A multi-dimensional microcanonical Monte Carlo study of S_0→T_1 intersystem crossing of isocyanic acid

A general formula for the multi-dimensional Monte Carlo microcanonical nonadiabatic rate constant expressed in configuration space is applied to calculate the rate of intersystem crossing(ISC) between the ground(S0) and first excited triplet(T1) states for isocyanic acid.One-,two-and three-dimensional potential energy surfaces are constructed by coupled-cluster single-double CCSD calculations,which are used for Monte Carlo sampling.The calculated S0→T1 ISC rate is in good agreement with experimental findings,which gives us a reason to believe that the multi-dimensional Monte Carlo microcanonical nonadiabatic rate theory is a very effective method for calculating nonadiabatic transition rate of a polyatomic molecule.

Potential energy surface of the photolysis of isocyanic acid HNCO

The dissociation curves of the photolysis of the isocyanic acidHNCOHN+CO corresponding to the ground state (S0), the first triplet excited state (T1) and the first singlet excited state (S1) have been studied respectively at the UHF/6-311G** and CIS/6-311G** levels using ab initio method. The energy surface crossing points, S1/T1, T1/S0 and S1/S0, have been found and the characteristics of the energy minimum crossing point were given, based on which, the changes of the crossing points' geometries along the lower electronic energy surface and its end-result have been located according to the steepest descent principle. The computational result indicates that the photolysis of the isocyanic acid HNCOHN+CO has three competitive reaction channels ((A)-(C)), and from the kinetic piont of view, channel (A) is the most advantageous.

Theoretical Research on the Multi-channel Reaction Mechanism of CHF Radical with HNCO by Density Functional Theory

The reaction mechanism of CHF radical with HNCO was investigated by the B3LYP method of density functional theory （DFT）, while the geometries and harmonic vibration frequencies of reactants, intermediates, transition states and products were calculated at the B3LYP/6-311＋＋G＊＊ level. In the temperature range of 100-2600 K, the statistical thermody- namics and Eyring transition state theory with Winger correction were used to study the thermodynamic and kinetic characters of the channel with low energy barrier. In addition, the analysis on the combining interaction between CHF radical and HNCO was performed by atom-in-molecules theory （AIM） and natural bond orbitals （NBO） analysis. The calculation results indicated that the reaction of CHF radical with HNCO had ten channels, and the channel of NH direct extraction （CHF ＋ HNCO→IM6→TS7→IM7→CHFNH ＋ CO） in singlet state was the main channel with low potential energy and high equilibrium constant and reaction rate constant. CHFNH and CO were the main products.

Mass-Spectrometric Method of Measurement of Isotopic Content of Nitrogen in Organic Compounds

Nitrogen-15 isotope-modified compounds are widely used in medicine, pharmacology, agriculture and various fields of science and their nomenclature is gradually increasing. Their widespread use depends on the availability of inexpensive and simple isotope analysis methods. The present article is an attempt to determine the nitrogen-15 isotope content directly in organic compounds without their conversion. The general principle of possibility of determination of the isotopes of nitrogen directly in organic compounds is proposed. Based on the study of mass-spectra of Carbamide Carbonyldiamide, isocyanic acid and nitrobenzene the mass peaks are selected, by which it is possible to determine the atomic fraction of the isotopes of nitrogen. The respective formulas are proposed.

Effect of SO_2 on the performance of Ag-Pd/Al_2O_3 for the selective catalytic reduction of NOx with C_2H_5OH

The influence of SO2 on the performance of Ag-Pd/Al2O3 for the selective catalytic reduction （SCR） of NOx with C2H5OH was investigated experimentally. The activity test results suggest that Ag-Pd/Al2O3 shows a small activity loss in the presence of SO2 when using C2H5OH as a reductant. In situ DRIFTS spectra show that the activity loss originates from the formation of surface sulphate species on the Ag-Pd/Al2O3. The surface sulphate species formation inhibits the formation of nitrate, whereas hardly changes the partial oxidation of C2H5OH. Compared with the NOx reduction by C3H6, an obvious suppression of the surface sulphate species formation was observed by DRIFTS experiment when using C2H5OH as a reductant. This phenomenon reveals the better catalytic performance and strong SO2 tolerance of Ag-Pd/Al2O3-C2H50H system.

SYNTHESIS AND CHARACTERIZATION OF NEW STABILIZERS WITH OPTIMAL MOLECULAR WEIGHT

Over 2 x 10(8) tons of polymers are produced every year, and a large portion of polymers faces the degradation problem. There are many effective methods to protect polymers against degradation and the addition of stabilizers to polymer remains the most convenient and effective way of enhancing polymer life and performance. In this article, a series of effective stabilizers with optimal molecular weight (MW), including common, monomeric and polymeric stabilizers (antioxidant and light stabilizer) were synthesized using isocyanation, controlled isocyanation, hydrosilylation, epoxide addition, macroreaction of stabilizing functional compounds and polymerization of monomeric stabilizers. The structure and performance of these new stabilizers were characterized by using IR, NMR, MS, UV-spectra, XPS and elemental analysis. The current development of stabilizer synthesis was also reviewed.

