CO Double Bond Research Articles

C[sbnd]O bond enhancing direct bonding strength between plastic and pure titanium

Direct bonding process by using the conventional hot pressing was applied to prepare the dissimilar materials consisting of the thermoplastic resin and pure titanium (Ti) material. In employing the pressing temperature at the melting point of plastics, the interfacial bonding shear strength of the dissimilar material using polyamide66 (PA66) was drastically increased. Microstructure and phase analysis clarified that CO double bonds of the carbonyl group was thermally decomposed and oxygen atoms contributed to diffusion into pure Ti or oxides formation at the interface. In addition, the chemical reaction of CH and NTi formation was also effective to the interfacial bonding improvement. On the other hand, when polystyrene (PS) with no functional group including CO/CO bond was employed, for example, the PS-Ti dissimilar material showed no bonding strength even then the bonding temperature was close to 300 °C.

Adsorption behavior of formaldehyde on ZnO [formula omitted] surface: A first principles study

In a first principles study of the formaldehyde adsorption on ZnO surface, we found a novel chain adsorption structure on ZnO (101¯0) plane. This adsorption structure results from the electrostatic interactions between those adsorbed formaldehyde molecules and the unique arrangement of Zn-O surface dimers on (101¯0) plane. This adsorption mechanism has the potential to extend to other wurtzite materials’ (101¯0) plane and other similar cases. As the physical adsorption configurations are unstable, the chemical adsorption has to happen. The electronic properties show that the CO double bond in CH2O turns into CO single bond and the highest occupied molecule orbital (HOMO) of formaldehyde is lifted into ZnO band gap becoming the hole trapping center. These results may be meaningful for formaldehyde degradation and detection.

Photoinduced electron transfer-promoted decarboxylative radical reactions of aliphatic carboxylic acids by organic photoredox system

This feature article covers our efforts to develop a new method for radical reactions of aliphatic carboxylic acids via a photoinduced electron transfer-promoted decarboxylation using an organic photoredox system. Stable, inexpensive, and neutral organic molecules, such as phenanthrene and 1,4-dicyanobenzene, are employed as the photocatalyst to generate alkyl radicals. The photoinduced decarboxylative radical reactions are proven to be useful for reduction, deuteration, addition to CC, CN, and CO double bonds, modification of peptides, cyclization, ring expansion, substitution of dicyanobenzenes, and formation of a carbanion under mild conditions.

Detection of CO2 using CNT-based sensors: Role of Fe catalyst on sensitivity and selectivity

The adsorption of CO2 on surfaces of graphene and carbon nanotubes (CNTs), decorated with Fe atoms, are investigated using the self-consistent-charge density-functional tight-binding (SCC-DFTB) method, neglecting the heat effects. Fe ad-atoms are more stable when they are dispersed on hollow sites. They introduce a large density of states at the Fermi level (NF); where keeping such density low would help in gas sensing. Furthermore, the Fe ad-atom can weaken the CO double bonds of the chemisorbed CO2 molecule, paving the way for oxygen atoms to drain more charges from Fe. Consequently, chemisorption of CO2 molecules reduces both NF and the conductance while it enhances the sensitivity with the increasing gas dose. Conducting armchair CNTs (ac-CNTs) have higher sensitivity than graphene and semiconducting zigzag CNTs (zz-CNTs). Comparative study of sensitivity of ac-CNT-Fe composite towards various gases (e.g., O2, N2, H2, H2O, CO and CO2) has shown high sensitivity and selectivity towards CO, CO2 and H2O gases.

