SciFinder's CASREACT database should be a first choice, but there are free online sources that you might also consider.
- Organic Syntheses
Organic Syntheses publishes annual collections of detailed and verified synthetic procedures. Full text of procedures freely available. Browse via volume tables of contents or by conducting structure and keyword searches across all volumes. Structure searching requires the ChemDraw plugin.
- The Chemical Thesaurus Reaction Chemistry Database
A reaction chemistry information system that extends traditional references by providing hyperlinks between related information. A particular interaction, reaction or process can either be found by searching for the chemical entities.
- Bordwell pKa Table (Acidity in DMSO)
This page was created by Professor Hans J Reich at the University of Wisconsin-Madison as reference material for organic chemists. It provides equilibrium constants pKa of many organic compounds with pKa values from 0-35 in DMSO.
A free access service providing a structure-centric community for chemists with millions of chemical structures and integration to a multitude of other online services, ChemSpider is the richest single source of structure-based chemistry information.
- Household Products Database (NLM)
What's under your kitchen sink, in your garage, in your bathroom, and on the shelves in your laundry room? Learn more about what's in these products, about potential health effects, and about safety and handling. Links to Material Safety Data Sheets (MSDS).
- Landolt-Börnstein Substance / Property Index
Landolt-Börnstein Substance / Property Index is the quickest and most convenient way to find information about substances and related properties. Organic Compounds are best searched by molecular formula whereas a search for element system is most suitable for inorganic substances. Syracuse University owns this reference work.
- Material Safety Data Sheets (MSDS)
Material Safety Data Sheets are a summary of the health hazards of the material and associated recommended safe work practices. MSDS are required by OSHA to be sent by chemical manufacturers to the purchasers of their chemicals.
- NIST Chemistry WebBook
Provides easy access to chemical and physical property data for chemical species. The WebBook system allows users to search for chemical species by various means. Once the desired species has been identified, the system will display data for the species.
PubChem Substance, Compound, and BioAssay are 3 NCBI Entrez linked databases that provide information on the biological activities of small molecules. PubChem also provides a fast chemical structure similarity search tool.
Databases on toxicology, hazardous chemicals, environmental health, and toxic releases.
Wolfram|Alpha contains a wealth of chemistry data, and provides you with chemical computations in the context of a given search. Wolfram|Alpha is an effective learning tool for students looking for ways to learn and test their knowledge of chemistry basics.
Full-text reference books on chemistry, chemical engineering, biochemistry, environmental studies and other sciences. You can search this collection using your chemical compound name and desired property.
Ex: Xylene and molar entropy
- Spectral Database for Organic Compounds : SDBS
SDBS integrated spectral database includes electron impact Mass (EI-MS), Fourier transform infrared (FT-IR), 1H nuclear magnetic resonance (NMR), 13C NMR, laser Raman, and an electron spin resonance (ESR) spectra.
SciFinder provides links from chemical structure records in the REGISTRY database to spectra data licensed from several third-party sources including SDBS, Bio-Rad/Sadtler, and Wiley.