WS_2/WO_3光催化选择性氧化苯甲醇制备苯甲醛

采用H2S高温硫化WO3的方法制备了一系列WS2/WO3光催化剂,利用X射线粉末衍射仪、紫外可见光谱仪分析了产物的结构及光吸收性能,考察了WS2/WO3光催化剂光催化选择性氧化苯甲醇制备苯甲醛的性能,讨论了WS2的含量、反应时间、反应液pH对光催化选择性氧化反应过程的影响.结果表明:与WO3和经深度硫化的WO3相比,适当的硫化能显著改善催化剂对苯甲醇的选择性氧化行为,反应时间及pH对苯甲醇的转化率及生成苯甲醛的选择性均有重要影响.     

非均相Schiff碱配合物上苯甲醇的选择性氧化：制备条件对其结构和催化性能的影响

以常见的非均相Schiff碱配合物Cr（salten）-MCM-41（salten：N,N-双水杨醛缩二乙烯三胺）的制备过程为例,考察了均相配合物制备过程中金属盐的种类、配位体系的pH值及固载过程中的偶联剂用量对所制备的非均相配合物的结构和催化性能的影响.结果表明,由阴离子配位能力较弱的氯化物和硝酸盐提供金属中心,保持...     

Selective hydrogenation of o-xylene on noble metals: Thermal effect in selectivity

Selective hydrogenation of o-xylene on silica supported noble metals Pd, Rh, Ni, Pt, Ir, Ru, Os and Re has been studied. A correlation between the heat capacity of the metal conduction electrons and the selectivity towards the cis-product was found. Thermal effect in activity and selectivity is reported.

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- Pd, Rh, Ni, Pt, Ir, Ru, Os Re, Al₂O₃. -. .

     

Extension of the benzyl alcohol route to metal sulfides: "nonhydrolytic" thio sol-gel synthesis of ZnS and SnS2

Crystalline ZnS and SnS(2) particles were synthesized by a modified benzyl alcohol route using benzyl mercaptan as solvent.     

Selective hydrogenation of carbonyl group ofα,β-unsatueated aldehydes in the presence of iridium catalyst

Conclusions ,-Unsaturated aldehydes (furylacrolein, crotonaldehyde, cinnamaldehyde, citral) are quantitatively hydrogenated to the corresponding unsaturated alcohols in the presence of iridium catalyst. The hydrogenation of acrolein gives a mixture of products, containing mainly allyl alcohol.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 1993–1998, September 1972.     

Selective attachment of benzaldehyde on Si(100)-2 x 1: structure, selectivity, and mechanism

The interaction of benzaldehyde with the Si(100) surface has been investigated as a model system for understanding the interaction of conjugated pi-electron systems with semiconductor surfaces. Vibrational features of chemisorbed benzaldehyde unambiguously demonstrate that the carbonyl group directly interacts with the Si surface dangling bonds, evidenced in the disappearance of the C=O stretching mode around 1713 cm(-1) coupled with the retention of all vibrational signatures of its phenyl ring. X-ray photoemission spectroscopy shows that both C 1s and O 1s binding energies of the carbonyl group display large downshifts by 1.9 and 1.3 eV, respectively. Vibrational and electronic results show that the covalent attachment of benzaldehyde on Si(100) occurs in a highly selective manner through the direct interaction of both C and O atoms of the carbonyl group with a Si=Si dimer to form a four-membered Si-C-O-Si ring at the interface, leaving a nearly unperturbed phenyl ring protruding into vacuum. This conclusion is further confirmed by the observation of a predominant protrusion for benzaldehyde adsorbed on Si(100)-2 x 1 in scanning tunneling microscopy experiments, consistent with the predication of density-functional theory calculation.     

