Resorcin4arenes are not as extensively studied as their sister compounds, calix4arenes, owing to challenges in synthetic methodologies for their derivatization from the perceptive of molecular ...economy. In this tutorial review, we briefly illustrate the summary of their access methodologies together with their limitations, focusing at the derivatization of the ortho‐positions in the upper rim. We hope to spark a refreshed surge in the development of these derivatization strategies, allowing access to novel molecules and futuristic applications, putting resorcin4arenes at the center stage of research for which they were meant.
PhotolysisPhotolysis is a key method for approaching to a more functional system in chemical biology. However, the photoreaction of aryl azides usually leads to various products. In article number ...2307318, Frank Biedermann, Stefan Bräse, and co‐workers presented a novel method to steer the photoreaction of the aryl azide pathway forming a phosphorescent carboline by reacting in the supramolecular host cucurbit7uril.
Oxygenated organic molecules (OOMs) produced by the oxidation of aromatic compounds are key components of secondary organic aerosol (SOA) in urban environments. The steric effects of substitutions ...and rings and the role of key reaction pathways in altering the OOM distributions remain unclear because of the lack of systematic multi-precursor study over a wide range of OH exposure. In this study, we conducted flow-tube experiments and used the nitrate adduct time-of-flight chemical ionization mass spectrometer (NO3--TOF-CIMS) to measure the OOMs produced by the photooxidation of six key aromatic precursors under low-NO.sub.x conditions. For single aromatic precursors, the detected OOM peak clusters show an oxygen atom difference of one or two, indicating the involvement of multi-step auto-oxidation and alkoxy radical pathways. Multi-generation OH oxidation is needed to explain the diverse hydrogen numbers in the observed formulae. In particular, for double-ring precursors at higher OH exposure, multi-generation OH oxidation may have significantly enriched the dimer formulae. The results suggest that methyl substitutions in precursor lead to less fragmented OOM products, while the double-ring structure corresponds to less efficient formation of closed-shell monomeric and dimeric products, both highlighting significant steric effects of precursor molecular structure on the OOM formation. Naphthalene-derived OOMs however have lower volatilities and greater SOA contributions than the other-type of OOMs, which may be more important in initial particle growth. Overall, the OOMs identified by the NO3--TOF-CIMS may have contributed up to 30.0 % of the measured SOA mass, suggesting significant mass contributions of less oxygenated, undetected semi-volatile products. Our results highlight the key roles of progressive OH oxidation, methyl substitution and ring structure in the OOM formation from aromatic precursors, which need to be considered in future model developments to improve the model performance for organic aerosol.
The chemical group of polycyclic aromatic compounds (PAC), including the better-known subgroup of polycyclic aromatic hydrocarbons (PAH) and the heterocyclic aromatic compounds (NSO-PAC, ...heterocycles), comprise several thousand individual compounds. It is hard to find a comprehensive overview in the literature of these PACs that includes a substantial amount of relevant properties. Here an attempt is made to summarize the most studied but also some less well-known PACs. In addition to basic data such as recommended names, abbreviations, CAS numbers, molecular formulas, chemical structures, and exact mono-isotopic molecular weights, physico-chemical properties taken from the literature like boiling points, vapor pressures, water solubilities, Henry's Law constants, n-octanol-water partition coefficients (log K
OW
), and pK
a
are summarized. Selected toxicological data are listed indicating carcinogenic and mutagenic activity or effects on different organisms.
PAC nomenclature is a complex topic, so suggestions for practical use are made. Regarding available data, estimated (instead of measured) values should be used with caution because considerable deviations from experimentally determined values can occur. For an enhanced understanding of the behavior of single PACs in comparison with each other, some of the properties mentioned above are plotted vs. the number of rings or the degree of alkylation. Also, some physico-chemical data are correlated with different functional groups as substituents of the PAHs.
This article reveals that rather little is known about the less common PACs, e.g., higher molecular weight compounds, alkylated or otherwise substituted aromatics, for instance, keto-, oxo-, amino-, nitro-, cyano-PAHs, or some heterocyclic aromatic compounds, including their derivatives. It mirrors the limited state of knowledge about the variety of PACs that do not belong to the 16 EPA PAHs.
