Urea Adduct Research Articles

Urea as hydrogelator of surfactants

HypothesisThe formation of adducts via urea interaction with distinct classes of surfactants (cationic, anionic, nonionic, and zwitterionic), leading to their assembly into lamellar structures and subsequent formation of hydrogels. The characteristics of these hydrogels are associated with both, the length of the alkyl chain, and the specific head group of the surfactant molecules. ExperimentsCharacterization of adduct formation was conducted using Wide-Angle X-ray Scattering (WAXS), while Small-Angle X-ray Scattering (SAXS) was employed to probe the subsequent assembly into lamellar structures. The kinetics of hydrogel formation were assessed through rheological measurements and observed thermal transitions utilizing Differential Scanning Calorimetry (DSC). FindingsThe investigation revealed a universal propensity for hydrogel formation across all surfactant classes. The formation arises from the interactions between urea molecules via hydrogen bonding, forming adducts around the surfactant chains. In sequence, the adducts self-assemble in lamellae. This process constructs the intricate three-dimensional network characteristic of the hydrogel. Furthermore, the kinetics of hydrogel formation, and their rheological properties under equilibrated conditions, were found to be significantly influenced by the nature of the polar head group of the surfactant molecules. This is the first evidence on the formation of adducts of urea with classes of surfactants. As they are common components in cosmetic, supramolecular hydrogels have high potential to be used in formulations.

DEWAXING OF DISTILLATE OIL FRACTION (400- 500 ºC) USING UREA

De-waxing of lubricating oil distillate (400-500 ºC) by using urea was investigated in the present study. Lubricating oil distillate produced by vacuum distillation and refined by furfural extraction was taken from Al-Daura refinery. This oil distillate has a pour point of 34 ºC. Two solvents were used to dilute the oil distillate, these are methyl isobutyl ketone and methylene chloride. The operating conditions of the urea adduct formation with n-paraffins in the presence of methyl isobutyl ketone were studied in details, these are solvent to oil volume ratio within the range of 0 to 2, mixer speed 0 to 2000 rpm, urea to wax weight ratio 0 to 6.3, time of adduction 0 to 71 min and temperature 30-70 ºC). Pour point of de-waxed oil and yield of wax produced were determined to show the effect of these operating conditions. The most favorable operating conditions were solvent to oil volume ratio of 1, mixer speed of 1500 rpm, urea to wax weight ratio of 5, time of adduction of 13 min and temperature of 30-52 ºC.

Urea‐Hydrogen Peroxide (UHP): Comparative study on the experimental detonation pressure of a non‐ideal explosive

AbstractCarbamide Peroxide, an adduct of Urea and Hydrogen Peroxide (UHP) industrially used as a solid source of hydrogen peroxide, exhibits the behaviour of a tertiary explosive but a detailed performance characterisation is still lacking in the literature. In this work, we calculated a 20 % experimental TNT equivalence for brisance, i. e. the shattering effect from the shock wave transmitted from the detonating high explosive into adjacent materials, by experimental indirect measurement of UHP detonation pressure. We determined a 3.5 GPa detonation pressure for 5 kg unconfined UHP charges (0.87 g/cm3, 120 mm charge diameter) by measuring the attenuated shock wave velocity (ASV) in adjacent inert materials using passive optical probes. Particle velocity measurements at the interface of a PMMA impedance window carried out with Photonic Doppler Velocimetry on scaled‐down charges of 90 g UHP under heavy confinement (0.85 g/cm3, 30 mm charge diameter, 4 mm thick steel) are consistent with ASV results in the PMMA acceptors but further investigations are required to determine the detonation pressure, using a small‐scale experimental setup. The ASV method has proven reliable to assess the brisance of a non‐ideal explosive for risk assessment purposes.

