Formaldehyde Carbonyl Research Articles

Electron Density Geometry and the Quantum Theory of Atoms in Molecules.

A novel form of charge density analysis, that of isosurface curvature redistribution, is formulated and applied to the toy problem of carbonyl oxygen activation in formaldehyde. The isosurface representation of the electron charge density allows us to incorporate the rigorous geometric constraints of closed surfaces toward the analysis and chemical interpretation of the charge density response to perturbations. Visual inspection of 2D isosurface motion resulting from applied external electric fields reveals how the isosurface curvature flows within and between atoms and that a molecule can be uniquely and completely partitioned into chemically significant regions of positive and negative curvatures. These concepts reveal that carbonyl oxygen activation proceeds primarily through curvature and charge redistribution within rather than between Bader atoms. Using gradient bundle analysis─the partitioning of formaldehyde into infinitesimal volume elements bounded by QTAIM zero-flux surfaces─the observations from visual isosurface inspection are verified. The results of the formaldehyde carbonyl analysis are then shown to be transferable to the substrate carbonyl in the ketosteroid isomerase enzyme, laying the groundwork for extending this approach to the problems of enzymatic catalysis.

How Does the Guest—Host Hydrogen Bonding Affect the Thermal Properties of Clathrate Hydrates?

Herein, molecular dynamics simulations are performed to study the effect of the guest-host hydrogen bonding on the thermal properties, such as isothermal compressibility, isobaric thermal expansivity, and heat capacity, in the sI clathrate hydrate phases of trimethylene oxide (TMO), ethylene oxide (EO), and formaldehyde (FA) as polar guests. The results of these simulations are compared with those of nonpolar guests with analogous structures, cyclobutane (CB), cyclopropane (CP), and ethane (Et). Binary hydrates are constructed with the above guests in large 14-sided cages and methane placed in small 12-sided cages of the structure of sI clathrate hydrates. We present the temperature dependence of the lattice parameter and also the pressure dependence of the unit cell volume for variety guests with different sizes, polarity, and guest-host hydrogen bonding capability. The lattice parameters for some of the guest species obtained in this work are in good agreement with experimental values. The oxygen atom of the formaldehyde carbonyl group and the ether oxygen atoms of TMO and EO molecules can form hydrogen bonds with sI large cage water hydrogen atoms while CB, CP and Et molecules do not. The consequences of the guest-host hydrogen bonding on the isothermal compressibility, thermal expansivity, and heat capacity of the clathrate are discussed.

How does the guest—host hydrogen bonding affect the thermal properties of clathrate hydrates?

Herein, molecular dynamics simulations are performed to study the effect of the guest—host hydrogen bonding on the thermal properties, such as isothermal compressibility, isobaric thermal expansivity, and heat capacity, in the sI clathrate hydrate phases of trimethylene oxide (TMO), ethylene oxide (EO), and formaldehyde (FA) as polar guests. The results of these simulations are compared with those of nonpolar guests with analogous structures, cyclobutane (CB), cyclopropane (CP), and ethane (Et). Binary hydrates are constructed with the above guests in large 14-sided cages and methane placed in small 12-sided cages of the structure of sI clathrate hydrates. We present the temperature dependence of the lattice parameter and also the pressure dependence of the unit cell volume for variety guests with different sizes, polarity, and guest—host hydrogen bonding capability. The lattice parameters for some of the guest species obtained in this work are in good agreement with experimental values. The oxygen atom of the formaldehyde carbonyl group and the ether oxygen atoms of TMO and EO molecules can form hydrogen bonds with sI large cage water hydrogen atoms while CB, CP and Et molecules do not. The consequences of the guest—host hydrogen bonding on the isothermal compressibility, thermal expansivity, and heat capacity of the clathrate are discussed.

