scholarly journals Spectrophotometric study of the protonation processes of some indole derivatives in sulfuric acid

1999 ◽  
Vol 64 (12) ◽  
pp. 775-787 ◽  
Author(s):  
Blagoja Andonovski ◽  
Goran Stojkovic
Keyword(s):  
Sulfuric Acid ◽  
Carboxylic Acid ◽  
Dissociation Constants ◽  
Uv Spectroscopy ◽  
Spectrophotometric Study ◽  
Protonated Form ◽  
Indole Derivatives ◽  
Acid Media ◽  
Solvent Parameter ◽  
Pka Value

The protonation of 3-methylindole, D-tryptophan, 3-formylindole, 3-acetylindole and indolyl-2-carboxylic acid in sulfuric acid media was studied by UV spectroscopy. The measurement of the absorbance at four selected wavelengths enabled the calculation of the corresponding molar absorptivities. The results were used to calculate the pKa value of the protonated form of the indole derivatives by the Hammett Method. The Hammett postulate (the slope of the plot log [c(BH+)/c(B)]vs. H should be equal to 1) was tested. The dissociation constants and solvent parameter m* were also obtained by applying the Excess Acidity Method. The position of the additional protons in the protonated compounds is discussed.

scholarly journals UV Spectrophotometric Determination of Thermodynamic Dissociation Constants of Some Aromatic Hydrazones in Acid Media

2019 ◽  
Vol 63 (4) ◽  
Author(s):  
Mirjana Jankulovska ◽  
Ilinka Spirevska ◽  
Vesna Dimova ◽  
Milena Jankulovska
Keyword(s):  
Proton Affinity ◽  
Dissociation Constants ◽  
Uv Spectroscopy ◽  
Sodium Perchlorate ◽  
Atomic Charge ◽  
Protonated Form ◽  
Uv Spectra ◽  
Semiempirical Methods ◽  
Acid Media ◽  
Protonation Site

The spectral behavior of some p-nitro-p-substituted benzoylhydrazones in the perchloric acid media was followed, applying the UV spectroscopy. The position of the absorption maximum in the spectra was defined in acidic media and the electronic transitions were discussed, as well (7<pH<1). The equilibrium between neutral and protonated form was investigated in the ethanol-water (V/V, 1:1) solutions. The observed changes in the UV spectra suggested that protonation process took place in one step. The pH region of protonation ranges between 1.4 and 2.9. Using the changes in the UV spectra which appear as a result of the protonation reaction the stoichiometric dissociation constants were determined numerically (pKBH+ = n·pH + logI) and graphically (intercept of the dependence of logI on pH). Thermodynamic dissociation constants were estimated as an intercept of dependence of pKBH+ on square root of the ionic strength. In order to achieve that, measurements were performed at different ionic strengths: 0.1, 0.25 and 0.5 mol/dm3, adjusted with sodium perchlorate. The obtained thermodynamic pKBH+ values ranged between 2.07 and 2.58. In order to predict proton transfer at a given pH, semiempirical methods AM1 and PM3 were applied. The influence of the substituents present in the p-position of the benzene ring on pKBH+ values of investigated hydrazones was discussed, too. Total energy, binding energy, enthalpy of formation, Gibbs energies of formation, atomic charge and proton affinity values were used to predict protonation site in hydrazone molecule. Furthermore, the stability and the proton affinity of the isomers (E and Z) in which hydrazones exist and their protonated forms were defined.

scholarly journals Comparison of theoretical and experimental investigation of protonation process of some thiones in acid media

2021 ◽  
Vol 62 (1) ◽  
pp. 9-21
Author(s):  
Mirjana Jankulovska ◽  
Vesna Dimova ◽  
Ilinka Spirevska ◽  
Milena Jankulovska
Keyword(s):  
Hydrochloric Acid ◽  
Phosphoric Acid ◽  
Dissociation Constants ◽  
Uv Spectroscopy ◽  
Semiempirical Method ◽  
Mineral Acid ◽  
Acidity Function ◽  
Acid Media ◽  
One Step ◽  
Absorbance Data

PM3 semiempirical method was used for quantum chemical investigation in order to investigate the electronic properties and to determine the protonation centre in 1,2,4-triazoline-3-thione molecule. Confirmation of protonation center in acid media of investigated compounds was made using the values of atomic charges, as well as, proton affinity values. The results from semiempirical calculations indicated that the protonation center in the thione molecule was the sulphur atom. The behavior of thiones was investigated in mineral acid media using UV spectroscopy. The influence of the strength of the acid and its anion on the protonation process was discussed using three different mineral acids (perchloric, hydrochloric and phosphoric acid) for protonation. The protonation process in perchloric and hydrochloric acid took place in one step, while in phosphoric acid was not finished even when its concentration was to the highest degree. The dissociation constants of protonated forms (pKBH + ) and the solvation parameter m* values were calculated in accordance with "excess acidity" function method (Cox and Yates) using the absorbance data from the experimental and reconstructed spectra (Characteristic Vector Analysis (CVA)). The determined pKBH + values in hydrochloric acid had more negative value than those obtained in perchloric acid media. The pKBH + values were in agreement with the literature data for this class of compounds.

