42 research outputs found
Quantum Chemistry Calculations on the Mechanism of Isoquinoline Ring-Opening and Denitrogenation in Supercritical Water
Computational
studies at the M06/6-311GÂ(d,p) and M06-2<i>X</i>/6-311+GÂ(d,p)
levels were performed to explore the detailed mechanism
of isoquinoline ring-opening and denitrogenation in a supercritical
water system. Three reaction paths with the same product, 2-(2-oxoethyl)
benzaldehyde, were supported by the computational results. The rate-limiting
step in the major degradation reaction is an addition reaction at
the N position. H<sub>2</sub>O is added to both the 1C–2N double
bond (1C–2N addition reaction) and the 2N–3C double
bond (2N–3C addition reaction) of the isoquinoline molecule,
where the oxygen of H<sub>2</sub>O is added to the carbon atom. The
energy barrier of the 1C–2N addition reaction is 52.7 kcal/mol,
while that of 2N–3C addition (from Path 6) is 60.1 kcal/mol.
From catalysis by two water molecules, the barrier of 1C–2N
addition (Reaction (1)) is reduced to 27.5 kcal/mol. Catalysis from
water molecule clusters is shown to considerably affect the process
of isoquinoline ring-opening and denitrogenation, as indicated by
comparing the reaction energy barrier heights with and without water
catalysts
Detection of Liquid Penetration of a Micropillar Surface Using the Quartz Crystal Microbalance
A quantitative characterization
of the wetting states of droplets
on hydrophobic textured surfaces requires direct measurement of the
liquid penetration into surface cavities, which is challenging. Here,
the use of quartz crystal microbalance (QCM) technology is reported
for the characterization of the liquid penetration depth on a micropillar-patterned
surface. The actual liquid–air interface of the droplet was
established by freezing the droplet and characterizing it using a
cryogenically focused ion beam/scanning electron microscope (cryo
FIB-SEM) technique. It was found that a direct correlation exists
between the liquid penetration depth and the responses of the QCM.
A very small frequency shift of the QCM (1.5%) was recorded when the
droplet was in the Cassie state, whereas a significant frequency shift
was observed when the wetting state changed to the Wenzel state (where
full liquid penetration occurs). Furthermore, a transition from the
Cassie to the Wenzel state can be captured by the QCM technique. An
acoustic–structure-interaction based numerical model was developed
to further understand the effect of penetration. The numerical model
was validated by experimentally measured responses of micropillar-patterned
QCMs. The results also show a nonlinear response of the QCM to the
increasing liquid penetration depth. This research provides a solid
foundation for utilizing QCM sensors for liquid penetration and surface
wettability characterization
Quantification of Particle Filtration Using a Quartz Crystal Microbalance Embedded in a Microfluidic Channel
To
quantify colloidal filtration, a quartz crystal microbalance
(QCM) with a silicon dioxide surface is embedded on the inner surface
of a microfluidic channel to monitor the real-time particle deposition.
Potassium chloride solution with micrometer-size polystyrene particles
simulating bacterial strains flows down the channel. In the presence
of intrinsic Derjaguin–Landau–Verwey–Overbeek
(DLVO) intersurface forces, particles are trapped by the quartz surfaces,
and the increased mass shifts the QCM resonance frequency. The method
provides an alternative way to measure filtration efficiency in an
optically opaque channel and its dependence on the ionic concentration
Current variation obtained during the preparation of CLTO and CSTO.
<p>The total anodization time was 1 h.</p
Pd-Catalyzed Divergent C(sp<sup>2</sup>)–H Activation/Cycloimidoylation of 2‑Isocyano-2,3-diarylpropanoates
A Pd-catalyzed site-selective
CÂ(sp<sup>2</sup>)–H activation/cycloimidoylation
of 2-isocyano-2,3-diarylpropanoates to construct diverse cyclic imine
products has been developed. Six-membered 3,4-dihydroisoquinolines
containing a C3 quaternary carbon center were generated dominantly
by using bulky Ad<sub>2</sub>P<i>n</i>-Bu as a ligand, while
five-membered 1,1-disubstituted 1<i>H</i>-isoindoles were
formed preferentially in the presence of bidentate phosphine ligand
DPPB. The selectivity for 1<i>H</i>-isoindole formation
was enhanced by using steric hindered aryl iodides. DFT calculations
suggested that the experimentally observed ligand-controlled selectivity
was a result of <i>trans</i> effect
SEM images of the CLTO films formed in the electrolyte of EG +10%H<sub>2</sub>O +0.25%H<sub>3</sub>PO<sub>4</sub>+3%NH<sub>4</sub>F.
<p>(a) top view; (b) a fragment (c) the magnification of (a); (d) cross-sectional view.</p
XRD patterns of (a) the as-prepared coral-like Ta<sub>2</sub>O<sub>5</sub> and (b) the calcined sample.
<p>XRD patterns of (a) the as-prepared coral-like Ta<sub>2</sub>O<sub>5</sub> and (b) the calcined sample.</p
Synthesis of [2.2]Paracyclophane-Fused Heterocycles via Palladium-Catalyzed C–H Activation/Annulation of [2.2]Paracyclophanecarboxamides with Arynes
[2.2]Paracyclophane-fused heterocycles
represent an
important
scaffold. Traditional approaches often suffer from tedious synthetic
routes, and the development of catalytic synthesis of them remains
in its infancy. Herein, by employing highly strained aryne intermediates
as partners, we have developed a concise protocol by palladium-catalyzed
C–H activation/annulation from [2.2]paracyclophanecarboxamide
substrates. [2.2]Paracyclophane-fused quinolinone products are obtained
in good yields (up to 84%). Furthermore, the utility of the process
has been shown through the synthesis of [2.2]paracyclophane-fused
heterocyclic catalysts
SEM image of the CSTO film formed in the electrolyte of EG +70%H<sub>2</sub>O +0.25%H<sub>3</sub>PO<sub>4</sub>+3.6%NH<sub>4</sub>F.
<p>SEM image of the CSTO film formed in the electrolyte of EG +70%H<sub>2</sub>O +0.25%H<sub>3</sub>PO<sub>4</sub>+3.6%NH<sub>4</sub>F.</p
Characterization of Diterpenes from Euphorbia prolifera and Their Antifungal Activities against Phytopathogenic Fungi
Euphorbia prolifera is a poisonous
plant belonging to the Euphorbiaceae family. In this survey on plant
secondary metabolites to obtain bioactive substances for the development
of new antifungal agents for agriculture, the chemical constituents
of the plant <i>E. prolifera</i> were investigated. This
procedure led to the isolation of six new and two known diterpenes.
Their structures, including absolute configurations, were elucidated
on the basis of extensive NMR spectroscopic data analyses and time-dependent
density functional theory ECD calculations. Biological screenings
revealed that these diterpenes possessed antifungal activities against
three phytopathogenic fungi. The results of the phytochemical investigation
further revealed the chemical components of the poisonous plant <i>E. prolifera</i>, and biological screenings implied the extract
or bioactive diterpenes from this plant may be regarded as candidate
agents of antifungal agrochemicals for crop protection products