O–H Bond dissociation enthalpies in hydroxyphenols. A time-resolved photoacoustic calorimetry and quantum chemistry study

Correia, Catarina F.; Guedes, Rita C.; Santos, Rui M. Borges dos; Cabral, Benedito J. Costa; Simões, José A. Martinho

doi:10.1039/b314093h

Cited by 27 publications

(38 citation statements)

References 55 publications

(34 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In summary, the results show that the abstraction results are virtually solvent independent at pH values that provide fully protonated parent molecules. This agrees with the former conclusion that the BDEs in phenols are not strongly solvent dependent 22. 25…”

Section: Resultssupporting

confidence: 93%

“…These ratios seem to slightly disagree with the 70:30 values obtained from pulse radiolysis experiments 9c. However, a higher extent of abstraction from the B ring as shown by CIDNP, relative to pulse photolysis studies, is in a better agreement with bond dissociation energies 22…”

Section: Resultsmentioning

confidence: 54%

“…Clearly, this is in agreement with the experimental CIDNP results since the percentage of hydrogen abstraction from the B ring is always slightly bigger for all model compounds; also being in line with the lower calculated value of 347 kJ for C(4′)OH (Table 1). Experimental values in acetonitrile are available for catechol of 342 and pyrogallol of 329 kJ mol −1 22. To provide a double check, steady‐state CIDNP experiments were performed with ITX/catechol, ITX/resorcinol, and ITX with a 1:1 molar mixture of catechol and resorcinol.…”

Section: Resultsmentioning

confidence: 99%

See 2 more Smart Citations

Probing the Antioxidant Activity of Polyphenols by CIDNP: From Model Compounds to Green Tea and Red Wine

Neshchadin

Levinn

Gescheidt

et al. 2010

Chemistry A European J

View full text Add to dashboard Cite

Polyphenols occur naturally in a vast variety of plants. One of their predominant properties is their antioxidant activity. To provide a deeper understanding of the antioxidant mechanism, (1)H CIDNP spectroscopy (CIDNP=chemically induced dynamic nuclear polarization) is used to study model hydrogen abstraction reactions with four catechin-based polyphenols: catechin (CA), gallocatechin (GC), epigallocatechin (EGC), and epigallocatechin gallate (EGCG). The experiments involve photoinduced hydrogen-atom transfer to a hydrogen abstractor (e.g., excited isopropylthioxanthone) followed under steady-state conditions and in a time-resolved fashion (resolution 500 ns-1 ms). It is found that hydrogen abstraction is an essentially stochastic process with a slight preference for the B rings in the catechin-based polyphenols. Remarkably, analogous reactivity patterns could be followed in the "real systems", green tea and red wine. We also show that CIDNP can be used as a semiquantitative tool to assess chemical reactivity.

show abstract

Section: Resultssupporting

confidence: 93%

Section: Resultsmentioning

confidence: 54%

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

Probing the Antioxidant Activity of Polyphenols by CIDNP: From Model Compounds to Green Tea and Red Wine

Neshchadin

Levinn

Gescheidt

et al. 2010

Chemistry A European J

View full text Add to dashboard Cite

show abstract

“…For the past 10 years, we have been using PAC to determine BDEs in solution for a number of model compounds [12][13][14][15][16][17][18][19][20][21][22]. On the other hand, high-level quantum chemical (QC) studies have provided the BDEs of the isolated molecules and have also allowed us to test increasingly complex solvent models, aiming to bridge solution-and gas-phase data by quantifying the solvent effect [16,17,[23][24][25][26][27][28]. In this overview, we describe the recent advances in solvation models when trying to make those ends meet, and strive to provide the answers to the questions raised above.…”

Section: Introductionmentioning

confidence: 99%

Bond-dissociation enthalpies in the gas phase and in organic solvents: Making ends meet

Santos

Cabral

Simões

2007

Pure and Applied Chemistry

Self Cite

View full text Add to dashboard Cite

Solvent effects are responsible for the difference between gas- and solution-phase bond-dissociation enthalpies (BDEs), and are thus crucial for understanding reactivity in solution. While solvation effects can be negligible (e.g., in reactions involving carbon-centered radicals), they may be rather significant (e.g., when oxygen-centered radicals are formed). This paper reviews a number of models which have been proposed to deal with the difference between the solvation energetics of a radical and its parent molecule. It is concluded that the radical-solvent interaction may be larger than previously anticipated.

show abstract

“…In spite of being a recent technique, time‐resolved photoacoustic calorimetry (TR‐PAC) has been widely used to probe the thermochemistry of reactions involving short‐lived species and to extract photochemical information (quantum yields and decay lifetimes) 1–25. TR‐PAC has also been applied to determine rate constants of photoinitiated processes 6,17.…”

Section: Introductionmentioning

confidence: 99%

Web search strategies and human individual differences: A combined analysis

Ford

Miller

Moss

2005

J. Am. Soc. Inf. Sci.

View full text Add to dashboard Cite

This is the second of two articles published in this issue of JASIST reporting the results of a study investigating relationships between Web search strategies and a range of human individual differences. In this article we provide a combined analysis of the factor analyses previously presented separately in relation to each of three groups of human individual difference (study approaches, cognitive and demographic features, and perceptions of and approaches to Internet-based information seeking). It also introduces two series of regression analyses conducted on data spanning all three individual difference groups. The results are discussed in terms of the extent to which they satisfy the original aim of this exploratory research, namely to identify any relationships between search strategy and individual difference variables for which there is a prima facie case for more focused systematic study. It is argued that a number of such relationships do exist. The results of the project are summarized and suggestions are made for further research.

show abstract

O–H Bond dissociation enthalpies in hydroxyphenols. A time-resolved photoacoustic calorimetry and quantum chemistry study

Cited by 27 publications

References 55 publications

Probing the Antioxidant Activity of Polyphenols by CIDNP: From Model Compounds to Green Tea and Red Wine

Probing the Antioxidant Activity of Polyphenols by CIDNP: From Model Compounds to Green Tea and Red Wine

Bond-dissociation enthalpies in the gas phase and in organic solvents: Making ends meet

Web search strategies and human individual differences: A combined analysis

Contact Info

Product

Resources

About