The Synthesis of Cyclic Amino Acids

Several cyclic amino acids (1-4) were synthesized from glycine. Isocyanate ester was prepared as the key intermediate and reacted with dibromoalkanes to afford the target compounds.

Polymerization of Phenyl Isocyanate by Divalent Samarium Complex (ArO)_2Sm(THF)_4 (ArO=2,6-di-tert-butyl-4-methylphenoxo)

Phenyl isocyanate was for the first time successfully polymerized by divalent samarium complex (ArO)2Sm(THF)4. The monomer concentration and temperatur affected the polymerization greatly.

Efficient Synthesis of 3,5,6,7-Tetrahydro-4H-cyclopenta [4,5] thieno [2,3-d] Pyrimidin-4-ones

The title compounds 3,5,6,7-tetrahydro-4H-cyclopenta[4,5]thieno[2,3-d]pyrimidin-4-ones（6） were synthesized by base catalytic reactions of secondary amines with carbodiimides 4, which were obtained from the aza-Wittig reaction of iminophosphoranes（3） with aromatic isocyanates.

Polymerization of n-Hexyl Isocyanate Initiated by Novel Rare Earth Tris(2,6-di-tert-butyl-4-methylphenolate)

The polymerization of n-hexyl isocyanate(HNCO) was carried out in the presence of a novel single initiator, rare earth tris(2,6-di-tert-butyl-4-methylphenolate)[Ln(OAr)_3]. The influences of reaction conditions such as the monomer concentration, the polymerization temperature and time, and the types of solvents on the polymerization of HNCO were studied. Polymerizations of phenyl, i-propyl, p-tolyl, n-butyl and n-octyl isocyanates with La(OAr)_3 were also examined.

Efficient synthesis of 5,6-dihydrothieno[3′,2′:4,5]-thieno[2,3-d]pyrimidin-4(3H)-ones via an iminophosphorane

5,6-Dihydrothieno[3＇,2＇：4,5]thieno[2,3-d]pyrimidin-4（3H）-ones 6 were synthesized in yields of 71-87% by a consecutive method, which includes aza-Wittig reaction of iminophosphorane 3 with aromatic isocynate to give carbodiimide 4 and subsequent reaction of 4 with various amines, phenols or alcohols in the presence of catalytic amount of sodium ethoxide or solid potassium carbonate. 2009 Ming Wu Ding. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.

Synthesis and Properties of Novel Polyurethane-Imide Elastomers

Novel polyurethane-imide elastomers were prepared from isocyanates (hexamethylene, and 4,4’-dicyclohexyl diisocyanates), polytetramethylene glycol (PTMG1000, Mw = 1000), pyromellitic dianhydride, and 4,4’-diphenylmethane diamine. The formation of PUIEs was confirmed by Fourier transform infrared spectroscopy. The resultant films were studied through X-ray diffraction analysis, contact angle measurement, atomic force microscopy, solubility and swelling tests, tensile test, differential scanning calorimetry, dynamic mechanical analysis, and thermogravimetric analysis.

Insertion Reactions of PhEtCCO and PhNCO into Ln-S (Ln=Er, Y, Yb) Bond of [Cp_2Ln(μ-SEt)]_2

The reactivity of lanthanocene thiolates [Cp2Ln（μ-SEt）]2（Ln = Er, Y, Yb） with PhEtCCO and with PhNCO was examined. Treatment of [ Cp2Ln（μ-SEt）]2 with PhEtCCO gives the α-thiolate-substituted enolate complexes [ Cp2Ln （μ-η^1 ：η^3-OC（SEt）CPhEt）]2（Ln = Yb, Y）, while [Cp2Ln（μ-SEt）]2 react with PhNCO to give the lanthanocene amido derivatives [Cp2Ln（OC（SEt）NPh ）]2（Ln = Er, Yb）. In both cases, the insertion reaction is independent of the stoichiometric ratio and the nature of lanthanides, demonstrating that lanthanocene thiolates are high reactive toward PhEtCCO and PhNCO under the conditions involved. All complexes are characterized by elemental analysis and spectroscopic properties, of which the structures of ytterbium enolate and erbium amido are also determined by X-ray single crystal diffraction analysis, indicating that both of them are centrosymmetric binuclear structures.