气相色谱-四极杆高分辨飞行时间质谱分析复杂芳烃体系中的苯甲醛、苯甲醇、苯乙酮与苯乙醛

建立了气相色谱-四极杆高分辨飞行时间串联质谱分析复杂芳烃体系样品中苯甲醛、苯甲醇、苯乙酮与苯乙醛的方法。该方法通过使用高分辨质谱得到目标化合物特征离子的精确质量数,结合色谱保留时间,有效排除了复杂芳烃体系样品本底中碎片离子的干扰,提高了定性与定量分析的准确性。使用目标化合物特征离子的质谱峰面积作为定量计算依据。苯甲醛、苯甲醇、苯乙酮与苯乙醛在各自的质量浓度范围内呈现良好的线性响应,回收率为87.97%~103.01%,定量限分别为0.04、0.10、0.08与0.03 mg/L,检出限分别为0.01、0.03、0.02与0.01 mg/L。对3份实际样品中的苯甲醛、苯甲醇、苯乙酮与苯乙醛进行了定量分析。本研究为气相色谱-四极杆高分辨飞行时间质谱技术应用于复杂体系中的微量杂质分析提供了一种新的思路和手段。通过精确的质量分辨和测定可以降低对色谱分离的依赖,弥补传统气相色谱-四极杆低分辨质谱技术的不足。     

Theoretical studies on the mechanism of α-hydroxy-acid gas-phase elimination process and its substituent effect

The α-hydroxy-acid gas-phase elimination process has been studied theoretically by HF/3-21G.The calculated results can be summed up as follows:(1) The elimination process is a stepwise reaction.In the first step,a 3-membered ring intermediate is formed via a 5-membered ring transition state;while the product is formed in the second step via a 3-membered ring transition state.(2) The obtained results of the substituent effect show that the increase of electronic donation of the alkyl groups is favorable for the reaction.Other substituents which show the electron-withdrawing inductive effect (e.g.-Cl,-CN,-CF3) are unfavorable for this process.     

Investigation of the catalytic activity of metal complexes fixed on a solid support. 10. Selective hydrogenation of allylbenzene in the presence of heterogeneous Pt-Sn-citrate complexes

New heterogeneous catalysts based on the complexes of platinum with tin(II) citrate were prepared. The catalysts exhibit high selectivity in the hydrogenation of allylbenzene to propylbenzene without increasing the rate of isomerization of the C=C bond. The activity of the complexes depends on the conditions and decreases with increase in the Sn:Pt ratio.N. D. Zelinskii Institute of Organic Chemistry, Russian Academy of Sciences, 117913 Moscow. St. Petersburg Technological Institute. Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 6, pp. 1287–1290, June, 1992.     

Chemiluminescence in model membrane structures. Chemiluminescence of lucigenin in the presence of Mg(OH)2 and benzyl alcohol. Temperature effects

The quantum yields of the lucigenin light reaction in didodecyldimethylammonium bromide (DDAB) are affected by the presence of Mg(OH)₂; a 35% increase is observed in lamellar and a 65% increase in vesicular aggregates. The system is insensitive to benzyl alcohol. The quantum yields inDDAB versus those in water, as a function of temperature show a slope change in the region of the phase transition in lamelar aggregates. This effect is far less pronounced in vesicular aggregates. In contrast to theDDAB aggregates, anionic sodium dimethyldidodecylphosphate (SDDP) sonicated aggregates are associated with lower quantum yields and no apparent slope change in the region of the phase transition.

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Chemilumineszenz in Modell-Membranstrukturen. Die Chemilumineszenz von Lucigenin in der Gegenwart von Mg(OH)₂ und Benzylalkohol. Temperatureffekte

Zusammenfassung Die Quantenausbeuten der Lichtreaktion von Lucigenin in Didodecyldimethylammoniumbromid (DDAB) werden durch die Gegenwart von Mg(OH)₂ beeinflußt. Es wird 35% Verstärkung in lamellaren und 65% Verstärkung in vesicularen Aggregaten beobachtet. Das System ist Benzylalkohol gegenüber unempflindlich. Eine Gegenüberstellung der Quantenausbeuten inDDAB bzw. in Wasser als eine Funktion der Temperatur zeigt eine Änderung des Anstiegs im Bereich des Phasenüberganges bei lamellaren Aggregaten. Dieser Effekt ist in vesicularen Aggregaten nicht so ausgeprägt. Im Gegensatz zu denDDAB-Aggregaten sind die beschallten anionischen Natriumdimethyldodecylphosphat (SDDP)-Aggregate durch geringere Quantenausbeuten und keine offensichtlichen Anstiegsänderungen im Bereich des Phasenüberganges gekennzeichnet.

