Formaldehyde Hydrazone Research Articles

Bismuth-coated screen-printed carbon electrodes for quantitative voltammetric determination of formaldehyde in urotropin

For the first time, a bismuth-modified electrode is used for the quantitative voltammetric determination of formaldehyde (FA) in urotropin. The well-established method of forming formaldehyde hydrazone (FAH) in the presence of hydrazine sulphate (HRZ) was employed to transform the hydrated form of FA into its electrochemically active derivative. The reduction current of FAH was recorded in a phosphate buffer solution (PBS, pH 5.2±0.1) in the presence of 0.09 M HRZ on a screen-printed carbon electrode that had been preliminarily modified with a bismuth film. A 20-second electrolysis at an applied potential of –0.28 V in a solution comprising 1 M HCl, 0.5 M NaBr, and 4 g/L Bi(III) resulted in the formation of a well-developed metal layer with an active surface. The determination of FA in technical urotropin yielded satisfactory results, indicating the potential for further applications of Bi/SPCE in pharmaceutical analysis.

Neutral Red as a Redox Probe for Comparative Evaluation of Electrochemical Performance of Bismuth Modified Electrodes

For the first time, Neutral Red (NR) has been used as a redox probe for comparative evaluation of the electrochemical performance of screen-printed carbon electrodes (SPCEs) modified with bismuth under different potentiostatic pre-plating conditions (Bi/SPCEs). It was shown that protonated NR undergoes quasi-reversible redox transformations at bare-SPCE and Bi/SPCEs in the pH range 5–6 in phosphate buffer solutions (PBS) in the potential range of (−0.2)–(−0.8) V, where bismuth is not electroactive. Bi/SPCEs have been characterized morphologically by scanning electron microscopy (SEM) and electrochemically by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) employing NR as a redox probe. The obtained SEM, CV, and EIS data are in good agreement. The highest charge transfer resistance (Rct) values (3.9 and 3.3 kΩ) were obtained at bare-SPCE and Bi/SPCE having low degree of bismuth coverage. Contrarily, the lowest Rct value (8 Ω) was recorded at Bi/SPCE, with the highest degree of bismuth coverage. CV experiments showed a significant increase in the electrochemical performances of Bi/SPCEs, whose surface is half or more covered with bismuth, in comparison to the bare-SPCE. Nickel (II) ions and formaldehyde (FM), in the form of formaldehyde hydrazone (FAH), were used as model analytes to determine the electroanalytical performance of Bi/SPCEs. A comparison of roughness factor and sensitivity toward both analytes for Bi/SPCEs with two-tailed Pearson’s criterion showed a high degree of correlation between their electrochemical and electroanalytical characteristics. The data acquired indicates that the use of NR as a redox probe may be quite helpful to control modification processes when developing novel bismuth-containing sensors.

3,3,4,4-Tetracyanoalkanones as expedient reagents for utilization of N,N-dimethylhydrazine

To utilize N,N-dimethylhydrazine, the corresponding +formaldehyde hydrazone was reacted with 1,1,2,2-tetra-cyanoethane or 3,3,4,4-tetracyanoalkanones. The first process yielded 5-amino-1-dimethylamino-1,2-dihydro-3H-pyrrole-3,3,4-tricarbonitrile while the second afforded pyrrolo[3,4-c]quinolone multifunctional derivatives. These resultant products hold promise in molecular design and pharmaceutical chemistry.

Bismuth-coated screen-printed electrodes for the simple voltammetric determination of formaldehyde.

For the first time, bismuth modified electrodes have been used for the voltammetric detection of formaldehyde (FM). The well-known method of forming formaldehyde hydrazone (FAH) in the presence of hydrazine sulphate was used to convert the hydrated form of FM into its electrochemically active derivative. Various experimental conditions for differential pulse voltammetry were studied to achieve the best analytical performance. The FAH reduction current (FM response) reaches its maximum value at a pH of a phosphate buffer solution of 5.2 ± 0.1 in the presence of 0.09-0.12 M hydrazine sulfate on a bismuth film preliminarily precipitated for 8-12 min from acidic Bi(III) acetate solutions at an electrolysis potential of -1.0 V on the surface of a screen-printed carbon electrode (SPCE). A dendritic-like film structure was created on the SPCE surface. Under the optimized conditions a linear calibration curve over the range of 0.01-5 mg L-1 (0.33-167 μM) FM was achieved, with a detection limit of 0.002 mg L-1 (0.06 μM). The determination of FM in waste water, melt water from snow within the city industrial zone, and a widely used pharmaceutical preparation "Endofalk®" with good results revealed the potential applicability of a bismuth modified SPCE (BiSPCE) for trace analysis.