The conformational analysis of push-pull enaminones using FTIR and NMR spectroscopy, and quantum chemical calculations. VI. β−N−Methyl-aminovinyl trifluoromethyl ketone and α−methyl−β−N−methylaminovinyl trifluoromethyl ketone

X-Ray analysis, NMR and IR Fourier spectra of two enaminoketones 4-(N-methylamino)-1,1,1-trifluorobut-3-en-2-one F3CCOCHCHNH(CH3) (1) 4-(N-methylamino)-1,1,1-trifluoro-3-methylbut-3-en-2-one F3CCOC(CH3)CHNH(CH3) (2) were studied in solid state and solutions. It was shown that the substitution of proton at α-position of vinyl moiety with methyl group changes significantly electronic and spatial structure of enaminoketone. In solid state enaminoketone 1 is found to be exclusively as Z-s-Z-ap isomer with intramolecular hydrogen bond. At the same time molecules of enaminoketone 2 have E-s-E-ap stereoisomeric structure forming dimers due to intermolecular NH⋯OC hydrogen bonds. Exposure of Ar-matrix isolated 1 to UV-radiation results in appearance of various E forms with free methylamino- and hydroxy groups. The same effect was observed for 2 in solutions in CCl4 under addition of polar HMPA or DMSO during spontaneous E ⇌ Z isomerization. For enaminoketone 1 under similar conditions we observed reverse process of Z ⇌ E isomerization, E stereoisomeric forms with hydroxy group being trace quantity only.Study of solvent influence on FTIR spectra revealed that introduction of methyl group as substituent at α-position of vinyl moiety increases electron population of CO double bond. Consequently, in contrast with enaminoketone 1 where the main contribution to the ν˜ (CO) band shift to lower wavenumbers in all three stereoisomeric structures makes solvent polarity/polarizability term (π*), influence of solvent's hydrogen bond acceptor (HBA) basicity (β) on ν˜ (CO) band shift of 2 predominates in the E-s-Z-ap and Z-s-Z-ap isomers. Similarly to enaminoketone 1, negative shift of the ν˜ (CC) band to lower wavenumbers occurs due to hydrogen bond formation between π system of vinyl moiety and hydrogen bond donor solvents in all stereoisomeric forms of enaminoketone 2.

An insight into the gas-phase fragmentations of potential molecular sensors with porphyrin-chalcone structures

Porphyrin-chalcone derivatives with potential cation sensing ability have been studied by ESI-MS and multistage ESI-MS. The presence of conjugated CC and CO double bonds in the chalcone moiety is responsible for the formation of diagnostic fragment ions common to all the studied meta and para chalcones. The ortho isomers show different fragmentation patterns that can be explained by different electronic charge distributions.

Electronic states of alkali metal-NTCDA complexes: A DFT study

Structures and electronic states of organic–inorganic compound of 1,4,5,8-naphthalene-tetracarboxylic-dianhydride (NTCDA) with alkali metals, Mn(NTCDA) (MLi and Na, n = 0–2), have been investigated by means of hybrid density functional theory (DFT) calculations. From the DFT calculations, it was found that the electronic state of the complex at the ground state is characterized by a charge-transfer state expressed by (M)+(NTCDA)−. The alkali metals were bound equivalently to the carbonyl oxygen and ether oxygen atoms of NTCDA. The CO double bond character of NTCDA was changed to a C–O single bond like character by the strong interaction of M to the CO and O sites. This change was the origin of the red-shift of the IR spectrum. The UV–vis absorption spectra of Mn(NTCDA) were theoretically predicted on the basis of theoretical results.

Azo dicarboxylates are not conjugated: X-ray crystal structure and theoretical calculations on di-t-butylazodicarboxylate

