Spectrophotometric determination and kinetic studies of condensation of aromatic aldehydes with 1,3-dimethylbarbituric acid

The condensation reaction of 1,3-dimethylbarbituric acid with aromatic aldehydes in ethanol has been investigated spectrophotometrically at 25–35°C. The reaction follows overall second-order kinetics, first-order each in reactant. From the dependence of the rate constants on temperature, activation parameters have been calculated. The rate of condensation increases with the presence of electron donating groups on the aromatic ring of the aldehyde. The rate-determining step involves dehydration of the aldol intermediate. The reaction was found to be catalyzed by HCl solutions. Based on this reaction, determination of 10 aromatic aldehydes in a concentration range of 0.13–70.25 μg/ml is proposed. The method was applied for determination of barbituric and 1,3-dimethylbarbituric acids also.     

Fluorometric determination of aromatic aldehydes with 1,2-Diaminonaphthalene

A new fluorometric method for the determination of aldehydes is presented. 1,2-Diaminonaphthalene reacts with aldehyde in dilute sulphuric acid to give a compound which fluoresces intensely in alkaline medium. The fluorescences produced from aromatic aldehydes in this method are fairly characteristic of individual aldehydes and their intensities are generally higher than those of fluorescences from aliphatic aldehydes. The only interference is from 2-oxo acids. The method may be suitable for the determination of aldehyde in complex samples.     

Photometric determination of alpha-ketoglutaric acid with diazotized sulphanilic acid

A new photometric method for the determination of alpha-ketoglutaric acid is presented. It is based on the colour reaction of alpha-ketoglutaric acid in sodium hydroxide solution with diazotized sulphanilic acid in the presence of sodium sulphite and sodium hypophosphite. This method is highly sensitive and fairly selective for alpha-ketoglutaric acid, and may be suitable for the determination of the acid in complex samples.     

The determination of some aliphatic alcohols and aldehydes by oxidation with acid potassium dichromate

The oxidation of n-propanol and n-butanol and the corresponding aldehydes by dilute acid potassium dichromate has been investigated. Some carbon -carbon bond fission occurs, and it has been shown that this takes place via the enol form of the aldehyde formed in the first stage of the oxidation. However, the proportion of this degradation is constant over a wide range of conditions and the method is capable of being used for the quantitative determination of simple aliphatic alcohols and aldehydes.     

Alginic acid hydrazide and its reactions with aromatic aldehydes

Alginic acid hydrazide was prepared, and its reactions with aromatic aldehydes were studied. The effect of a substituent in the benzene ring of the aldehyde on the number of arylidene groups introduced into the polymer was examined.     

Reaction of diethyldithi ophosphorus acid anilide with aromatic aldehydes

Conclusions The reaction of S,S-diethyl N-phenylamidodithiophosphite with benzaldehyde and p-nitrobenzaldehyde leads to the formation of the corresponding-anilinodithiophosphonates.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1643–1644, July, 1982.     

Fluorimetric determination of aromatic aldehydes with 4,5-dimethoxy-1,2-diaminobenzene

A sensitive fluorimetric method for the determination of aromatic aldehydes is described based on their reaction in dilute acid with 4,5-dimethoxy-1,2-diaminobenzene to give a compound which fluoresces intensely in alkaline solution. The fluorescence is stabilized by β-mercaptoethanol. The method is simple, selective for aromatic and arylaliphatic aldehydes, and sensitive; almost all the aldehydes can be determined at concentrations of 10^-8–10^-7 M.     

Knoevenagel condensation of α,βunsaturated aromatic aldehydes with barbituric acid under non-catalytic and solvent-free conditions

An efficient route for the synthesis of 5-(arylpropenylidine)-2,4,6-pyrimidinetrione 3 from an appropriateα,β-unsaturated aromatic aldehydes 1 and barbituric acid 2 under both non-catalytic and solvent-free microwave irradiation conditions was described.In this way,a range of biologically important compounds 3 was obtained in good to excellent yields (86-98%) in a very short reaction time (30-80s).     

