Condensed structures containing double bond

It may be mentioned that in heterocyclic systems as well as in hydrocarbon condensed ring systems the contribution to the normal state of structures associated with all of the possible positions of the double bonds is dependent on the existence of a coplanar arrangement of the per-tinent atoms, with bond angles of about 120°, which requires that the rings contain five or six or possibly seven atoms. 

Bismaleimides are produced by the condensation reaction of a diamine, such as methylenedianiline, with maleic anhydride. The reaction product tends to be crystalline with a high melting point. Eutectic blends of different bismaleimides reduce the melting point. However, a coreactant generally is required to improve the processing properties of the material. Bismaleimides owe their reactivity to the double bonds on each end of the molecule, which can react with themselves or with other compounds containing functional groups (vinyls, allyls. or amines). A typical bismaleimide structure is shown by ... 

The nearly planar structure of Pd(II) complex 123 enabled a twofold connection of the bicyclic units in imino ether condensations brought about by Meerwein s salt and diisopropylethylamine in methylene chloride. Protonation of 124 (Scheme 14) generates a Pd(II) complex (125) of an octahy-droporphyrin, with complete saturation of the peripheral double bonds containing the 7t-system of l,5,9,13-tetraaza[16]annulene (68AG622). 

When a condensed structural formula is written for a compound containing double or triple bonds, the multiple bonds are often drawn as they would be in a Lewis structure. Table 1-3 shows examples of condensed structural formulas containing multiple bonds. Notice that the —CHO group of an aldehyde and the —COOH group of a carboxylic acid are actually bonded differently from what the condensed notation suggests. Condensed structures are assumed to follow the octet rule even if the condensed notation does not show the bonding. 

Dyes generally contain two or more cyclic rings that may or may not be aromatic and condensed. From a chemical point of view, a dye molecule can be characterised, on the one hand, by the basic structure, which is related to a dye family and contains chromophores (conjugated double bonds, aromatic rings), which induce the dye solution coloration, and, on the other hand, by the substituents or auxochromic groups, which infer aqueous solubility by ionisation (NH2, OH, COOH, SO3H, etc.) and can enhance conjugation in the dye molecule. 

Alkenes are hydrocarbons that have the general formula C H2n and contain a carbon—carbon double bond. (These eompounds are also called olefins.) The simplest alkene, ethylene, has the condensed formula CH2=CH2 and the structural formula... 

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