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We computationally study the chiral transition process of the α-Ala molecule under confined different sizes of armchair SWBNNTs to explore the confinement effect. We find that the influence of a confinement environment (in armchair SWBNNTs) on the α-Ala molecule would lead to different reaction pathways. Meanwhile, the preferred reaction pathway is also different in various sizes of armchair SWBNNTs, and their energy barriers for the rate-limiting step decrease rapidly with the decreasing of the diameters of the nanotubes. It is obvious that significant decrease of the chiral transition energy barrier occurs compared with the isolated α-Ala molecule chirality conversion mechanism, by ∼15.6 kcal mol-1, highlighting the improvement in the activity the enantiomers of α-Ala molecule. We concluded that the confinement environment has a significant impact at the nanoscale on the enantiomer transformation process of the chiral molecule. [ABSTRACT FROM AUTHOR]

Hydroxyacetone (CH3C(O)CH2OH) is observed as a stable end product from reactions of the (CH3)2COO Criegee intermediate, acetone oxide, in a flow tube coupled with multiplexed photoionization mass spectrometer detection. In the experiment, the isomers at m/z = 74 are distinguished by their different photoionization spectra and reaction times. Hydroxyacetone is observed as a persistent signal at longer reaction times at a higher photoionization threshold of ca. 9.7 eV than Criegee intermediate and definitively identified by comparison with the known photoionization spectrum. Complementary electronic structure calculations reveal multiple possible reaction pathways for hydroxyacetone formation, including unimolecular isomerization via hydrogen atom transfer and -OH group migration as well as self-reaction of Criegee intermediates. Varying the concentration of Criegee intermediates suggests contributions from both unimolecular and self-reaction pathways to hydroxyacetone. The hydroxyacetone end product can provide an effective, stable marker for the production of transient Criegee intermediates in future studies of alkene ozonolysis. [ABSTRACT FROM AUTHOR]

A novelseries of donor–acceptor star-shaped conjugatedmacroelectrolytes (CMEs), denoted as 4FTs, including anionic carboxylicacid sodium groups (4FNaT), neutral diethanolamine groups (4FNOHT),and cationic ammonium groups (4FNBrT), were designed, synthesized,and explored as an excellent platform to investigate the impact ofvarious polar pendent groups on self-assembly behaviors. The resultingCMEs with donor–acceptor star-shaped architectures exhibiteddistinct light-harvesting properties. The interactions between 4FTsand TrNBr, a star-shaped monodisperse CME grafted with cationic quaternaryammonium side chains, were investigated in H2O and CH3OH using steady-state, time-resolved fluorescence, dynamiclight scattering (DLS), and transmission electron microscopy (TEM).Highly favored energy transfer has been proven by the excellent spectraloverlap between TrNBr fluorescence and 4FTs absorptions which canbe tuned by adjusting the pendent polar groups and solvents. It issuggested that self-assembled structures are formed between TrNBrand 4FNaT, while there is no obvious change for TrNBr/4FNOHT and TrNBr/4FNBrTin both H2O and CH3OH at low concentrations(<10–6M). This result is confirmed by the changeof the TrNBr and 4FTs fluorescence properties and the time-resolvedfluorescence data. The overall results manifest that at low concentrationsthe self-assembly between TrNBr and 4FTs is dominated by the electrostaticinteractions. This study suggests that the functionalization of pendentpolar groups of star-shaped CMEs has proven to be effective to modulatethe self-assembly behaviors in dilute solutions and thus provide astrategy to further manage the optoelectronic properties. [ABSTRACT FROM AUTHOR]

Se--N dynamic covalent bond is a new dynamic covalent bond which has applications in the fabrication of stimuli responsive and self-healing functional materials. Although recent advances have been achieved in the experimental aspect, little is known about the formation mechanism of Se--N dynamic covalent bond. Here the structures and nature of Se--N dynamic covalent bond between three kinds of pyridine derivatives R-C5H4N, [pyridine (R = H), 4-methylpyridine (R = CH3), 4-dimethylamino-pyridine (R = N(CH3)2)] and phenylselenyl bromine (PhSeBr) have been analyzed using density functional theory. The interactions between Se atom in PhSeBr and N atom in pyridine or pyridine derivatives can be divided into three models: dissociation, nonbonding interaction and covalent bond interaction. Quantum chemical calculations on three series compounds show that these three models can convert mutually, which results in the generation of Se--N dynamic covalent bond. Solvent effects produced in polar solvents such as CH2Cl2 can make the conversion between Se--N covalent bond and Se...N nonbonding interactions easier. The kind of the substituents in pyridine ring can affect the conversion process: the stronger the electron-donating ability of the substituent, the easier the structure transformation. [ABSTRACT FROM AUTHOR]

To enhance the interfacial interaction between rubber and hybrid nanofiller (HS) consisting of halloysite nanotubes and silica, and simultaneously prevent migration and volatilization of rubber additives, commercial vulcanization accelerator N-cyclohexyl-2-benzothiazole sulfenamide (CZ) was chemically grafted onto HS to obtain a functionalized nanofiller (HS-s-CZ). It was found that the grafted CZ molecules within an inorganic host structure have better efficiency to accelerate cross-linking reaction than free CZ molecules. In addition, HS-s-CZ could be evenly dispersed into styrene butadiene rubber (SBR) with further improved filler-rubber interaction compared with that between HS and SBR. Consequently, SBR/HS-s-CZ composites exhibited greater mechanical strength than SBR/HS composites containing equivalent accelerator component, showing 45% increase in tensile strength when the filler content was 40 phr. Potentially, this work offers a new design strategy for the surface modification of nanofiller and preparation of high-efficiency rubber additives, which may represent a new path for preparing high-performance elastomer composites. [ABSTRACT FROM AUTHOR]

We report the atom-economic and environmentally friendly synthesis of Z-β-sulfonyl-a,β-unsaturated carbonyl compounds in water. The mechanism study reveals that the hydrosulfonylation of alkynylcarbonyl compounds with sulfinic acids proceeds via a mechanism that features a sulfinic acid molecule protonating an alkynyl motif to form the ethenium intermediate, which subsequently reacted with a sulfonyl anion to afford the desired products. The ethenium intermediate differentiated electronic and steric demands between the two substituents on the CC triple bond of the alkyne substrates to exhibit high regio- and stereoselectivity from a wide range of Z-β-sulfonyl-a,β-unsaturated carbonyl compounds. [ABSTRACT FROM AUTHOR]