Direct Observation of Photoinduced Ultrafast Generation of Singlet and Triplet Quinone Methides in Aqueous Solutions and Insight into the Roles of Acidic and Basic Sites in Quinone Methide Formation

2017 ◽  
Vol 139 (50) ◽  
pp. 18349-18357 ◽  
Author(s):  
Jiani Ma ◽  
Xiting Zhang ◽  
Nikola Basarić ◽  
David Lee Phillips
Keyword(s):  
Aqueous Solutions ◽  
Direct Observation ◽  
Quinone Methide ◽  
Quinone Methides ◽  
Basic Sites ◽  
Insight Into

scholarly journals Insight on Solution Plasma in Aqueous Solution and Their Application in Modification of Chitin and Chitosan

2021 ◽  
Vol 22 (9) ◽  
pp. 4308
Author(s):  
Chayanaphat Chokradjaroen ◽  
Jiangqi Niu ◽  
Gasidit Panomsuwan ◽  
Nagahiro Saito
Keyword(s):  
Aqueous Solutions ◽  
Atmospheric Pressure ◽  
Scientific Progress ◽  
Biological Properties ◽  
Environmental Concerns ◽  
Plasma Process ◽  
Renewable Materials ◽  
Chemical Structures ◽  
Chitin And Chitosan ◽  
Insight Into

Sustainability and environmental concerns have persuaded researchers to explore renewable materials, such as nature-derived polysaccharides, and add value by changing chemical structures with the aim to possess specific properties, like biological properties. Meanwhile, finding methods and strategies that can lower hazardous chemicals, simplify production steps, reduce time consumption, and acquire high-purified products is an important task that requires attention. To break through these issues, electrical discharging in aqueous solutions at atmospheric pressure and room temperature, referred to as the “solution plasma process”, has been introduced as a novel process for modification of nature-derived polysaccharides like chitin and chitosan. This review reveals insight into the electrical discharge in aqueous solutions and scientific progress on their application in a modification of chitin and chitosan, including degradation and deacetylation. The influencing parameters in the plasma process are intensively explained in order to provide a guideline for the modification of not only chitin and chitosan but also other nature-derived polysaccharides, aiming to address economic aspects and environmental concerns.

A new dehydrogenative [4 + 1] annulation between para-quinone methides (p-QMs) and iodonium ylides for the synthesis of 2,3-dihydrobenzofurans

2018 ◽  
Vol 5 (23) ◽  
pp. 3483-3487 ◽  
Author(s):  
Yan-Jie Xiong ◽  
Shao-Qing Shi ◽  
Wen-Juan Hao ◽  
Shu-Jiang Tu ◽  
Bo Jiang
Keyword(s):  
Quinone Methide ◽  
Quinone Methides ◽  
Iodonium Ylides

A new dehydrogenative [4 + 1] annulation of para-quinone methides (p-QMs) with acyclic and cyclic iodonium ylides has been established, delivering a variety of functionalized 2,3-dihydrobenzofurans with the retention of the quinone methide unit in generally good yields.

THE ADSORPTION OF ALIPHATIC ACIDS ON ACTIVATED CHARCOALS

1947 ◽  
Vol 25b (5) ◽  
pp. 440-448 ◽  
Author(s):  
R. U. Lemieux ◽  
J. L. Morrison
Keyword(s):  
Aqueous Solutions ◽  
Activation Process ◽  
Aliphatic Acids ◽  
Surface Areas ◽  
Insight Into

The adsorptions of acetic, propionic, butyric, and valeric acids from aqueous solutions on a series of coconut charcoals of different degrees of activation were determined. For purposes of interpretation the numbers of millimoles adsorbed per gram of charcoal were compared for pairs of acids. Unimolecular adsorption of the acids is indicated. Surface areas of the charcoal series were estimated. They range from 130 to 625 sq. m. per gm. of charcoal, depending on the adsorbate used and the degree of activation of the charcoal. Some insight into the activation process is given.

Solvolysis and ring closure of quinone methides photogenerated from biaryl systems

2005 ◽  
Vol 83 (9) ◽  
pp. 1306-1323 ◽  
Author(s):  
Yijian Shi ◽  
Peter Wan
Keyword(s):  
Ring Closure ◽  
Quinone Methide ◽  
High Yield ◽  
Nanosecond Laser ◽  
Quinone Methides ◽  
Molecular Mechanics Calculations ◽  
Fluorescence Studies ◽  
Long Wavelength ◽  
Thermal Chemistry ◽  
Nanosecond Laser Photolysis

A variety of biaryl quinone methides have been photogenerated with a range of efficiencies from biaryl precursors 4–6 and 8, 10, and 11, all having hydroxyl and hydroxymethyl substituents on alternate rings. These novel biaryl quinone methides, which cannot be readily generated via thermal chemistry, are trapped by added nucleophiles such as MeOH and ethanolamine; two that cannot undergo electrocyclic ring closure (from 8 and 11) are readily observable by nanosecond laser photolysis, with long wavelength maxima (λmax) of 600 and 520 nm, respectively. Photogenerated o,o′-biaryl quinone methides undergo electrocyclic ring closure to give the corresponding chromene (pyran) products in high yield. Since the precursor biaryl alcohols have highly twisted structures in the ground state (dihedral angle of up to 90° by molecular mechanics calculations), a significant twisting motion to planarity is required to achieve reaction. Using steady-state fluorescence studies, we present evidence to suggest that the mechanism of quinone methide formation may occur via one of the following mechanisms: (i) dissociation of the proton from ArOH that precedes twisting; or (ii) ArOH dissociation and twisting taking place either simultaneously or in quick succession.Key words: biaryl quinone methide, photosolvolysis, photodeprotonation, photocyclization.

