Activation Of Carbonyl Group Research Articles

Glutaraldehyde as Ambient Temperature Crosslinking Agent of Latex Films from Natural Rubber Grafted with Poly(diacetone acrylamide)

The concept of using glutaraldehyde (GTA) to crosslink natural rubber (NR) particles bearing diacetone acrylamide (DAAM) functional groups during film formation was investigated in the present work. The primary advantage of this curing system is that it is feasible under ambient conditions, which can lower operating costs of the curing process. Graft copolymers of NR and poly(diacetone acrylamide) prepared with 5 wt% of DAAM (NR–g–PDAAM5) were synthesized by seeded emulsion polymerization at 50 °C. Then, the tensile properties were measured for cast films formed from NR–g–PDAAM5 latex in the absence and presence of GTA. The results revealed increased tensile strength of the NR–g–PDAAM5 film, when GTA was added into the latex prior to film casting. The crosslinking of NR–g–PDAAM5 latex film by reaction with GTA, after film casting, was also investigated using attenuated total reflection Fourier transform infrared (ATR–FTIR) and dynamic mechanical thermal analysis (DMTA). ATR–FTIR analysis demonstrated that crosslinking reactions formed conjugated C=C double bonds between the active carbonyl groups of DAAM and GTA. The complementary use of DMTA also corroborated that crosslinking reactions took place involving the grafted PDAAM chains on the NR particles. This was evidenced by a clear shift towards higher temperatures of the tan δ peak, corresponding to the Tg of NR–g–PDAAM phase, when GTA was incorporated into the NR–g–PDAAM5 latex before film formation. Additionally, a noticeable increase in thermal stability of the NR–g–PDAAM5 film was also observed with added GTA. Hence, it can be concluded that GTA is an efficient room-temperature crosslinker for NR particles functionalized with DAAM. This curing system can also be considered an alternative, simple, and inexpensive method for curing NR latex compounds, as only one component (GTA) is required in the curing process.

Synthesis and reactions of some novel 1-(2,7-dimethyl-1,8-naphthyridin-4-yl)hydrazine candidates

A series of novel 1,8-naphthyridine derivatives containing Schiff bases and amino substituents were synthesized starting from the reaction of 4-hydrazinyl-2,7-dimethyl-1,8-naphthyridine with different active carbonyl groups, acid monoanhydrides and tetracarboxylic acid anhydrides. Structures of new compounds were elucidated by means of physical and spectroscopic analyses.

The physicochemical properties and catalytic performance of carbon-covered alumina for oxidative dehydrogenation of ethylbenzene with CO2

In order to correlate the physicochemical properties of carbon-covered alumina (CCA) materials with their catalytic performance for oxidative dehydrogenation of ethylbenzene with CO2 (CO2-ODEB), a series of CCA materials with diverse carbon contents (8.7–31.3wt%) and pyrolysis temperatures (600–800°C), which were synthesized via an impregnation method followed by pyrolysis, were applied. These catalytic materials were characterized by TGA, N2 physisorption, XRD, Raman spectroscopy and XPS techniques. It was found that the catalytic performance of these CCA materials highly depended on their physicochemical properties, and the optimum CCA catalyst exhibited much better catalytic stability than conventional hydroxyl carbon nanotubes. Below an optimum value of carbon content, the CCA catalyst preserved the main pore characteristics of the Al2O3 support and its catalytic activity increased with the carbon content. Excessive carbon loading resulted in significant textural alterations and thereby decreased both the ethylbenzene conversion and styrene selectivity. On the other hand, high pyrolysis temperature was detrimental to the ordered graphitic structure of the carbon species within the Al2O3 pore. The decreased ordered graphitic degree was found to be associated with the loss of the surface active carbonyl groups, consequently hampering the catalytic efficiency of the CCA catalyst.

