Implicit Solvation Models: Equilibria, Structure, Spectra, and Dynamics.

The hydroxyl radical (•OH) is one of the most powerful oxidizing agents, able to react unselectively and instantaneously with the surrounding chemicals, including organic pollutants and inhibitors. The •OH radicals are omnipresent in the environment (natural waters, atmosphere, interstellar space, etc.), including biological systems where •OH has an important role in immunity metabolism. We provide an extensive view on the role of hydroxyl radical in different environmental compartments and in laboratory systems, with the aim of drawing more attention to this emerging issue. Further research on processes related to the hydroxyl radical chemistry in the environmental compartments is highly demanded. A comprehensive understanding of the sources and sinks of •OH radicals including their implications in the natural waters and in the atmosphere is of crucial importance, including the way irradiated chromophoric dissolved organic matter in surface waters yields •OH through the H2O2-independent pathway, and the ...

Environmental Implications of Hydroxyl Radicals ((•)OH).

Engineering applications of synthetic polymers are widespread due to their availability, processability, low density, and diversity of mechanical properties (Figure 1a). Despite their ubiquitous nature, modern polymers are evolving into multifunctional systems with highly sophisticated behavior. These emergent functions are commonly described as “smart” characteristics whereby “intelligence” is rooted in a specific response elicited from a particular stimulus. Materials that exhibit stimuli-responsive functions thus achieve a desired output (O, the response) upon being subjected to a specific input (I, the stimulus). Given that mechanical loading is inevitable, coupled with the wide range of mechanical properties for synthetic polymers, it is not surprising that mechanoresponsive polymers are an especially attractive class of smart materials. To design materials with stimuli-responsive functions, it is helpful to consider the I-O relationship as an energy transduction process. Achieving the desired I-O linkage thus becomes a problem in finding how to transform energy from the stimulus into energy that executes the desired response. The underlying mechanism that forms this I-O coupling need not be a direct, one-step transduction event; rather, the overall process may proceed through a sequence of energy transduction steps. In this regard, the network of energy transduction pathways is a useful roadmap for designing stimuli-responsive materials (Figure 1b). It is the purpose of this review to broadly survey the mechanical to chemical * To whom correspondence should be addressed. Phone: 217-244-4024. Fax: 217-244-8024. E-mail: jsmoore@illinois.edu. † Department of Chemistry and Beckman Institute. ‡ Department of Materials Science and Engineering and Beckman Institute. § Department of Aerospace Engineering and Beckman Institute. Chem. Rev. XXXX, xxx, 000–000 A

Mechanically-induced chemical changes in polymeric materials

Reactive species in advanced oxidation processes: Formation, identification and reaction mechanism

The conductor-like polarizable continuum model (CPCM) using several cavity models is applied to compute aqueous solvation free energies for a number of organic molecules (30 neutral molecules, 21 anions, and 19 cations). The calculated solvation free energies are compared to the available experimental data from the viewpoint of cavity models, computational methods, calculation time, and aqueous pKa values. The HF/6-31+G(d)//HF/6-31+G(d) and the HF/6-31+G(d)//B3LYP/6-31+G(d) with the UAKS cavities, in which radii are optimized with PBE0/6-31G(d), provide aqueous solvation effects in best agreement with available experimental data. The mean absolute deviations from experiment are 2.6 kcal/mol. The MP2/6-31++G(d,p)//HF/6-31+G(d) with the CPCM-UAKS(HF/6-31+G(d)) calculation is also performed for the base-catalyzed hydrolysis of methyl acetate in water.

Benchmarking the Conductor-like Polarizable Continuum Model (CPCM) for Aqueous Solvation Free Energies of Neutral and Ionic Organic Molecules.

Solvent effects on protonation equilibria of various aliphatic, alicyclic, and aromatic amines were estimated by means of a self-consistent isodensity-polarized electrostatic continuum model in combination with the B3LYP/6-31G* and B3LYP/aug-cc-pVDZ//B3LYP/6-31G* calculation schemes. Our results suggest that the found relationship between calculated relative and experimental basicities in water can be used for interpolation or extrapolation in order to calculate pKa values of organic bases with variable structural properties. The found standard deviation of calculated pKa values amounts to 0.7 pKa units. In this paper, we note successful use of this strategy as well as its limits.

pKa Values of Amines in Water from Quantum Mechanical Calculations Using a Polarized Dielectric Continuum Representation of the Solvent

In this work we present theoretical studies of the hydrolytic reaction of methyl formate, formamide and urea with one water molecule. The studied systems contain two additional water molecules which can act as bifunctional acid-base catalysts. These water molecules catalyze proton transfers between the primary reacting species. Our models describe the concerted transfer of two protons in every reaction step. The calculations have been carried out with the Becke3LYP/6-31G* method. Unspecific solvation effects have been included by means of a polarizable continuum model. Substrate reactivity differences as well as preferences for different reaction pathways can be discussed with the aid of these molecular systems. The studied alternative mechanisms include the common addition-elimination mechanism via a tetrahedral intermediate, and a concerted SN-like mechanism without a reaction intermediate. Our results suggest that the proved decreasing substrate reactivity in the order ester, amide, urea is caused by a rising resonance stabilization of the reaction centre, and not by a different positive partial charge of the carbonyl carbon. It is also concluded, that the probability of a concerted addition of a nucleophile and elimination of a leaving group without a tetrahedral intermediate rises in the order ester, amide, urea. The ordering of reactivity is not influenced by this behaviour.