Quantification of Formaldehyde Residue in Wet Noodles Marketed in Indonesia using RP-HPLC Derivatization Method

Illegal practices of formaldehyde as preservatives in wet noodles have been proven. These formaldehyde-preserved wet noodles are sold in West Java, Indonesia. This compound may be harmful to the body due to a decreasing of blood pressure, coma, acidosis, and acute renal failure. In this study we proposed a quantification method using high performance liquid chromatography (HPLC). A simulation was carried out as comparison. This simulation comprised of formaldehyde-spiked fish then the process was continued by washing, frying, and distilling the fish in a closed-system distillation. Similar condition was applied onto wet noodles purchased from traditional markets in Bandung. Method used was RP-HPLC derivatization method based on the reaction of formaldehyde carbonyl with two different reagents of DNPH (2,4-dinitrophenylhydrazine) and Nash (acetyl acetone, ammonium acetate and acetic acid) reagents. Result showed that formaldehyde residue was detected and quantified in all wet noodle samples with a range of 21-59 ppm. In conclusion, this method can be used for routine analysis to control illegal practices of formaldehyde in wet noodles. Moreover, washing and frying the formaldehyde-preserved food were proven could significantly help reducing formaldehyde level in food. Keywords: 2,4-dinitrophenylhidrazine, formaldehyde, RP-HPLC, wet noodles

A formaldehyde carbonyl groups-modified self-crosslinked polystyrene resin: Synthesis, adsorption and separation properties

Abstract Based on our previous work and calculational chemistry, the pore-size distribution is the key factor which influences glabridin uptakes on resins. In addition, micropores and mesopores in the range of 1.8–5.4 nm are proper for glabridin adsorption. Based on this, a series of novel microporous and mesoporous self-crosslinked polystyrene resins (named as XT2) were synthesized by Friedel–Crafts reaction after different reaction time and utilized to adsorb glabridin in aqueous solution. The adsorption behaviors of the synthetic resins were studied systematically in terms of adsorption capacity, equilibrium time, isotherm adsorption and regeneration properties and compared with a commercial adsorbent (BMKB-1) which was screened out as the optimal macroporous adsorption resin (MAR) for glabridin based on our previous work. The characteristic methods of BET surface area, pore size distribution, Fourier transform infrared spectroscopy and scanning electron microscopy were investigated to analyze the resins and adsorption process. The glabridin uptakes on XT2-10 were remarkably larger than those of macroporous adsorption resin BMKB-1. The maximum adsorption capacity of XT2-10 is up to 43.69 mg/g for glabridin. The adsorption isotherms could be well described by the Freundlich model, and the adsorption kinetics were fitted by both pseudo-second-order kinetic equation and intra-particle diffusion model. The adsorption mechanism was a synergistic effect of specific surface area, molecular sieving effect, and multiple adsorption interactions including hydrogen bonding and π–π stacking. The glabridin uptakes decreased to approximately 93.23% after five cycles of adsorption–desorption, exhibiting an excellent reusability and remarkable regeneration. Based on these results, this research not only opens up the possibility of synthesizing microporous and mesoporous self-crosslinked polystyrene resins, but also provides guidance for understanding the adsorption mechanism of purification of flavones from herbal plants.

Comparison of Cu‐ZSM‐5 Zeolites and Cu‐MOF‐505 Metal‐Organic Frameworks as Heterogeneous Catalysts for the Mukaiyama Aldol Reaction: A DFT Mechanistic Study

The density functional theory (DFT) model ONIOM(M06L/6-311++G(2df,2p):UFF was employed to reveal the catalytic activity of Cu(II) in the paddle-wheel unit of the metal-organic framework (MOF)-505 material in the Mukaiyama aldol reaction compared with the activity of Cu-ZSM-5 zeolites. The aldol reaction between a silyl enol ether and formaldehyde catalyzed by the Lewis acidic site of both materials takes place through a concerted pathway, in which the formation of the CC bond and the transfer of the silyl group occurs in a single step. MOF-505 and Cu-ZSM-5 are predicted to be efficient catalysts for this reaction as they strongly activate the formaldehyde carbonyl carbon electrophile, which leads to a considerably lower reaction barrier compared with the gas-phase system. Both MOF-505 and Cu-ZSM-5 catalysts stabilize the reacting species along the reaction coordinate, thereby lowering the activation energy, compared to the gas-phase system. The activation barriers for the MOF-505, Cu-ZSM-5, and gas-phase system are 48, 21, and 61 kJ mol(-1) , respectively. Our results show the importance of the enveloping framework by stabilizing the reacting species and promoting the reaction.

