{"term":{"id":"15416","title":"<i>Q-e<\/i> scheme","longtitle":"IUPAC Gold Book - <i>Q-e<\/i> scheme","doi":"10.1351\/goldbook.15416","code":"15416","status":"current","synonym":"<em>synonym<\/em>: Alfrey–Price scheme","definitions":[{"id":1,"text":"Empirical equations expressing the monomer reactivity ratios in a binary radical copolymerization, \\(r_{12}\\) and \\(r_{21}\\), in terms of the empirical parameters \\(Q\\) and \\(e\\) for the two monomers, namely, \\(\\rm{Q}_{1}\\), \\(\\rm{Q}_{2}\\), \\(\\rm{e}_{1}\\), and \\(\\rm{e}_{2}\\), with\\(r_{12} = (Q_{1}\/Q_{2})\\exp [-{e_{1}}(e_{1} - e_{2})]\\) and \\(r_{21} = (Q_{2}\/Q_{1}) \\exp [-{e_{2}}(e_{2} - e_{1})]\\)","notes":{"1":"Although the parameters are empirically derived, the parameter \\(Q\\) is considered to be a measure of the stabilization by conjugation of a monomer and the radical derived from it, while the parameter \\(e\\) is considered to be a measure of the polar effects of substituents on the monomer and the radical derived from it.","2":"The Q-e scheme is known also as the Alfrey–Price scheme."},"links":[{"term":"binary radical copolymerization","url":"https:\/\/goldbook.iupac.org\/\/terms\/view\/15383"},{"term":"monomer reactivity ratios","url":"https:\/\/goldbook.iupac.org\/\/terms\/view\/15410"}],"sources":["PAC, 2008, 80, 2163. 'Glossary of terms related to kinetics, thermodynamics, and mechanisms of polymerization (IUPAC Recommendations 2008)' on page 2182 (https:\/\/doi.org\/10.1351\/pac200880102163)"]}],"altoutputs":{"html":"https:\/\/goldbook.iupac.org\/terms\/view\/15416\/html","xml":"https:\/\/goldbook.iupac.org\/terms\/view\/15416\/xml","plain":"https:\/\/goldbook.iupac.org\/terms\/view\/15416\/plain"},"citation":"Citation: '<i>Q-e<\/i> scheme' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. 10.1351\/goldbook.15416","license":"The IUPAC Gold Book is licensed under Creative Commons Attribution-ShareAlike CC BY-SA 4.0 International (https:\/\/creativecommons.org\/licenses\/by-sa\/4.0\/) for individual terms.","collection":"If you are interested in licensing the Gold Book for commercial use, please contact the IUPAC Executive Director at executivedirector@iupac.org .","disclaimer":"The International Union of Pure and Applied Chemistry (IUPAC) is continuously reviewing and, where needed, updating terms in the Compendium of Chemical Terminology (the IUPAC Gold Book). Users of these terms are encouraged to include the version of a term with its use and to check regularly for updates to term definitions that you are using.","accessed":"2026-04-18T06:53:42+00:00"}}