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: Analysis of data obtained from relative nucleophilicity/electrophilicity, condensed Fukui and softness functions indicated that the sites for electrophilic attacks for the amino acids in skeletons I and II are in the amine bonds but for those in skeleton III the sites were in their respective phenyl ring.
79 citations
TL;DR: In this article, the rate constants for group transfers of the MeS, PhS and PhSe groups from chalcogen-substituted acetate, acetonitrile, malonate, and malonitrile derivatives were determined by competition kinetics using PTOC esters as the radical precursors and competing trapping agents.
Abstract: Rate constants for group transfers of the MeS, PhS, PhSe, and PhTe groups from chalcogen-substituted acetate, acetonitrile, malonate, and malononitrile compounds, from N-(phenylthio)phthalimide and from Me 2 S 2 and Ph 2 S 2 to primary alkyl radicals, have been determined by competition kinetics using PTOC esters as the radical precursors and competing trapping agents. This group transfers from malononitrile derivatives are marginally faster than the corresponding group transfer from the symmetrical disulfide, and the rate constant for PhSe group transfer from PheSePh is greater than those from the derivatives studied here. Substituent effects suggest that the chalcogen transfer reactions may be concerted. For three cases in which direct comparisons can be made, the rate constants for reactions of phenylchalcogenides are approximately equal to those for halogen atom transfer when the chalcogen and halide are in the same row of the periodic table and the radical resulting from dispkacement is the same. The rate constants reported in this work will be usefull for the rational design of synthetic schemes based on homolytic group transfer chemistry
79 citations
TL;DR: In this article, the substituent effect on the optical properties of both the closed-ring and open-ring isomers of a series of dithienylethene photochromic molecules was studied.
Abstract: We have studied the substituent effect on the optical properties of both the closed-ring and open-ring isomers of a series of dithienylethene photochromic molecules. We demonstrate that TDDFT method, in conjunction with moderate size basis set, provides an accurate tool for the determination of the lowest singlet excitation energies of dithienylethene compounds. We have seen that the absorption spectrum of both the closed-ring and open-ring isomers can be easily shifted to longer wave wavelengths by introducing (1) acetylenic groups at the 5-position of the thiophene rings and (2) electron-withdrawing substituents in the upper cyclopentene structure.
79 citations
TL;DR: The reaction of copper beta- octabromo- meso-triarylcorrole derivatives with methyl 2,2-difluoro-2-(fluorosulfonyl)acetate has provided four beta-octakis(trifluoromethyl)corrole complexes, Cu[(CF 3) 8T( p-XP)C] (X = F, H, Me, OMe), in moderate yields.
Abstract: The reaction of copper β-octabromo-meso-triarylcorrole derivatives with methyl 2,2-difluoro-2-(fluorosulfonyl)acetate has provided four β-octakis(trifluoromethyl)corrole complexes, Cu[(CF3)8T(p-XP)C] (X = F, H, Me, OMe), in moderate yields. The new complexes present a conglomeration of remarkable substituent effects, both steric and electronic. DFT (OLYP/TZP) geometry optimization of Cu[(CF3)8TPC] (i.e., X = H) indicates a sterically hindered, strongly saddled geometry, with numerous short F···F nonbonded contacts of 2.5−2.9 A and certain β carbons displaced by over 1.5 A relative to the mean corrole plane. The CF3 groups generally appear as quartets in the 19F NMR spectra, with unexpectedly large 5JFF coupling constants of about 14 Hz, apparently a manifestation of the highly crowded structure. The eight CF3 groups together exert a powerful influence on the redox potentials of the copper corrole core. Thus, the E1/2ox of Cu[(CF3)8TPC] (1.4 V vs saturated calomel electrode) is a full half of a volt above ...
79 citations
TL;DR: In this paper, second-order Moller-Plesset (MP2) perturbation calculations were used to obtain energies, dipole and quadrupole moments, and polarizabilities of CO2, three alkanes (CH4, CH3CH3, and CH3 CH2CH3), and three fluoroalkanes (CF4,CH3CF3 and CH 3CH2CF3).
79 citations