Synthesis of Novel Glycidol Copolymers with Pendant Alkene and Hydroxyl Groups

A series of linear poly glycidol copolymers, tethering with both alkene and hydroxyl groups, were prepared by a combination of anionic ring-opening polymerization （ROP） using specific reactions of ethoxy ethyl glycidyl ether （EEGE） and allyl glycidyl ether （AGE） firstly, and subsequently removal of the protection group of glycidol in EEGE to achieve the linear copolymer pendant with both hydroxyl groups and double bonds. The EEGE/AGE monomer reactivity ratio is measured to be 3.30/1.13. The chemical compositions of the as-synthesized polymers were characterized by tH NMR and GPC, and the glass transition temperatures （Tg） of as-synthesized polymers were determined by DSC. The final copolymers have abundant double bonds and hydroxyl as side groups. Furthermore, the ratio of the double bonds to hydroxyl groups can be controlled by the ratio of the starting materials in a wide range.     

利用脱镁叶绿酸甲酯的化学修饰合成红紫素酰亚胺衍生物

A series of novel purpurin-18 imide derivatives exhibiting long wavelength absorption and amphiphilicity wereobtained from methyl pheophorbide-a(MPa)by modification of the peripheral functional groups.The vinyl groupat 3-position was oxidized with OsO_4 and NaIO_4 to form the formyl group and the Grignard reaction of this alde-hyde with the alkyl magnesium bromide was carried out to give the corresponding 3-(1-hydroxylalkyl)pheophor-bide-a.The E-ring of these chlorines was converted into anhydride ring to give purpurin derivatives by air oxidation.The trans-3~2-alkyl purpurin derivatives were obtained by dehydration of hydroxyl group at 3~1-position.TheN-hydroxyl purpurin imide was generated by treatment of the anhydride ring with bydroxylamine hydrochloride.The 3~1-alkylacyl-N-hydroxyl purpurin imides were obtained by oxidation of hydroxyl group at 3~1-position.Theacylation of N-hydroxyl group was completed to afford N-acyloxy purpurin imides.The photocytoxicity of severalcompounds in vitro were tested.     

A novel direct synthesis of polyol from soybean oil

As the oil crisis and environment concerning deepen,the uses of renewable resources have attracted considerable attention.Polyol intended for synthesis of polyurethane polymers was prepared by a novel direct hydroxylation of soybean oil,alternative to petroleumbased process.The transformation can afford soybean oil polyol in excellent yield with a hydroxyl number up to 467.7 mg KOH/g in the presence of OsO 4 as catalyst and NMO as oxidant.The major advantages of this approach are:two hydroxyl groups can be readily added to one double bond,replacing conventional two-step methods by an epoxidation step and then a ring opening step;a wide range of hydroxyl numbers can be obtained via varying catalyst loadings;the reaction can be performed at room temperature.The chemical structure of the polyol prepared was further characterized by chemical methods(hydroxyl number and iodine number) and spectra(1 H NMR and FTIR spectroscopy),which confirmed the cleavage of the double bonds and the produce of hydroxyl groups.     

S掺杂纳米多孔碳的光催化活性:表面化学和孔隙率的重要性(英文)

This minireview summarizes our recent findings on the photoactivity of S-doped nanoporous carbons. The materials were either synthesized from the sulfur-containing polymers or obtained by heat treatment of commercial carbon with hydrogen sulfide. Their surface was extensively charac terized from the points of view of its surface chemistry, porosity, morphology, and electronic properties. The carbons showed enhanced activity towards oxidation of arsine and removal of diben-zothiophenes from model diesel fuel. The latter were oxidized to various oxygen containing intermediates and the cleavage of C–C bonds in aromatic ring was detected when carbon with adsorbed species was exposed to UV or visible light. Irradiation resulted in generation of photocurrent in a broad range of wavelength. The presence of sulfur led to the reduction of oxygen and contributed to an increased capacitive performance. We link these effects to the presence of reduced sulfur in the small pores which enhances the dispersive interactions via inducing a positive charge to carbon atoms, to sulfur in oxygenated forms which contribute to Faradaic reactions and increase the polar interactions, and to the hydrophobicity of a surface in small pores where oxygen can be reduced by excited electrons from chromophoric-like sulfur containing groups.     