Determination of Formaldehyde Yields in E-Cigarette Aerosols: An Evaluation of the Efficiency of the DNPH Derivatization Method

Recent reports have suggested that (1) formaldehyde levels (measured as a hydrazone derivative using the DNPH derivatization method) in Electronic Nicotine Delivery Systems (ENDS) products were underreported because formaldehyde may react with propylene glycol (PG) and glycerin (Gly) in the aerosol to form hemiacetals; (2) the equilibrium would shift from the hemiacetals to the acetals in the acidic DNPH trapping solution. In both cases, neither the hemiacetal nor the acetal would react with DNPH to form the target formaldehyde hydrazone, due to the lack of the carbonyl functional group, thus underreporting formaldehyde. These reports were studied in our laboratory. Our results showed that the aerosol generated from formaldehyde-fortified e-liquids provided a near-quantitative recovery of formaldehyde in the aerosol, suggesting that if any hemiacetal was formed in the aerosol, it would readily hydrolyze to free formaldehyde and, consequently, form formaldehyde hydrazone in the acidic DNPH trapping solution. We demonstrated that custom-synthesized Gly and PG hemiacetal adducts added to the DNPH trapping solution would readily hydrolyze to form the formaldehyde hydrazone. We demonstrated that acetals of PG and Gly present in e-liquid are almost completely transferred to the aerosol during aerosolization. The study results demonstrate that the DNPH derivatization method allows for an accurate measurement of formaldehyde in vapor products.

Determination of formaldehyde in air in selected hospital-histopathology laboratories in Cagayan de Oro, Philippines

The study focused on the occupational exposure of gaseous formaldehyde (HCHO) in selected hospital-histopathology laboratories in Cagayan de Oro. This was carried to estimate the potential levels of HCHO during gross-cutting period using absorbent medium between two time intervals. Modified passive sample set-ups of 2,4-dinitrophenylhydrazine (DNPH) and DNPH-coated silica were used for air sample collection between 1 h and 3 h intervals and were analyzed spectrometrically. Infrared (IR) analysis for DNPH-coated silica sample showed relevant peaks of the known IR spectra of formaldehyde hydrazone: 1,600–1,636 cm −1 (C N); 1,000–1,350 cm −1 (C N); 2,945–2,900 cm −1 (aliphatic stretch); 3,218–3,080 cm −1 (NH N); and 880–900 cm −1 (meta disubstituted aromatic). Generally, gaseous HCHO concentrations in three histopathology laboratories during its gross-cutting period exceeded the recommended exposure ceiling limits of American Conference of Industrial Hygienists (ACGIH) and United States Department of Labor-Occupational Safety and Health Administration (USDOL-OSHA) (0.3–0.75 ppm). Absorbing efficiency of DNPH set-up was statistically different from that of DNPH-coated silica set-up. Increased concentration was observed for the 3 h interval using DNPH-coated (0.93 ± 0.32 ppm (Hospital A), 0.80 ± 0.59 ppm (Hospital B), and 1.03 ± 0.36 ppm (Hospital C)). Thus, the installation of exhausts ventilation system was seen necessary to minimize occupational exposure.

ChemInform Abstract: “On Water” Nucleophilic Addition of Formaldehyde N,N‐Dialkylhydrazones to α‐Keto Esters.

AbstractThe use of water as the reaction mixture is key for the nucleophilic addition of formaldehyde hydrazones to α‐keto esters, leading to highly functionalized carbinols in high yields and short reaction times.