Structure-dependent selective hydrogenation of cinnamaldehyde over high-surface-area CeO2-ZrO2 composites supported Pt nanoparticles

Tetravalent metal oxides, such as ceria and zirconia, are widely used as support materials in a broad range of heterogeneous catalytic processes. Herein, high-surface-area CeO2-ZrO2 composite supports with micro/mesoprous structures were first fabricated successfully by a low temperature solution-phase method without the use of any additional templates and surfactants and resulting supported platinum nanoparticles were employed in liquid-phase selective hydrogenation of cinnamaldehyde to cinnamyl alcohol, a key reaction for the production of important chemicals. It was found that the component of CeO2-ZrO2 composites strongly influenced surface structures of catalysts, and consequently determined the nature of platinum species and the catalytic properties of catalysts. When platinum was dispersed on the CeO2-ZrO2 composite with the Ce/Zr molar ratio of 1:1, a high cinnamyl alcohol yield of 89%, together with an extremely high turnover frequency value of 10423h–1, could be achieved without the use of additional alkali. Such high catalytic performance, which was superior to those of most known supported Pt-based catalysts previously reported, was mainly attributable to the synergism between electron-rich metallic Pt species and surface defects (i.e., Ce3+ species and oxygen vacancies), thereby greatly promoting the chemisorption and activation of carbonyl group in cinnamaldehyde. Moreover, the porous network of CeO2-ZrO2 composites is beneficial to the stabilization of Pt nanoparticles, thereby preventing the leaching and the growth of Pt particles in the course of reaction. This work offers a better understanding of the role of high-surface-area porous CeO2-ZrO2 composite supports for highly efficient selective hydrogenation of α,β-unsaturated aldehydes in supported precious-metal-based catalysts.

Ionic liquids that form adducts with alcohols

Ionic liquids bearing an activated carbonyl group in the cation are shown to form adducts with alcohols without the aid of any catalysts. How these functionalised ionic liquids could be used in altering vapour phase compositions of alcohols and in alcohol separations are demonstrated.

Porous, Hyper-cross-linked, Three-Dimensional Polymer as Stable, High Rate Capability Electrode for Lithium-Ion Battery.

Organic materials containing active carbonyl groups have attracted considerable attention as electrodes in Li-ion batteries due to their reversible redox activity, ability to retain capacity, and, in addition, their ecofriendly nature. Introduction of porosity will help accommodate as well as store small ions and molecules reversibly. In the present work, we introduce a mesoporous triptycene-related, rigid network polymer with high specific surface area as an electrode material for rechargeable Li-ion battery. The designed polymer with a three-dimensional (3D), rigid porous network allows free movement of ions/electrolyte as well as helps in interacting with the active anhydride moieties (containing two carbonyl groups). Considerable intake of Li+ ions giving rise to very high specific capacity of 1100 mA h g-1 at a discharge current of 50 mA g-1 and ∼120 mA h g-1 at a high discharge current of 3 A g-1 are observed with excellent cyclability up to 1000 cycles. This remarkable rate capability, which is one of the highest among the reported organic porous polymers to date, makes the triptycene-related rigid 3D network a very good choice for Li-ion batteries and opens up a new method to design polymer-based electrode materials for metal-ion battery technology.

Polymer composite reinforced with nanoparticles produced from graphitic carbon-rich fly ash

Carbon nanotubes and graphene are considered effective reinforcement materials for various polymers because of their superior properties. However, they are expensive and difficult to separate and incorporate individually into matrix systems because of their tendency to exist in clustered form. In this work, carbon nanoparticles produced from graphitic carbon-rich fly ash by high-energy ball milling are evaluated as a reinforcement in a high-performance epoxy matrix system. They were used in various weight fractions ranging from 0.1 to 2 wt.%. The obtained carbon nanoparticles have an average particle size of around 20 nm, while XPS spectrum shows active carbonyl groups on their surfaces. The mechanical tensile properties of the carbon nanoparticles/epoxy nanocomposite, including their Young's modulus, stiffness, and load at fracture, were investigated. Moreover, the effect of ethanol as a dispersion medium was studied. The obtained results indicate that the Young's modulus and load at fracture changed only slightly upon the addition of carbon nanoparticles to the epoxy matrix system. On the other hand, the stiffness was improved by 60% over that of the pure epoxy matrix system. This improvement was obtained at 0.6 wt.% carbon nanoparticle content. The test results indicate that ethanol is effective in modifying the nanocomposite mechanical properties. Additionally, results show that low-cost CNPs might be useful as a reinforcement material for high-stiffness products.

