Reactive groups (such as “Bases” or “Ethers”) are categories of chemicals that typically react in similar ways because they are similar in their chemical structure. For the purposes of predicting reactivity between mixed chemicals, each chemical in CRW's database is assigned to one or more reactive groups, based on the known structure, reactivity, and chemistry of that chemical.

There are nearly 50 reactive groups in the CRW. To see descriptions of all of the reactive groups, open the CRW program. Then, from the Reactivity Worksheet screen, click on the "Add Reactive Group" button. On the screen that appears, select a reactive group from the list to see its description on the right side of the screen.

To see the reactive group assignments for a particular chemical, perform a search for the chemical in the CRW. On the search results page, double-click on the chemical name to open its datasheet; click on the "Reactivity" tab of the chemical datasheet to see the reactive group assignments.

Once you've added two or more chemicals to the Reactivity Worksheet, the CRW will show you reactivity predictions about what might happen if any of those substances were to mix together.

To make those predictions, the CRW first identifies each substance's reactive groups and then predicts the kind of pair-wise chemical reactions likely to occur when members of these groups are mixed together.

The CRW only accounts for reactions between two chemicals at a time. If you have more than two substances in your reactivity mixture, it predicts the reactivity between all possible pairs of those chemicals.

Important Note: When there are three or more substances in the mix, they may react together in ways that CRW's pair-wise reactions can't predict:

• For example, glycerin and nitric acid react very little when they're mixed together. However, if sulfuric acid is added to the mix, the three chemicals react together to produce the powerful explosive nitroglycerin. CRW doesn't predict this reaction, because it looks at the pairs (glycerin + nitric acid; glycerin + sulfuric acid; and nitric acid + sulfuric acid) rather than all three chemicals together.
• In other cases, one of the chemicals may act as a catalyst that accelerates the rate of reaction between other chemicals in the mixture. For example, nickel carbonyl catalyzes many polymerization reactions and other kinds of synthetic organic reactions. In such cases, the reactivity hazard may be greater than predicted.

However, reactions among more than two chemicals are relatively uncommon in nature (except for the catalyzed reactions that are common components of the metabolic processes of living organisms).

Most of the time, you'll be adding chemicals to your reactivity mixture, and the CRW will be using those chemicals' reactive group assignments to predict the reactivity between the chemicals. However, there may be times when you want to add reactive groups themselves—rather than chemicals—to the mixture. For example, if:

• You know the chemical class of a chemical, but not its exact name or CAS (Chemical Abstracts Service) registry number. For instance, you may be able to tell it's a powdered metal (which would typically be used in manufacturing processes as a reducing agent or catalyst).
• It’s not in the CRW's database, but its MSDS (Material Safety Data Sheet) tells you what chemical class it's in (or you happen to know its chemical class). This would be most likely for a new compound that hasn't yet been included in major chemical databases.
• You work with (or store) proprietary chemicals that are not included in the CRW's chemical database. In this case, you can either use a reactive group to approximate the chemical or you create a custom chemical datasheet in the CRW.
• You want to add water to the mixture. Water is a special reactive group that you can add directly from the Reactivity Worksheet.

Questions: Contact us with questions, comments, or suggestions about the Chemical Reactivity Worksheet.