CeAlPO-5分子筛催化剂上二苯基甲烷选择性氧化生成二苯甲酮(英文)

Selective oxidation of diphenylmethane to benzophenone requires active and selective catalysts. The framework incorporation of cerium in AlPO-5 molecular sieves creates active cerium sites in isolation. These active sites are responsible for selective oxidation. Cerium incorporated AlPO-5 with different Al/Ce ratios were synthesized, and the vapor phase oxidation of diphenylmethane in air over these catalysts was studied at 250, 275, 300, 325, and 350 °C. The diphenylmethane conversion and selectivity for benzophenone were more than 90%. CeAlPO-5(25) was found to be more active than other catalysts. The stability of the catalyst was verified by the time on stream study which indicated steady diphenylmethane conversion and benzophenone selectivity. Hence framework incorporated CeAlPO-5 molecular sieves are stable and active catalysts for the selective oxidation of diphenylmethane.     

Bonding of Hydroxyl and Epoxy Groups on Graphene： Insights from Density Functional Calculations

Density functional theory and GGA-PW91 exchange correlation function were performed to simulate the bonding behavior of hydroxyl and epoxy groups on the graphene surface. We compared the different binding energies for two epoxy groups, as well as one hydroxyl group and one epoxy group on all possible positions within a 6-fold ring, respectively. The calculated results suggest that two oxygen-containing groups always tend to bind with the neighboring carbon atoms at the opposite sides. Moreover, two hydroxyl groups on the meta position are unstable, and one of the hydroxyl groups easily migrates to the para position. In contrast to the disperse arrangement, the aggregation of multiply hydroxyl groups largely enhances the binding energy of every hydroxyl group. It is worth noting that the binding sites and hydrogen bonds play an important role in stability. Our work further points out the number of oxygen-containing groups and the location of oxide region largely influence the electronic properties of graphene oxide.     

In situ chemical oxidation of aniline by persulfate with iron(Ⅱ) activation at ambient temperature

<正>The kinetics of aniline degradation by persulfate processes with iron(Ⅱ) activation at ambient temperature was investigated in this study.With iron(Ⅱ) as initiator,the oxidation reactions were found to follow a biphasic rate phenomenon:a rapid transformation followed by a slow but sustained oxidation process.In the first 30 s,the reaction mainly relies on the persulfate-Fe~(2+) reaction in which aniline is oxidized rapidly.After 30 s,the aniline was still oxidized but the rate of reaction tended to be slower and the rates were clearly linear-proportional.After the initial fast oxidation,the reactions appeared to follow a pseudo-first-order model.     

Selective Oxidation of Propane by Lattice Oxygen of Vanadium-Phosphorous Oxide in a Pulse Reactor

Selective oxidation of propane by lattice oxygen of vanadium-phosphorus oxide (VPO) catalysts was investigated with a pulse reactor in which the oxidation of propane and the re-oxidation of catalyst were implemented alternately in the presence of water vapor. The principal products are acrylic acid (AA),acetic acid (HAc), and carbon oxides. In addition, small amounts of C1 and C2 hydrocarbons were also found, molar ratio of AA to HAc is 1.4-2.2. The active oxygen species are those adsorbed on catalyst surface firmly and/or bound to catalyst lattice, i.e. lattice oxygen; the selective oxidation of propane on VPO catalysts can be carried out in a circulating fluidized bed (CFB) riser reactor. For propane oxidation over VPO catalysts, the effects of reaction temperature in a pulse reactor were found almost the same as in a steady-state flow reactor. That is, as the reaction temperature increases, propane conversion and the amount of C1 C2 hydrocarbons in the product increase steadily, while selectivity to acrylic acid and to acetic acid increase prior to 350℃ then begin to drop at temperatures higher than 350℃, and yields of acrylic acid and of acetic acid attained maximum at about 400℃. The maximum yields of acrylic acid and of acetic acid for a single-pass are 7.50% and 4.59% respectively, with 38.2% propane conversion. When theamount of propane pulsed decreases or the amount of catalyst loaded increases, the conversion increases but the selectivity decreases. Increasing the flow rate of carrier gases causes the conversion pass through a minimum but selectivity and yields pass through a maximum. In a fixed bed reactor, it is hard to obtainhigh selectivity at a high reaction conversion due to the further degradation of acrylic acid and acetic acid even though propane was oxidized by the lattice oxygen. The catalytic performance can be improved inthe presence of excess propane. Propylene can be oxidized by lattice oxygen of VPO catalyst at 250℃, nevertheless, selectivity to AA and to HAc are even lower, much more acetic acid was produced (molar ratio of AA to HAc is 0.19:1-0.83:1) though the oxidation products are the same as from propane.     

