<i>m</i>-Quinone Methides from <i>m</i>-Hydroxy-1,1-Diaryl Alkenes via Excited-State (Formal) Intramolecular Proton Transfer Mediated by a Water Trimer

Fischer, Maike; Wan, Peter

doi:10.1021/ja974144y

Cited by 32 publications

(35 citation statements)

References 15 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Reports for the excited state intramolecular proton transfer processes mediated by the water molecule without any participation from electrons are available. 49 – 52 However, no direct evidence for the involvement of a water molecule in transferring the proton from the donor to the acceptor during the electron transfer process was established until now.…”

Section: Resultsmentioning

confidence: 99%

“…Being both a hydrogen bond donor and acceptor facilitates the water molecule to build a bridge between the proton donor (acid) and acceptor (base). Transfer of the proton across this water mediated bridge is observed in many excited state intra- and intermolecular proton transfer processes, photochemical reactions 49 – 52 and even in the case of photoacids. 1 For example, in photoacids the solvent mediated proton transfer bridge facilitates the exchange of proton between the acid and base by adopting a Von Grotthus type proton hopping mechanism.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Deciphering the incognito role of water in a light driven proton coupled electron transfer process

et al. 2018

View full text Add to dashboard Cite

show abstract

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Deciphering the incognito role of water in a light driven proton coupled electron transfer process

et al. 2018

View full text Add to dashboard Cite

show abstract

“…The rapid decrease in the activation energy barrier is likely due to the formation of an efficient proton bridge as evidenced by the buildup of the conventional hydrogen bonds in the calculated TS nw in which the water molecules form a water trimer and water tetramer as shown in Figure 4. [13] On the other hand, as more water molecules are involved in the reaction system, the hydrogen bonds between the water molecules and 3 [KP] will further stabilize TS nW , which will also provide a significant contribution to the decrease in the activation energy barrier. Therefore, the proton transfer appears to take place by means of a proton bridge formed by the network of the clustered water molecules.…”

Section: Resultsmentioning

confidence: 99%

“…[11] In these cases, water or hydroxylic solvent molecules are required to mediate the proton transfer for it to occur to a noticeable extent. [12,13] ESIPT has been suggested as the initial step in a number of decarboxylation processes. [14,15] It has been proposed by Monti and co-workers that the main pathway for the formation of the decarboxylated photoproducts involveds intramolecular electron transfer and subsequent production of triplet biradicals.…”

Section: Introductionmentioning

confidence: 99%

Water‐ and Acid‐Mediated Excited‐State Intramolecular Proton Transfer and Decarboxylation Reactions of Ketoprofen in Water‐Rich and Acidic Aqueous Solutions

Yeung

Guan

et al. 2011

Chemistry A European J

View full text Add to dashboard Cite

We present an investigation of the decarboxylation reaction of ketoprofen (KP) induced by triplet excited-state intramolecular proton transfer in water-rich and acidic solutions. Nanosecond time-resolved resonance Raman spectroscopy results show that the decarboxylation reaction is facile in aqueous solutions with high water ratios (water/acetonitrile ≥50%) or acidic solutions with moderate and strong acid concentration. These experimental results are consistent with results from density functional theory calculations in which 1) the activation energy barriers for the triplet-state intramolecular proton transfer and associated decarboxylation process become lower when more water molecules (from one up to four molecules) are involved in the reaction system and 2) perchloric acid, sulfuric acid, and hydrochloric acid can shuttle a proton from the carboxyl to carbonyl group through an initial intramolecular proton transfer of the triplet excited state, which facilitates the cleavage of the C-C bond, thus leading to the decarboxylation reaction of triplet state KP. During the decarboxylation process, the water molecules and acid molecules may act as bridges to mediate intramolecular proton transfer for the triplet state KP when KP is irradiated by ultraviolet light in water-rich or acidic aqueous solutions and subsequently it generates a triplet-protonated carbanion biradical species. The faster generation of triplet-protonated carbanion biradical in acidic solutions than in water-rich solutions with a high water ratio is also supported by the lower activation energy barrier calculated for the acid-mediated reactions versus those of water-molecule-assisted reactions.

show abstract

“…In these cases, water or hydroxylic solvent molecules are required to mediate the proton transfer for it to occur to a noticeable extent 12. 13…”

Section: Introductionmentioning

confidence: 99%

Morphology and thermal and mechanical properties of PBT/HIPS and PBT/HIPS‐g‐GMA blends

Yang

Lai

Liu

et al. 2002

J of Applied Polymer Sci

View full text Add to dashboard Cite

ABSTRACT:The modification of high-impact polystyrene (HIPS) was accomplished by melt-grafting glycidyl methacrylate (GMA) on its molecular chains. Fourier transform infrared spectroscopy and electron spectroscopy for chemical analysis were used to characterize the formation of HIPS-g-GMA copolymers. The content of GMA in HIPSg-GMA copolymer was determined by using the titration method. The effect of the concentrations of GMA and dicumyl peroxide on the degree of grafting was studied. A total of 1.9% of GMA can be grafted on HIPS. HIPS-g-GMA was used to prepare binary blends with poly(buthylene terephthalate) (PBT), and the evidence of reactions between the grafting copolymer and PBT in the blends was confirmed by scanning electron microscopy (SEM), dynamic mechanical analysis, and its mechanical properties. The SEM result showed that the domain size in PBT/HIPS-g-GMA blends was reduced significantly compared with that in PBT/HIPS blends; moreover, the improved strength was measured in PBT/HIPS-g-GMA blends and results from good interfacial adhesion. The reaction between ester groups of PBT and epoxy groups of HIPS-g-GMA can depress crystallinity and the crystal perfection of PBT.

show abstract

m-Quinone Methides from m-Hydroxy-1,1-Diaryl Alkenes via Excited-State (Formal) Intramolecular Proton Transfer Mediated by a Water Trimer

Cited by 32 publications

References 15 publications

Deciphering the incognito role of water in a light driven proton coupled electron transfer process

Deciphering the incognito role of water in a light driven proton coupled electron transfer process

Water‐ and Acid‐Mediated Excited‐State Intramolecular Proton Transfer and Decarboxylation Reactions of Ketoprofen in Water‐Rich and Acidic Aqueous Solutions

Morphology and thermal and mechanical properties of PBT/HIPS and PBT/HIPS‐g‐GMA blends

Contact Info

Product

Resources

About