The reaction of formaldehyde carbonyl oxide with the methyl peroxy radical and its relevance in the chemistry of the atmosphere

The reaction of formaldehyde carbonyl oxide (H2COO) with the methyl peroxy radical (CH3OO), a prototype of the reactions of carbonyl oxides with alkyl peroxy radicals of potential interest in atmospheric chemistry, has been investigated by means of quantum-mechanical electronic structure methods (CASSCF, CASPT2, UQCISD, and UCCSD(T)) and DFT functionals (B3LYP, BH&HLYP, M05 and M06-2X). Two reaction paths have been found for the lowest-barrier reaction, namely the CH3OO radical addition to the carbon atom of H2COO leading to the formation of the CH3OOCH2OO radical adduct. Both pathways begin with the formation of a pre-reactive complex with binding energies of 5.39 and 5.13 kcal mol(-1). The corresponding transition states are predicted to lie 2.64 and 0.25 kcal mol(-1), respectively, below the energy of the reactants and the rate constant of the global reaction is calculated to be 3.74 × 10(-12) cm(3) molecules(-1) s(-1) at 298 K. Since the CH3OOCH2OO radical adduct is formed with an internal energy excess of about 45 kcal mol(-1), it can decompose unimolecularly into formaldehyde and the CH2(O)OOCH radical. This unimolecular decomposition involves an intramolecular H-atom transfer followed by the decomposition of the CH2OOCH2OOH radical intermediate. Kinetic calculations based on the collision-reaction master equation employing the MultiWell Program Suite reveal that the CH3OOCH2OO radical adduct is stabilized in 86.9%, whereas 13.10% of the reaction corresponds to the formation of H2CO plus the CH2(O)OOH radical. It is concluded that the methyl peroxy radical addition to substituted carbonyl oxides might be the source of low volatility oligomers observed in secondary organic aerosols in chamber studies.

Hydroquinone modified hyper‐cross‐linked resin to be used as a polymeric adsorbent for adsorption of salicylic acid from aqueous solution

AbstractHydroquinone modified hyper‐cross‐linked resin (HJ‐Y15) was prepared from macroporous crosslinked chloromethylated polystyrene and the adsorption behaviors of HJ‐Y15 for salicylic acid were studied from aqueous solution. The results indicated that the surface of HJ‐Y15 was modified by formaldehyde carbonyl, quinone carbonyl, and phenolic hydroxyl groups. Freundlich model was suitable for characterizing the isotherms and the adsorption was shown to be an exothermic, spontaneous, and more ordered process. The pseudosecond‐order rate equation was appropriate for describing the kinetic curves and the intraparticle diffusion was the rate‐controlling step. Hydrogen bonding between formaldehyde carbonyl groups of HJ‐Y15 and carboxyl groups of salicylic acid was one of the primary driving forces for the adsorption. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Surface chemical modification on hyper-cross-linked resin by hydrophilic carbonyl and hydroxyl groups to be employed as a polymeric adsorbent for adsorption of p-aminobenzoic acid from aqueous solution

In this study, a novel hyper-cross-linked HJ-Y10 resin was synthesized and its adsorption behaviors for p-aminobenzoic acid were investigated from aqueous solution. The results indicated that the skeleton surface of HJ-Y10 resin was modified by formaldehyde carbonyl, quinone carbonyl and phenolic hydroxyl groups, the unadjusted p-aminobenzoic acid solution was favorable for the adsorption, the isotherms could be fitted by Langmuir model and the adsorption was an exothermic process, the adsorption kinetics could be characterized by pseudo-second-order rate equation and the initial stage was controlled by the intra-particle diffusion model. Hydrogen bonding between formaldehyde carbonyl, quinone carbonyl groups on HJ-Y10 resin and carboxyl groups of p-aminobenzoic acid was one of the primary driving forces for the adsorption.

