Imaging Isocyanic Acid Photodissociation at 193 nm:the NH(a^1△)+CO(X^1∑^+)Channel

The photodissociation dynamics of isocyanic acid （HNCO） has been studied by the time- sliced velocity map ion imaging technique at 193 nm. The NH（a1△） products were measured via （2＋1） resonance enhanced multiphoton ionization. Images have been accumulated for the NH（a1△） rotational states in the ground and vibrational excited state （v=0 and 1）. The center-of-mass translational energy distribution derived from the NH（a1△） images implies that the CO vibrational distributions are inverted for most of the measured 1NH（v｜j） internal states. The anisotropic product angular distribution observed indicates a rapid dissociation process for the N-C bond cleavage. A bimodal rotational state distribution of CO（v） has been observed, this result implies that isocyanic acid dissociates in the S1 state in two different pathways.

Potential energy surface of the photolysis of isocyanic acid HNCO

The dissociation curves of the photolysis of the isocyanic acid $HNCO\xrightarrow{{hv}}HN + CO$ 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 usingab 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 $HNCO\xrightarrow{{hv}}HN + CO$ has three competitive reaction channels ((A)—(C)), and from the kinetic piont of view, channel (A) is the most advantageous.

Theoretical Study on the Reaction Mechanism of CH2F Radical with HNCO

The reaction mechanism of CH2F radical with HNCO was investigated by density functional theory （DFT） at the B3LYP/6-311＋＋G（d,p） level. The geometries of the reactants, the intermediates, the transition states and the products were optimized. The transition states were verified through the vibration analysis. The relative energies were calculated at the QCISD（T）/6-311＋＋G^＊＊//B3LYP/6-311＋＋G（d,p） level. Seven feasible reaction pathways of the reaction were studied. The results indicate that the pathway （5） is the most favorable to occur, so it is the main pathway of the reaction.

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.

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.

AIM Study on Reaction HNCX→HXCN （X=O, S and Se）

The reactions of HNCO to HOCN, HNCS to HSCN and HNCSe to HSeCN have been studied at MP2/6-311 ＋ ＋ G（2df, pd）//B3LYP/6-311 ＋ ＋G（2df, pd） level. Geometries of the reactants, transition states and products have been optimized and geometries of the transition states are reported for the first time. The reasons why HNCO and HNCS instead of HOCN and HSCN were easily detected have been explained. It was predicted that HNCSe will be more easily detected than HSeCN. The breakage and formation of the chemical bonds in the reactions have been discussed by the topological analysis method of electronic density. The calculated results show that there are two kinds of structure transition states （STS） in reactions studied.

Synthesis of Hyperbranched Polymer for 3D Printing

3D printing has been developing rapidly in recent years owing to its application in academic and industry areas,but the poor mechanical property of printing materials limits its application.Herein,a photocurable resin with good mechanical property was obtained based on hyperbranched polymer synthesized through the reaction of carboxylic acids with isocyanates catalyzed by magnesium stearate.Three kinds of hyperbranched polymers with different molecular weight were fabricated by modulating the content of isocyanates.By mixing hyperbranched polymer with acryloylmorpholine,polyethylene glycol diacrylate 400 and photoinitiator of 819,the photocurable resin was obtained.The influence of various factors on mechanical properties of samples was investigated such as molecular weight of hyperbranched polymer and the light exposure time.Comparing with the commercial resin,the flexural strength(116.06 MPa)and impact strength(34.59 kJ/m^(2))of the resultant resin increased by 21.2%and 20.8%,respectively.