Biphenylene, stabilization energy

Exercise 21-10 Suggest reasons why (a) the stabilization energy of biphenylene is less than twice that of benzene, and (b) the heat of combustion of naphthalene is less than that of azulene. 

In dibenzothiophene-S,S-dioxide the S atom is in a ring, and hence more constrained. The yield of SOz in the radiolysis is linear with the dose to about 13 Mrad after which it levels off as in p,p -ditolyI sulfone. However, the yield of S02 in this case is much lower (a factor of 25) than in the case of p,p -ditolyl sulfone (G = 0.002 compared to G = 0.05). This stability of the dibenzothiophene sulfone could be partially due to back reaction to reform the parent sulfone and partially due to more efficient energy delocalization. The expected biphenylene product was not detected due to limitations of the analytical method. Bowmer and O Donnell70 studied the volatile products in y-radiolysis of dialkyl, alkyl aryl and diaryl sulfones. Table 2 gives the radiolytic yields of S02 and of the hydrocarbon products of the alkyl or aryl radicals. The hydrocarbon products are those obtained either by H atom abstraction or by radical combination. The authors69 suggested the mechanism... 

Researchers at Clemson University [142-145] have shown that inclusion of 0.5-4 mole% of naphthalene dicarboxylate or biphenylene dicarboxylate in a PET synthesis results in polymers with increased UV stability, which they demonstrated was at least partly due to energy transfer processes to the copolymerised units, which could then safely dissipate the energy. Milligan [146] later suggested that such copolymers could be useful in fibres for automotive upholstery applications. 

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