Journal: Journal of the American Chemical Society

Abbreviation

J. Am. Chem. Soc.

Publisher

American Chemical Society

Journal Volumes

ISSN

0002-7863
1520-5126

Description

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Publications 1 - 10 of 831
  • C₁-Based Route for Vinyl Chloride Synthesis with Environmental and Economic Benefits
    Item type: Journal Article
    Wang, Yue; Zou, Shihui; Nabera, Abhinandan; et al. (2025)
    Journal of the American Chemical Society
    Selective coupling of C-1 platform molecules to C-2 olefins is a cornerstone for establishing a sustainable chemical industry based on nonpetroleum sources. Vinyl chloride (C2H3Cl), one of the top commodity petrochemicals, is commercially produced from coal- or oil-derived C-2 hydrocarbon (acetylene and ethylene) feedstocks with a high carbon footprint. Here, we report a C-1-based route for vinyl chloride synthesis via the selective oxidative coupling of methyl chloride. This is enabled by a solid catalyst, featuring tungstate nanoclusters embedded in a zirconia matrix, which effectively captures CH2Cl radicals homogeneously generated in CH3Cl oxy-pyrolysis and selectively couples them into C2H3Cl. In situ synchrotron-based vacuum ultraviolet photoionization mass spectrometry provides direct experimental evidence of the homogeneous-heterogeneous reaction mechanism. The process achieves methyl chloride conversion of 10-65% with a high vinyl chloride selectivity (60-75%) at a reaction temperature of 650-750 degrees C, which is much lower than the traditional pyrolysis (>850 degrees C). The catalyst delivers stable performance (at a vinyl chloride yield of ca. 30%) with no deactivation observed during a 50 h test. Furthermore, combining with reaction of methanol and HCl to produce methyl chloride, we establish a methanol-to-vinyl chloride (MTV) route with the potential for significant reductions in climate change impact (24%) and cost (38%) compared to the state-of-the-art ethylene-based balanced process. A more remarkable 237% reduction in climate change impacts can be anticipated in the future-oriented green scenario for the MTV process primarily attributed to the utilization of renewable C-1 feedstocks that results in negative net contributions to the overall impacts.
  • Can Anions Be Inserted into MXene?
    Item type: Journal Article
    Shpigel, Netanel; Chakraborty, Arup; Malchik, Fyodor; et al. (2021)
    Journal of the American Chemical Society
    Despite the continuous progress in the research and development of Ti3C2Tx (MXene) electrodes for high-power batteries and supercapacitor applications, the role of the anions in the electrochemical energy storage and their ability to intercalate between the MXene sheets upon application of positive voltage have not been clarified. A decade after the discovery of MXenes, the information about the possibility of anion insertion into the restacked MXene electrode is still being questioned. Since the positive potential stability range in diluted aqueous electrolytes is severely limited by anodic oxidation of the Ti, the possibility of anion insertion was evaluated in concentrated aqueous electrolyte solutions and aprotic electrolytes as well. To address this issue, we have conducted in situ gravimetric electrochemical quartz crystal microbalance with dissipation monitoring (EQCM-D) measurements in highly concentrated LiCl and LiBr electrolytes, which enable a significant extension of the operation range of the MXene electrodes toward positive potentials. Also, halogens are among the smallest anions and should be easier to intercalate between MXene layers, in comparison to multiatomic anions. On the basis of mass change variations in the positive voltage range and complementary density functional theory calculations, it was demonstrated that insertion of anionic species into MXene, within the range of potentials of interest for capacitive energy storage, is not likely to occur. This can be explained by the strong negative charge on Ti3C2Tx sheets terminated by functional groups.
  • Formaldehyde N, N-dialkylhydrazones as neutral formyl anion equivalents in iridium-catalyzed asymmetric allylic substitution
    Item type: Journal Article
    Breitler, Simon; Carreira, Erick M. (2015)
    Journal of the American Chemical Society
  • Self-Assembly of Focal Point Oligo-catechol Ethylene Glycol Dendrons on Titanium Oxide Surfaces
    Item type: Journal Article
    Gillich, Torben; Benetti, Edmondo M.; Rakhmatullina, Ekaterina; et al. (2011)
    Journal of the American Chemical Society
  • Initial Primer Synthesis of a DNA Primase Monitored by Real-Time NMR Spectroscopy
    Item type: Journal Article
    Wu, Pengzhi; Zehnder, Johannes; Schröder, Nina; et al. (2024)
    Journal of the American Chemical Society
    Primases are crucial enzymes for DNA replication, as they synthesize a short primer required for initiating DNA replication. We herein present time-resolved nuclear magnetic resonance (NMR) spectroscopy in solution and in the solid state to study the initial dinucleotide formation reaction of archaeal pRN1 primase. Our findings show that the helix-bundle domain (HBD) of pRN1 primase prepares the two substrates and then hands them over to the catalytic domain to initiate the reaction. By using nucleotide triphosphate analogues, the reaction is substantially slowed down, allowing us to study the initial dinucleotide formation in real time. We show that the sedimented protein-DNA complex remains active in the solid-state NMR rotor and that time-resolved P-31-detected cross-polarization experiments allow monitoring the kinetics of dinucleotide formation. The kinetics in the sedimented protein sample are comparable to those determined by solution-state NMR. Protein conformational changes during primer synthesis are observed in time-resolved H-1-detected experiments at fast magic-angle spinning frequencies (100 kHz). A significant number of spectral changes cluster in the HBD pointing to the importance of the HBD for positioning the nucleotides and the dinucleotide.
