56179-83-0Relevant articles and documents
Acid-Catalyzed Skeletal Rearrangements in Arenes: Aryl versus Alkyl Ring Pirouettes in Anthracene and Phenanthrene
Skraba-Joiner, Sarah L.,Brulet, Jeffrey W.,Song, Min K.,Johnson, Richard P.
, p. 13076 - 13083 (2017/12/26)
In 1 M triflic acid/dichloroethane, anthracene is protonated at C9, and the resulting 9-anthracenium ion is easily observed by NMR at ambient temperature. When heated as a dilute solution in triflic acid/dichloroethane, anthracene undergoes conversion to phenanthrene as the major volatile product. Minor dihydro and tetrahydro products are also observed. MALDI analysis supports the simultaneous formation of oligomers, which represent 10-60% of the product. Phenanthrene is nearly inert to the same superacid conditions. DFT and CCSD(T)//DFT computational models were constructed for isomerization and automerization mechanisms. These reactions are believed to occur by cationic ring pirouettes which pass through spirocyclic intermediates. The direct aryl pirouette mechanism for anthracene has a predicted DFT barrier of 33.6 kcal/mol; this is too high to be consistent with experiment. The ensemble of experimental and computational models supports a multistep isomerization process, which proceeds by reduction to 1,2,3,4-tetrahydroanthracene, acid-catalyzed isomerization to 1,2,3,4-tetrahydrophenanthrene with a predicted DFT barrier of 19.7 kcal/mol, and then reoxidation to phenanthrene. By contrast, DFT computations support a direct pirouette mechanism for automerization of outer ring carbons in phenanthrene, a reaction demonstrated previously by Balaban through isotopic labeling.
Characterization of the combustion products of polyethylene
Piao, Mingjun,Chu, Shaogang,Zheng, Minghui,Xu, Xiaobai
, p. 1497 - 1512 (2007/10/03)
Polyethylene (PE) was burned in a tube-type furnace with an air flow at a temperature of 600~900°C. Combustion products were collected with glass wool, glass fiber filter, and XAD-2 adsorbent. The analysis of the products was performed with GC-FID and GC-MSD. At low temperature, hydrocarbons were the major components, while at higher temperature the products were composed of polycyclic aromatic hydrocarbons. With the high performance of the Hewlett-Packard 6890GC-5973MSD, more compounds were identified in comparison with previous studies.
Base-Induced Proton Tautomerism in the Primary Photocyclization Product of Stilbenes
Somers, J. B. M.,Couture, A.,Lablache-Combier, A.,Laarhoven, W. H.
, p. 1387 - 1394 (2007/10/02)
The mechanism of the photoformation of 1,4-dihydrophenanthrenes (1,4-DHP) and 9,10-dihydrophenanthrenes from 1,2-diarylethylenes in amine solution is clarified by demonstrating that the amine reacts as a base with the initially formed 4a,4b-dihydrophenanthrene.The predominant formation of 1,4-DHP from stilbene is ascribed to an easy proton transfer from C(4b) to C(4) in 4a,4b-DHP via a deprotonation/protonation step, in which the amine operates as the transferring agent.The product formation in basic methanolic solutions proceeds with another mechanism or with less selectivity.When propyl thiolate, having a weak hydrogen-bonding capability, is used as the base, the solvent-mediated protonation in the deprotonation/protonation step occurs exclusively at C(9) and leads eventually to 9,10-DHP.When the stronger base sodium methoxide is used, solvent-mediated protonation proceeds rather unselectively at C(2), C(4), and C(9) and causes the ultimate formation of a mixture of 1,2-, 1,4-, and 9,10-DHP.Deuteration experiments indicate that 1,2- and 3,4-DHP are intermediates in the formation of 1,4-DHP (Scheme VII).The former compounds isomerize photochemically in the presence of a base.Larger diarylethylenes give only compounds analogous to 9,10-DHP.
