Heterogeneous uptake and reactivity of formic acid on calcium carbonate particles: a Knudsen cell reactor, FTIR and SEM study

The heterogeneous uptake and reactivity of formic acid (HCOOH), a common gas-phase organic acid found in the environment, on calcium carbonate (CaCO(3)) particles have been investigated using a Knudsen cell reactor, Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM). FTIR measurements show that the adsorption of formic acid on the surface of calcium carbonate results in the formation of calcium formate. Besides calcium formate, carbonic acid is also a reaction product under dry conditions (<1% RH). Under dry conditions and at low pressures, the initial uptake coefficient of formic acid on CaCO(3) particles is measured to be 3 +/- 1 x 10(-3) and decreases as the surface saturates with adsorbed products. The maximum surface coverage of formic acid under dry conditions is determined to be (3 +/- 1)x 10(14) molecules cm(-2). Under humidified conditions (RH >10%), adsorbed water on the surface of the carbonate particles participates in the surface reactivity of these particles, which results in the enhanced uptake kinetics and extent of reaction of this organic acid on CaCO(3) as well as opens up several new reaction pathways. These reaction pathways include: (i) the water-assisted dissociation of carbonic acid to CO(2) and H(2)O and (ii) the formation of calcium formate islands and crystallites, as evident by SEM images. The results presented here show that adsorbed water plays a potentially important role in the surface chemistry of gas-phase organic acids on calcium carbonate particles.     

Synthesis of new chiral macrocycles-based glycolipids and its application in asymmetric Michael addition

A series of new mix aza- and thia-macrocyclic glycolipids (9, 10, 16 and 17) have been synthesized and their enantiomeric selectivity was studied. The synthesis of the macrocycles involved a simple protection of two hydroxyl groups of the glycolipids followed by building up the mix-heteroatom macrocyclic in simple sequences. The macrocycles and previously investigated analogues (18, 19, 20 and 21) have been applied as phase transfer catalysts in the enantioselective Michael addition of 2-nitropropane to chalcone and showed good-to-excellent enantiomer excess (ee). Among the catalysts, the galactose aza-crown ether-based glycolipid 21 proved to be the most effective with 90% ee.

Graphic abstract

     

Isolation of palm tocols using supercritical fluid chromatography

Crude palm oil contains 600 to 1000 ppm of tocols in the form of tocopherols and tocotrienols. These palm tocols have been isolated and analyzed in the past by various chromatographic techniques such as open column chromatography, high-performance liquid chromatography, as well as thin-layer chromatography. Supercritical fluid chromatography (SFC) has emerged as a more advanced chromatographic technique in recent years. The tocols present in palm oil are successfully isolated using SFC. Identification of these tocols is supported by various spectroscopic techniques such as 1H NMR, 13C NMR, and mass spectrometry.     

Synthesis, Crystal Structure and ab initio Studies of Cyclohexyl N-Phenylcarbamate

Abstract  

Cyclohexyl N-phenylcarbamate, C₁₃H₁₇NO₂ (I), which is a useful target for biotransformations by fungi, has been synthesized and the structure has been solved by X-ray diffraction. The crystals are triclinic, space group P [`1] bar{1} , with a = 5.2581 (2) ?, b = 9.5080 (3) ?, c = 12.6165 (4) ?, α = 70.544 (2)°, β = 89.075 (2)°, γ = 80.447 (2)°, M _r = 219.28, V = 585.96 (3) ?³, Z = 2 and R = 0.065. In the title compound the phenyl ring makes a dihedral angle of 30.68(7)° with the carbamate group The molecules are linked into infinite chains via N–H···O hydrogen bonds along the a axis. These hydrogen-bonded chains are further linked by weaker C–H···π interactions. Quantum-mechanical ab initio calculations for the free molecule reproduce well the observed bond lengths and valency angles but show that the crystal packing might be responsible for the rotation of the phenyl ring out of the carbamate plane in the solid state conformation.     

Aberrant proteins in the saliva of patients with oral squamous cell carcinoma

Confirmation of oral squamous cell cancer (OSCC) currently relies on histological analysis, which does not provide clear indication of cancer development from precancerous lesions. In the present study, whole saliva proteins of patients with OSCC (n = 12) and healthy subjects (n = 12) were separated by 2DE to identify potential candidate biomarkers that are much needed to improve detection of the cancer. The OSCC patients’ 2DE saliva protein profiles appeared unique and different from those obtained from the healthy subjects. The patients’ saliva α1‐antitrypsin (AAT) and haptoglobin (HAP) β chains were resolved into polypeptide spots with increased microheterogeneity, although these were not apparent in their sera. Their 2DE protein profiles also showed presence of hemopexin and α‐1B glycoprotein, which were not detected in the profiles of the control saliva. When subjected to densitometry analysis, significant altered levels of AAT, complement C3, transferrin, transthyretin, and β chains of fibrinogen and HAP were detected. The increased levels of saliva AAT, HAP, complement C3, hemopexin, and transthyretin in the OSCC patients were validated by ELISA. The strong association of AAT and HAP with OSCC was further supported by immunohistochemical staining of cancer tissues. The differently expressed saliva proteins may be useful complementary biomarkers for the early detection and/or monitoring of OSCC, although this requires validation in clinically representative populations.     

A new rosane-type diterpenoid from Stachys parviflora and its density functional theory studies

A new rosane-type diterpenoid (1) has been isolated from the chloroform fraction of Stachys parviflora. Structure of 1 was proposed based on 1D and 2D NMR techniques including correlation spectroscopy, heteronuclear multiple quantum coherence, heteronuclear multiple bond correlation and nuclear Overhauser effect spectroscopy. A theoretical model for the electronic and spectroscopic properties of compound 1 is also developed. The geometries and electronic properties were modelled at B3LYP/6-31G^* and the theoretical scaled spectroscopic data correlate nicely with the experimental data.