Adsorption behaviors of a novel carbonyl and hydroxyl groups modified hyper-cross-linked poly(styrene-co-divinylbenzene) resin for β-naphthol from aqueous solution

A series of novel hyper-cross-linked resins were synthesized from macroporous cross-linked chloromethylated poly(styrene-co-divinylbenzene) by adding different dosage of hydroquinone in Friedel-Crafts reaction. The results of the pore structures revealed that the prepared resins possessed micropores, mesopores and macropores, and the chloromethyl groups and the uploaded hydroquinone were partly oxidized according to the results of Fourier-transformed infrared ray spectra. Among these hydroquinone modified resins, HJ-Y06 resin held the largest adsorption capacity for β-naphthol, and its adsorption capacity was comparable with XAD-4 while much larger than X-5. The adsorption kinetics could be characterized by pseudo-second-order rate equation and intra-particle diffusion model was the rate-limiting step at the initial process. The adsorption was favorable at solution pH lower than 6.5. The adsorption isotherms could be fitted by Langmuir model and the adsorption was an endothermic process. Hydrogen bonding between formaldehyde carbonyl and quinone carbonyl groups on HJ-Y06 and phenolic hydroxyl groups of β-naphthol was the main driving force for the adsorption.

Removal of p-nitrophenol by a water-compatible hypercrosslinked resin functionalized with formaldehyde carbonyl groups and XAD-4 in aqueous solution: A comparative study

Chloromethylated styrene-divinylbenzene copolymers were post-crosslinked through Fredel–Crafts alkylation reaction and a water-compatible hypercrosslinked resin HJ-1 was developed successfully. It can be wetted directly by water and can be used without any wetting process. It was applied to remove p-nitrophenol in aqueous solution in comparison with the commercial Amberlite XAD-4 resin. Their adsorption behaviors for p-nitrophenol were conducted and it was found the adsorption dynamics obeyed the pseudo-second-order rate equation and the intra-particle diffusion was the rate-limiting step. The adsorption isotherms can be correlated to Freundlich isotherm and the adsorption capacity onto HJ-1 resin was much larger than XAD-4. The maximum adsorption capacity of p-nitrophenol for HJ-1 resin was measured to be 179.4 mg/g with the equilibrium concentration at 178.9 mg/l and the maximum removal percentage was predicted to be 98.3%. The adsorption thermodynamic parameters were calculated and the adsorption was mainly driven by enthalpy change. The micropore structure, the size matching between the pore diameter of HJ-1 resin and the molecular size of p-nitrophenol, and polarity matching between the formaldehyde carbonyl groups of HJ-1 resin and p-nitrophenol bring the larger adsorption capacity and higher adsorption affinity.

Adsorption of Rhodamine B and methyl orange on a hypercrosslinked polymeric adsorbent in aqueous solution

In the present study, a hypercrosslinked polymeric adsorbent functionalized with formaldehyde carbonyl groups, HJ-1 was prepared and its adsorption behaviors for two dyes, Rhodamine B (RB) and methyl orange (MO), were tested in aqueous solution. Batch adsorption results indicated that semi-empirical Freundlich isotherm described the adsorption isotherms better and kinetic studies demonstrated that the adsorption obeyed the pseudo-second-order rate model and both of film diffusion and intra-particle diffusion were the rate limiting steps. Adsorption thermodynamic parameters displayed that the adsorption was an exothermic, spontaneous, and more ordered arrangement process, and the polar functional groups of the adsorbent and the matching between the pore diameter of the adsorbent and the molecular size of the adsorbate are the two primary factors influencing the adsorption.

