Tetracene, reactivity

The first photochemical reactions to be correlated with PMO theory were the dimerizations of anthracene, tetracene, pentacene, and acenaphthylene. 36> More detailed energy surfaces for the photodimerization reactions of butadiene have also been calculated. 30> In the category of simplified calculations lie studies of the regiospecificity of Diels-Alder reactions 37>, and reactivity in oxetane-forming reactions. 38,39) jn these... 

The sextet formula for tetracene, for pentacene and for hexacene are respectively depicted in Fig.7 these structures correspond to the properties of the hydrocarbons. Anthracene is colourless but rather reactive and easily adds maleic anhydride tetracene is orange yellow and more reactive pentacene is violet and so reactive that it must be prepared under CO. ... 

Table 7.4 lists the thermal reactivity data for a number of polyacenes and it can be seen that the first three members all boil below 400°C, but do not react at their boiling point and atmospheric pressure, whilst tetracene and pentacene, although stable at 400°C, do react at the higher temperatures shown. The reactivity can also be related to the ionization potential, which is a measure of the ease of removal of an electron from the molecule. The lower the ionization potential the more readily a molecule will react and Table 7.5 lists the thermal reactivity of a number of polynuclear aromatic hydrocarbons. 

The centrosymmetric dimer 24 formed by reaction between the two most reactive sites (C7 and C14) and in this sense resembles the photodimers of parent anthracene, tetracene, and pentacene [38]. The dimer 25 formed in the dark reaction resulted from reaction of the most reactive ring of one monomer with the next to terminal ring of the other molecule [33]. Another interesting dimer 26 was isolated as a by-product of the hexacene synthesis by the Anthony group [33]. It is formed by Diels-Alder reaction between the reactive ring containing the C7 and C14 atoms and the alkynyl group of another TIBS-hexacene. As one intact hexacene unit is... 

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