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Monomers Containing Different Multiple Bonds (Functionally Unsymmetrical Monomers)
Published in George B. Butler, Cyclopolymerization and Cyclocopolymerization, 2020
Intramolecular cyclization of allyl ethers of vinylacetylenic alcohols underwent cyclization in xylene containing 4-(t-butyl)catechol.76 The compound, CH2 = CHCH2OCRR′-C ≡ CC(CH3) = CH2, gave the dihydrophthalan structure shown (6-14). The compound, CH2 = CHCH2OC(CH3)2C ≡ CCH = CH2, gave the oxatricyclododecene shown in Structure 6-14. Vinylacetylenic ketones undergo acid catalyzed cyclization to give γ-hydroxypyrones.77 For example, the α-(β,β-dichlorovinyl)-α′-acetylenic ketone, 3,4-R1R2C6H3C ≡ C-COCR = CCl2 (R = H, CH3, R1R2 = H2, OCH2O) gave the pyrone ether structure shown (R3 = H). This compound, when methylated, gave a mixture of the two structures shown (R3 = CH3) (6-15). Polymerization of (9-anthryl)methyl methacrylate or (9-anthryl)methyl propiolate at room temperature, in the presence of TiCl4, gave polymers (72 and 64% yield, respectively) with spectral properties indicating the presence of units of structure (6-16), formed by Diels-Alder polymerization.2-65
Alcohols and Phenols as Hydrogen Bonding Catalysts
Published in Andrew M. Harned, Nonnitrogenous Organocatalysis, 2017
Hine and coworkers reported a series of studies between 1984 and 1987 that constituted a major breakthrough in the area of hydrogen bonding catalysis [13–19]. In this pioneering work, 1,8-biphenylenediol was demonstrated to be a highly effective dual hydrogen bond donor to bind to oxygen-containing functional groups such as carbonyls, epoxides, and phosphoramides. The initial studies by Hine and coworkers, published in 1984, reported the crystal structures of the parent 1,8-biphenylenediol (1) complexed with hexamethylphosphoramide (HMPA), 1,2,6-trimethyl-4-pyridone, and 2,6-dimethyl-γ-pyrone (Figure 2.1) [13]. In all three crystal structures, biphenylenediol was found to make dual hydrogen bonds to the Lewis basic oxygen atoms present in each hydrogen bond acceptor. The distances between two oxygens (O-H•••O) in all three complexes were between 2.54 Å and 2.61 Å, which indicate the presence of two strong hydrogen bonds in each complex [20]. In addition, all the O-H•••O angles were found to be between 168° and 178°, which are close to the ideal angle of 180° for strong hydrogen bonds.
Kinetic Study of the Acylation of Phenol with Acetic Acid Over A HZSM5 Zeolite
Published in Mike G. Scaros, Michael L. Prunier, Catalysis of Organic Reactions, 2017
I. Neves, F. Jayat, D. B. Lukyanov, P. Magnoux, G. Pérot, F. R. Ribeiro, M. Gubefmann, M. Guisnet*
Reaction scheme. Under all the operating conditions examined, the main reaction products were phenylacetate (PA), ortho- and para-hydroxyacetophenones (o- and p-HAP) resulting from O- and C-acylation of phenol (P), and acetone resulting from the condensation of acetic acid8. Traces of para – ace toxyace top hen one (p-AXAP), 4-acetoxy 6-methyl 2-pyrone and 2-methylchromone were also observed. From a preliminary study at 553 K9 it has been shown that: i) O-acylation was much more rapid than C-acylation (at least 20 times), ii) the modes of formation of o- and p-hydroxyacetophenones were completely different. o-Hydroxyacetophenone would result from a selective C-acylation of P by PA, this reaction being more rapid than the direct acyiation of P by AA. The great selectivity towards the ortho-isomer was attributed to a pronounced stabilization of the transition state involved in the ortho acyiation of phenol, p-Hydroxyacetophenone was formed mainly through a complex pathway involving the acyiation of PA followed by the hydrolysis of the resulting p-AXAP9.
Solute dynamics in a block copolymer: effect of additives and temperature
Published in Molecular Physics, 2022
Sanyukta Bhattacharjee, Souvik Pandit, Debabrata Seth
Benzo α-pyrones, familiarly known as Coumarins represents an important family of fluorescent compounds. These are characterised by the presence of fused pyrone and benzene rings with the pyrone carbonyl group at position 2 [21]. These group of dyes are highly responsive to the local environment; the degree of responsiveness changing substantially with polarity and viscosity of the medium [22]. Coumarin 6 (C-6) (Scheme 2) have been used as the fluorescence probe in this study.