Hydrogenation of biomass-derived compounds containing a carbonyl group over a copper-based nanocatalyst: Insight into the origin and influence of surface oxygen vacancies

New Mn-containing spinel-supported copper nanocatalysts were directly generated via a Cu–Mn–Al layered double hydroxide precursor route and employed in gas-phase hydrogenation of dimethyl succinate (DMS) to γ-butyrolactone (GBL). It was found that the introduction of manganese into catalyst precursors led to the formation of Mn-containing spinel phases, thereby giving rise to highly dispersive Cu0 nanoparticles and a large number of surface defects (i.e., oxygen vacancies (Ov), Mn2+ species) in reduced catalysts. As-formed copper-based nanocatalysts exhibited exceptional catalytic hydrogenation performance with stability enduring up to 100h. Such high catalytic efficiency could reasonably be attributed to the surface synergism between Mn2+–Ov–Mn2+ defect structures and active metallic copper species, which controlled the key to hydrogenation related to the adsorption of DMS molecules and following activation of carbonyl groups and the dissociation of hydrogen. Most importantly, such copper-based nanocatalysts displayed great potential applicationsin the hydrogenations of other biomass-derived compounds containing carbonyl groups (e.g., acetol, levulinic acid, levulinic acid esters, and furfural). The present strategy enables us to tune the surface structures of catalysts for designing new type of copper-based catalysts with significantly enhanced catalytic performance.

ChemInform Abstract: Facile, Novel and Efficient Synthesis of New Pyrazolo[3,4‐b]pyridine Products from Condensation of Pyrazole‐5‐amine Derivatives and Activated Carbonyl Groups.

An efficient synthesis of novel ethyl-1,3,4-triphenyl-1H-pyrazolo[3,4-b]pyridine-6-carboxylate products has been achieved via condensation of pyrazole-5-amine derivatives and activated carbonyl groups, in refluxing acetic acid. This process has been found to be useful in the preparation of new N-fused heterocycle products in good to excellent yields.

Strain-driven direct cross-aldol and -ketol reactions of four-membered heterocyclic ketones.

Owing to the ring strain and α-heteroatom effect, the four-membered heterocyclic ketones can undergo direct cross-aldol and -ketol reactions without the need for preformed enol or "enolate-like" intermediates. Besides the organocatalyzed cross-ketol addition onto their highly active carbonyl group, their ability to act as a nucleophilic donor has also been explored. As a result, a number of discrete aldol adducts were synthesized and the distinct reactivities were successfully combined into a double-aldol one-pot reaction.

Facile, novel and efficient synthesis of new pyrazolo[3,4-b]pyridine products from condensation of pyrazole-5-amine derivatives and activated carbonyl groups

A novel, simple and efficient route for the synthesis of new fused pyrazolo[3,4-b]pyridines is described.

Acceptorless dehydrogenative coupling of primary alcohols to esters by heterogeneous Pt catalysts

Supported platinum catalysts have been studied for the acceptor-free dehydrogenative coupling of primary alcohols to esters in the liquid phase under solvent-free conditions in N2 at 180 °C. The activity depends on the support material, and Pt-loaded SnO2 (Pt/SnO2) gives the highest activity. Pt/SnO2 shows higher activity than various transition metals (Ir, Re, Ru, Rh, Pd, Ag, Co, Ni, Cu) loaded on SnO2. The Pt/SnO2 catalyst (1 mol%) selectively converted various primary alcohols to their corresponding esters in moderate to high isolated yield (53–91%). This is the first example of reusable heterogeneous catalysts for the acceptor-free dehydrogenative coupling of primary alcohols to esters under additive-free and solvent-free conditions. Mechanistic and infrared (IR) studies are also shown to discuss the reaction pathway and a possible role of the SnO2 support as Lewis acid sites that activate carbonyl groups of adsorbed aldehyde intermediates.

