TY  - GEN
A1  - Rasovic, Aleksandar
A1  - Blagojevic, Vladimir
A1  - Baranac-Stojanovic, Marija
A1  - Kleinpeter, Erich
A1  - Markovic, Rade
A1  - Minic, Dragica M.
T1  - 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
N2  - 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 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.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 322 
Y1  - 2016
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-394523
SP  - 6364
EP  - 6373
ER  - 
TY  - JOUR
A1  - Rasovic, Aleksandar
A1  - Blagojevic, Vladimir
A1  - Baranac-Stojanovic, Marija
A1  - Kleinpeter, Erich
A1  - Markovic, Rade
A1  - Minic, Dragica M.
T1  - 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
JF  - New journal of chemistry
N2  - 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 CQC double bond to quantify the push-pull effect in biologically important 2-alkylidene-4-oxothiazolidines. While olefinic proton chemical shifts and differences in C-13 NMR chemical shifts of the two carbons constituting the CQC 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 ( Delta S-double dagger, Delta H-double dagger and Delta G(double dagger)), 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 Delta G(double dagger) 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 CQC bond lengths and corroborate the applicability of Delta G(double dagger) for estimation of the strength of the push-pull effect in these and related systems.
Y1  - 2016
U6  - https://doi.org/10.1039/c6nj00901h
SN  - 1144-0546
SN  - 1369-9261
VL  - 40
SP  - 6364
EP  - 6373
PB  - Royal Society of Chemistry
CY  - Cambridge
ER  -