  • Origin of Reactivity Trends of an Elusive Metathesis Intermediate from NMR Chemical Shift Analysis of Surrogate Analogues
    Item type: Journal Article
    Kakiuchi, Yuya; Docherty, Scott; Berkson, Zachariah J.; et al. (2024)
    Journal of the American Chemical Society
    Olefin metathesis has become an efficient tool in synthetic organic chemistry to build carbon-carbon bonds, thanks to the development of Grubbs- and Schrock-type catalysts. Olefin coordination, a key and often rate-determining elementary step for d0 Schrock-type catalysts, has been rarely explored due to the lack of accessible relevant molecular analogues. Herein, we present a fully characterized surrogate of this key olefin-coordination intermediate, namely, a cationic d0 tungsten oxo-methylidene complex bearing two N-heterocyclic carbene ligands─[WO(CH2)Cl(IMes)2](OTf) (1) (IMes = 1,3-dimesitylimidazole-2-ylidene, OTf-triflate counteranion), resulting in a trigonal bipyramidal (TBP) geometry, along with its neutral octahedral analogue [WO(CH2)Cl2(IMes)2] (2)─and an isostructural oxo-methylidyne derivative [WO(CH)Cl(IMes)2] (3). The analysis of their solid-state 13C and 183W MAS NMR signatures, along with computed 17O NMR parameters, helps to correlate their electronic structures with NMR patterns and evidences the importance of the competition among the three equatorial ligands in the TBP complexes. Anchored on experimentally obtained NMR parameters for 1, computational analysis of a series of olefin coordination intermediates highlights the interplay between σ- and π-donating ligands in modulating their stability and further paralleling their reactivity. NMR spectroscopy descriptors reveal the origin for the advantage of the dissymmetry in σ-donating abilities of ancillary ligands in Schrock-type catalysts: weak σ-donors avoid the orbital-competition with the oxo ligand upon formation of a TBP olefin-coordination intermediate, while stronger σ-donors compromise M≡O triple bonding and thus render olefin coordination step energy demanding.
  • Facile and General Preparation of Multifunctional Main-Chain Cationic Polymers through Application of Robust, Efficient, and Orthogonal Click Chemistries
    Item type: Journal Article
    Saha, Animesh; De, Swati; Stuparu, Mihaiela C.; et al. (2012)
    Journal of the American Chemical Society
  • Evaluation of Hydrogen-Bond Acceptors for Redox-Switchable Resorcin[4]arene Cavitands
    Item type: Journal Article
    Pochorovski, Igor; Milic, Jovana; Kolarski, Dušan; et al. (2014)
    Journal of the American Chemical Society
    Various H-bond acceptor groups were evaluated for their propensity to induce conformational switching between the kite and vase forms of diquinone-diquinoxaline resorcin[4]arene cavitands upon redox interconversion. The H-bond acceptors were placed on the quinoxaline walls with the purpose of stabilizing the vase form only in the reduced hydroquinone state of the cavitand by forming H-bonds with the hydroquinone OH groups. Design guidelines for successful acceptors were derived. The carboxamide acceptor was shown to be the best candidate. Based on this moiety, a redox-switchable triptycene-based basket that can completely sterically encapsulate a guest in its closed vase conformation was prepared. The basket binds small molecule guests with association constants of up to 104 M–1 in mesitylene-d12 and exhibits slow guest exchange kinetics with a half-life for guest release in the order of 104 s.
  • Iridium-Catalyzed Enantioselective Allylic Vinylation
    Item type: Journal Article
    Hamilton, James Y.; Sarlah, David; Carreira, Erick M. (2013)
    Journal of the American Chemical Society
  • Oligodimethylsiloxane-Oligoproline Block Co-Oligomers: the Interplay between Aggregation and Phase Segregation in Bulk and Solution
    Item type: Journal Article
    Lamers, Brigitte A.G.; Herdlitschka, Andreas; Schnitzer, Tobias; et al. (2021)
    Journal of the American Chemical Society
    Discrete block co-oligomers (BCOs) assemble into highly ordered nanostructures, which adopt a variety of morphologies depending on their environment. Here, we present a series of discrete oligodimethylsiloxane-oligoproline (oDMS-oPro) BCOs with varying oligomer lengths and proline end-groups, and study the nanostructures formed in both bulk and solution. The conjugation of oligoprolines to apolar siloxanes permits a study of the aggregation behavior of oligoproline moieties in a variety of solvents, including a highly apolar solvent like methylcyclohexane. The apolar solvent is more reminiscent of the polarity of the siloxane bulk, which gives insights into the supramolecular interactions that govern both bulk and solution assembly processes of the oligoproline. This extensive structural characterization allows the bridging of the gap between solution and bulk assembly. The interplay between the aggregation of the oligoproline block and the phase segregation induced by the siloxane drives the assembly. This gives rise to disordered, micellar microstructures in apolar solution and crystallization-driven lamellar nanostructures in the bulk. While most di- and triblock co-oligomers adopt predictable morphological features, one of them, oDMS15-oPro6-NH2, exhibits pathway complexity leading to gel formation. The pathway selection in the complex interplay between aggregation and phase segregation gives rise to interesting material properties.
Publications 1 - 10 of 831