The QUALIFIED heading to find links to references grouped by type of nonspecific modification	Follow Butanoic acid (QUALIFIED)[107-92-6] esters to locate studies on nonspecific esters of butanoic acid

Updated 3/18/2007 11:07:35 AM