The effects of ring substitution on the pK(a) value of benzenesulfonic acid (BSA) were investigated using a combined quantum mechanical and classical approach. Ring substitution with strong electron-withdrawing elements such as F, Cl, and Br is found to enhance the acidity of the BSA. More importantly, ring substitution with -NO(2) groups which form an extended conjugated pi-system with the benzene ring exhibits the strongest enhancement of the acidity. The effects of polymerization on the styrenesulfonic acid (SSA) were also investigated by solving the classical Poisson-Boltzmann equation. It is found that polymerization significantly decreases the acidity of SSA due to the alteration of the electrostatic environment surrounding the acid group upon polymerization. The average pK(a) value converges to 2.9 from the corresponding monomer value of -0.53 at a degree of polymerization of 8-12. These results shed significant light on how to design sulfonic-acid-based solid acid catalysts to achieve desired catalytic properties.
Download full-text PDF |
Source |
|---|---|
| http://dx.doi.org/10.1021/jp906087c | DOI Listing |
Publication Analysis
Top Keywords
Similar Publications
Assembly of Pyrenes through a Quadruple Photochemical Cascade: Blocking Groups Allow Diversion from the Double Mallory Path to Photocyclization at the Bay Region.
J Am Chem Soc
December 2024
Department of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida 32306, United States.
We present a six-step cascade that converts 1,3-distyrylbenzenes (-stilbenes) into nonsymmetric pyrenes in 40-60% yields. This sequence merges photochemical steps, ,-alkene isomerization, a 6π photochemical electrocyclization (Mallory photocyclization); the new bay region cyclization, with two radical iodine-mediated aromatization steps; and an optional aryl migration. This work illustrates how the inherent challenges of engineering excited state reactivity can be addressed by logical design.
View Article and Find Full Text PDFModulation of the Magnetic Anisotropy via the Ligand Field in Sandwiched Erbium Complexes.
Inorg Chem
December 2024
Institute of Nano Science and Technology, Sector-81, Mohali, Punjab 140306, India.
Among lanthanide-based single-molecule magnets (SMMs), erbium(III) is a Kramers ion, apart from dysprosium(III), which provides magnetic bistability in the presence of a suitable coordination environment. However, Er-based SMMs exhibit significantly less magnetic anisotropy than Dy because their prolate electronic density necessitates equatorially correlated ligands to minimize the charge contact with the Er atom. Here, in this work, we have computationally investigated the heteroleptic organometallic complexes with an Er(III) atom sandwiched between two distinct cyclic rings (five- and eight-membered) with the aim of tuning the magnetic anisotropy via exploiting the ligand field.
View Article and Find Full Text PDFSelective Synthesis of Tetrahydroisoquinoline and Piperidine Scaffolds by Oxidative Ring Opening/Ring Closing Protocols of Substituted Indenes and Cyclopentenes.
ChemistryOpen
December 2024
MTA TTK Lendület Artificial Transporter Research Group, Institute of Materials and Environmental Chemistry, HUN-REN Research Center for Natural Sciences, H-1117, Budapest, Magyar tudósok krt. 2, Hungary.
Novel tetrahydroisoquinoline and piperidine derivatives were selectively synthesized from substituted indenes or cyclopentenes. The process starts with an oxidative cleavage of the ring olefin bond, which gives reactive diformyl intermediates. By a ring-closing step using chiral (R) or (S) α-methylbenzylamine under a reductive amination protocol facilitated ring formation with ring expansion of the corresponding nitrogen-containing heterocycles.
View Article and Find Full Text PDFA cross-shaped organic framework: a multi-functional template arranging chromophores.
Org Chem Front
December 2024
Department of Chemistry, University of Basel St Johanns-Ring 19 Basel 4056 Switzerland https://www.chemie1.unibas.ch/Bmayor/.
This work explores the use of a cross-shaped organic framework that is used as a template for the investigation of multi-functionalized chromophores. We report the design and synthesis of a universal cross-shaped building block bearing two bromines and two iodines on its peripheral positions. The template can be synthesized on a gram scale in a five-step reaction comprising an oxidative homo-coupling macro-cyclization.
View Article and Find Full Text PDFGeneral access to furan-substituted -difluoroalkenes enabled by PFTB-promoted cross-coupling of ene-yne-ketones and difluorocarbene.
Chem Sci
December 2024
Department of Spine Surgery and Musculoskeletal Tumor, Zhongnan Hospital of Wuhan University, School of Pharmaceutical Sciences, Wuhan University Wuhan 430071 China
Replacement of a carbonyl group with fluorinated bioisostere (, CF[double bond, length as m-dash]C) has been adopted as a key tactical strategy in drug design and development, which typically improves potency and modulates lipophilicity while maintaining biological activity. Consequently, new -difluoroalkenation reactions have undoubtedly accelerated this shift, and conceptually innovative practices would be of great benefit to medicinal chemists. Here we describe an expeditous protocol for the direct assembly of furan-substituted -difluoroalkenes PFTB-promoted cross-coupling of ene-yne-ketones and difluorocarbene.
View Article and Find Full Text PDFWant AI Summaries of new PubMed Abstracts delivered to your In-box?
Enter search terms and have AI summaries delivered each week - change queries or unsubscribe any time!