| Bifunctional acid-base ionic liquid organocatalysts with a controlled distance between acid and base sites. | |
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MedLine Citation:
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PMID: 20013773 Owner: NLM Status: PubMed-not-MEDLINE |
Abstract/OtherAbstract:
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Bifunctional acid-base ionic liquid organocatalysts with different distances between the two sites have been synthesised, and their activity for the Knoevenagel condensation has been tested. As has been found to be the case with enzymes, the distance between the acidic and basic sites determines the activity of the bifunctional organocatalyst, and at the optimal distance the reaction rate increases by two orders of magnitude with respect to the purely acidic or basic counterpart organocatalysts. The experimental results have been rationalised through the study of the reaction mechanism of the Knoevenagel condensation between malononitrile and benzaldehyde by means of DFT calculations. It has been found that it consists of two consecutive steps. First, deprotonation of malononitrile on the basic site to obtain a methylene carbanion intermediate takes place, and second, co-adsorption and activation of benzaldehyde on the acid centre of this intermediate followed by the C-C bond-formation reaction. The calculations and the kinetic study indicate that there is an inversion of the rate-controlling step when the distance between the acidic and the basic sites is modified, with a direct implication on the reaction rate. |
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Authors:
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Mercedes Boronat; Maria J Climent; Avelino Corma; Sara Iborra; Raquel Mont?n; Maria J Sabater |
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Publication Detail:
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Type: Journal Article |
Journal Detail:
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Title: Chemistry (Weinheim an der Bergstrasse, Germany) Volume: 16 ISSN: 1521-3765 ISO Abbreviation: Chemistry Publication Date: 2010 Jan |
Date Detail:
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Created Date: 2010-01-26 Completed Date: 2010-03-30 Revised Date: - |
Medline Journal Info:
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Nlm Unique ID: 9513783 Medline TA: Chemistry Country: Germany |
Other Details:
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Languages: eng Pagination: 1221-31 Citation Subset: - |
Affiliation:
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Instituto de Tecnolog?a Qu?mica (UPV-CSIC), Av. de los Naranjos s/n, 46022 Valencia, Spain. |
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From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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