[4+n] Annulation Reactions Using ortho-Halomethyl Anilines as Aza-ortho-Quinone Methide Precursors

Synthesis ◽  
2021 ◽  
Author(s):  
Xiao-Yu He ◽  
Yu-Hong Ma ◽  
Qing-Qing Yang ◽  
Wen-Jing Xiao
Keyword(s):  
Convenient Method ◽  
Reactive Intermediates ◽  
Quinone Methide ◽  
Synthetic Chemistry ◽  
Important Class ◽  
Quinone Methides ◽  
Aniline Derivatives

Aza-ortho-quinone methides are an important class of reactive intermediates, which have found broad applications in synthetic chemistry. Recently, 1,4-elimination of ortho-halomethyl aniline derivatives has emerged as a new powerful and convenient method for aza-ortho-quinone methide generation. This review will highlight their recent applications as aza-ortho-quinone methide precursors in annulation reactions to access various biologically important nitrogen-containing heterocycles. The general mechanisms are briefly discussed as well.

Moving Past Quinone-Methides: Recent Advances toward Minimizing Electrophilic Byproducts from COS/H2S Donors

2021 ◽  
Vol 21 ◽  
Author(s):  
Michael Pluth
Keyword(s):  
Hydrogen Sulfide ◽  
Carbonic Anhydrase ◽  
Therapeutic Potential ◽  
Carbonyl Sulfide ◽  
Quinone Methide ◽  
Quinone Methides ◽  
On Demand ◽  
Physiological Processes ◽  
Recent Approach ◽  
Alternative Approaches

: Hydrogen sulfide (H2S) is an important biomolecule that plays key signaling and protective roles in different physiological processes. With the goals of advancing both the available research tools and the associated therapeutic potential of H2S, researchers have developed different methods to deliver H2S on-demand in different biological contexts. A recent approach to develop such donors has been to design compounds that release carbonyl sulfide (COS), which is quickly converted to H2S in biological systems by the ubiquitous enzyme carbonic anhydrase (CA). Although highly diversifiable, many approaches using this general platform release quinone methides or related electrophiles after donor activation. Many such electrophiles are likely scavenged by water, but recent efforts have also expanded alternative approaches that minimize the formation of electrophilic byproducts generated after COS release. This mini-review focuses specifically on recent examples of COS-based H2S donors that do not generate quinone methide byproducts after donor activation.

Thermodynamic insight into the thermoresponsive behavior of chitosan in aqueous solutions: A differential scanning calorimetry study

2020 ◽  
Vol 229 ◽  
pp. 115558 ◽  
Author(s):  
V.Y. Grinberg ◽  
T.V. Burova ◽  
N.V. Grinberg ◽  
V.E. Tikhonov ◽  
A.S. Dubovik ◽  
...  
Keyword(s):  
Differential Scanning Calorimetry ◽  
Aqueous Solutions ◽  
Scanning Calorimetry ◽  
Differential Scanning Calorimetry Study ◽  
Insight Into

1995 Merck Frosst Award Lecture Quinone methides: relevant intermediates in organic chemistry

1996 ◽  
Vol 74 (4) ◽  
pp. 465-475 ◽  
Author(s):  
Peter Wan ◽  
Beverly Barker ◽  
Li Diao ◽  
Maike Fischer ◽  
Yijian Shi ◽  
...  
Keyword(s):  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Aqueous Media ◽  
Laser Flash ◽  
Alder Reaction ◽  
Quinone Methide ◽  
Quinone Methides ◽  
Chemical Systems ◽  
The One ◽  
Chroman Ring

ortho and para-Quinone methides (2-methylene-3,5-cyclohexadien-1-one and 4-methylene-2,5-cyclohexadien-1-one, respectively) are intermediates in a variety of important chemical systems. In particular, o-quinone methides are useful in synthesis for the construction of chroman ring systems. A brief account of the relevance of quinone methide chemistry will be provided. This is followed by a review of recent studies from our laboratory on efficient methods for the photogeneration of quinone methides, concentrating on the use of hydroxy-substituted benzyl alcohols in aqueous media. It is shown that this method is general since it provides access to o-, m-, and p-quinone methide isomers. When appropriately substituted, all of these quinone methide isomers have been spectroscopically characterized by laser flash photolysis, making this technique the one of choice for studying the dynamics of these reactive intermediates. The mechanism of photochemical generation from hydroxybenzyl alcohols and extensions of the reaction to photogeneration of fluorenyl and biphenyl quinone methides will also be presented. Key words: quinone methide, biphenyl quinone methide, carbocation, photosolvolysis, photodehydroxylation, hetero-Diels–Alder reaction.

Scalable synthesis of an environmentally benign graphene–sand based organic–inorganic hybrid for sulfide removal from aqueous solution: an insight into the mechanism

2019 ◽  
Vol 43 (8) ◽  
pp. 3500-3512 ◽  
Author(s):  
Anjali Achazhiyath Edathil ◽  
Jerina Hisham Zain ◽  
Mohammad Abu Haija ◽  
Fawzi Banat
Keyword(s):  
Aqueous Solution ◽  
Green Chemistry ◽  
Aqueous Solutions ◽  
Environmentally Benign ◽  
Inorganic Hybrid ◽  
Sulfide Removal ◽  
Desert Sand ◽  
Scalable Synthesis ◽  
Insight Into

In this study, a graphene–sand hybrid (GSH) was successfully synthesized from locally available desert sand and sugar using a green chemistry approach and used as an adsorbent for the removal of dissolved sulfides from aqueous solutions.

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