Conjugated bonding

Bonds Single, double, triple, and aromatic (or conjugated) bonds are indicated by the symbols and " respectively single and aromatic bonds should be omitted. 

Ultraviolet The determination of organic compounds, expecially aromatic and heterocyclic substances or compounds with conjugated bonds. ... 

We generally write a for a diagonal element and p for a bonded off-diagonal element in particular uq and Pec for carbon atoms and carbon-carbon conjugated bonds. The physical interpretation is that each of the r-electrons experiences an average field due to the nuclei, the cr-electrons and the remaining TT-electrons. 

Moreover, it has been established that dehydrocondensation can also be applied to 3,5-diethynyl-l-methylpyrazole, which makes it possible to produce polymer (88%) with an extended system of conjugate bonds possessing semiconductor properties (2001UP2). 

Ultron ES-OVM ovomucoid-conjugated bonded to aminopropyl-silica. 

Carbon materials which have the closest-packed hexagonal structures are used as the negative electrode for lithium-ion batteries carbon atoms on the (0 0 2) plane are linked by conjugated bonds, and these planes (graphite planes) are layered. The layer interdistance is more than 3.35 A and lithium ions can be intercalated and dein-tercalated. As the potential of carbon materials with intercalated lithium ions is low,... 

It is known that the overlap of wave functions of -electrons of conjugated bonds gives rise to a common multicenter system of electrons delocalized along the... 

In the process of radical polymerization a monomolecular short stop of the kinetic chain arises from the delocalization of the unpaired electron along the conjugated chain and from the competition of the developing polyconjugated system with the monomer for the delivery of rr-electrons to the nf-orbitals of a transition metal catalyst in the ionic coordination process. Such a deactivation of the active center may also be due to an interaction with the conjugated bonds of systems which have already been formed. 

The effect of local activation accounts for such features of PCSs as catalytic and stabilizing properties, autocatalysis, specific properties of thermal degradation, structural modification, and a number of other phenomena typical of polymers with a system of conjugated bonds. 

Notice the alternating double and single bonds between the carbon atoms. These are called conjugated bonds, or resonance bonds. The electrons in those bonds are not locked on to one atom—instead they spend their time bouncing from atom to atom. This gives the effect of something in between a double bond and a single bond, more of a one-and-a-half bond. 

A molecule of lycopene can absorb blue light because the electrons are not orbiting a single atom, they are sloshing around orbiting many atoms, and the energy needed to move them is a lot less than in a smaller molecule, or one without conjugated bonds. 

Butadiene-1,3 and Cyclopentadiene.—The value 1.46 A. for the single bond between conjugated double bonds in butadiene-1,3 and cyclopentadiene has been discussed already in connection with the values found in other hydrocarbons containing conjugated systems.16 Penney s10 predicted value for the conjugated bond in butadiene, 1.43 A., appears to be a little too low. 

As in the case of ordinary polymers, copolymerization of two or more different monomers to a conductive polymer is possible, although evidently more stringent compatibility requirements exist in view of the conjugate bonding desired. 

The question of electronic conductivity in the polyphosphazenes inevitably raises questions regarding the electronic structure of the phosphazene linkage.7-12 This matter has been the subject of controversy in the literature, but experimentally the situation is now well known.4,13 In spite of the fact that the phosphazene backbone is fully conjugated, bond equalized and possesses bond lengths which are indicative of partial double bond character, the evidence suggests that these are localized systems. 

The Lewis acid, HX, promotes further decomposition eventually giving a conjugated polyene (>6 conjugated bonds are coloured). The mechanism is possibly,... 

The relatively high electronic conductivity of conducting polymers is connected with the presence in polymers of internal system of poly-7t-conjugated bonds. This is easy to understand on the example of a simplest type of conducting polymer (polyacetylene) in the main and activated states (Figure 6). 

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. 

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