Detonation performance of urea‐hydrogen peroxide (UHP)**

AbstractCarbamide Peroxide, an adduct of Urea and Hydrogen Peroxide, is commonly used in the cosmetic and pharmaceutical industries as a solid source of hydrogen peroxide. However, it exhibits explosive properties and can be easily manufactured from readily available household chemicals, making it a potential emerging threat. We carried out a detailed performance assessment, combining experiments, thermochemical calculations and numerical simulations and highlighted a good level of agreement between experimental data from lab, field and underwater firings. A maximum detonation velocity of 3.65 km/s was recorded for unconfined 25 kg UHP charges at 0.85 g/cm3(200 mm charge diameter). We determined in these conditions an infinite diameter detonation velocity of 3.94 km/s. These results are also consistent with previous results obtained at small scale under heavy confinement. Airblast measurements highlighted an average 40 % TNT equivalence for impulse and 55 % for peak overpressure at short distance, which are in good agreement with the 57 % (Power Index) calculated from Explo5, while 50 % for bubble energy (explosive power) and 20 % for shock pressure (brisance) were obtained from underwater experiments. The use of different experimental approaches has proven useful to characterise the performances parameters of a non‐ideal explosive for risk assessment purposes.

A new urea adducts method for PUFA concentration using green food grade solvents and avoiding ethyl carbamate formation

This study aimed to selectively enrich stearidonic acid (SDA) together with γ-linolenic acid (GLA) in Echium plantagineum oil by urea complexation. The complexation process at room temperature was carried out replacing common organic solvents, such as hexane and ethanol, by alternative compounds, included in Green Solvent and Food Grade categories, adapting this process towards the principles of Green Chemistry. This substitution was also intended to avoid the generation of the toxic compound ethyl carbamate. Among all the solvents studied, the mixture propionic acid and α-pinene provided the best results, leading to a final product comprised of ∼99% of PUFA, with ∼45% SDA (∼14% in the original oil), and without apparition of ethyl carbamate. The procedure was tested on other raw materials (salmon and microalgae oils). The solvent was efficiently recuperated from the liquid phase (∼87% recovery) and reutilized once with almost identical results.

Small‐Scale Detonation of Industrial Urea‐Hydrogen Peroxide (UHP)

AbstractThe adduct of Urea and Hydrogen Peroxide (UHP), also called Carbamide Peroxide, is industrially produced as a solid source of hydrogen peroxide for bleaching, disinfection, and oxidation reactions. As a chemical combination of fuel and oxidiser, UHP has explosive potential but it is unclear whether it could sustain a detonation at small scale. In the configuration we tested, we succeeded in recording self‐sustained detonation at relatively small scale under heavy confinement, measuring a maximum experimental velocity of detonation of 3860 m/s at an optimum 1.1 g/cm3 loading density. UHP can sustain a detonation, even at the 100 g scale, but this is strongly dependant on booster size, confinement material, loading density, charge length and diameter. According to our performance assessment, pure UHP exhibits the behaviour of a non‐ideal tertiary explosive. Maximum calculated detonation pressures are below 10 GPa, the order of magnitude for commercial blasting explosives. Small‐scale results are consistent with literature values from large‐scale experiments, although literature on the matter is quite limited. The proposed experimental method can be used to quantify the detonability and performance of other industrial materials that may have energetic properties, or small samples of homemade explosive compositions, avoiding time‐consuming, expensive and potentially hazardous large‐scale experiments.

High-pressure investigations on urea hydrogen peroxide

The effect of high-pressure on the crystal structure of urea hydrogen peroxide has been investigated to 30 GPa. Through in-situ Raman scattering and ADXRD measurements, a first-order phase transition is concluded at 2.5GPa, and the new phase is indexed to a triclinic phase using Rietveld refinement method. Further increase in pressure up to 30 GPa does not show any structural phase transition. From the Raman analysis, the irreversible phase transition should be correlated with the twist structure of urea in the adduct of urea and hydrogen peroxide as a result of the cooperation and competition of inter-molecular hydrogen bonds.

Development of a Sensitive High-Resolution Mass Spectrometry Approach for Urea Nitrogen Quantitation in Small Volumes of Bronchoalveolar Lavage Fluid (BALF).