Diastereodivergent organocatalytic asymmetric vinylogous Michael reactions

One of the major challenges of modern asymmetric catalysis is the ability to selectively control the formation of all diastereoisomers of reaction products possessing multiple stereocenters. Pioneers of such diastereodivergent catalytic asymmetric processes have focused on reactions where the newly formed stereogenic centres are proximal to the active carbonyl group. To date, however, diastereodivergent reactions at remote positions remain an unmet challenge. Herein, we describe a catalyst-controlled diastereodivergence in the formation of remote stereocenters in the direct vinylogous Michael reactions of β, γ-unsaturated butenolides to α, β-unsaturated ketones. The reactions are enabled by two complementary, non-enantiomeric multifunctional catalysts, which mutually activate and organise both reactants, affording either the syn- or anti-adduct with high diastereo- and enantioselectivity. These two catalytic systems are also applicable in the Mukaiyama-Michael reactions and tandem Michael-Michael reactions.

ChemInform Abstract: Traceless Chemical Ligation from S‐, O‐, and N‐Acyl Isopeptides

AbstractReview: 54 refs.

Traceless Chemical Ligation from S-, O-, and N-Acyl Isopeptides

Peptides are ubiquitous in nature where they play crucial roles as catalysts (enzymes), cell membrane ion transporters, and structural elements (proteins) within biological systems. In addition, both linear and cyclic peptides have found use as pharmaceuticals and components of various conjugate molecular systems. Small wonder then that chemists throughout the ages have sought to mimic nature by synthesis of the amide polymers known as peptides and proteins. The fundamental reaction in the formation of a peptide bond is condensation of an amine of one amino acid with the activated carbonyl group of another. This "fragment condensation" has been achieved in many ways both in solution and by solid-phase peptide synthesis (SPSS) on resin. The most successful method for in-solution coupling is known as native chemical ligation (NCL), and the technique dates back to the pioneering work of Wieland (1953) and subsequently Kent (1994) among many others. This Account builds on the established principles of NCL as applied specifically to S-, O-, and N-isopeptides, molecules that are generally more soluble and less prone to aggregation than native peptides. This Account also covers NCL of isopeptides containing terminal and nonterminal S-acylated cysteine units, reactions that enable the synthesis of native peptides from S-acyl peptides without the use of auxiliaries. With C-terminal S-acyl isopeptides, NCL was carried out under microwave irradiation in phosphate buffer (pH 7.3) at 50 °C. Intramolecular acyl migration was observed through 5-19-membered transition states with relative rates, as assessed by product analysis, in the order, 5 > 10 > 11 > 14, 16, or 17 > 12 > 13, 15, or 19 > 18 ≫ 9 > 8. The rate/pH profile for the 15-membered TS showed a maximum for ligated product versus transacylation at pH 7.0-7.3 presumably associated with the pKa of the N-nucleophile in the hydrogen-bonded TS. Cysteine occurs at low abundance (1.7%) in natural peptides and is rarely available in a terminal position thus limiting the utility of the method. This Account reports, however, NCL at nonterminal acyl cysteine through 5-, 8-, 11-, and 14-membered TSs with relative rates of ligation in the order, 5 ≫ 14 > 11 ≫ 8, thus paralleling the results with acylated terminal cysteine residues. In an obvious sequel to the work with acylated cysteine, we discuss intramolecular O- to N-acyl shift in O-acyl serine and O-acyl tyrosine isopeptides where the story becomes more complex in terms of viable conditions and optimum size of the cyclic TS. N- to N-acyl migration in acyl tryptophan isopeptides is described, and finally, chemical ligation is applied to the synthesis of cyclic peptides. Conformational analysis and quantum chemical calculations are used to rationalize ligation through a range of cyclic transition states. This Account highlights the fact that NCL of acyl isopeptides is an extremely useful strategy for the synthesis of a wide variety of native peptides in good yields and under mild conditions. Mechanistic aspects of the ligations are not fully resolved, but theoretical studies indicate that hydrogen bonding within the various cyclic transition states plays a major role.

