New 1,3-digermacyclobutanes, with two exocyclic C=PMes* bonds, and the corresponding first bis(methylenethioxo)phosphoranes with C=P(S)Mes* moieties have been synthesized.Petronela Maria PetrarBabes-Bolyai University1Kogalniceanu Street Cluj-Napoca Romania isi@chem.ubbcluj.roGabriela Nemes...
Nucleic acids, particularly DNA, are known chromophores of UVB energy. Absorption of UVB opens the double bonds in pyrimidine bases (i.e.,thymineand cytosine) in the nucleic acid, allowing reactions to occur between adjacent bases. When a pyrimidine base is next to a UV-modified base, direct...
The authors replaced the previously used ladderene with ladderane, which can be mechanically activated into a structure that is not completely conjugated, allowing for a detailed study of stereoselectivity. It was found that while the first cyclobutane formed E,E double bonds, the second cyclobutane...
10.23.9.3.2(ii)(b) By formation of two bonds No advances in this area have been found since the publication of CHEC-II(1996) <1996CHEC-II(7)921>. 10.23.9.3.3 Compounds with two heteroatoms in each heterocyclic ring 10.23.9.3.3(i) Synthesis of the heterocyclic ring 10.23.9.3.3(i)(...
Bicyclobutane (1) adopts a so-called “butterfly” conformation, with the two cyclopropane rings distorting from a planar conformation by 120–125° (Fig. 1A)12. Interestingly, all C–C bonds also have approximately the same length of 1.50 Å12. For BCB derivatives, the bond lengths an...
Reactions of singlet and triplet carbenes with carbon-carbon double bonds Direct and sensitized irradiation of methyl diazomalonate gives singlet and triplet biscarbomethoxy-carbene, respectively. The reactions of these species with carbon-carbon double bonds are described. Cyclopropanes are formed with ...
The lack of NMR signals for the typical terminal double bonds at C-16/C-17, a feature usually presents in ent-kauranoids, in both monomers of compound 4, implies that these double bonds are involved in the dimerization. This, combined with the one remaining degree of unsaturation and key...
Strong hydrogen bonds are thought to be partially resolved by formation of T< > T dimers after UVC irradiation. One possible explanation for the detectability is the distortion of DNA and the structure of dithymine sites, which may result in slight changes in the interaction with surrounding...
Why does methylene chloride sink to the bottom when mixed with water? Why don't lipids and water mix? Why is the electrical double layer concept so important for flotation, flocculation, and coagulation? Why do amines show high solidity in water? Why is it necessary to dry the puri...
However, when two methyl groups are present, the gem isomers are the most stable for molecules B2P2(CH3)2H6 with P–C and B–C bonds, respectively. Transition structures present barriers to the interconversion of two equilibrium structures or to the interchange of axial and equatorial positions...