Resolving Quinoid Structure in Poly(para-phenylene) Chains

2020 ◽  
Vol 142 (22) ◽  
pp. 10034-10041 ◽  
Author(s):  
Bingkai Yuan ◽  
Can Li ◽  
Yan Zhao ◽  
Oliver Gröning ◽  
Xieyu Zhou ◽  
...  
Keyword(s):  
Quinoid Structure

On the Reaction of 2,5-Dihydroxy-[1,4]-benzoquinone with Diamines – Strain-induced Reactivity Effects

2020 ◽  
Vol 24 ◽  
Author(s):  
Hubert Hettegger ◽  
Andreas Hofinger ◽  
Thomas Rosenau
Keyword(s):  
Nucleophilic Substitution ◽  
Product Structure ◽  
Carbonyl Groups ◽  
Reaction Products ◽  
Double Bonds ◽  
Oh Groups ◽  
Natural Geometry ◽  
Quinoid Structure ◽  
Bond Localization

: The regioselectivity of the reaction of 2,5-dihydroxy-[1,4]-benzoquinone (DHBQ) with diamines could not be explained satisfactorily so far. In general, the reaction products can be derived from the tautomeric ortho-quinoid structure of a hypothetical 4,5-dihydroxy-[1,2]-benzoquinone. However, both aromatic and aliphatic 1,2-diamines form in some cases phenazines, formally by diimine formation on the quinoid carbonyl groups, and in other cases the corresponding 1,2- diamino-[1,2]-benzoquinones, by nucleophilic substitution of the OH groups, the regioselectivity apparently not following any discernible pattern. The reactivity was now explained by an adapted theory of strain-induced bond localization (SIBL). Here, the preservation of the "natural" geometry of the two quinoid C–C double bonds (C3=C4 and C5=C6) as well as the N–N distance of the co-reacting diamine are crucial. A decrease of the annulation angle sum (N–C4–C5 + C4–C5–N) is tolerated well and the 4,5-diamino-ortho-quinones, having relatively short N–N spacings are formed. An increase in the angular sum is energetically unfavorable, so that diamines with a larger N–N distance afford the corresponding ortho-quinone imines. Thus, for the reaction of DHBQ with diamines, exact predictions of the regioselectivity, and the resulting product structure, can be made on the basis of simple computations of bond spacings and product geometries.

scholarly journals Detecting and Quantifying Polyhaloaromatic Environmental Pollutants by Chemiluminescence-Based Analytical Method

Molecules ◽  
2021 ◽  
Vol 26 (11) ◽  
pp. 3365
Author(s):  
Ben-Zhan Zhu ◽  
Miao Tang ◽  
Chun-Hua Huang ◽  
Li Mao
Keyword(s):  
Analytical Method ◽  
Degradation Kinetics ◽  
Environmental Pollutants ◽  
Environmental Implications ◽  
Future Studies ◽  
System A ◽  
Quinoid Structure ◽  
Fenton System ◽  
Generating System ◽  
H2o2 System

Polyhaloaromatic compounds (XAr) are ubiquitous and recalcitrant in the environment. They are potentially carcinogenic to organisms and may induce serious risks to the ecosystem, raising increasing public concern. Therefore, it is important to detect and quantify these ubiquitous XAr in the environment, and to monitor their degradation kinetics during the treatment of these recalcitrant pollutants. We have previously found that unprecedented intrinsic chemiluminescence (CL) can be produced by a haloquinones/H2O2 system, a newly-found ●OH-generating system different from the classic Fenton system. Recently, we found that the degradation of priority pollutant pentachlorophenol by the classic Fe(II)-Fenton system could produce intrinsic CL, which was mainly dependent on the generation of chloroquinone intermediates. Analogous effects were observed for all nineteen chlorophenols, other halophenols and several classes of XAr, and a novel, rapid and sensitive CL-based analytical method was developed to detect these XAr and monitor their degradation kinetics. Interestingly, for those XAr with halohydroxyl quinoid structure, a Co(II)-mediated Fenton-like system could induce a stronger CL emission and higher degradation, probably due to site-specific generation of highly-effective ●OH. These findings may have broad chemical and environmental implications for future studies, which would be helpful for developing new analytical methods and technologies to investigate those ubiquitous XAr.

