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This installment of the Sixty-Four Free Chemistry Databases Series takes a look at Sigma-Aldrich Reaction Search. Reaction searching is an underrepresented, yet highly useful capability among chemistry databases in general. Sigma-Aldrich's service stands out in that it's both free to use and available over the Web.

In a nutshell, Reaction Search allows you to specify the structures of a starting material and a product and then search for matching reactions by either exact structure or substructure. Results are returned in the form of records containing a graphical representation of the reaction and information about starting materials. Some of this information consists of links to Aldrich's product pages, a convenient feature indeed.

One of the more interesting features of Reaction Search is something called "Reaction Relay" in which all of the transformations for a given structure can be visualized simultaneously.

Figuring out how to draw both a starting material and product was not as easy as it should have been. If you get stuck, the trick is to first draw a structure on either side of the arrow. Then click on the arrow button at the top of the editor. A structure will automatically be drawn on the other side of the arrow which you can then edit.

The relatively limited scope of Reaction Search makes it unlikely to replace more comprehensive reaction databases such as that accessible through SciFinder. But if you're looking for a way to supplement your regular search routine, Reaction Search makes an excellent choice.

Kudos

• Results returned very quickly.
• Easy to navigate.
• Large collection of useful reactions.
• Primary literature citations.
• Reaction Relay - every reaction database needs something like this.

Ideas for Improvement

• Make drawing reactions more obvious.
• Include citations after the late 1990s.
• Enable reaction results to be sorted by yield and year of publication.
• Hyperlink citations to publisher site (or better, use DOI).