Of conjugated double bond

Figure 2-50. Representations of a) 1,3-butadIene and b) benzene, as examples of conjugated double bonds in RAMSES.

Addition of dihydrosilane to a, /J-unsaturated carbonyl compounds such as citral (49), followed by hydrolysis, affords saturated citroneJlal (50) directly. The reaction is used for the selective reduction of conjugated double bonds[45,46]. In addition to Pd catalyst, the use of a catalytic amount of... 

Many chemical compounds have been described in the Hterature as fluorescent, and since the 1950s intensive research has yielded many fluorescent compounds that provide a suitable whitening effect however, only a small number of these compounds have found practical uses. Collectively these materials are aromatic or heterocycHc compounds many of them contain condensed ring systems. An important feature of these compounds is the presence of an unintermpted chain of conjugated double bonds, the number of which is dependent on substituents as well as the planarity of the fluorescent part of the molecule. Almost all of these compounds ate derivatives of stilbene [588-59-0] or 4,4 -diaminostilbene biphenyl 5-membeted heterocycles such as triazoles, oxazoles, imidazoles, etc or 6-membeted heterocycles, eg, coumarins, naphthaUmide, t-triazine, etc. 

In addition to thermal polymerization, it is possible to polymerize CPD with inorganic haUdes as catalyst. With trichloroacetic acid as the catalyst, deeply colored, blue polymers that conduct electricity in nonpolar solvents such as benzene in the presence of acid can be obtained. The conductivity and color are caused by blocks of conjugated double bonds present in the polymers (20—21). 

Cesca, S., Priola, A. and Bruzzone, M. Synthesis and Modification of Polymers Containing a System of Conjugated Double Bonds. Vol. 32, pp. 1—67. 

Decarboxylation of copolymers of propynoic acid and phenylacetylene of varying composition was found to manifest an increase in reactivity of the carboxylic groups with increasing concentration of conjugated double bonds in the chain. 

Substances that can oxidize to form a system of conjugated double bonds are frequently oxidized by atmospheric oxygen, iodine or iron(lll) salts. The products are chromo-phoric systems frequently containing ortho- or para-quinoid structure. 

The characteristic system of conjugated double bonds in the carotenoid molecule in which the Tt electrons are delocahzed over the whole polyene chain is responsible for both absorption of visible light and chemical reactivity, resulting in unstable and easily destroyed compounds. Based on this information, the following precautions must be taken during analysis ... 

Number of conjugated double bonds — As the length of a chromophore increases, it becomes easier to promote the electrons to the excited state, with consequent reduced energy necessary for the transitions, and thus the absorption occurs at longer wavelengths. 

These compounds contain a developed system of conjugated double bonds imparting distinct semiconductor properties on them. Metal ions of variable valency can serve as the central ion M cobalt, nickel, iron, manganese, copper, and so on. In such systems, electron transitions can occur in the conjugated system of the ligands and in the electronic system of the central metal ion. These transitions are the basis for their catalytic activity toward various reactions. 

Extension of conjugated double bond system at 2 - and/or 6 -positions makes it possible for fluoran compounds to have an absorption in the near infrared region up to 1200 nm. These include 2 -anilino-6-(4-anilinoanilino)-3 -methylfluoran (62),63 6 -[4-(4-anilinoanilino)anilino]-2 -chloro-3 -methylfluoran (63),7 6 -[4-(4-dimethylaminoanilino)anilino]-2 -methylflu-... 

Polyene and polymethine dyes are two structurally related groups of dyes which contain as their essential structural feature one or more methine (-CH=) groups. Polyene dyes contain a series of conjugated double bonds, usually terminating in aliphatic or alicyclic groups. They owe their colour therefore simply to the presence of the conjugated system. In polymethine dyes, electron-donor and electron-acceptor groups terminate either end of the polymethine chain, so that they may be considered as typical donor-acceptor dyes. 

The pattern of the II-NMR spectrum of lycopene differs from the spectra of the other carotenoids because lycopene consists of conjugated double bonds. At 6.6ppm the multiplet of protons 11/11 (6.63ppm) and of proton pairs 15/15 (6.60ppm) resonate adjacent to the doublet of proton pair 7/7 (6.44 ppm), the doublet of proton pair 12/12 (6.29 ppm), the doublet of proton pair 14/14 (6.22 ppm), the doublet of proton pairs 8/8 (6.15ppm), and finally the doublet of proton pair 10/10. The resonance of proton pairs 6/6 and 2/2 are shifted to a higher field at 5.85 and 5.00 ppm due to their position in the conjugated system. 

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