MECHANISM OF GUANIDINE NITRATION: II. TETRAETHYLNITROGUANIDINE

1957 ◽  
Vol 35 (6) ◽  
pp. 527-540 ◽  
Author(s):  
M. W. Kirkwood ◽  
George F Wright
Keyword(s):  
Nitric Acid ◽  
Sulphuric Acid ◽  
Kinetic Studies ◽  
Side Reaction ◽  
Irreversible Reaction

The preparation of sym-tetraethylnitroguanidine now shows that a ketimino group can be nitrated directly. The mode of nitration has been evaluated first by determination of the ionization of guanidine bisulphate (prepared anew) and tetraethylguanidine in nearly-anhydrous sulphuric acid by means of an improved cryoscope, and by comparison of these ionizations with those of substances the ionizing behavior of which may be reliably predicted. Subsequent studies show that the stronger base, sym-tetraethylguanidine, is nitrated more slowly than guanidine, both reactions being reversible. Detailed kinetic studies were not made because of the irreversible side-reaction yielding tetraethylurea. This irreversible reaction, which is suppressed by sodium bisulphate but not by nitric acid, is presumptive for the existence of an intermediate nitrotetraethylguanidinium salt out of which the tetraethylnitroguanidine or tetraethylurea may arise.

scholarly journals Determination of Methylene blue Number to Characterize the Lapsi Based Activated carbon Prepared by Chemical Carbonization

2020 ◽  
Vol 15 (1) ◽  
pp. 177-180
Author(s):  
Rajeshwar Man Shrestha
Keyword(s):  
Methylene Blue ◽  
Activated Carbon ◽  
Nitric Acid ◽  
Sulphuric Acid ◽  
Activated Carbons ◽  
Single Point ◽  
Batch Adsorption ◽  
Adsorption Method ◽  
Methylene Blue Number

 Determination of Methylene blue Number of the activated carbons prepared by Chemical Carbonization from waste material, seed stone of Lapsi has been studied. Methylene blue Number has been determined by single point method using batch adsorption method. Acids like concentrated sulphuric acid and a mixture of concentrated sulphuric acid and concentrated nitric acid have been used to prepare activated carbon. The activated carbon prepared by using a mixture of concentrated sulphuric acid and concentrated nitric acid has been found to have higher methylene blue number than the activated carbon prepared by using concentrated sulphuric acid. The activated carbons thus prepared can be used as effective adsorbents for the remediation of pollutants from water.

Stability Indicating Liquid Chromatographic Method for the Determination of Fenofibrate and its Application to Kinetic Studies

2013 ◽  
Vol 5 (4) ◽  
pp. 1866-1874
Author(s):  
K. Srinivasa Rao ◽  
Keshar N K ◽  
N Jena ◽  
M.E.B Rao ◽  
A K Patnaik
Keyword(s):  
Degradation Products ◽  
Kinetic Studies ◽  
Pharmaceutical Formulations ◽  
Assay Method ◽  
Pharmaceutical Dosage Form ◽  
Stability Indicating ◽  
Zero Order Kinetics ◽  
Relative Standard ◽  
Liquid Chromatographic

A stability-indicating LC assay method was developed for the quantitative determination of fenofibrate (FFB) in pharmaceutical dosage form in the presence of its degradation products and kinetic determinations were evaluated in acidic, alkaline and peroxide degradation conditions. Chromatographic separation was achieved by use of Zorbax C18 column (250 × 4.0 mm, 5 μm). The mobile phase was established by mixing phosphate buffer (pH adjusted 3 with phosphoric acid) and acetonitrile (30:70 v/v). FFB degraded in acidic, alkaline and hydrogen peroxide conditions, while it was more stable in thermal and photolytic conditions. The described method was linear over a range of 1.0-500 μg/ml for determination of FFB (r= 0.9999). The precision was demonstrated by relative standard deviation (RSD) of intra-day (RSD= 0.56– 0.91) and inter-day studies (RSD= 1.47). The mean recovery was found to be 100.01%. The acid and alkaline degradations of FFB in 1M HCl and 1M NaOH solutions showed an apparent zero-order kinetics with rate constants 0.0736 and 0.0698  min−1 respectively and the peroxide degradation with 5% H2O2 demonstrated an apparent first-order kinetics with rate constant k = 0.0202 per min. The t1/2, t90   values are also determined for all the kinetic studies. The developed method was found to be simple, specific, robust, linear, precise, and accurate for the determination of FFB in pharmaceutical formulations.  

Oxidation scheme of symmetrically disulphonated naphthidines with cerium(IV) sulphate

1981 ◽  
Vol 46 (3) ◽  
pp. 561-572 ◽  
Author(s):  
Karel Komers
Keyword(s):  
Sulphuric Acid ◽  
Rate Constants ◽  
Oxidation Product ◽  
Side Reaction ◽  
Reaction Scheme ◽  
Second Order ◽  
Intermediate Products ◽  
Stable Intermediate ◽  
Starting Compound ◽  
Oxidation Agent

The author derived theoretical dependences of preasymptotic slopes of the currentless E-t curves (potential of an indicator redox electrode against time) on the number of equivalents, n, of added oxidation agent, assuming a reaction scheme of two consecutive concurrent second-order reactions involving the formation of intermediate products ( a side reaction of the starting compound with the final oxidation product leading to an adduct, which undergoes consecutive bimolecular oxidations leading again to the final product). The dependences enable to determine the type of the relatively stable intermediate products and the ratios of the rate constants. The theory was applied to the oxidation of four symmetrically disulphonated naphthidines with cerium(IV) sulphate in aqueous sulphuric acid and the results were substantiated spectrophotometrically

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