Decarbonylation of ANQ

Decarbonylation of ANQ and PHQ proceeded at 500- 600 C in the presence of hydrogen to form initially fluorenone (FLR), followed by successive hydrogenolyses of FLR to biphenyl and CO, finally of biphenyl to benzene. Progress of similar reactions were examined for 1,4- and 1,2-naphthoquinone (NPQ) and p-benzoquinone (BNQ) (, ... 

Figures 1 and 2 illustrate the change of product distribution with reaction period for the decarbonylation of ANQ at about 570 C and that of PHQ at about 560 C, respectively. There is an apparent induction period for both compounds. The batch system apparatus adopted in these experiments was responsible for this induction period since 2-3 minutes were needed to heat up the inserted ampule to a temperature within 95% of the temperature in C of that of the furnace block. It was concluded that no real induction period exists in these reactions.

They said that the formation of such an intermediate is thermally allowed from the orbital symmetry rule (18). Since the same symmetrical situation is expected for the structure of ANQ, a prediction of the thermal decarbonylation of ANQ to proceed via such an intermediate may be possible in accordance with the symmetry rule. However, the same reasoning is difficult in the case of PHQ in which the decarbonylation proceeds more rapidly than ANQ. 

Based on Figures 1 and 2, typical consecutive reaction schemes 1 and 2 occur during the decarbonylation reactions of ANQ and PHQ. Such a conclusion seems justified even though the reac-... 

Formation of carbon dioxide was observed during the initial stage of the reaction. It equilibrated rapidly after the consumption of feed quinones maintaining a constant amount throughout the reaction period. The amount of carbon dioxide formation was in the order 1,2-NPQ > p-BNQ > 1,4-NPQ > PHQ > ANQ. No carbon dioxide was detected in the decarbonylation of FLR to biphenyl and benzene. Information obtained above suggests that carbon dioxide is formed solely from quinones and that it is produced in a unimolec-ular way, i.e., not through intermolecular reaction between two carbonyl groups. 

Namely, in the case of ANQ and FLR, the action of hydrogen on the substrate is necessary for the progress of decarbonylation even at the first step of the reaction. 

Non-catalytic thermal decarbonylation of quinones proceeded for 9,10-anthraquinone (ANQ), 9,10-phenanthrenequinone (PHQ), 1,4-and 1,2-naphthoquinone(NPQ) and p-benzoquinone (BNQ) in the presence of atmospheric hydrogen at 500- 600 C. ANQ or PHQ decar-bonylated in the presence of hydrogen to form fluorenone (FLR) at the first step, followed by successive hydrodecarbonylation and hydrocracking to form biphenyl and benzene. In the case of 1,4-NPQ, the reaction did not proceed in any obvious stoichiometric relation. Only 60- 70 % of 1,4-NPQ decarbonylated and was hydrogenated yielding styrene, ethylbenzene, toluene, benzene and lower hydrocarbons the remainder polymerized or partly polycondensed. Similar, or less selective results were obtained for 1,2-NPQ and p-BNQ. Analyses of kinetic treatments are reported for the consecutive reaction schemes of ANQ or PHQ as well as of FLR. The kinetic parameters for decarbonylation, polymerization, polycondensation reactions of quinones are discussed. 

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