The X-ray crystal structure of trans-di-t-butyl azodicarboxylate (DTBAD, 2) was determined and this revealed that the torsion angle between the NN and CO double bonds is 84.0(2)°, and that between the anti-disposed CO vectors is 180°. This is the first report of the solid state structure of an azodicarboxylate ester. The molecule was subjected to Density Functional Theory geometry optimization at the B3LYP/6-31G(d) level in cyclohexane medium, and the global minimum structure agreed in principle with that determined in the solid state by crystallography. The N–C(O) torsion angle in the optimized structure is 107.7°, and the CO vectors lie in an anti relationship. Similar calculations on the unknown cis-NN isomer revealed an optimum geometry whose energy is predicted to lie only 11.9 kJ/mol higher than that of the trans isomer. M062X/6-311+G(d) model chemistry was used to determine relative electronic energies and to conduct Natural Bond Orbital (NBO) calculations. Exploration of the energetics of rotations about the N–C(O) bonds revealed a clear preference for near-orthogonality in azodicarboxylates, and suggests almost complete absence of classical conjugation between the neighbouring π bonds. Electronic transitions were simulated using the time-dependent DFT (TD-DFT) approach at the B3LYP/6-311+G(d) level, and the weak band in the near-UV for 2 in cyclohexane was reproduced in the calculations. The electronic isolation of the NN bond may be important in the numerous applications of azodicarboxylates in organic synthesis, and the small energy difference between the trans and cis isomers implies the likely involvement of the latter in the successful photochemical diaza-Diels–Alder reaction of diethyl azodicarboxylate with 1,3-cyclohexadiene.

Conformational and spectroscopic study of xanthogen ethyl formates, ROC(S)SC(O)OCH2CH3. Isolation of CH3CH2OC(O)SH

ROC(S)SC(O)OCH2CH3, with R=CH3, (CH3)2CH and CH3(CH2)2, were obtained through the reaction between potassium xanthate salts, ROC(S)SK, and ethyl chloroformate, ClC(O)OCH2CH3. The liquid compounds were identified and characterized by 1H and 13C NMR and mass spectrometry. The conformations adopted by the molecules were studied by DFT methods. 6 conformers were theoretically predicted for R=CH3 and (CH3)2CH, while the conformational flexibility of the n-propyl substituent increases the total number of feasible rotamers to 21. For the three molecules, the conformers can be associated in 3 groups, being the most stable the AS forms – the CS double bond anti (A) with respect to the CS single bond and the SC single bond syn (S) with respect to the CO double bond – followed by AA and SS conformers. The vibrational spectra were interpreted in terms of the predicted conformational equilibrium, presenting the ν(CO) spectral region signals corresponding to the three groups of conformers. A moderated pre-resonance Raman enhancement of the ν(CS) vibrational mode of CH3(CH2)2OC(S)SC(O)OCH2CH3 was detected, when the excitation radiation approaches the energy of a n→π∗ electronic transition associated with the CS chromophore. UV–visible spectra in different solvents were measured and interpreted in terms of TD-DFT calculations. The unknown molecule CH3CH2OC(O)SH was isolated by the UV–visible photolysis of CH3OC(S)SC(O)OCH2CH3 isolated in Ar matrix, and also obtained as a side-product of the reaction between potassium xanthate salts, ROC(S)SK, and ethyl chloroformate, ClC(O)OCH2CH3.

A pyridyl-triazole ligand for ruthenium and iridium catalyzed C[dbnd]C and C[dbnd]O hydrogenations in water/organic solvent biphasic systems

The water soluble pyridyl-triazole ligand sodium 2-(1-((pyridin-2-yl)methyl)-1H-1,2,3-triazol-4-yl)ethyl sulfate (Na1) has been successfully employed in combination with ruthenium and iridium for catalytic hydrogenation of CC and CO double bonds in water/toluene biphasic systems. Reaction of the ligand with [RuCl2(η6-p-cymene)]2 affords the new water soluble complex [RuCl(η6-p-cymene)(1)] (2) which has been found to be catalytically active in the water/organic solvent biphasic hydrogenation using styrene and 2-cyclohexen-1-one as model substrates. Very conveniently, the iridium based catalytic system is prepared by simply stirring in water [Ir(η4-COD)Cl]2 with Na1 (Ir:Na1 molar ratio=1:4), the resulting solution is catalytically active and appears more efficient than 2. With both the Ru- and Ir-based systems the catalytically active aqueous phases can be used at least three times without loss of activity.