A sensitive, selective, and quantitative method incorporating high-resolution mass spectrometry was developed for the determination of blood urea nitrogen (BUN) in bronchoalveolar lavage fluid. The method requires no sample cleanup or derivatization prior to analysis. High-performance liquid chromatography (HPLC) on a Hypersil Gold PFP column (100 × 3 mm, 3 μm particle size) connected to a C18 guard column was employed for a 10 min chromatographic separation. The detection of urea was achieved using a Thermo Scientific Q-Exactive Plus instrument incorporating selected ion monitoring (SIM) modes for the protonated adduct of urea. The urea analytical measuring range for the method is 0.047-17.134 mg/dL, resulting in a BUN analytical measurement range of 0.022-8.007 mg/dL, which allows for quantitation over 3 orders of magnitude (R2 = 0.999). In addition, the method is suitable for small sample volumes (15 μL) with a high level of accuracy, precision, and specificity.

Crystalline adducts of urea with magnesium iodide

The crystal structures of newly obtained [Mg(OC(NH2)2)2(H2O)4]I2 (tetraaqua bis (urea-O) magnesium diiodide), [Mg(OC(NH2)2)4(H2O)2]I2 (diaqua tetra(urea-O) magnesium diiodide) and [Mg(OC(NH2)2)6]I2 . 4OC(NH2)2 (hexa(urea-O) magnesium diiodide tetraureate) are reported. It is found that the studied compounds crystalize in one and the same space group P21/c and exhibit structure isotypical with the corresponding chlorides and bromides. The complexes were characterized by experimental IR spectroscopic and DTA-TG analyses, and DFT/B3LYP free energy and vibrational calculations at molecular level. The observed trans-conformation in the crystaline (MgX6)2+units was supported by calculated larger thermodynamic stability of trans- conformers as compared to cis ones. The inclusion of Urea in Mg2+ complexes was preferred over water in agreement with the calculated exothermic exchange reactions. The comparative IR spectroscopic analysis of urea and the three Mg2+ complexes studied revealed that ν(C = O)U band shift could be an indication of Mg - OU bond formation and its relative strength. The thermal analyses and calculated exchange reaction energies predicted larger stability of the Mg2+ complexes with an increase of the number of the urea (respectively a decrease of water's number in the first coordinating shell) due to formation of specific network of hydrogen bonds.

Ionic Liquids and Deep Eutectic Solvents and Their Use for Dissolving Animal Hair

In recent years, one of the priority areas of research in chemistry has become the processes carried out in an environment of liquid organic salts, the so-called ionic liquids (ILs), which are assessed as environmentally friendly or “green” alternatives to conventional organic solvents. ILs are non-volatile, highly polar solvents that dissolve many organic, inorganic, and organometallic compounds. Since they have no detectable vapor pressure, ILs are considered as potential substitutes for volatile organic compounds traditionally used as solvents. So-called deep eutectic solvents (DES) is a group of ILs that are liquid mixtures of a number of organic and (or) inorganic components taken in a certain ratio (eutectic or close to eutectic). DES deserve a special attention due to their negligible saturated vapor pressure, availability, low cost, as well as ability to dissolve at relatively high concentration of metal salts, metal oxides and various polymers. Particularly DES based on a mixture of choline chloride with urea (DES-1) or a mixture of choline chloride and adduct of urea with hydrogen peroxide (DES-2) give eutectics that are liquid at ambient temperature and have unusual solvent properties, including an ability to dissolve an animal hair in the presence of low concentration of sodium sulfide or ammonium thioglycolate. It was found that depending on the ratio between DES-1 and DES-2 in the mixture of two Deep Eutectic Solvents and the nature of sulfur-containing additive, the solubility of rabbit hair under used conditions, varies from 51% to 79%.

New Urea Derivatives as Potential Antimicrobial Agents: Synthesis, Biological Evaluation, and Molecular Docking Studies.