Models of Water-Assisted Hydrolyses of Methyl Formate, Formamide, and Urea from Combined DFT-SCRF Calculations

The oxidative degradation of binuclear azaarenes is studied in a number of environmentally relevant radical reactions. The comparison between oxidation mechanisms of hydroxyl and sulfate radicals, as well as between dark and photoreactions, is done. Most of the products formed are identified. With the change from dark to photoreactions of quinoline and isoquinoline, a shift of the oxidation center from the benzene to the pyridine rings is observed. The reaction behavior of the benzodiazines can be derived from the reaction patterns of quinoline and isoquinoline. The rate constants of second order are determined for the reactions of the azaarenes with carbonate radicals. The rate constants and the differences in the products formed conformably prove the importance of the inclusion of excited states in the reaction mechanism. The application of the frontier orbital concept allows an easy interpretation. Electron transfer reactions resulting in radical oxygen species are shown to be product determining in di...

Investigations of Reactions of Selected Azaarenes with Radicals in Water. 1. Hydroxyl and Sulfate Radicals

Geometries and energies of small proton-bound symmetric dimers and minimum energy pathways for the proton transfer from one subunit to the other were calculated both at the semiempirical MNDO/PM3 and at ab initio HF and post HF levels. Except for systems, in which carbon atoms are involved or oxygen atoms are part of acceptor molecules, PM3 can be used for a good quantitative description of hydrogen bonds near the equilibrium geometry. If the subunits are separated by more than 2.5 A, attractive forces will be lost quickly. Proton transfer reactions are modeled in a qualitative acceptable manner. The global barrier of proton transfer rises as well as the calculated association enthalpy of the hydrogen bonded dimer rises. If proton transfer occurs between nitrogen acid/base pairs, PM3 barriers of activation are about 5 - 10 kcal/mol higher than corrected ab initio results.

The Ability of the Semiempirical PM3 Method to Model Proton Transfer Reactions in Symmetric Hydrogen Bonded Systems

The mechanism of the hydrolytic decomposition of phenylureas in basic media in the pH range 12 to 14 is investigated. In this pH range a levelling of the rate–pH curve is observed as well as a change of the substituent influence on the hydrolysis rate. These experimental findings suggest the formation of an unreactive side product of the phenylurea in a parasitic side equilibrium at sufficiently high pH. The urea dissociates at the aryl–NH group to give its conjugate base. For the hydrolytic decomposition of phenylureas an addition–elimination mechanism is proposed as has been established for the alkaline hydrolysis of carboxylic acid esters and amides.

Phenylureas. Part 1. Mechanism of the basic hydrolysis of phenylureas

Handle everyday research tasks with reliable, citation-backed results

Your personal Research Agent to handle research tasks with citation-backed results

Popular Tasks used by Researchers

How can I help with your research?

Meet SciSpace

Get more enhanced response by uploading the PDFs you want me to reference.

No relevant PDFs in your library

SciSpace is the AI research assistant for academics. Run systematic literature reviews on 280M+ papers, and write papers with cited sources. Trusted by 1M+ students, PhDs & researchers.

SciSpace | AI for Research

Analyze PDFs

Code & Manuscripts

Funding & Grants

Literature & Patents

Medical & Clinical Data

Systematic Review

Visualize & Present

Web & Data

Build a Google Scholar-like website for your research.

Build a website

Create charts and images for your research

Create a Chart

Write a paper for submission to a journal

Draft a manuscript

Patent Search

Design eye-catching scientific posters in minutes.

Scientific Poster Generation

Systematic Literature Review

One task is running at the moment. Your messages will be shown right after.

Drag and drop or click here to browse

Loved by <highlight>1 million+</highlight> researchers

Extract a list of specific topics and their sources from unstructured text

Topics

Compare and analyze relevant papers that matches with your search

Papers

Get insights from PDFs and bookmarked papers from your library

My library

Recent searches

Try searching for:

Catch AI-generated content in scholarly and non-scholarly content

{ai} Detector

Ai Writer

Get PDF Summaries, highlighted text explanations 

Chat with PDF

Effortlessly create in-text citations and bibliographies in APA and 2,500 other formats

Citation generator

Get explanations, summaries, and answers on academic papers

Ease up your research workflow with {scispace}'s cohort of exciting AI tools

Elevate your academic writing skills and convey your ideas the way you want

Paraphraser

Explore our range of reading and writing tools

Your file is being prepared and should be ready in a few minutes. If it's a large file, it might take a bit longer. You can close this window, and we'll email you the file when it's done.

You have reached a maximum limit of <strong>{limit}</strong> columns in the table. Remove at least <strong>1</strong> column to add or create another one.

Rolf Mitzner

Author Tools

Chat about Author