“On Water” Nucleophilic Addition of Formaldehyde N,N‐Dialkylhydrazones to α‐Keto Esters

Water solves the problem: The use of pure water as the reaction mixture is key for the nucleophilic addition of formaldehyde hydrazones to α-keto esters, leading to highly functionalized carbinols in high yields and short reaction times. The need for heterogeneous conditions and the observed solvent kinetic isotope effect are in agreement with the proposed “on water” activation.

Reactions of Arenediazonium o‐Benzenedisulfonimides with Aliphatic Triorganoindium Compounds

AbstractThe reaction of various arenediazonium o‐benzenedisulfonimides with aliphatic triorganoindium compounds is described. Surprisingly, with triethyl‐ or tributylindium we obtained N‐ethyl‐ or N‐butylanilines, respectively. This is the first case in which, at least formally, the reactive site of a diazonium salt is the nitrogen atom directly bonded to the aromatic ring. In contrast, with trimethylindium we obtained only formaldehyde (aryl)hydrazones. In order to explain the difference between trimethyl‐ and triethylindium we have proposed some reaction mechanisms, supported by detailed density functional (DFT) calculations. The possible role of diazene/hydrazone tautomerism initially assumed was discarded and therefore three mechanisms for the key step (nucleophilic addition of the trialkylindium to the N=N double bond of diazene) were studied. For the favoured mechanism there is a difference in the energy barriers of 2 kcal mol–1 between the reactions with trimethyl‐ and triethylindium. This difference is explained on the basis of the different C–In bond energies in the two organometallics and it is assumed to be enough to explain their different behaviour under the experimental conditions.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

Organocatalytic Conjugate Addition of Formaldehyde N,N-Dialkylhydrazones to β,γ-Unsaturated α-Keto Esters

(1S,2R)-1-Aminoindan-2-ol-derived thioureas behave as efficient H-bonding organocatalysts for the nucleophilic conjugate addition of formaldehyde hydrazones to beta,gamma-unsaturated alpha-keto esters as enoate surrogates, affording the corresponding adducts in good yields and enantioselectivities.

Development of a Passive Sampler for Long-Term Measurements of Formaldehyde and Total Oxidants in Air

A diffusive sampling device is described that is capable of reliable measurements of formaldehyde and total oxidants (Ox = ozone + nitrogen dioxide) at sub-ppbv concentration levels in ambient air. These species are collected on silica gel particles coated with 1-methyl-1-(2,4-dinitrophenyl)hydrazine (MDNPH) and phosphoric acid. The formaldehyde hydrazone (HCHO-MDNPh) and the N-methyl-2,4-dinitroaniline (MDNA) formed are extracted with acetonitrile and determined by HPLC with UV detection at 365anm. The measured sampling rate for HCHO, 15.0 mLmin-1, agrees well with the theoretical value of 16.0, whilst an experimental sampling rate of 10.7 mLmin-1 (25% lower than the calculated one) is observed for Ox. The sampling rates seem to be independent of the sampling duration up to one month. The precision of the measurements for co-located passive samplers averaged is 7.3% for HCHO and 7.2% for Ox in urban air.

Determination of airborne formaldehyde by active sampling on 3-methyl-2-benzothiazolinone hydrazone hydrochloride-coated glass fibre filters.

Formaldehyde was sampled with the use of a standard miniature glass fibre filter coated with 3-methyl-2-benzothiazolinone hydrazone hydrochloride (MBTH). The formaldehyde hydrazone formed [i.e., the adduct of formaldehyde (HCHO) and MBTH] was desorbed from the filter with water and then oxidised by an iron(III) chloride-sulfamic acid solution to form a blue cationic dye in acidic medium which was subsequently determined by visible absorption at 628 nm. The recovery of HCHO as the cationic dye from MBTH-coated filters is 87-102% in the range 0.065-2.9 micrograms of HCHO. This corresponds to 4.3-193.3 micrograms m-3 in a 15 L air sample. The collection efficiency of the MBTH-coated filter is higher than 90%. When the filter sampling system is used in active mode, air can be sampled at a rate of up to 1 L min-1, affording an overall sensitivity of about 3 micrograms m-3, corresponding to about 2 ppb v/v HCHO at 1 atm and 273 K. The method was successfully applied to the determination of HCHO in samples of indoor and outdoor air with satisfactory results.