INFLUENCE OF SURFACE ACIDITY ON THE CATALYTIC PERFORMANCE IN OLIFIN OXIDATION OVER MO-Te BASED MIXED OXIDES

Partial oxidation of propylene and isobutene was performed over avariety of Mo-Te based mixed oxides.Results indicated that catalytic behaviorfor propylene and isobutene was different over the same catalyst.The differ-ence depended on surface acid-base properties of the catalyst.The relation ofsurface acidity to activity/selectivity can be explained on the basis of mecha-nism of oxidation over mixed oxide catalyst.     

Theoretical Investigation on the Relationship between the Structures and Antioxidant Activities of Myricetin and Dihydromyricetin

The geometry of myricetin and dihydromyricetin was optimized by DMol3 program based on DFT. The optimized structures have been proved to be stable by real frequencies obtained.The parameters of geometry optimization,vibration frequencies,atomic charges,thermodynamics,Fukui functions,and frontier molecular orbital had been obtained. The thermodynamic properties of 2 molecules were fitted and the relationship between the thermodynamic function and temperature was obtained. The correlation coefficient of the obtained equations is larger than 0.99,indicating that the function is approximately linear in the whole temperature range. The calculated results showed the O–H molecular structures were the main group affecting the antioxidant activity and the oxygen in the benzene ring is the electrophilic reaction site. Ortho-OH on the benzene formed intramolecular hydrogen bonds,which contributed to the stability of the benzene ring. It may be the active site for the occurrence of the reaction.     

Kinetics and products of the reactions of ozone with toluene and its derivatives in acetic anhydride

The reactions of ozone with toluene and its derivatives in acetic anhydride were studied. It was found that competing parallel reactions of ozone with the aromatic ring and substituents occurred in the ozone-arene-acetic anhydride system. The ratio between these reaction paths depended on the arene structure and reaction conditions. The selectivity of the oxidation of toluene and its derivatives at the methyl group varied from 0 to 40%. The fraction of aromatic products decreased as the number of methyl groups at the ring was increased. Tri- and tetramethylbenzenes were oxidized only at the aromatic ring. The stability of an aromatic system increased upon the introduction of electron-acceptor substituents into the benzene ring. Aminotoluenes and hydroxytoluenes were oxidized with ozone mainly at the NH₂ and HO groups; however, as in the case of toluene, the aromatic ring and methyl group became the main directions upon their acylation. The oxidation of the methyl group in acetic anhydride in the presence of sulfuric acid was finished at the step of the formation of the acylated derivatives of benzyl alcohols and benzaldehydes, which are resistant to the action of ozone.     

Reactivity of Tyr–Leu and Leu–Tyr dipeptides: identification of oxidation products by liquid chromatography–tandem mass spectrometry

The exposure of peptides and proteins to reactive hydroxyl radicals results in covalent modifications of amino acid side‐chains and protein backbone. In this study we have investigated the oxidation the isomeric peptides tyrosine–leucine (YL) and leucine–tyrosine (LY), by the hydroxyl radical formed under Fenton reaction (Fe²⁺/H₂O₂). Through mass spectrometry (MS), high‐performance liquid chromatography (HPLC‐MS) and electrospray tandem mass spectrometry (HPLC‐MSⁿ) measurements, we have identified and characterized the oxidation products of these two dipeptides. This approach allowed observing and identifying a wide variety of oxidation products, including isomeric forms of the oxidized dipeptides. We detected oxidation products with 1, 2, 3 and 4 oxygen atoms for both peptides; however, oxidation products with 5 oxygen atoms were only present in LY. LY dipeptide oxidation leads to more isomers with 1 and 2 oxygen atoms than YL (3 vs 5 and 4 vs 5, respectively). Formation of the peroxy group occurred preferentially in the C‐terminal residue. We have also detected oxidation products with double bonds or keto groups, dimers (YL–YL and LY–LY) and other products as a result of cross‐linking. Both amino acids in the dipeptides were oxidized although the peptides showed different oxidation products. Also, amino acid residues have shown different oxidation products depending on the relative position on the dipeptide. Results suggest that amino acids in the C‐terminal position are more prone to oxidation. Copyright © 2009 John Wiley & Sons, Ltd.     

