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Showing 1 to 20 of 113 for “"Steric hindrance"”.
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Probing the Role of Amines in Aqueous Electrochemical Reduction of Captured-state CO₂
… how amine physicochemical properties, namely steric hindrance and pKₐ, impact speciation, product selectivity, and cell performance. We chose a subset of primary alkylamines with varied steric hindrance and pKₐ and evaluated each on the basis of Faradaic efficiency, partial current density to …
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Syntheses of Azido- and Diazido- 10-Methylacridinium Salts.
… was unsuccessful at the methylation stage due to steric hindrance of the 4-acetamido group. An improved yield of 4-nitro-9-aminoacridine is also reported.
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The synthesis of biodegradable polymers using aluminium alkoxide initiators
… general bulkier alkoxide groups provide greater steric hindrance around the active site at the beginning of the reaction. This causes an induction or a build up period that is related to the both the steric hindrance and also the electronic effects provided by the alkoxide group. The alkyl group …
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Design and Syntheses of Potential Drugs Based on GABA(A) Receptor Pharmacophores
… to either the unexpected side reactions or the steric hindrance of enolate alkylation. In the case of tetrahydro-1,4-benzodiazepin-2-ones, computational studies suggested that steric hindrance by both the benzo ring and N4-allyl group might retard deprotonation at C3 by bulky bases like KHMDS or …
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Reactivity of the Vinylogous Epoxyketone Moiety
… but by other factors such as ring strain and steric hindrance of the epoxide ring.
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Triptycene side unit effects on compressive yield strength in polycarbonates
… due to the interlocking mechanism and the steric hindrance of the triptycene units. The design of strengthening polymers by adding triptycene units could prove useful to improve high performing polymers, or to give low molecular weight polymers more stability.
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Development of an Enzyme-Linked ImmunoSorbent Assay (ELISA) with Enhanced Sensitivity in a Nanofluidic System
… at high antigen concentration decreased due to steric hindrance. Binding kinetics in nanochannels was limited by convective transport of analytes, instead of diffusion or reaction. We also found that enzymatic reactions in nanochannels were very effective due to short diffusion length and high …
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Investigation of the Steric and Electronic Properties of 3-Iminophosphine Ligands in Chelated Palladium Allyl Complexes for Use in the Regioselective Hydroamination of Allenes
… triflate complexes varying in both steric and electronic features was isolated and characterized. The propensity of the complexes in this series to regioselectively catalyze the hydroamination of 3-methyl-1,2-butadiene with aryl amines to form solely the kinetic product at room …
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Mechanistic studies of diastereoselective cyclopropanations of homochiral ene-ketals and synthesis and resolution of diastereomeric alpha-hydroxycycloalkanone ketals.
… of the Simmons-Smith reagent at the least sterically hindered lone pair of electrons on the dioxolane oxygen proximal to the alkene. The role of dioxolane oxygen was inferred from studies with a hydrocarbon model system. The effect of cyclohexene ring conformation on the …
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Polymerizable Peptide Monomers for the Targeted and Intracellular Delivery of Cancer Therapeutics
… intracellular delivery cancer drugs. Initially, steric hindrance was investigated for enhancing the stability and delivery properties of disulfide-linked polymer-BIM conjugates. Two methyl groups were introduced onto the peptide’s disulfide-adjacent carbon by substituting BIM’s C-terminal …
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Turning stealth liposomes into cationic liposomes for anticancer drug delivery
… with cancer cells has been minimal due to the steric hindrance of the PEG coating. This dissertation reports two approaches to enhance the interaction of stealth liposomes with cancer cells. First, we designed a lipid-hydrazone-PEG conjugate that removes the PEG coating at acidic pH as in the …
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A Study of Reactive Intermediates Generated by One-Electron Transfers (Diazoalkane, Cieel, Chemiluminescence, Carbene, Peroxide)
… products. In the thermolysis of photolysis of 1, steric hindrance provided by the mesityl group prevents bimolecular reactions while the 1,2-migrations normally observed for diazoethanes remain facile, giving only stable monomeric olefins as decomposition products. In the diazoalkane radical …
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Synthesis and Evaluation of New Antimicrobial Agents and Novel Organic Fluorophores
… with zinc(II) salts. We believe this was due to steric hindrance generated by the relatively large pyrazaole ligands. Several smaller pyrazole ligands were synthesized, some of which successfully complexed with zinc suggesting that steric hindrance had indeed been a factor for the first set of …
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Ab Initio Density Functional Theory Optimized Geometries of Vinyl Trialkylammonium, Vinylpyridinium and Vinyldiazonium Tetrafluoroborate Salts with Natural Bond Orbital Charge Distributions in the Gas Phase
… of these compounds despite their large steric hindrance. It is concluded that the powerful inductive electron-withdrawing effects of the trialkylammonium and immonium groups substantially increase the net charge at the dienophilic carbons, making them more reactive in thermal …
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Synthesis and characterization of binuclear and unsymmetrical phthalocyanines
… <p>The unique unsymmetrical phthalocyanines with steric hindrance tetraphenyl or “opposite” octaphenyl substitution have been synthesized with the aid of computer modeling. The compounds are characterized by UV-visible near IR absorption and NMR spectroscopy. Mesophase is observed by optical …
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Michael addition of amines to α-ß unsaturated esters
… The reaction rate was highly affected by the steric hindrance of the amine. Aromatic amines did not have a significant rate of reaction with simple acrylates. Lewis acid catalysts significantly increased the rate. The highest rate increase due to Lewis acid catalysts was obtained with aromatic …
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Alkyl, alkenyl and cycloalkyl substituted triphenylmethane dyes
… have been correlated with the electronic and steric effects of the methyl, ethyl, propyl, butyl and vinyl substituents in the phenyl ring. The linear relationship between the wavelength of maximum absorption for the x-band of the meta- and para- substituted derivatives of Malachite Green and …
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