Enantioselective Synthesis of 4-Unsubstituted 3-Alkoxy- and 3-Aminoazetidin-2-ones from Formaldehyde N,N-Dialkylhydrazones

Playing two roles at once, chiral amines from L-proline or D-mannitol act as protecting groups and as chiral auxiliaries in the [2+2] cycloaddition of formaldehyde hydrazones, such as 1, to ketenes. This strategy, based on the stability of the hydrazones as methanimines and on the development of a new oxidative cleavage of hydrazides, provides a short entry to enantiopure 4-unsubstituted 3-alkoxy- and 3-aminoazetidinones with desired configurations. X=OBn, N(CO2Bn)Bn; Bn=benzyl; MMPP=magnesium monoperoxyphthalate.

Molecular Orbital Calculations on the Electronic Structures of Some Arylhydrazones

The geometry and electronic structure of the parent formaldehyde hydrazone and some ethylcyanoacetate phenylhydrazones (ECPHs) are studied at the semiempirical level of MO theory using the AM1 method. The effect of substitution on the geometry of the hydrazone moiety is investigated. The optimized geometry of formaldehyde hydrazone is nonplanar while in the ECPHs the planarity of the hydrazone group and its coplanarity with the phenyl ring increase in the direction of the electron-attracting ability of the para substituent. This has been attributed to an increase in the p–π conjugation between the lone pair of electrons on the amine nitrogen and the phenyl ring. Variations of ionization potentials and bond orders with the Hammett constant, σ p , are examined and straight-line relationships are obtained. The results are correlated with the observed variations in the experimentally measured electrical conductivities of the studied compounds.

Determination of sub-ppbv levels of formaldehyde in ambient air using Girard's reagent T-coated glass fiber filters and adsorption voltammetry

Formaldehyde (HCHO) present in ambient air was trapped on a standard minature glass fiber filter impregnated with Girard's reagent T (GRT). The formaldehyde hydrazone formed (i.e. the adduct of formaldehyde and Girard's reagent T, FGA) is desorbed from the filter with water and determined by adsorption voltammetry. Recovery of formaldehyde as the FGA from a 13 mm impregnated filter is 87–104% in the range 0.06–30 μg of formaldehyde. This corresponds to 2.0–1000 μg m −3 in a 30 1 air sample. The collection efficiency of the coated filter is greater than 90%. The GRT-coated glass fiber filter can be sampled at a rate of up to 1 l min −1 when the system is used in the active mode, and a detection limit of about 1 μg m −3 (corresponding to about 0.7 ppbv HCHO at standard state) based on a 30 1 air sample is obtained. Results are given from measurements of formaldehyde in ambient air of both indoor and outdoor environments.

Certification of reference materials related to the monitoring of aldehydes in air by derivatization with 2,4-dinitrophenylhydrazine

Reference materials related to the monitoring of aldehydes in air by derivatization with 2,4-dinitrophenylhydrazine (DNPH) and subsequent determination of the hydrazone by HPLC were prepared and certified. The materials are the solid hydrazones of formaldehyde (CRM 546), acetaldehyde (CRM 547), acrolein (CRM 548); acetone (CRM 549); and glutaraldehyde (CRM 550); a mixture of the hydrazones of formaldehyde, acetaldehyde, acrolein and acetone in acetonitrile with excess DNPH (CRM 551); a blank solution of DNPH in acetonitrile (CRM 552); formaldehyde hydrazone on a glass-fibre filter impregnated with DNPH (CRM 553); and a blank filter impregnated with DNPH (CRM 554). The materials were found to be homogeneous and stable. These Community Bureau of Reference (BCR) Certified Reference Materials (CRMs) are recommended for quality control and for calibration purposes.

Methylation status of DNA cytosine during the course of induction of liver cancer in hamsters by hydrazine sulfate.

