Conjugated bonding system

Molecular fluorescence involves the emission of radiation as excited electrons return to the ground state. The wavelengths of the radiation emitted are different from those absorbed and are useful in the identification of a molecule. The intensity of the emitted radiation can be used in quantitative methods and the wavelength of maximum emission can be used qualitatively. A considerable number of compounds demonstrate fluorescence and it provides the basis of a very sensitive method of quantitation. Fluorescent compounds often contain multiple conjugated bond systems with the associated delocalized pi electrons, and the presence of electron-donating groups, such as amine and hydroxyl, increase the possibility of fluorescence. Most molecules that fluoresce have rigid, planar structures. 

A template mechanism was also proposed for spontaneous polymerization of propargyl chloride in the presence of poly(4-vinylpyridine). The reaction consists of partial (6-8%) alkylation of P4VPy by propargyl chloride which leads to stable complex P4VPy with monomer and then to polymerization. The product obtained contains a conjugated bond system formed by opening triple bonds in the monomer according to reaction ... 

In only a few cases is there direct proof that remote attack takes place when complexes containing conjugated bond systems extending from a remote polar group (for example... 

A relationship between a reaction rate involving electron transfer through a conjugated bond system and the mobile bond (4) order has been suggested (13) and... 

The mechanism of the hydrogen atom contribution to the >v electronic interaction of a molecule seems not to be uniform, but to depend upon the structure of the molecular system. One may suppose that the nature of such a hydrogen bond is due to the electron ability of the hydrogen atom (under certain conditions) to participate in the interaction with -electrons of neighbouring atoms and transmit this interaction throughout the conjugated bond system, which in its turn favours sharing the electrons in a molecule. 

Since the discovery of doped polyacetylene, a range of polymeric semiconductor devices has been studied, including normal transistors, field-effect transistors (FETs) photodiodes, and light-emitting diodes (LEDs). Like conductive polymers, these materials obtain their properties from their electronic nature, specifically the presence of conjugated -bonding systems. 

Roginskii, S. Z., Berlin, A. A., Kutseva, L. N., Aseeva, R. M., Cherkashina, L. G., Sherle, A. I., Matseeva, N. G. Catalytic Properties of Organic Polymers with a Conjugated Bond System. The Formation of Hydroperoxides by Oxidation of Alkylaromatic Hydrocarbons and Cychlohexane. Dokl. SSSR, Chemistry Section (English Transl.) 148,35 (1963) (1963),... 

Ruedenberg, K. Quantum mechanics of mobile electrons in conjugated bond systems I. J. Chem. Phys. 34, 1861 (1961). 

If the CSA is large (10-20 kHz, as for carbons in aromatic and in other conjugated bond systems), spinning at 3 kHz will not be sufficient and spinning side bands (SSB) will be obtained around the isotropic resonance line. By application of special pulse techniques these side bands (time dependent effects, (4)) can be removed or at least minimised in most of the cases. 

The molecular structure of beta-carotene, The double bonds alternate with single bonds in this molecule, called a conjugated bonding system. 

Phenazine (1), as a 9,10-diazaanthracene, exhibits a fully conjugated bond system which may be represented as a resonance hybrid of a number of canonical structures. Both heterocyclic nitrogen atoms are similar to the quinoline nitrogen atom. 

FIGURE 1.2 Resonance stabilization of conjugated bond systems, (a) Chains (b) rings... 

Neither of the two molecules depicted in the margin is aromatic. The 1,3,5-hexatriene molecule has six ir electrons in its conjugated bonding system, but it is not cyclic. The 1,3-cyclopentadiene molecule is cyclic, but has only four tt electrons in a conjugated bonding system that does not extend completely around the ring. 

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