|Author||Kresge, A. J. ♦ Chiang, Y.|
|Source||United States Department of Energy Office of Scientific and Technical Information|
|Publisher||American Chemical Society (ACS)|
|Subject Keyword||INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY ♦ ACIDS ♦ AROMATIC HYDROCARBONS ♦ AROMATICS ♦ BENZENE ♦ BROENSTED THEORY ♦ CATALYSIS ♦ HYDROGEN ♦ ISOTOPIC EXCHANGE ♦ METHOXY RADICALS ♦ PROTONS ♦ REACTION KINETICS ♦ TRANSFER FUNCTIONS ♦ TRITIUM ♦ WATER|
|Abstract||General acid catalysis was detected in the exchange of aromatic hydrogen of trimethoxybenzene: rates of loss of tritium from 1,3,5-trimethoxybenzene-2-t to seven acids ranging in strength from H<sub>3</sub>O<sup>+</sup> to H<sub>2</sub>O conform to the Bronsted relation k<sub>A</sub> = 4.72 x 10<sup>-2</sup> (K<sub>A</sub>)<sub>0.5</sub><sub>18</sub> . This fact is inconsistent with a previously assigned mechanism for aromatic The si le formation of a loose complex between proton and aromatic substrate followed by slow intramolecular isomerization of this complex. Instead, general acid catalysis indicates a simple slow proton transfer mechanism for exchange. The loss of tritium from 1,3,5-trimethoxybenzene2-t is not catalyzed by bases. This shows that the proton transfer is not a concerted process, but that reaction takes place in two discrete steps: proton addition to give a phenonium ion followed by proton abstraction to give exchanged trimethoxybenzene. This mechanism, unlike the one first proposed for aromatic hydrogen exchange, is wholly consistent with generally accepted mechanistic schemes for other electrophilic aromatic substitutions.|
|Learning Resource Type||Article|
|Publisher Department||Brookhaven National Lab., Upton, N.Y.|
|Journal||Journal of the American Chemical Society|
|Organization||Brookhaven National Lab., Upton, N.Y.|
Ministry of Human Resource Development (MHRD) under its National Mission on Education through Information and Communication Technology (NMEICT) has initiated the National Digital Library of India (NDLI) project to develop a framework of virtual repository of learning resources with a single-window search facility. Filtered and federated searching is employed to facilitate focused searching so that learners can find out the right resource with least effort and in minimum time. NDLI is designed to hold content of any language and provides interface support for leading vernacular languages, (currently Hindi, Bengali and several other languages are available). It is designed to provide support for all academic levels including researchers and life-long learners, all disciplines, all popular forms of access devices and differently-abled learners. It is being developed to help students to prepare for entrance and competitive examinations, to enable people to learn and prepare from best practices from all over the world and to facilitate researchers to perform inter-linked exploration from multiple sources. It is being developed at Indian Institute of Technology Kharagpur.
NDLI is a conglomeration of freely available or institutionally contributed or donated or publisher managed contents. Almost all these contents are hosted and accessed from respective sources. The responsibility for authenticity, relevance, completeness, accuracy, reliability and suitability of these contents rests with the respective organization and NDLI has no responsibility or liability for these. Every effort is made to keep the NDLI portal up and running smoothly unless there are some unavoidable technical issues.
Ministry of Human Resource Development (MHRD), through its National Mission on Education through Information and Communication Technology (NMEICT), has sponsored and funded the National Digital Library of India (NDLI) project.
For any issue or feedback, please write to firstname.lastname@example.org