Hydrazine, which is toxic and carcinogenic to rodent liver, has been shown to react with endogenous formaldehyde in the liver to form formaldehyde hydrazone (CH2 = N-NH2), an alkylating intermediate that methylates DNA guanine at the N7- and O6-positions. Studies were conducted to investigate the role of chronic hydrazine-induced hepatotoxicity on DNA maintenance methylation (formation of 5-methyldeoxycytosine) and the development of liver cancer. Male Syrian golden hamsters were given hydrazine sulfate (0, 170, 340 and 510 mg/l) in drinking water for 21 months (average dose 0, 4.2, 6.7 and 9.8 mg/kg body wt hydrazine as the free base). Hepatotoxicity was evaluated histologically, and regenerative DNA synthesis and maintenance methylation were measured as the incorporation of [methyl-14C]thymidine into DNA and the methyl moiety of [methyl-3H]methionine into 5-methyldeoxycytosine in DNA, respectively. Methylguanines were detected in liver DNA at the first observation time of 6 months of treatment; levels of these aberrant bases decreased or became undetectable at 14 months, and increased in a dose-related manner for the remainder of the study. DNA adducts persisted in the highest dose group throughout the study, repeating the results of a similar study previously reported by this laboratory (Bosan et al., Carcinogenesis, 8, 439-444, 1987). Linear regression analysis of thymidine and methionine methyl moiety incorporation into liver DNA suggested impairment of maintenance methylation of DNA (5-methyldeoxycytosine) in the middle and high exposure animals. Hepatic adenomas and hepatocellular carcinomas developed in a dose-related manner and were highly correlated to decreased uptake of radiolabel from methionine into DNA 5-methylcytosine. These results are part of a continuing study on alteration of maintenance methylation during hydrazine induction of liver cancer.

Oxidation of 1,1-dimethylhydrazine (UDMH) in aqueous solution with air and hydrogen peroxide

The degradation of 1,1-dimethylhydrazine (UDMH), a component of some rocket fuels, was investigated using atmospheric oxygen and hydrogen peroxide. The reactions were carried out in the presence and absence of copper catalysis and at varying pH. Reactions were also carried out in the presence of hydrazine, a constituent, along with UDMH, of the rocket fuel Aerozine-50. In the presence of copper, UDMH was degraded by air passed through the solution; the efficiency of degradation increased as the pH increased but the carcinogen N-nitrosodimethylamine (NDMA) was formed at neutral and alkaline pH. Oxidation was not seen in the absence of copper. Production of NDMA occurred even at copper concentrations of < 1 ppm. Oxidation of UDMH with hydrogen peroxide also gave rise to NDMA. When copper was absent degradation of UDMH did not occur at acid pH but when copper was present some degradation occurred at all pH levels investigated. The production of NDMA occurred mostly at neutral and alkaline pH. In general, higher concentrations of hydrogen peroxide and copper favored the production of NDMA. Dimethylamine, methanol, formaldehyde dimethylhydrazone, formaldehyde hydrazone, and tetramethyltetrazene were also produced. The last three compounds were tested and found to be mutagenic.

Mechanism of the Beckmann rearrangement of formaldehyde oxime and formaldehyde hydrazone in the gas phase

The potential energy surfaces corresponding to the Beckmann rearrangement of protonated formaldehyde oxime and formaldehyde hydrazone in the gas phase have been explored using ab initio molecular orbital calculations. Geometries of stationary points were optimized at the HF and MP2/6–31G(d,p) level while relative energies were estimated at the MP4SDTQ/6–311++ G(d,p) level and corrected for zero-point energies. Both rearrangements are calculated to be concerted with a single transition structure, connecting the protonated species and the product complex. In the transition structure, the 1,2-hydrogen shift from C to N is accompanied by a lengthening of the N–O (in oxime) or N–N (in hydrazone) distance, and the migrating hydrogen is in trans relative to the leaving group across the CN bond. The transition structure in the hydrazone case is much closer to the final products than that in the oxime. This is also manifested by the energy barriers that amount to 44 and 189 kJ mol–1 for oxime and hydrazone, respectively. These results suggest that the Beckmann rearrangement of oxonium ion is a facile process, while that of hydrazonium ion is reachable under thermal conditions. The experimentally observed loss of HCN from hydrazonium ion can be better rationalized in terms of a Beckmann rearrangement than a 1,2-cis-elimination as recently proposed. The proton affinities at different sites in oxime and hydrazone are also evaluated.

Photoelectronic spectrum and electronic structure of formaldehyde hydrazone

Photoelectronic spectrum and electronic structure of formaldehyde hydrazone