Reactions of aromatic aldehydes and their acetals with phosphorous acid esters

Russian Journal of General Chemistry -     

Ternary condensation of cyclic azomethines,aromatic aldehydes,and barbituric acid: A new approach to the synthesis of 8,15,17-triaza-d-homogonanes

New fused heterocyclic compounds of the 8,15,17-triaza-d-homogonane series have been obtained by ternary condensation of cyclic azomethines (1-methyl-3,4-dihydroisoquinolines) with aromatic aldehydes and barbituric acid in DMF.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 2353–2355, September, 1996.     

Thermogravimetric characteristics of barbituric acid and some of its derivatives

The thermolysis curves of barbituric acid and some of its derivatives have been determined. Barbituric acid, violuric acid and dilituric acid form hydrates while 1,3-dimethylvioluric acid and barbital are anhydrous. Barbital and 1,3-dimethylvioluric acid sublime before decomposition. The differential thermal analysis for dilituric acid showed a sharp exotherm at 190° indicating a violent explosion.     

Detection of some nitrogen compounds and the semiquantitative determination of diphenylamine with p-dimethylaminobenzaldehyde by capillary solid-state spot-tests

Capillary solid-state spot-tests for nitrogen compounds by reaction with p-dimethylamino-benzaldehyde are described. The tests are neither specific nor universally applicable for nitrogen compounds.     

Spectrophotometric determination of hydralazine using p-dimethylaminobenzaldehyde

A new spectrophotometric method for the assay of hydralazine hydrochloride in bulk and dosage forms has been developed. The procedure is based on a condensation reaction between alcoholic solution of hydralazine and acidic solution of p-dimethylaminobenzaldehyde to generate an instant greenish-yellow coloured product. The hydrazone formed absorbed visible light strongly and optimal detector response was obtained at a wavelength of 470 nm with a molar absorptivity of 3.652 × 10³ l mol^?1 cm^?1. Optimization of temperature and time revealed 30 °C and 10 min as the best conditions for optimal color formation, while methanol was found to be the most suitable alcohol as diluting solvent. The reaction product is stable for at least 24 h. Beer’s law was obeyed in the concentration range of 2–10 μg ml^?1. Recovery studies over three days gave a mean recovery of 101.87% with a relative standard deviation of 1.29%. There was no interference from commonly used tablet excipients. There was no significant difference between the results obtained with the new method and the BP iodimetric method (p > 0.05). The proposed method is simple, sensitive, rapid and economical, and could find application as an in-process quality control method for hydralazine.     

Spectrophotometric determination of some aromatic amines

A method for spectrophotometric determination of four aromatic amines is described. The method is based on the reaction between the amine and the colorless Fe(III)-ferrozine complex. The amine reduces iron from Fe(III) to Fe(II) which forms a violet colored complex with ferrozine. The method is suitable for to the determination of 1,4-phenylenediamine, 2,4-diaminotoluene, 8-aminoquinoline and 2-amino-3-hydroxypyridine. The effect of different factors such as; pH, stability of the complex, temperature, ferrozine concentration, Fe(III) concentration and methanol concentration have been studied. The composition of the complex as well as the tolerance amount of other amines have been reported. Maximum absorbance is at 562 nm and Beer's law is obeyed over the ranges 0.17-1.6 ppm for 1,4-phenylenediamine, 0.45-3.7 ppm for 2,4-diaminotoluene, 0.51-3.4 ppm for 8-aminoquinoline and 0.53-4.4 ppm for 2-amino-3-hydroxypyridine. The obtained molar absorbtivities were 4.7x10(4), 2.0x10(4), 1.6x10(4), 1.5x10(3) l mol(-1) cm(-1) respectively.     

A simple method for knoevenagel condensation of α,β‐conjugated and aromatic aldehydes with barbituric acid

Several aromatic and α,β‐conjugated aromatic aldehydes were condensed with barbituric acid in methanol solution in the absence of acid or base as a catalyst, affording 5‐ylidenebarbituric acid derivatives in almost quantitative yields.