     

2 + 3] cycloaddition of nitrones to platinum-bound organonitriles: effect of metal oxidation state and of nitrile substituent

The ligated benzonitriles in the platinum(II) complex [PtCl2(PhCN)2] undergo metal-mediated [2 + 3] cycloaddition with nitrones -ON+(R3)=C(R1)(R2) [R1/R2/R3 = H/Ph/Me, H/p-MeC6H4/Me, H/Ph/CH2Ph] to give delta 4-1,2,4-oxadiazoline complexes, [PtCl2(N=C(Ph)O-N(R3)-C(R1)(R2))2] (2a, 4a, 6a), as a 1:1 mixture of two diastereoisomers, in 60-75% yields, while [PtCl2(MeCN)2] is inactive toward the addition. However, a strong activation of acetonitrile was reached by application of the platinum(IV) complex [PtCl4(MeCN)2] and both [PtCl4(RCN)2] (R = Me, Ph) react smoothly with various nitrones to give [PtCl4(N=C(R)O-N(R3)-C(R1)(R2))2] (1b-6b). The latter were reduced to the corresponding platinum(II) complexes [PtCl2(N=C(R)O-N(R3)-C(R1)(R2))2] (1a-6a) by treatment with PhCH2NHOH, while the reverse reaction, i.e. conversion of 1a-6a to 1b-6b, was achieved by chlorination with Cl2. The diastereoisomers of [PtCl2(N=C(R)O-N(R3)-C(R1)(R2))2] (1a-6a) exhibit different kinetic labilities, and liberation of the delta 4-1,2,4-oxadiazolines by substitution with 1,2-bis(diphenylphosphino)ethane (dppe) in CDCl3 proceeds at different reaction rates to give free N=C(R)O-N(R3)-C(R1)(R2) and [PtCl2(dppe)] in almost quantitative NMR yield. All prepared compounds were characterized by elemental analyses, FAB mass spectrometry, and IR and 1H, 13C(1H), and 195Pt (metal complexes) NMR spectroscopies; X-ray structure determination of the first (delta 4-1,2,4-oxadiazoline)Pt(II) complexes was performed for (S,S)/(R,R)-rac-[PtCl2(N=C(Me)O-N(Me)-C(H)Ph)2] (1a) (a = 9.3562(4), b = 9.8046(3), c = 13.1146(5) A; alpha = 76.155(2), beta = 83.421(2), gamma = 73.285(2) degrees; V = 1117.39(7) A3; triclinic, P1, Z = 2), (R,S)-meso-[PtCl2(N=C(Ph)O-N(Me)-C(H)Ph)2] (2a) (a = 8.9689(9), b = 9.1365(5), c = 10.1846(10) A; alpha = 64.328(6), beta = 72.532(4), gamma = 67.744(6) degrees; V = 686.82(11) A3; triclinic, P1, Z = 1), (S,S)/(R,R)-rac-[PtCl2(N=C(Me)O-N(Me)-C(H)(p-C6H4Me))2] (3a) (a = 11.6378(2), b = 19.0767(7), c = 11.5782(4) A; beta = 111.062(2) degrees; V = 2398.76(13) A3; monoclinic, P2(1)/c, Z = 4), and (S,S)/(R,R)-rac-[PtCl2(N=C(Me)O-N(CH2Ph)-C(H)Ph2] (5a) (a = 10.664(2), b = 10.879(2), c = 14.388(3) A; alpha = 73.11(3), beta = 78.30(3), gamma = 88.88(3) degrees; V = 1562.6(6) A3; triclinic, P1, Z = 2).     

