Topic
Substituent
About: Substituent is a research topic. Over the lifetime, 42877 publications have been published within this topic receiving 516716 citations. The topic is also known as: side chain & side group.
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TL;DR: In this article, 1,2,3-Triazolium-based poly(ionic liquid)s containing a triethylene glycol spacer were synthesized from the polyaddition of an α-azide-ω-alkyne monomer by copper-catalyzed azide-alkne cycloaddition (CuAAC) followed by quaternization reactions with alkyl halides and subsequent anion exchanges with different fluorinated salts.
Abstract: 1,2,3-Triazolium-based poly(ionic liquid)s containing a triethylene glycol spacer were synthesized from the polyaddition of an α-azide-ω-alkyne monomer by copper-catalyzed azide–alkyne cycloaddition (CuAAC) followed by quaternization reactions with alkyl halides and subsequent anion exchanges with different fluorinated salts. A detailed structure–property relationship for solubility, thermal stability, and ionic conductivity was investigated by means of 1H NMR spectroscopy, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and broadband dielectric spectroscopy (BDS). One of these poly(ionic liquid)s with a methyl substituent and bis(trifluoromethylsulfonyl)imide anion exhibits an ionic conductivity of 2 × 10–5 S cm–1 at 30 °C, which is on par with the best PILs with side-chain charge carriers reported so far and is much higher than any previously reported ionenes. The straightforward synthesis along with the broad structural design and enhanced properties of this new class of poly...
114 citations
TL;DR: In this paper, the 60 Mc high-resolution nuclear magnetic resonance spectra of ten simple α-amino acids in alkaline and acidic medium have been analyzed and the relative signs of the geminal and vicinal coupling constants, the substituent effects on these two couplings and on the relative residence times of the rotational isomers as well as their dependence on the pH of the solution are discussed.
114 citations
TL;DR: The p-styrenyl substituent borne by the organoimido-ligand in the Lindqvist derivative as discussed by the authors allows the polyoxometalate complex to be introduced as a pendant group in polystyrene compositions via conventional free radical-induced copolymerization.
114 citations
TL;DR: The pH dependence of the observed spectra, and the detection of additional species at some pH values, suggest that at least some of the initial radicals undergo base-catalysed rearrangement reactions which result in strand-breakage and the formation of low-molecular-weight fragments.
113 citations
TL;DR: Deuterium labeling experiments revealed an unusual mechanism involving a hydride transfer from the amido substituent to the alpha carbon explaining the high levels of enantioselectivity attained in controlling this alpha chiral center.
Abstract: Conjugate addition of potassium trifluoro(organo)borates 2 to dehydroalanine derivatives 1, mediated by a chiral rhodium catalyst and in situ enantioselective protonation, afforded straightforward access to a variety of protected α-amino esters 3 with high yields and enantiomeric excesses up to 95%. Among the tested chiral ligands and proton sources, Binap, in combination with guaiacol (2-methoxyphenol), an inexpensive and nontoxic phenol, afforded the highest asymmetric inductions. Organostannanes have also shown to participate in this reaction. By a fine-tuning of the ester moiety, and using Difluorophos as chiral ligand, increased levels of enantioselectivity, generally close to 95%, were achieved. Deuterium labeling experiments revealed, and DFT calculation supported, an unusual mechanism involving a hydride transfer from the amido substituent to the α carbon explaining the high levels of enantioselectivity attained in controlling this α chiral center.
113 citations