Structure‐Dependent Selective Hydrogenation of α,β‐Unsaturated Aldehydes over Platinum Nanocrystals Decorated with Nickel

AbstractThe shape sensitivity of monometallic Pt and bimetallic PtNi nanocrystals in α,β‐unsaturated aldehydes is studied by using a cubic shape enclosed by six {100} facets as well as an octahedral shape surrounded by eight {111} facets. Compared with monometallic Pt and bimetallic PtNi cubic/octahedral shapes, Pt3Ni cubes enhanced the selective hydrogenation of the CO double bond and suppressed the selective hydrogenation of the CC double bond of the α,β‐unsaturated aldehyde. The Pt, Pt3Ni, or PtNi octahedral shape is an unfavorable structure for CO hydrogenation and enables the activation of the whole conjugated system of the molecule, which leads to complete hydrogenation to form the saturated alcohol product. The synergistic effects of the surface structure and electronic properties of Pt or PtNi nanocrystals play a key role in controlling the selective hydrogenation of CC and CO bonds of α,β‐unsaturated aldehydes.

The role of substituents in the molecular and crystal structure of 1-(adamantane-1-carbonyl)-3-(mono)- and 3,3-(di) substituted thioureas

Three novel 1-(adamantane-1-carbonyl) thioureas were synthesized by the reaction of adamantyl isothiocyante with corresponding amines and fully characterized by spectroscopy methods. Two isomeric species, i.e. 1-(adamantane-1-carbonyl)-3-(3-nitrophenyl)thiourea (1) and 1-(adamantane-1-carbonyl)-3-(4-nitrophenyl)thiourea (2), are structurally characterized and a third related compound, namely 1-(adamantane-1-carbonyl)-3,3-(methyl-phenyl)thiourea (3) has been also included for assessing the role of the nitrogen substitution on the structural properties. As determined by X-ray analysis, compounds 1 and 2 exhibit the S conformation with the CO and CS double bonds in a pseudo-antiperiplanar orientation, whereas the U form is found for compound 3. These conformational features are mainly dictated by the substitution degree on the thiourea core and the ability of forming an intra-molecular NH⋯OC hydrogen bond for mono-substituted analogues 1 and 2. These dissimilar interactions affect the vibrational properties, which have been determined by infrared and Raman spectroscopies and quantum chemical calculations at the B3LYP/6-311++G** level of approximation.

Synthesis, spectroscopic characterization and theoretical calculations of ClF2CC(O)N[dbnd]PCl3 ([chloro(difluor)acetyl]phosphorimidic trichloride)

The synthesis of [chloro(difluor)acetyl]phosphorimidic trichloride (ClF2CC(O)NPCl3), together with a tentative assignment of the vibrational, NMR and mass spectra, are reported. Quantum chemical calculations (MP2 and B3LYP methods with 6-311+G(d) and 6-311+G(2df,p) basis sets) predict three stable conformers in the gas phase (syn, gauche and anti, defined according to the rotation around both the ClCCN and the CCNP dihedral angles). However, only a single C1 symmetry conformer is observed in the liquid phase, possessing the CO double bond in synperiplanar orientation with respect to the PN double bond, and the ClC bond distorted from the plane defined by the CC(O)NP entity. A Natural Bond Orbital (NBO) analysis was carried out for the title compound and related molecules in order to provide an explanation about the electronic properties.

Theoretical study on thermal decomposition kinetics of allyl formates in the gas phase

The study of the kinetics and mechanisms of the gas-phase thermal decarboxylation of allyl formate and 2-methylallyl formate was carried out by means of electronic structure calculations using Density Functional Theory (DFT) functionals: B3LYP, B3PW91, MPW1PW91 and PBEPBE. Two possible molecular mechanisms were investigated: a concerted [1,5] hydrogen shift through a six-centered cyclic transition state, and a [1,3] hydrogen shift mechanism through a four-centered cyclic transition state. Calculation results suggest these reactions to be unimolecular and proceed in a concerted mechanism through a six-membered cyclic transition state (TS) geometry. Despite the similar activation energies, differences were found when comparing the two elimination processes. In the case of allyl formate, the reaction shows small predominance of the change in the terminal allyl moiety bond order and the COester bond breaking. Conversely, for 2-methylallyl formate, the process is highly controlled by the new CO double bond development leading to carbon dioxide formation. Moreover, in the 2-methylallyl formate decomposition, the α-carbonyl hydrogen transfer to the terminal allyl carbon to produce 2-methyl propene is at a very early stage in the TS compared to allyl formate.

