Search results for "ring strain"
showing 10 items of 15 documents
Chemical and Spectroscopical Properties of Medium Sizedtrans- andcis-Bicyclo[n.1.0]alk-2-ynes
1997
Chemical and spectroscopical properties of cis- and trans-cyclopropano-anellated cycloalkynes of medium ring size are investigated and compared with results from force field calculations. IR and 13C-NMR data of the alkynes reflect the deformation of the triple bond due to ring strain. Parallel to bending the reactivity increases with decreasing ring size, the trans fused alkynes prove to be nearly as reactive as the cis fused with a two carbon smaller ring size. The bicycloalkynes are complexed with silver triflate. 13C NMR reveals that the triple bond as well as the cyclopropane serve as ligands.
Strain Release Chemistry of Photogenerated Small‐Ring Intermediates
2021
Abstract Photochemical processes, such as isomerizations and cycloadditions, have proven to be very useful in the construction of highly strained molecular frameworks. Photoinduced ring strain enables subsequent exergonic reactions which do not require the input of additional chemical energy and provides a variety of attractive synthetic options leading to complex structures. This review covers the progress achieved in the application of sequences combining excitation by ultraviolet light to form strained intermediates, which are further transformed to lower energy products in strain‐release reactions. As ring strain is considerable in small ring systems, photogenerated three‐ and four‐memb…
Frontispiece: Strain Release Chemistry of Photogenerated Small‐Ring Intermediates
2021
2-(1-Aryliminoethyl)-9-arylimino-5,6,7,8- tetrahydrocycloheptapyridyl iron(II) dichloride: synthesis, characterization, and the highly active and tun…
2014
A series of 2-(1-arylimino)ethyl-9-arylimino-5,6,7,8-tetrahydrocycloheptapyridine derivatives was synthesized and fully characterized, and thereafter reacted with iron dichloride to form their corresponding iron(II) complexes. The single crystals of representative organic and iron complex compounds were obtained and analyzed by the X-ray diffraction analysis, indicating the distorted bipyramidal geometry around the iron core. Moreover, DFT calculations were performed on selected species to determine their structural features. On treatment with either MAO or MMAO, all iron complex pre-catalysts showed high activities (up to 1.56 × 10(7) gPE mol(-1)(Fe) h(-1)) toward ethylene polymerization. …
Untersuchungen zur Konformation und elektronischen Struktur von Cyclooctadieninen
1985
Die mit semiempirischer Quantenmechanik vorhergesagten Konformationen und elektronischen Strukturen der Cyclooctadienine 1 und 2 werden experimentell an Hand von 1H-NMR- und PE-Spektren verifiziert. Dabei wird Bezug genommen auf eine Reihe von anderen, verwandten Cycloalkinen 3–5 und Cycloalkenen 6–11. Wahrend die hohe geometrische Ringspannung entscheidenden Einflus auf 1 und 2 hat, ist eine Homoaromatizitat, die auf sechs nahezu eben angeordneten π-Elektronen-Zentren beruht, nicht signifikant. Investigations on the Conformation and the Electronic Structure of Cyclooctadienynes Conformations and electronic structures of the cyclooctadienynes 1 and 2, predicted by semi-empirical quantum mec…
1‐Oxa‐3‐cyclooctin
1990
1-Oxa-3-cyclooctyne According to an MNDO calculation, 1-oxa-cyclooctyne (13) and 1-oxa-3-cyclooctyne (14) are 8-membered heterocyclic ring systems with high steric energy (ring strain). On the basis of THF (1) and acetoacetic ester (4), a multi-step synthesis is described for 14. The triple bond is introduced in the last step by a thermal fragmentation of the 1,2,3-selenadiazole 12.
Cyclooctadienine — hoch gespannte C 8 H 8 ‐Kohlenwasserstoffe
1985
Mit Hilfe der MNDO-Methode werden die energiearmsten Konformationen der vier strukturisomeren Cyclooctadienine 1–4 berechnet. Aus ihren Bildungswarmen ΔHf konnen durch Bezug zu den Cyclooctatrienen 5 und 6 die geometrischen Ringspannungen Eg abgeschatzt werden. Als experimentelle Sonde fur die Ringspannung dienen die UV-, IR (Raman)- und 13C-NMR-Spektren. Cyclooctadienynes — Highly Strained C8H8-Hydrocarbons Applying the MNDO-method the conformations with lowest energy of the isomeric cyclooctadienynes 1–4 are calculated. The geometrical ring strains Eg can be evaluated from the enthalpies of formation ΔHf in relation to the cyclooctatrienes 5 and 6. UV, IR (Raman) and 13C NMR spectra serve…
The Influence of Intramolecular Coordination and Ring Strain on the Polymerization Potential of Cyclic Stannasiloxanes
2008
ChemInform Abstract: Chemical and Spectroscopical Properties of Medium Sized trans- and cis- Bicyclo(n.1.0)alk-2-ynes.
2010
Chemical and spectroscopical properties of cis- and trans-cyclopropano-anellated cycloalkynes of medium ring size are investigated and compared with results from force field calculations. IR and 13C-NMR data of the alkynes reflect the deformation of the triple bond due to ring strain. Parallel to bending the reactivity increases with decreasing ring size, the trans fused alkynes prove to be nearly as reactive as the cis fused with a two carbon smaller ring size. The bicycloalkynes are complexed with silver triflate. 13C NMR reveals that the triple bond as well as the cyclopropane serve as ligands.