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Quantification of the push–pull effect in 2-alkylidene-4-oxothiazolidines by using NMR spectral data and barriers to rotation around the C=C bond

  • Information about the strength of donor–acceptor interactions in push–pull alkenes is valuable, as this so-called “push–pull effect” influences their chemical reactivity and dynamic behaviour. In this paper, we discuss the applicability of NMR spectral data and barriers to rotation around the C[double bond, length as m-dash]C double bond to quantify the push–pull effect in biologically important 2-alkylidene-4-oxothiazolidines. While olefinic proton chemical shifts and differences in 13C NMR chemical shifts of the two carbons constituting the C[double bond, length as m-dash]C double bond fail to give the correct trend in the electron withdrawing ability of the substituents attached to the exocyclic carbon of the double bond, barriers to rotation prove to be a reliable quantity in providing information about the extent of donor–acceptor interactions in the push–pull systems studied. In particular all relevant kinetic data, that is the Arrhenius parameters (apparent activation energy Ea and frequency factor A) and activation parametersInformation about the strength of donor–acceptor interactions in push–pull alkenes is valuable, as this so-called “push–pull effect” influences their chemical reactivity and dynamic behaviour. In this paper, we discuss the applicability of NMR spectral data and barriers to rotation around the C[double bond, length as m-dash]C double bond to quantify the push–pull effect in biologically important 2-alkylidene-4-oxothiazolidines. While olefinic proton chemical shifts and differences in 13C NMR chemical shifts of the two carbons constituting the C[double bond, length as m-dash]C double bond fail to give the correct trend in the electron withdrawing ability of the substituents attached to the exocyclic carbon of the double bond, barriers to rotation prove to be a reliable quantity in providing information about the extent of donor–acceptor interactions in the push–pull systems studied. In particular all relevant kinetic data, that is the Arrhenius parameters (apparent activation energy Ea and frequency factor A) and activation parameters (ΔS‡, ΔH‡ and ΔG‡), were determined from the data of the experimentally studied configurational isomerization of (E)-9a. These results were compared to previously published related data for other two compounds, (Z)-1b and (2E,5Z)-7, showing that experimentally determined ΔG‡ values are a good indicator of the strength of push–pull character. Theoretical calculations of the rotational barriers of eight selected derivatives excellently correlate with the calculated C[double bond, length as m-dash]C bond lengths and corroborate the applicability of ΔG‡ for estimation of the strength of the push–pull effect in these and related systems.show moreshow less

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Metadaten
Author:Aleksandar Rasovic, Vladimir Blagojevic, Marija Baranac-Stojanovic, Erich Kleinpeter, Rade Markovic, Dragica M. Minic
URN:urn:nbn:de:kobv:517-opus4-394523
Series (Serial Number):Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe (322)
Document Type:Postprint
Language:English
Date of first Publication:2016/05/10
Year of Completion:2016
Publishing Institution:Universität Potsdam
Release Date:2017/04/20
Pagenumber:10
First Page:6364
Last Page:6373
Source:New J.Chem. (2016) Nr. 40, S. 6364-6373. - DOI: 10.1039/C6NJ00901H
Organizational units:Mathematisch-Naturwissenschaftliche Fakultät / Institut für Chemie
Dewey Decimal Classification:5 Naturwissenschaften und Mathematik / 54 Chemie / 540 Chemie und zugeordnete Wissenschaften
Peer Review:Referiert
Publication Way:Open Access
Grantor:RSC
Licence (German):License LogoKeine Nutzungslizenz vergeben - es gilt das deutsche Urheberrecht