Synthesis and Crystal Structure of [Cp_2Ln(OC(SEt)NPh )]_2

Treatment of Cp3Y with EtSH, followed by reaction with an equivalent of PhNCO, yielded the dinuclear complex [Cp2Y（μ-η^1：η^3-OC（SEt）NPh）]2. The structure was characterized by elemental analysis, IR, MS and single-crystal X-ray diffraction analysis. The title compound crystallizes in triclinic, space group P1^- with a = 8.643（3）, b = 10.752（4）, c = 11.161（4）A°, α= 117.840（5）, β = 94.086（5）, γ= 101.008（5）°, V = 884.8（6） A°^3, Z = 1, Mr = 798.66 （C38H40N2O2S2Y2）, λ（MoKα） = 0.710730 .A°, ,μ= 3.417 mm^-1, Dc = 1.499 g/cm^3, F（000） = 408, the final R = 0.0453 and wR = 0.1007 for 3067 unique reflections （Rint = 0.0317） with 2357 observed ones （I 〉 2σ（I））. X-ray analysis reveals an unusual bonding mode of the OC（SEt）NPh ligand and the OCN fragment acts as a both bridging and side-on chelating ligand. Each yttrium atom is coordinated by two η^5-cyclopentadienyl groups, one chelating η^3-OC（SEt）NPh ligand and one bridging O atom from another η^3-OC（SEt）NPh ligand.

Study on Oligomerization of Phenyl Isocyanate Catalyzed by Bis(methylcyclopentadienyl)samarium Complex

The oligomerization of phenyl isocyanate catalyzed by divalent his (methylcyclopentadienyl)samarium complex was studied. The initiating reaction and the effect of coordination environment around the samarium atom were mainly discussed. It is found that the initiation reaction has a great influence on the apparent catalytic activity. The oligomers can be split into two fractions. The methanol insoluble fraction is mainly composed of dimers, while the methanol soluble fraction is mainly composed of trimers. Neither SmI2 nor SmI2(hmpa)(4)(hmpa = hexamethylphosphoric triamide) shows catalytic activity for the oligomerization of phenyl isocyanate.

Facile Synthesis of Ureas in Ionic Liquid

The reaction of isocyanates with aliphatic and aromatic amines in the 1-n-butyl-3- methylimidazolium tetrafluoroborate (bmimBF4) ionic liquid in good to excellent yields is described. Due to its insolubility, the desired urea solids could be recovered by simple filtration from the ionic liquid after reaction.

Urethane Modified Hydrophobic Compact Wood Pulp Paper for Oil Spill Cleanup: A Preliminary Study

Oil spills and oil/water wastewater are among the great concerns regarding oil pollution.Existing technologies face many limitations and in some cases are responsible for causing secondary pollution,therefore there is as seek for environmental friendly solutions.Biomass,from which celluloses are highlighted,are being employed for oil/water separation or oil absorbents membranes.Usually,these membranes are obtained by freeze drying of CNF(cellulose nano-fibrils)suspensions followed by chemical modification for hydrophobization,which involves expensive process as chemical vapor deposition and expensive reactants as sylanes,turning these processes hardly scalable.Here,we produced a natural porous structure paper from eucalyptus pulp fibers modified by a dipping and heating process in a blocked diisocyanate solution.After the surface treatment,contact angle with water reached 144°and water absorption reduced seven times,keeping the good oil absorbance.The chemical modification process is simple to be performed and use a very low quantity of reactant estimated to be less than 0.1 wt%based on cellulose.The good mechanical properties of the material allows its use in non usual conditions which can be of great importance depending on the environmental conditions.

A Facile Synthesis of 0,0-Dialkyl-α-(Phenyl Carbamyloxy) Alkyl Phosphonates

A series of title compounds were synthesized by the addition reaction of dialkyl-α-hydroxyphosphonates and phenyl isocyanate under base catalysis. All new compounds have beenidentified by 1H NMR, 31P NMR, IR and elemental analysis.

Reaction of Bis(Methylcyclopentadienyl) Lanthanide Amido Complex with n-Hexyl isocyanate-Synthesis and Characterization of {(MeC_5H_4)_2YbOC(NPh_2)N(n-hexyl)}_2

Bis （methylcyclopentadienyl） lanthanide amido complex （MeCp） 2YbNPh2 （THF） reacted with n-hexyl isocyanate （n-nexylNCO） in 1：1 molar ratio to give {（MeC5H4）2Yb[OC（NPh2）N（n-hexyl）] }2（1）. Complex 1 was characterized by elemental analyses and X-ray diffraction. The title complex belongs to trigonal system and R-3 space group. Its unit cell parameters are a =2.9533（11） nm, b =2.9533（11） nm, c = 1.5873（6） nm, V= 11.9896（80） nm^3, Z =9, Dc= 1.562 mg·m^-3, μ = 3.536 mm^-1（Mo Kα）, F（000） =5670, R =0.034, Rw =0.064. It is a dimeric structure with two symmetrical bridged oxygen atoms. Nitrogen atom is coordinated to the ytterbium atom to form a tricyclic backbone. The coordination number of ytterbium is 9. The whole molecule shows central symmetry.

LOW-VALENT TITANIUM INDUCED REDUCTIVE REACTION OF THIOCYANATES AND ISOCYANATE

Low-valent titanium reagent prepared from titanium tetrachloride and zinc was empolyed to induce the coupling reaction of thiocyanates with tetrahydrofuran yield alkyl 4-hydroxy butyl sulfide and isocyanate yield substituted urea.