Theoretical Investigation of Gas-Phase Thermal Reactions between Carbon Monoxide and Water

Ground-state potential energy surface of the CO−H2O system was explored using ab initio calculations at the CCSD(T)/6-311++G**//MP2/6-311++G** level. Providing energy of about 74 kcal/mol, the initial bimolecular complex CO−H2O can associate into formic acid (HCOOH) or dihydroxycarbene (HOCOH). Both HCOOH and HOCOH can further dissociate into CO2 and H2 through three reaction channels. Providing energy more than 100 kcal/mol, CO−H2O complexes can dissociate into hydroxyl (OH) and formyl (HCO) radicals. Further association of the two radicals leads to formaldehyde carbonyl oxide, dioxirane, and some highly unstable species, including triangular CO2 and linear carbon peroxide COO.

Theoretical study of photochemical processes involving singlet excited states of formaldehyde carbonyl oxide in the atmosphere

Abstract We report a theoretical study on the photochemical reactivity of formaldehyde carbonyl oxide H2COO, a compound of atmospheric relevance. Calculations are carried out at the CASSCF and CASPT2 levels with extended basis sets. We are particularly interested in three important unimolecular processes: isomerization into dioxirane, syn/anti isomerization and dissociation into formaldehyde and atomic oxygen. The results suggest that the photochemical reactivity of H2COO in the troposphere is strongly linked to the properties of the second singlet excited state a 1 A ′ ( π → π * ) because it is energetically accessible from the ground state and has a large oscillator strength. Construction of potential energy curves reveals that photochemical isomerization into dioxirane is very unlikely to occur whereas syn/anti isomerization should be favorable. Besides, in the a1A′ state, carbonyl oxide spontaneously dissociates into formaldehyde H2CO and atomic oxygen O ( 1 D ) in close relationship to the excited 1 B 2 state of the isoelectronic ozone molecule occurring in Hartley’s band.

Computer modelling of electron paramagnetic resonance-active molybdenum(V) species in xanthine oxidase †

Density Functional Theory calculations have been used to investigate structural models for the ‘Very Rapid’ and ‘Inhibited’ EPR signals ascribed to xanthine oxidase MoV species. Analysis of the observed hyperfine coupling tensors has suggested close Mo–C contacts in both cases and a side-on interaction between the substrate’s carbonyl group and the Mo centre has been proposed. Attempts to confirm this for several model ‘Very Rapid’ species, based on a previous structure for the active site, either give short Mo–C contacts but too small a spin density on Mo or long Mo–C distances and a more reasonable Mo spin. Either the model system or the interpretation of the experimental data requires revision. In contrast, a good model can be developed for the ‘Inhibited’ species, which arises during reaction with formaldehyde, which is consistent with the EPR and other experimental data. However, rather than involving side-on co-ordination of the formaldehyde carbonyl group, the ‘Inhibited’ species forms a C–S bond between the formaldehyde and the sulfido ligand.

Unimolecular Isomerizations and Oxygen Atom Loss in Formaldehyde and Acetaldehyde Carbonyl Oxides. A Theoretical Investigation

The lowest singlet and triplet potential energy surfaces of formaldehyde carbonyl oxide (1) and acetaldehyde carbonyl oxide (2) have been investigated in the regions concerning the most relevant unimolecular reactions by means of CASSCF and MRDCI ab initio quantum-chemical calculations. The questions related to the mechanism of O-atom loss from carbonyl oxides, as well as the competition between the cyclization to dioxirane and the tautomerization to hydroperoxide in methyl-substituted carbonyl oxides are addressed in this investigation. The theoretical predictions are consistent with experimental findings obtained from stopped-flow studies of the gas-phase ozonation of both trans-butene and tetramethylethylene. An unexpected result is that the most reasonable pathway for O-atom loss from “hot” singlet carbonyl oxides 1 and 2 involves internal rotation about the CO bond axis, followed by intersystem crossing to the lowest triplet state and subsequent scission of the OO bond.