Predicting H2S Oxidative Dehydrogenation over Graphene Oxides from First Principles

Spin-polarized periodic density functional theory was performed to characterize H₂S adsorption and dissociation on graphene oxides (GO) surface. The comprehensive reaction network of H₂S oxidation with epoxy and hydroxyl groups of GO was discussed. It is shown that the reduction reaction is mainly governed by epoxide ring opening and hydroxyl hydrogenation which is initiated by H transfer from H₂S or its derivatives. Furthermore, the presence of another OH group at the opposite side relative to the adsorbed H₂S activates the oxygen group to facilitate epoxide ring opening and hydroxyl hydrogenation. For H₂S interaction with -O and -OH groups adsorption on each side of graphene, the pathway is a favorable reaction path by the introduction of intermediate states, the predicted energy barriers are 3.2 and 10.4 kcal/mol, respectively, the second H transfer is the rate-determining step in the whole reaction process. In addition, our calculations suggest that both epoxy and hydroxyl groups can enhance the binding of S to the C-C bonds and the effect of hydroxyl group is more local than that of the epoxy.     

Surface oxidation process of a diamond‐like carbon film analyzed by difference X‐ray photoelectron spectroscopy

Difference X‐ray photoelectron spectroscopy (D‐XPS) revealed the surface oxidation process of a diamond‐like carbon (DLC) film. Evaluation of surface functional groups on DLC solely by the C 1s spectrum is difficult because the spectrum is broad and has a secondary asymmetric lineshape. D‐XPS clarified the subtle but critical changes at the DLC surface caused by wet oxidation. The hydroxyl (C―OH) group was dominant at the oxidized surface. Further oxidized carbonyl (C?O) and carboxyl (including carboxylate) (COO) groups were also obtained; however, the oxidation of C?O to COO was suppressed to some extent because the reaction required C―C bond cleavage. Wet oxidation cleaved the aliphatic hydrogenated and non‐hydrogenated sp² carbon bonds (C―H sp² and C―C sp²) to create a pair of C―OH and hydrogenated sp³ carbon (C―H sp³) bonds. The reaction yield for C―H sp² was superior at the surface, suggesting that the DLC film was hydrogen rich at the surface. Oxidation of aromatic sp² rings or polycyclic aromatic hydrocarbons such as nanographite to phenols did not occur because of their resonance stabilization with electron delocalization. Non‐hydrogenated sp³ carbon (C―C sp³) bonds were not affected by oxidation, suggesting that these bonds are chemically inert. Copyright © 2014 John Wiley & Sons, Ltd.     

Heteronuclear NMR Spectroscopy as a Surface‐Selective Technique: A Unique Look at the Hydroxyl Groups of γ‐Alumina.

The surface hydroxyl groups of γ‐alumina dehydroxylated at 500 °C were studied by a combination of one‐ and two‐dimensional homo‐ and heteronuclear ¹H and ²⁷Al NMR spectroscopy at high magnetic field. In particular, by harnessing ¹H–²⁷Al dipolar interactions, a high selectivity was achieved in unveiling the topology of the alumina surface. The terminal versus bridging character of the hydroxyl groups observed in the ¹H magic‐angle spinning (MAS) NMR spectrum was demonstrated thanks to ¹H–²⁷Al RESPDOR (resonance‐echo saturation‐pulse double‐resonance). In a further step the hydroxyl groups were assigned to their aluminium neighbours thanks to a {¹H}‐²⁷Al dipolar heteronuclear multiple quantum correlation (D‐HMQC), which was used to establish a first coordination map. Then, in combination with ¹H–¹H double quantum (DQ) MAS, these elements helped to reveal intimate structural features of the surface hydroxyls. Finally, the nature of a peculiar reactive hydroxyl group was demonstrated following this methodology in the case of CO₂ reactivity with alumina.     

Catalytic Oxidative Deformylation of Polyethylene Glycols with the Participation of Molecular Oxygen

The kinetics of oxidation of diethylene glycol, triethylene glycol, and polyethylene glycols (PEGs) with molecular weights ranging from 400 to 2000 in the presence of Cu(II) ions and bases was studied. It was found that ethylene glycols can be oxidized by molecular oxygen in anhydrous media in a temperature range of 30–60°C at anomalouosly high rates which are higher than the rates of chain-radical PEG autoxidation by several orders of magnitude. Only terminal hydroxyl groups were subjected to oxidation. The reaction occurs with the cleavage of a C–C bond and results in the formation of formic acid and a PEG with the number of –(CH₂CH₂O)– groups lower than that in the parent compound by unity. The rate and selectivity of PEG oxidation were found to strongly depend on the molecular weight of the polymer; from diethylene glycol to PEG 2000, the specific rate of oxidation increased by a factor of 60 in terms of terminal hydroxyl groups. An oxidation mechanism was suggested, which involves the formation of ternary complexes [Cu²⁺···A^–···O₂], which undergo further degradation by a many-electron concerted mechanism to form formic acid and, probably, an unstable hemiacetal {RO–CH₂OH}. The rapid oxidative degradation of the latter leads to the formation of PEG with a lower molecular weight.     