Kinetic Spectrophotometric Determination of Propellant Grade Hydrazines using Thiophenes with Active Carbonyl Groups

A simple, cost effective, highly sensitive and rapid kinetic spectrophotometric method was developed for hydrazines by using Thiophene-3-carboxaldehyde (3-Thienaldehyde) and 3-Butenone (E)-1,1,1-trifluoro-4-(3thienyl) (CF 3 enone). CF 3 enone was prepared by crossed aldol condensation of 3-Thienaldehyde and characterized by UV-Vis, FT-IR and NMR spectra. Reactions of 3-Thienaldehyde (with catalyst) and CF 3 enone (in acetonitrile medium without catalyst) with hydrazines were followed spectrophotometrically and compared. Variables such as temperature and concentration were optimized to determine hydrazines in the concentration range of 0.1 mM to 0.1 M for 3-Thienaldehyde and 0.1 mM to 1 mM for CF 3 enone. Minimum detectable limits were found to be 0.2 mM (Hydrazine) and 0.1 mM (MMH ) for 3-Thienaldehyde. For CF 3 enone, Minimum detectable limits were found to be 0.007 mM (Hydrazine) and 0.01 mM (MMH). Rate of the CF 3 enone reaction was studied as there is gradual decrease in absorbance for the peak at 320 nm for the interaction of hydrazines. Initial rate and fixed time methods were adopted for kinetic study. CF 3 enone based kinetic spectrophotometric method is rapid and sensitive with no catalyst requirement for interaction of hydrazines when compared with the classical CHO functional group based method.

Characterization of lime plasters used in 16th century Mughal monument

This paper addresses the results of mineralogical and physico-chemical investigation of 16th century Mughal plaster of Bibi Ka Maqbara, the Taj of Deccan. The study investigated micro-morphological structure of various components of the plaster for the great to provide a basis for future restoration. The investigation on particle size distribution of aggregates in the plaster was carried and the result correlated to the strength of the plaster. Sieve/petrological analysis indicate the addition of creamy white zeolites (also detected by Raman spectrum) along with crushed amygdaloidal basalt of different grain sizes as aggregate in the plaster. The component material of the plaster and its purity has been studied through thermal analysis. The outer plaster layer was characterized for addition of hygroscopic organic additive with active carbonyl group by FTIR spectroscopy. The SEM images show salt crystallization in the pores as one of the reason for failure of plaster at some location, probably due to recent conservation with cement mortars/plaster of paris.

Chlorizidine, a cytotoxic 5H-pyrrolo[2,1-a]isoindol-5-one-containing alkaloid from a marine Streptomyces sp.

Cultivation of an obligate marine Streptomyces strain has provided the cytotoxic natural product chlorizidine A. X-ray crystallographic analysis revealed that the metabolite is composed of a chlorinated 2,3-dihydropyrrolizine ring attached to a chlorinated 5H-pyrrolo[2,1-a]isoindol-5-one. The carbon stereocenter in the dihydropyrrolizine is S-configured. Remarkably, the 5H-pyrrolo[2,1-a]isoindol-5-one moiety has no precedence in the field of natural products. The presence of this ring system, which was demonstrated to undergo facile nucleophilic substitution reactions at the activated carbonyl group, is essential to the molecule's cytotoxicity against HCT-116 human colon cancer cells.

Unexpected efficiency of cyclic amidine catalysts in depolymerizing poly(ethylene terephthalate)

AbstractThis article describes studies on the catalytic activity of several nitrogen‐based organic catalysts for the depolymerization of poly(ethylene terephthalate) (PET), in which a few cyclic amidines work more effectively than a potent, bifunctional guanidine‐based catalyst 1,5,7‐triazabicyclo‐[4,4,0]‐dec‐5‐ene (TBD) in the presence of short chain diols that play a role in activation of carbonyl groups through hydrogen bonding. Further studies prove that the catalytic efficiency at the above specific conditions depends only on the extent of activation of a hydroxyl group rather than simply the pKa of the bases. For glycolysis with excess short‐chain alkanediols, 1,8‐diazabicyclo[5.4.0]undec‐7‐ene is the best catalyst. In contrast, TBD shows outstanding catalytic activity in depolymerizations of PET with mono‐alcohols and longer‐chain diols. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013

Reduction of Activated Carbonyl Groups Using Alkylphosphanes as Reducing Agents: A Mechanistic Study

AbstractA comprehensive mechanistic investigation on the reduction of activated carbonyl groups using alkylphosphanes as reducing agents has been conducted through a combination of experimental as well as computational studies. Both approaches show that this kind of reduction proceeds either through proton transfer from alkylphosphanes and cleavage by water during work‐up or through another reaction pathway involving the participation of water at the initial stage and a two‐fold proton transfer to afford the product.