ChemInform Abstract: STUDY OF THE REDOX PROPERTIES OF COMPOUNDS OF QUINOID STRUCTURE. I. HALIDE DERIVATIVES OF BENZOQUINONE

1977 ◽  
Vol 8 (16) ◽  
pp. no-no
Author(s):  
O. S. KSENZHEK ◽  
S. A. PETROVA ◽  
S. V. OLEINIK ◽  
M. V. KOLODYAZHNYI ◽  
V. Z. MOSKOVSKII
Keyword(s):  
Redox Properties ◽  
Quinoid Structure ◽  
Derivatives Of

scholarly journals The short wave near-infrared fluorescence properties of two p-azaquinodimethane (p-AQM)-based conjugated polymers

2020 ◽  
Vol 13 (05) ◽  
pp. 2041003 ◽  
Author(s):  
Yaowei Zhu ◽  
Yawei Miao ◽  
Tingting Xue ◽  
Youchang Liu ◽  
Chunying Zheng ◽  
...  
Keyword(s):  
Conjugated Polymers ◽  
Near Infrared ◽  
Signal To Noise Ratio ◽  
Biological Tissues ◽  
Infrared Region ◽  
Short Wave ◽  
Quinone Structure ◽  
Living Tissues ◽  
Quinoid Structure

The absorption, scattering, and autofluorescence of biological tissues in short-wave infrared region (SWIR, 900–1700[Formula: see text]nm) are relatively low, so SWIR fluorescence usually has deeper penetration into living tissues, and can show a higher signal-to-noise ratio when used for imaging in vivo. However, there are few types of organic SWIR fluorescent materials currently. In this work, [Formula: see text]-azaquinodimethane ([Formula: see text]-AQM) with a quinoid structure is used as the acceptor unit, and carbazole or fluorene with sp3 hybridization are used as the donor units, two conjugated polymers were synthesized. The quinone structure is conducive to the redshift of absorption and fluorescence spectra, and the sp3 hybridization structure is conducive to weakening the aggregation quenching of polymer fluorescence. PF and PCz exhibited absorption peaks of 492[Formula: see text]nm and 508[Formula: see text]nm, respectively. The emission peaks of the two polymers are 920[Formula: see text]nm and 950[Formula: see text]nm, respectively, both in the short-wave near infrared region. The quantum yield (QY) of PF and PCz is 0.4% and 0.3%, respectively.

Sub-5-fs spectroscopy of a thiophene derivative with a quinoid structure

2006 ◽  
Vol 426 (1-3) ◽  
pp. 105-110 ◽  
Author(s):  
Takayoshi Kobayashi ◽  
Haibo Wang ◽  
Zhuan Wang ◽  
Tetsuo Otsubo
Keyword(s):  
Thiophene Derivative ◽  
Quinoid Structure

Menadione reductase from Clostridium tyrobutyricum

1980 ◽  
Vol 26 (3) ◽  
pp. 324-329 ◽  
Author(s):  
H. Petitdemange ◽  
R. Marczak ◽  
G. Raval ◽  
R. Gay
Keyword(s):  
Molecular Weight ◽  
Coenzyme Q ◽  
Analysis Data ◽  
Carbon Chain ◽  
Clostridium Tyrobutyricum ◽  
Enzymatic Analysis ◽  
Prosthetic Group ◽  
Ping Pong ◽  
Enzymatic Reduction ◽  
Quinoid Structure

Menadione reductase (EC 1.6.99.2) has been purified 67-fold from Clostridium tyrobutyricum extracts. The molecular weight was found to be 60 000 and the prosthetic group was identified as FMN on the basis of the enzymatic analysis data. The binding of FMN to the menadione dehydrogenase apoenzyme was relatively weak with an apparent Km value of 2.5 × 10−6 M.The enzyme exhibited group substrate specificity for compounds with a quinoid structure; naphthoquinones and benzoquinones without long carbon chain substituents were the most active. The reactivity of the enzyme with vitamin K1, coenzyme Q6, and cytochrome c was negligible and, with 2,6-dichlorophenol indophenol, relatively low.It was shown that the enzymatic reduction of menadione with the participation of either NADH or NADPH takes place by a "Ping-Pong" mechanism. The enzyme catalyzed the oxidation of NADH and NADPH at equal rates and was inhibited by dicumarol and p-chloromercuribenzoate.

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