Selective reductions using visible light photocatalysts of supported gold nanoparticles

Photocatalytic synthesis using visible light is a desirable chemical process because of its potential to utilize sunlight. Supported gold nanoparticles (Au-NPs) were found to be efficient photocatalysts and the effects of the supports were identified including CeO2, TiO2, ZrO2, Al2O3, and zeolite Y. In particular Au/CeO2 exhibited the high catalytic activity to reduce nitro-aromatics to azo compounds, hydrogenate azobenzene to hydroazobenzene, reduce ketones to alcohols, and deoxygenate epoxides to alkenes at ambient temperatures, under irradiation of visible light (or simulated sunlight). The reactive efficiency depends on two primary factors: one is the light adsorption of catalysts and the other is the driving ability of catalysts corresponding to the reactants. The light absorption by Au-NPs is due to the surface plasmon resonance effect or interband electron transition; this is related to the reduction ability of the photocatalysts. Irradiation with shorter wavelengths can excite the conduction electrons in Au-NPs to higher energy levels and, as a result, induce reduction with more negative reduction potentials. It is known that when irradiated with light the Au-NPs can abstract hydrogen from isopropanol forming Au–H species on the Au-NP surface. Hence, we proposed that the active Au–H species will react with the NO, NN, CO double bonds or epoxide bonds, which are weakened by the interaction with the excited electrons in the Au-NPs, and yield the final reductive products. The reacting power of the Au–H species depends on the energy of the excited electrons in Au-NPs: the higher the electronic energy, the stronger the reduction ability of the Au–H species. This finding demonstrates that we can tune the reduction ability of the photocatalysts by manipulating the irradiation wavelength.

Planar integrated plasmonic mid-IR spectrometer

ABSTRACTA compact spectrometer-on-a-chip featuring a plasmonic molecular interaction region has been conceived, designed, modeled, and partially fabricated. The silicon-on-insulator (SOI) system is the chosen platform for the integration. The low loss of both silicon and SiO2 between 3 and 4 μm wavelengths enables silicon waveguides on SiO2 as the basis for molecular sensors at these wavelengths. Important characteristic molecular vibrations occur in this range, namely the bond stretching modes C-H (Alkynes), O-H (monomeric alcohols, phenols) and N-H (Amines), as well as CO double bonds, NH2, and CN. The device consists of a broad-band infrared LED, photonic waveguides, photon-to-plasmon transformers, a molecular interaction region, dispersive structures, and detectors. Photonic waveguide modes are adiabatically converted into SPPs on a neighboring metal surface by a tapered waveguide. The plasmonic interaction region enhances optical intensity, which allows a reduction of the overall device size without a reduction of the interaction length, in comparison to ordinary optical methods. After the SPPs propagate through the interaction region, they are converted back into photonic waveguide modes by a second taper. The dispersing region consists of a series of micro-ring resonators with photodetectors coupled to each resonator. Design parameters were optimized via electro-dynamic simulations. Fabrication was performed using a combination of photo- and electron-beam-lithography together with standard silicon processing techniques.

Copper-catalysed addition of α-alkyl azaarenes to ethyl glyoxylate via direct C(sp3)–H activation

A novel protocol for the copper-catalysed direct C(sp3)–H bond functionalisation of 2-alkyl azaarenes to CO double bonds has been developed, which expands the scope of C(sp3)–H bond activation reactions and provides new access to medicinally important azaarene derivatives.