A series of new urea derivatives, containing aryl moieties as potential antimicrobial agents, were designed, synthesized, and characterized by 1H NMR, 13C NMR, FT-IR, and LCMS spectral techniques. All newly synthesized compounds were screened in vitro against five bacterial strains (Escherichia coli, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Staphylococcus aureus) and two fungal strains (Candida albicans and Cryptococcus neoformans). Variable levels of interaction were observed for these urea derivatives. However, and of major importance, many of these molecules exhibited promising growth inhibition against Acinetobacter baumannii. In particular, to our delight, the adamantyl urea adduct 3l demonstrated outstanding growth inhibition (94.5%) towards Acinetobacter baumannii. In light of this discovery, molecular docking studies were performed in order to elucidate the binding interaction mechanisms of the most active compounds, as reported herein.

Preparation of High-Purity Trilinolein and Triolein by Enzymatic Esterification Reaction Combined with Column Chromatography.

High-purity trilinolein and triolein were prepared by Novozym 435-catalyzed esterification reaction combined with column chromatography purification in this study. Firstly, linoleic acid and oleic acid were respectively extracted from safflower seed oil and camellia seed oil by urea adduct method. Secondly, trilinolein and triolein were synthesized through Novozym 435 catalyzed esterification of glycerol and fatty acids. The best synthesis conditions were obtained as follows: reaction temperature 100°C, residual pressure 0.9 kPa, enzyme dosage 6%, molar ratio of glycerol to linoleic acid 1:3 and reaction time 8 h. Crude trilinolein and triolein were further purified by silica gel column chromatography. Finally, highpurity trilinolein (95.43±0.97%) and triolein (93.07±1.05%) were obtained.

Eutectic System Based on Urea and Potassium Sodium Tartrate

Deep eutectic solvents (DESs) are considered as better alternative solvents in chemical and physical processes. The binary mixture of urea and potassium sodium tartrate is explored in this study. A eutectic system is determined at composition made up of 33% potassium sodium tartrate and 67% urea (1:2 molar ratio). This eutectic system has a freezing point of 19.83 ± 0.76 °C, density of 1.1971 ± 0.0003 g mL-1, and viscosity of 34.4226 ± 0.0665 cP. The most stable conformation for the adduct of urea and potassium sodium tartrate with water molecules was determined through density functional calculations. The gas phase total energy for the adduct was determined as -5576863 kJ mol-1. Electrostatic interactions between the cations and the carboxylate sites are present, H-bonding between protons of urea and the hydroxyl oxygen of the tartrate, and intramolecular H-bonding between the hydroxyl and carboxylate sites of tartrate are accounted in the structure. The total energy associated with nonbonding interactions is computed as -826 kJ mol-1, which suggests that these interactions stabilize the formation of the DES system of potassium sodium tartrate and urea.

An Alternate Route of Transforming meso-Tetraarylporphyrins to Porpholactams, and Their Conversion to Amine-Functionalized Imidazoloporphyrins

A novel and efficient synthetic pathway toward known meso-tetraphenylporpholactams, also applicable to the synthesis of hitherto unknown and inaccessible meso-C6F5-substituted porpholactam, is detailed (dioxochlorin → dioxochlorin urea adduct → porpholactam). meso-Tetraphenylporpholactam was converted to an imidazoloporphyrin-α-triflate derivative that was demonstrated to be of utility for the generation of functionalized imidazoloporphyrins with a substituted amine adjacent to the outside N atom of the imidazole moiety (using pyridine, Et2NH, diethyliminodiacetic acetate, dipicolylamine (DPA), and cyclen). The DPA- and iminodiacetate-imidazoloporphyrin conjugates were structurally characterized. The chemosensing potential of the metal chelate-imidazoloporphyrin conjugates was evaluated, though their constrained metric parameters led to muted chemosensing responses to various divalent metal ions. The accessibility of the meso-arylporpholactams and the meso-tetraphenylimidazoloporphyrin triflate enables the continued exploration of porphyrin-like pyrrole-modified porphyrins that incorporate a nitrogen atom in place of a β-carbon atom in their macrocycles.

