The Chemical Reactivity Worksheet (CRW) is software that you use to find out about the potential reactive hazards of:
- Chemicals. The CRW contains a database of chemical datasheets for thousands of chemicals. Datasheets describe the intrinsic reactive hazards of each chemical, such as flammability, peroxidizability, polymerizability, explosivity, strong oxidizer or reducer capability, water or air reactivity, pyrophoricity, known catalytic activity, instability at elevated temperatures, and radioactivity. Datasheets also contain general descriptions of the chemicals, physical properties, and toxicity information.
- Mixtures of chemicals. The CRW includes a reactivity prediction worksheet that allows you to virtually "mix" chemicals to find out what dangers could arise from accidental mixing.
Note: The chemical database and reactivity prediction tool are also included in CAMEO Chemicals; however, the datasheets in the Chemical Reactivity Worksheet have been reduced to include primarily reactivity-related information, and the CRW allows you to add your own customized chemical datasheets to the database (this feature is not available in CAMEO Chemicals).
The CRW uses reactive groups to generate reactivity predictions. Reactive groups (such as "Strong 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 and reactivity of that chemical.
There are 64 reactive groups in the CRW. When you work in this software, you can see detailed descriptions of each of them. You also can see which reactive groups any chemical has been assigned to.
Making Reactivity Predictions
Once you've added two or more chemicals to the Reactivity Worksheet, the CRW shows you reactivity predictions of 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 pairwise 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 (i.e., pairwise reactions). If you add more than two substances to your reactivity mixture, the CRW 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 pairwise 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.
Using Reactive Groups
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 a mixture. Some examples:
- 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 that 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 situation 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 could create a custom chemical datasheet in the CRW.