Polyimide Characterization Studies — Effect of Pendant Alkyl Groups

Polyimides ◽  
1984 ◽  
pp. 417-428 ◽  
Author(s):  
Brian J. Jensen ◽  
Philip R. Young
2019 ◽  
Author(s):  
Sayad Doobary ◽  
Alexi Sedikides ◽  
Henry caldora ◽  
Darren poole ◽  
Alastair Lennox

Fluorinated alkyl groups are important motifs in bioactive compounds, positively influencing pharmacokinetics, potency and F conformation. The oxidative difluorination of alkenes represents an H important strategy for their preparation, yet current methods are limited in their alkene-types and tolerance of electron-rich, readily oxidized functionalities, as well as in their scalability. Herein, we report a method for the difluorination of a number of unactivated alkene-types that is tolerant of electron-rich functionality, giving products that are otherwise unattainable. Key to success is the electrochemical generation of a hypervalent iodine mediator (in the presence of nucleophilic fluoride and HFIP) using an ‘ex-cell’ approach, which avoids the oxidative decomposition of the substrate. The more sustainable conditions give good to excellent yields of product in up to decagram scales<br>


2016 ◽  
Vol 15 (7) ◽  
pp. 1629-1634
Author(s):  
Mihaela-Elena Dascalu ◽  
David Amaya Vias ◽  
Valentin Nedeff ◽  
Juan Antonio Lopez-Ramirez

1997 ◽  
Vol 36 (2-3) ◽  
pp. 69-74
Author(s):  
G. Bozarslan ◽  
S. K. Çelebi ◽  
F. Sengül

In this study, the wastewater of one of the cigarette factories in Izmir was characterized and treatability studies were done. The characterization studies of the wastewater showed that the COD, and the pH changes drastically. The chemical treatability studies of the influent wastewater were done by using Ca(OH)2, FeCl3 and Fenton Reagent. The optimum dose of FeCI3 was determined by jar tests. When using Ca(OH)2, the best flocculation, settling behaviour, and the highest COD removal occurred around pH 11. The optimum doses of Fenton Reagent (FeSO4 and H2O2) were determined. The supernatants of the previously chemically treated wastewaters were used for biological treatment. According to total COD removal efficiencies and the amount of sludge production during chemical treatment, FeCl3 was found to be the most economical and effective coagulant. Chemical treatment units were designed for a batch and a continuous system. The batch system has more advantages than a continuous system in this case.


2019 ◽  
Vol 19 (16) ◽  
pp. 1292-1297 ◽  
Author(s):  
Ali Mohd Ganie ◽  
Ayaz Mahmood Dar ◽  
Fairooz Ahmad Khan ◽  
Bashir Ahmad Dar

:Here in we report the number of strategies for the synthesis of differently substituted benzimidazole derivatives. The protocols involved in the syntheses of these derivatives were one-pot or multi-component. The characterization studies of these derivatives were carried by using different spectroscopic techniques (1H NMR, 13C NMR and MS) and elemental analyses. The biological screening studies revealed that these benzimidazole derivatives show potential antibacterial as well as antifungal behavior. These benzimidazole derivatives not only depicted potential antiulcer properties but also showed moderate to good anticancer/cytotoxic behavior against different cancer cell lines.


1979 ◽  
Vol 44 (6) ◽  
pp. 1731-1741 ◽  
Author(s):  
Andrej Staško ◽  
Ľubomír Malík ◽  
Alexander Tkáč ◽  
Vladimír Adamčík ◽  
Eva Maťašová

Reactions of R2,R3-alkyl substituted 2-hydroxybenzenecarboxylic acids 2-HO-C6H2R2-COOH with Grignard reagents R1MgBr in the presence of nickel give stable aryl alkyl ketyl radicals 2-O--R2-, R3-C6H2-CO--R1 where R1 = CH3, C2H5, C2D5, n-C3H7 and R2,R3 = CH3, C2H5, i-C3H7, t-C4H9. The β protons of ketyl group are equivalent (splitting constant 1.25 mT) and non-equivalent (splitting constants within 0.5 to 1.5 mT) for R1 = methyl and other alkyl groups, respectively. Interaction of the γ protons with the unpaired electron was only observed in the case of R1 = n-propyl (splitting constants about 0.07 mT). The substituents R1 have but slight effect on values of splitting constants of the protons in R2,R3 and vice versa. Also splitting constants of the benzene nucleus (a4H = 0.55 mT, a6H = 0.44 mT) are only slightly affected by the substituents R1,R2,R3, which indicates dominant electron-donor effect of the oxido-anion group eliminating the relatively smaller contributions of the alkyl substituents.


2006 ◽  
Vol 71 (4) ◽  
pp. 567-578 ◽  
Author(s):  
Alicja Stachelska ◽  
Zbigniew J. Wieczorek ◽  
Janusz Stępiński ◽  
Marzena Jankowska-Anyszka ◽  
Harri Lönnberg ◽  
...  

Second-order rate constants for the hydroxide-ion-catalyzed imidazolium ring-opening of several mono- and dinucleosidic analogs of mRNA 5'-cap have been determined. Intramolecular stacking of the two nucleobases in the dinucleosidic analogs, m7GpppN (m7G = 7-methylguanosine, N = 5'-linked nucleoside), and electrostatic interaction between the N-alkylated imidazolium ring and phosphate moiety have been shown to shield the m7G moiety against the nucleophilic attack of hydroxide ion. In addition, the effect of methylation of the nucleobase amino groups and replacement of the 7-methyl group with other alkyl groups have been studied. The influence of all the structural modifications studied turned out to be modest, the cleavage rates of the most and least reactive analogs (with the exception of non-phosphorylated nucleosides) differing only by a factor of 5.


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