Pyridine 1:1 adducts of urea (Z' = 1) and thiourea (Z' = 8).

During our studies of urea and thiourea adducts, we noticed that no adducts with unsubstituted pyridine had been structurally investigated. The 1:1 adduct of pyridine and urea, C5H5N·CH4N2O, crystallizes in the P21/c space group with Z= 4. The structure is of a standard type for urea adducts, whereby the urea molecules form a ribbon, parallel to the a axis, consisting of linked R22(8) rings, and the pyridine molecules are attached to the periphery of the ribbon by bifurcated (N-H...)2N hydrogen bonds. The 1:1 adduct of pyridine and thiourea, C5H5N·CH4N2S, crystallizes in the P21/n space group, with Z = 32 (Z' = 8). The structure displays similar ribbons to those of the urea adduct. There are two independent ribbons parallel to the b axis at z ≃ 0 and 1/2, and three at z ≃ 1/4 and 3/4; the latter are crosslinked to form a layer structure by additional long N-H...S interactions, which each formally replace one branch of a bifurcated hydrogen-bond system.

Enrichment of polyunsaturated fatty acids from seal oil through urea adduction and the fatty acids change rules during the process

The seal oil is a good resource of ω-3 polyunsaturated fatty acids (PUFA). Besides being rich in EPA and DHA, it also contains a synergism factor-DPA. Urea adduction is a method that is widely used for the concentration of ω-3 PUFA. The aim of this work was to optimize the concentration conditions (urea/oil ratio, crystallization temperature, and time) for EPA, DPA, and DHA by response surface method and study the change rules of fatty acids during the process. The results showed that the optimal conditions for the enrichment was at 2.38:1 urea/FAEE ratio (w/w) upon crystallization at 15 °C for 2.5 hr. The concentration and recovery were 71.35 and 82.31%, respectively, under the optimal conditions. EPA was more easily to be entrapped into the urea than DPA and DHA. SFA (C14:0, C16:0) can be completely removed by urea adduction, while the urea adduction has limited effect on reducing the content of MUFA (C16:1, C18:1, and C20:1). It is necessary to take other methods to remove it. Practical applications Seal oil is rich in PUFAs (EPA, DPA, and DHA), which are helpful to human health. Urea adduction method is a good way to enrich PUFA from seal oil. The changes in FAEE profiles of the urea inclusion compounds and nonincluded FAEEs versus time is fundamental for a proper design, control, and optimization for the processing of functional seal oil.

UPAYA PEREMAJAAN DAN PENYERAPAN LOGAM MINYAK GORENG BEKAS INDUSTRI MAKANAN TRADISIONAL DENGAN MEMANFAATKAN BIOADSORBEN TANDAN KOSONG KELAPA SAWIT (TKKS)

The research has been carried out in the Processing and Chemistry Laboratory of Politeknik Pertanian Negeri Payakumbuh and Post Harvest Laboratory in Bogor since July until November 2006. The research objectives was to prolong the using time of used cooking oil on food industries through applying the empty fruit bunch of palm bioadsorbent. The optimum condition of TKKS applied were 125 mm size and 5% bioadsorben from the weight of oil (Desminarti dan Rahzarni, 2004). The prolonging of cooking oil application can be done throughrefining used cooking oil so that the part of bad cooking oil can be lremoved. Statistical design used in this research was Completely Randomized Design with four treatments dan three replications. If the result was significant it will be followed by DMRT test on 5% significant level. Based on the experiment could be concluded that that four times titration could produced the oil based on SNI criterya in the relation to the water content (0.23%), peroxide value (0.82%) and free fatty acid value (0.23%) and it could also decrease Fe content from 76ppm to 22 ppm, Cu from 1.2 ppm to 0.40 ppm and Non Urea Adduct Forming (NAF) from 126 ppm to 102 ppm. The bioadsorbent sorption content on water varied from 78% to 80%; peroxide value from 14.71 to 59.80%, free fattyacid from 55.61 to 89.25%, Fe from 68.42 to 71.05%, Cu from 5% to 60% and NAF from 17.46 to 19.05%.