The alpha-effect in gas-phase SN2 reactions: existence and the origin of the effect

The origin of enhanced reactivity of alpha-nucleophiles in SN2 reactions was examined on the basis of computational results at the high level G2(+) method for 22 gas-phase reactions: Nu- + RCl --> RNu + Cl- [R = Et and i-Pr; Nu- = HO-, CH3O-, HS-, Cl-, Br-, NH2O-, HOO-, FO-, HSO-, ClO-, and BrO-]. The results clearly indicate the existence of the alpha-effect, whose size varies depending on the R group and the identity of the alpha-atom. The alpha-effect is larger for i-PrCl than EtCl, and for an alpha-nucleophile with a harder alpha-atom. Analyses of the present results, together with previously reported ones for MeF and MeCl reactions, reveal that several rationales so far presented to explain the alpha-effect, such as thermodynamic product stability, transition state (TS) tightness, electrostatic interaction, ET rationale, and polarizability, cannot explain the observed size of the alpha-effect. The importance of deformation energy on going from the reactant to the TS is presented.     

Selective oxidation of benzyl alcohol to benzaldehyde, 1‐phenylethanol to acetophenone and fluorene to fluorenol catalysed by iron (II) complexes supported by pincer‐type ligands: Studies on rapid degradation of organic dyes

Hexacoordinated non‐heme iron complexes [Fe^II(L¹)₂](ClO₄)₂ ( 1 ) and [Fe^II(L²)₂](PF₆)₂ ( 2 ) have been synthesized using ligands L¹ = (E)‐2‐chloro‐6‐(2‐(pyridin‐2ylmethylene) hydrazinyl)pyridine and L² = (E)‐2‐chloro‐6‐(2‐(1‐(pyridin‐2‐yl)ethylidene)hydrazinyl) pyridine]. These complexes are highly active non‐heme iron catalysts to catalyze the C (sp³)?H bonds of alkanes. These iron complexes have been characterized using ESI?MS analysis and molecular structures were determined by X‐ray crystallography. ESI ? MS analysis also helped to understand the generation of intermediate species like Fe^III?OOH and Fe^IV=O. DFT and TD?DFT calculations revealed that the oxidation reactions were performed through high‐valent iron center and a probable reaction mechanism was proposed. These complexes were also utilized for the degradation of orange II and methylene blue dyes.     

Morphology effect of ZnO support on the performance of Cu toward methanol production from CO2 hydrogenation

Recently, the chemical conversion of the greenhouse gas CO₂ into value-added methanol has been of great interest. To address this issue, ZnO nanorods were synthesized by a facile microwave assisted technique and selected as support in Cu/ZnO catalyst. Herein, structure-activity relationship of the as-prepared catalysts in CO₂ hydrogenation to methanol were elucidated in detail using different characterization technique including N₂ physisorption, XRD, TPR, TEM, XPS and insitu DRIFTS (CO chemisorption) etc. Interestingly, rodlike ZnO hosted the highly dispersed Cu species, stronger Cu-support interaction at the interface in comparison with another reference CuZn-C sample, which was supported on commercial ZnO. In particular, EPR and XPS analysis evidenced the direct electron transfer from ZnO support to Cu species in CuZn-R, thereby facilitating the formation of O vacancies. These positive factors could provide the extremely active sites for CO₂ hydrogenation and be correlated to the better catalytic activity. Indeed, the calculated TOF_methanol for CuZn-R was approximately ten times larger than that of CuZn-C sample. The results implied that the morphology structure of ZnO support, which could induce various crystal planes and amounts of defects and/or imperfections, possessed a critical role on the catalytic performance. This finding might shed light on the design of efficient catalysts for catalytic conversion of the undesirable CO₂.     

Selective removal of a benzyl protecting group in the presence of an aryl chloride under gaseous and transfer hydrogenolysis conditions

Selective removal of a benzyl protecting group in the presence of an aryl chloride using Pd/C under gaseous and transfer hydrogenolysis conditions is described. The addition of chloride salts to the debenzylation reaction provides excellent selectivity.