烃基硅铜酸盐与2-芳基-2-环烯酮1,4-加成反应的立体选择性及2-取代- 3-硅基环烷酮的合成

研究了烷基苯基硅铜酸盐与2-环烯酮的1,4-加成反应的立体选择性, 并合成了一系列新的2-取代-3-硅基环烷酮. 结果表明, 在0 ℃下用饱和NH₄Cl溶液处理, 烷基苯基硅铜酸盐与2-芳基-2-环烯酮的1,4-加成反应的立体选择性不同程度地受芳基和环的大小影响, 得到顺、反两种产物; 并首次发现室温下用甲醇处理反应时, 其立体选择性不受或者很少受环大小、芳基的性质以及与硅原子相连的取代基的影响, 只得到反式产物. 芳基溴甲烷与由烷基苯基硅铜酸盐与2-环烯酮1,4-加成所得的烯醇盐反应时, 只得到反式产物. 合成产物的结构用IR, ¹H NMR, ¹³C NMR, MS和HRMS等进行了表征.     

Electrochemically generated tungsten‐based active species as catalysts for metathesis‐related reactions: 2. Ring‐opening metathesis polymerization of norbornene

The present work reports the application of the WCl₆–e^?–Al–CH₂Cl₂ catalyst system to the ring‐opening metathesis polymerization of norbornene. Analysis of the polynorbornene microstructure by means of ¹H and ¹³C NMR spectroscopy indicates that the polymer contains a mainly cis stereoconfiguration of the double bonds (σ_c = 0.61) and a blocky distribution (r_tr_c > 1) of cis and trans double bonds (r_tr_c = 3.37). This catalytic system is reluctant to facilitate the competing addition reactions of cycloalkenes while proceeding with the polymerization reactions with good conversions and at short periods. Copyright © 2004 John Wiley & Sons, Ltd.     

Structure and reactivity of steroids—VI : Long range effects in a series of Δ1,3,5(10)-estratriene compounds

The kinetics of the oxidation of 17β-hydroxy-Δ^1,3,5(10)-estratrienes which differ in D ring size, in C₃, substituent and in the character of fusion of the B and C rings by CrO₃ in AcOH has been studied. An increase in size of the D ring in the substrate diminishes reactivity of the 17β-hydroxy group in the oxidation. It has been found that the reactivities of the 17β and 17β-hydroxy groups of the Δ^1,3,5(10)-estratriene derivatives depend upon the electronic nature of the substituent at C³, explained by a long range effect operating from the A to D ring. The pK'a's of phenolic steroids have been measured and it was shown that introduction of the Δ⁸⁽⁹⁾ double bond increases the degree of dissociation of the phenolic hydroxyl. Expansion of the D ring and also reduction of the 17(17a)-keto group to 17β (17aβ) hydroxy group decreases the degree of dissociation of the phenolic hydroxyl as a result of the long range effect from the D to A ring. A linear correlation has been established between the oxidation and dissociation rate constants, confirming the existence of an interaction between C₃ and C_17(17a) at the expense of the long range effects from the A to D ring and vice versa. The long range effect apparently arises from a combination of inductive and conformational effects of the substituent. The kinetics of enzymic oxidation of 17β-hydroxy-Δ^1,3,5(10)-estratrienes by soluble 17β-estradiol dehydrogenase from human placenta has been investigated. In the case of 17β-hydroxy-Δ^1,3,5(10)-estratrienes of natural configuration, a linear correlation has been established between the values of the maximum rate constant and the oxidation rate constant. An assumption can thus be made about the major role of the contribution of the specific reactivity of the substrate to that of the enzyme-substrate complex, involving the size of the D ring and the long range effect of the substituent at C₃ upon the reaction center at C_17(17a). For 17β-hydroxy-Δ^1,3,5,(10)-estratrienes of the 8-isoconfiguration it is the specific reactivity of the substrate that makes the major contribution to the maximum rate values; this specific activity is a result of the substrate's configuration, which is responsible for the stability of the enzyme-substrate complex.