Unusual Reactions of NacNacAl with Urea and Phosphine Oxides.

The reaction of cyclic urea 1,3-dimethyl-2-imidazolidinone with the aluminum(I) compound NacNacAl (1) gives an unexpected adduct of urea with the isomerized aluminum(III) hydride NacNac'AlH(O═SIMe) (3). A related reaction of 1 with phosphine oxides results in cleavage of the P═O bond and formation of hydroxyl derivatives NacNac'Al(OH)(O═PR3) [R = Ph (5) and Et (6)]. Density functional theory calculations revealed that these reactions proceed via a bimolecular mechanism in which either the basic aluminum(I) center or the transient Al═O species deprotonate the methyl group of the NacNac ligand.

Assessment of n-alkanes and acyclic isoprenoids (geochemical markers) in crudes: A case study of Iraq and Niger delta, Nigeria

This study was designed to determine the ratios of the isoprenoids and n-alkanes in an imported crude oil sample (Bassrah from Iraq) and four crude oil samples (Bodo, Bonny-Export, Escravos and Penningston) from the Niger Delta region of Nigeria to ascertain the levels of maturity and as an indicator of the depositional environment of the crudes. The physical properties of the crudes: viscosity, density and °API gravity were also determined. Fractionation of the crudes was done using a new approach coded NAASAR, (n-alkanes, asphaltenes, aromatics and resins) comprising urea adduction followed by gas chromatographic analyses (for n-alkanes), n-heptane precipitation (for asphaltenes) and column chromatography (for resins). Results showed °API gravities Bassrah 28.03°, Bodo 31.89°, Bonny-Export 33.8°, Escravos 33.8°, and Penningston 33.8° indicating that Escravos, Penningston and Bonny-Export crudes are light crudes while Bodo and Bassrah crudes are medium crudes. The n-alkanes profiles of the five crudes were determined by gas chromatography ranged from n-C8H18 to n-C40H82 with total weight percent n-alkane yield Bassrah 11.2, Bodo 47.41, Bonny-Export 32.47, Escravos 5.58, Penningston 30.75 were obtained by urea adduction. The pristane to phytane ratios were computed, Bassrah 1.51, Bodo 1.48, Bonny-Export 1.08, Escravos 1.01 and Penningston 2.41. Isoprenoids to n-alkane ratios Pr/n-C17 in the same order of the crudes were 0.85, 0.83, 0.67, 0.65, 0.95 while phytane to n-C18 ratios were 0.61, 0.55, 0.62, 0.61 and 0.43. The results established the increasing level of maturity as obtained from Pr/n-C17 ratio in the order: Penningston<Bassrah<Bodo<Bonny-Export<Escravos. The result of Pr/Ph ratios show the same trend in the level of maturity. Penningston crude with Pr/Ph ratio 2.41 shows that the crude is deposited in fluviomarine and coastal swamp environment while Bassrah, Bodo, Bonny-Export and Escravos crudes indicate aquatic depositional environment (anoxia) condition.

Identification and quantification of ethyl carbamate occurring in urea complexation processes commonly utilized for polyunsaturated fatty acid concentration.

The concentration of polyunsaturated fatty acids by formation of urea adducts from three different sources was studied to elucidate the formation of ethyl carbamates in the course of these procedures. Two different methodologies were performed: with ethanol at high temperature and with hexane/ethanol mixtures at room temperature. It was proved that the amount of urethanes generated at high temperature was higher than at room temperature. Besides, subsequent washing steps of the PUFA fraction with water were efficient to remove the urethanes from the final products. The methodology at room temperature with 0.4mL ethanol and 3g urea provided good relationship between concentration and yield of the main bioactive PUFA, with the lowest formation of ethyl carbamates in the process.