Knowledge of adsorption behavior of organic contaminants on high heat temperature treated biochars is essential for application of biochars as adsorbents in wastewater treatment and soil remediation. ...In this study, isotherms of 25 aromatic compounds adsorption on biochars pyrolyzed at 700 °C from biomass including wood chips, rice straw, bamboo chips, cellulose, lignin and chitin were investigated to establish correlations between adsorption behavior and physicochemical properties of biochars. Isotherms were well fitted by Polanyi theory-based Dubinin-Ashtakhov (DA) model with three parameters, i.e., adsorption capacity (Q0) and adsorption affinity (E and b). Besides the negative correlation of Q0 with molecular maximum cross-sectional areas (σ) of organic compounds, positive correlations of Q0 with total pore volume (Vtotal) and average diameter of micropore (D) of biochars were observed, indicating that adsorption by biochars is captured by the pore-filling mechanism with molecular sieving effect in biochar pores. Linear solvation energy relationships (LSERs) of adsorption affinity (E) with solvatochromic parameters of organic compounds (i. e., αm and π∗) were established, suggesting that hydrophobic effect, π-π interaction and hydrogen-bonding interaction are the main forces responsible for adsorption. The regression coefficient (π1) and intercept (C) of obtained LSERs are correlated with biochar H/C and Rmicro, respectively, implying that biochars with higher aromaticity and more micropores have stronger π-π bonding potential and hydrophobic effect potential with aromatic molecule, respectively. However, hydrogen-bonding potential of biochars for organic molecules is not changed significantly with properties of biochars. A negative correlation of b with biochar H/C is also obtained. These correlations could be used to predict the adsorption behavior of organic compounds on high heat temperature treated biochars from various biomass for the application of biochars as sorbents and for the estimating of environmental risks of organic compounds in the present of biochars.
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•Correlations of adsorption with chemical and biochar properties were developed.•Adsorption is captured by the pore-filling mechanism with molecular sieving effect.•Biochars with higher aromaticity have stronger π-π bonding potential.•Hydrophobic effect is much significant in biochar micropores.•Hydrogen-bonding potential of different biochars are almost the same.
Correlations of adsorption with physiochemical properties of aromatic compounds and biochars were developed for adsorption predicting and understanding the adsorption mechanisms.
Invited for the cover of this issue are Aiko Fukazawa and co‐workers at Kyoto University and Nagoya University. The image depicts the π‐electrons as people to highlight the effect of fused aromatic ...rings in the antiaromatic π‐electron systems. Read the full text of the article at 10.1002/chem.202004244.
Chirality transfer is widely observed in life processes, and many artificial chiral transfer systems have been developed. In these systems, chiral information is transferred from chiral inducers to ...chiral acceptors by a direct chiral induction process and a direct chiral memorization process. We have developed ternary nondirect chiral transfer systems based on pillar5arenes, in which a third factor was introduced as a regulator. The planar chirality of an acceptor was induced and memorized by a chiral inducer with precise control by a regulator. In the chiral induction period, the feed sequence of the chiral inducer and regulator affected the chiral induction behavior of the chiral acceptor. The chiral memory ability of the acceptor was substantially improved by the combined action of the chiral inducer and regulator.
Natural .sup.13C abundance and chemical structure of different organic matter (OM) pools of Haplic Chernozem in contrasting land use variants (steppe and long-term bare fallow) are described. The ...sequence of OM decomposition in soils is traced. The pattern of changes in OM chemical structure of virgin chernozems under steppe from free (LF.sub.fr) to occluded states (LF.sub.occ) follows the pattern characteristic of the initial stages in decomposition, namely, the degree of OM aromaticity and hydrophobicity increases as well as the degree of its microbial degradation. The products of LF.sub.occ microbial decomposition adsorb on clay particles of the corresponding fraction. The clay-bound OM has a pronounced aliphatic nature with a considerable contribution of long-chain alkyls; it displays the highest degree of decomposition and the maximum contribution of polypeptides, which is consistent with its "heaviest" isotope signature among all studied OM pools. The chemical structure of the residue fraction is in many respects similar to that of the clay fraction and is enriched in short-chain alkyls of predominantly microbial origin. An almost complete absence of fresh organic material input to the soil of a bare fallow over a long period (52 years) causes a sharp increase in the degree of microbial decomposition of the available organic material in all studied OM pools, which is confirmed by their "heavier" isotope signature. The amount of the most easily available and energetically attractive fragments of organic material (O-Alk) for microbial community decreases, whereas the degrees of OM decomposition and hydrophobicity increase. An increase in the share of aromatic fragments and the degree of OM aromaticity suggests a selective accumulation of the most chemically stable aromatic compounds.
The reactivity of benzo1,2‐b : 4,5‐b′dithiophene‐4,8‐dione in Pd‐catalyzed C−H arylation was investigated. Using aryl bromides as aryl source in the presence of carbonate bases in 1,4‐dioxane, the ...mono‐C2‐arylated benzo1,2‐b : 4,5‐b′dithiophene‐4,8‐diones were regioselectively obtained. This procedure allowed to introduce both electron‐rich and electron‐poor aryl substituents on the benzo1,2‐b : 4,5‐b′dithiophene‐4,8‐dione unit. These conditions were also effective for the coupling with 1‐bromonaphthalene, 9‐bromophenanthrene as well as aryl bromides bearing synthetically useful nitrile, chloro and methoxy substituents. The photophysical properties of representative arylated compounds have been performed by joint experimental and theoretical studies.
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