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Theoretical Consideration Of Solubility
Published in A. L. Horvath, Halogenated Hydrocarbons, 2020
The electron-withdrawing effect of halogens decreases with increasing size. The electron-releasing influence is greatest for fluorine. In electrophilic aromatic substitution, this effect influences the substitution in ortho or para directions. Chlorine, bromine, and iodine have electron-withdrawing effects, but fluorine can act as an electron release in some situations.
Degradation Pathway of Ozone Oxidation of Phenols and Chlorophenols as Followed by LC-MS-TOF
Published in Ozone: Science & Engineering, 2020
Ogheneochuko Utieyin Oputu, Olalekan Siyabonga Fatoki, Beatrice Olutoyin Opeolu, Michael Ovbare Akharame
Intermediates of 2-chlorophenol identified during the ozonation at different experimental conditions are presented in ST 2. Degradation of 2-chlorophenol (C6H5ClO 44, RT = 21.493; SF 12), produced catechol (C6H6O22; RT = 14.001), which was confirmed from the retention time of pure standard. Illustrative chromatograms are presented in SF 13 – SF 16. Since catechol (SF 17) is a major product of phenol degradation, it may be inferred that both phenol 1 and 2-chlorophenol 44 would degrade via identical reaction routes. The conversion of 2-chlorophenol to catechol involves cleavage (hydroxylative dechlorination) of the ortho chlorine atom with a simultaneous attack by a hydroxyl group in a manner similar to electrophilic aromatic substitution reactions.
Synthesis and mesomorphic properties of four ring, rod-like fluorene derivatives – the influence of the lateral substitution on mesomorphic properties of 2,7-bis(4-alkylphenyl)-fluorenes
Published in Liquid Crystals, 2020
Ewelina Dmochowska, Aneta Bombalska, Przemysław Kula
General synthetic methods of compounds 6P-FL-P6; 6P-FL-FPF5; 5FPF-FL-FPF5, 2,7-substituted fluorene derivatives non-substituted at 9th position are given in Figure 2. The synthesis was started from commercially available fluorene (1). At first, fluorene was halogenated with iodine and periodic acid in a mixture of acetic acid, water and sulfuric acid [17]. This electrophilic aromatic substitution reaction with appropriate amounts of iodine and periodic acid gave the main semiproducts 2-iodofluorene (2) and 2,7-diiodofluorene (3) with good yields ca. 50%. The next reaction, Suzuki-Miyaura cross-coupling with (2,3-difluoro-4-pentylphenyl)boronic acid (4) [18] and (4-hexylphenyl)boronic acid (5) (commercially available) gave main products 5FPF-FL-FPF5 and 6P-FL-P6, respectively.
Iodination of vanillin and subsequent Suzuki-Miyaura coupling: two-step synthetic sequence teaching green chemistry principles
Published in Green Chemistry Letters and Reviews, 2019
James J. Palesch, Beau C. Gilles, Jared Chycota, Moriana K. Haj, Grant W. Fahnhorst, Jane E. Wissinger
Like students at institutions across the nation, students in our laboratories gained hands-on experience with an electrophilic aromatic substitution reaction through the nitration of methyl benzoate. This experiment had many virtues in that the white crystalline product (methyl meta-nitrobenzoate) was ideal for learning the technique of recrystallization, and its 1H nuclear magnetic resonance (NMR) spectrum featured well-resolved meta and ortho aromatic coupling for student interpretation. However, the use of the strong mineral acid mixture of nitric and sulfuric acid posed significant hazards to the students both during experimentation and in producing a strong oxidizing waste. Improper disposal by students of the nitration experiment waste into an organic waste stream presented a high risk for explosion or fire. This scenario was most likely the case in a reported explosion and injury in a teaching laboratory performing this same experiment (2).