Methoxycarbonyl trifluoromethyl disulfide, CH3OC(O)SSCF3: synthesis, structure and conformational properties

Pure methoxycarbonyl trifluoromethyl disulfide, CH3OC(O)SSCF3, has been prepared quantitatively by the reaction of CH3OC(O)SCl and Hg(SCF3)2. The conformational properties of the novel molecule have been studied by vibrational spectroscopy [IR(gas) and Raman(liquid)] and quantum chemical calculations (B3LYP and MP2 methods). The gaseous compound exhibits a conformational equilibrium at room temperature where the most stable form has C1 symmetry with a synperiplanar (syn) orientation of the CO double bond with respect to the S–S disulfide bond. A second form is observed in the gaseous IR spectra corresponding to a conformer with the carbonyl bond CO in antiperiplanar (anti) position with respect to the S–S single bond. The structure of a single crystal of CH3OC(O)SSCF3 has been determined by X-ray diffraction analysis at low temperature using a miniature zone melting procedure. The crystalline solid (triclinic, P, a = 6.4698(5) A, b = 9.0499(8) A, c = 12.5700(11) A, α = 97.219(6)°, β = 93.131(5)°, γ = 96.888(5)° and Z = 4) consists exclusively of molecules with the synperiplanar conformation and the usual gauche orientation around the disulfide bond [ϕ(CS–SC) = 91.06(15)°] is adopted. The geometrical parameters agree with those obtained from quantum chemical calculations.

Effect of Electronic Factor in Ru‐phosphine‐diamine Complexes on Selective Hydrogenation of CC and CO Bonds

AbstractA series of ruthenium complexes bearing different phosphines and diamines were synthesized and their components and structures were characterized by NMR spectra and elemental analyses. The catalytic properties of these complexes for the hydrogenation of benzylideneacetone and the mixture of acetophenone and styrene were investigated. The results showed that the basicity increase of phosphine or diamine dramatically facilitates the hydrogenation activity and selectivity to CO double bond. On the contrary, the basicity decrease of phosphine or diamine not only slows down the catalytic activity, but also significantly suppresses the hydrogenation selectivity to CO double bond. Based on the effect of electron factors of these complexes on the hydrogenation activity and selectivity of benzylideneacetone and the mixture of styrene and acetophenone, the activation mechanism of dihydrogen in ruthenium‐phosphine‐diamine system was proposed.

Experimental and Theoretical Analysis of Asymmetric Induction in Heterogeneous Catalysis: Diastereoselective Hydrogenation of Chiral α-Hydroxyketones over Pt Catalyst

Assessing the origin of asymmetric induction in heterogeneously catalyzed hydrogenation is a challenging task. In this work, hydrogenation of a chiral compound, (R)-1-hydroxy-1-phenyl-2-propanone [(R)-PAC], in toluene over cinchonidine modified and unmodified Pt/Al(2)O(3) was studied. To reveal the detailed reaction mechanism and the origin of stereoselectivity in the Pt-catalyzed hydrogenation of the CO double bond, the structures and energies of several adsorption modes of (R)-PAC as well as whole reaction paths for hydrogenation were investigated on Pt(111) by density functional theory (DFT). In agreement with experimental results, the theoretically obtained potential energy profiles for the studied hydrogenation mechanisms implied that (1R,2S)-1-phenyl-1,2-propanediol is formed in excess with respect to the other diastereomeric product diol, (1R,2R)-1-phenyl-1,2-propanediol. Generally, if the elementary hydrogen addition step was thermodynamically more favorable on one of the two diastereotopic faces, it was also kinetically preferred on the same face, and vice versa. Pairwise addition of hydrogen was the most energetically favorable mechanism. Adsorption and hydrogenation of other structurally similar chiral alpha-hydroxyketones, (R)-3-hydroxy-2-butanone and (R)-2-hydroxy-1-cyclohexanone, were also studied computationally on Pt(111). The results showed that cluster model DFT calculations can be used to assess (dia)stereoselectivity in metal-catalyzed hydrogenation of even such complex organic molecules as studied here.