Thiohydantoins. VII. Ionization and ultraviolet spectra of 4-thiohydantoins and 2,4-dithiohydantoins

1969 ◽  
Vol 47 (7) ◽  
pp. 1117-1122 ◽  
Author(s):  
J. T. Edward ◽  
J. K. Liu
Keyword(s):  
Sulfuric Acid ◽  
Acid Solution ◽  
Dissociation Constants ◽  
Acid Media ◽  
Ultraviolet Spectra ◽  
Aqueous Sulfuric Acid ◽  
Different Types ◽  
Acid And Base ◽  
Methyl Derivatives ◽  
Acidity Functions

The acid and base dissociation constants of 5,5-pentamethylene-4-thiohydantoin, 5,5-pentamethylene-2,4-dithiohydantoin, and their 1-methyl derivatives, have been determined by ultraviolet studies in basic and acid media. In aqueous sulfuric acid the 4-thiohydantoins are protonated on oxygen at the 2-position, so that the extent of protonation varies with the HA function of the acid solution, while the 2,4-dithiohydantoins are protonated on sulfur at the 2-position, so that the extent of their protonation varies with H0′′′. The importance of using acidity functions appropriate to the different types of compounds when comparing their basicities is emphasized.

scholarly journals Protonation acidity constants for benzotoluidides in sulfuric acid solutions

2006 ◽  
Vol 4 (1) ◽  
pp. 56-67 ◽  
Author(s):  
Goran Stojković ◽  
Frosa Anastasova
Keyword(s):  
Sulfuric Acid ◽  
Dissociation Constants ◽  
Uv Spectroscopy ◽  
Principal Component ◽  
Medium Effect ◽  
Acid Solutions ◽  
Acidity Constants ◽  
Protonation Reaction ◽  
Conjugate Acid ◽  
Sulfuric Acid Solutions

AbstractThe protonation of o-, m-and p-benzotoluidide in sulfuric acid solutions is studied by UV spectroscopy in the 190–350 nm region. Principal component analysis is applied to estimate the contributions of the effect of protonation and the medium effect. For the substances studied in this work, the first principal component (PC) captures about 98 % of the variance and the second PC ∼100 % of the cumulative percentage variance in the 210–350 nm region. The same spectral region is used for calculation of the ionization ratio from the coefficients of the first PC and mole fractions of the base and its conjugate acid. Using these data and Hammett's equation (pK BH + = H X + log I), the pK BH + values for the protonation reaction are obtained. The dissociation constants as well as the solvent parameters m* (∼0.43) and ϕ (∼0.60) are calculated using the Excess Acidity Method (-pK BH += 2.28–2.30) and the Bunnett-Olsen Method (-pK BH += 2.24–2.28). The probable sites of protonation are discussed.

scholarly journals Determination and structural correlation of pK BH + for meta- and para- substituted benzamides in sulfuric acid solutions

2006 ◽  
Vol 71 (10) ◽  
pp. 1061-1071 ◽  
Author(s):  
Goran Stojkovic ◽  
Emil Popovski
Keyword(s):  
Sulfuric Acid ◽  
Dissociation Constants ◽  
Uv Spectroscopy ◽  
Principal Component ◽  
Medium Effect ◽  
Acid Solutions ◽  
Structural Correlation ◽  
Total Variability ◽  
Substituted Benzamides ◽  
Sulfuric Acid Solutions

The protonation of some meta and para substituted benzamides in sulfuric acid solutions was studied by UV spectroscopy in the 190-350 nm region. Principal component analysis was applied to separate the effect of protonation from the medium effect. The spectral region 200-350nm was used for the calculation of the ionization ratio from coefficient of the first principal component, which explains about 95-98% of the total variability. The dissociation constants as well as the solvation parameters m* and ? were calculated using the excess acidity method and the Bunnett-Olsen method. The pK BH + values obtained with the H A function (defined by the average m* - values) are in satisfactory agreement with those calculated with the previously mentioned methods. The pK BH + values were correlated with structure using the Hammett (?=-0.91) and Taft approach. It was found that the inductive effect is more relevant than the resonance one for both substituted benzamides (meta and para). .

scholarly journals Determination of protonation constants and structural correlations for some tertiary formamides and acetamides in sulfuric acid with UV spectroscopy

2015 ◽  
Vol 34 (2) ◽  
pp. 255
Author(s):  
Goran Stojković ◽  
Elizabeta Dimitrieska-Stojković ◽  
Emil Popovski
Keyword(s):  
Sulfuric Acid ◽  
Inductive Effect ◽  
Uv Spectroscopy ◽  
Protonation Constants ◽  
Polar Effect ◽  
Excellent Correlation ◽  
Acid Media ◽  
Solvation Parameters ◽  
Electron Donating Groups

<p>The protonation of ten aliphatic amides in sulfuric acid media was studied by UV spectroscopy. The p<em>K</em><sub>BH</sub><sup>+ </sup>values and solvation parameters were calculated using Yates and McClelland Method, Excess Acidity Method and Bunnett and Olsen Method. p<em>K</em><sub>BH</sub><sup>+</sup> values were –1.44, –1.15, –0.80, –0.32, –1.13 and –0.80 for formamide, dimethylformamide, diethylformamide, diisopropylformamide, diisobutyl­form­amide and dibutylformamide, respectively. According to the p<em>K</em><sub>BH</sub><sup>+</sup> values obtained for acetamide, dimethylacetamide, diethylacetamide and diisopropylacetamide (–0.57, –0.29, –0.32 and 0.36, respectively), analogous acetamides were more basic than formamides. Applying the Hammett’s equation, satisfactory correlation could be gained only for some formamides, the basicities of which increased linearly with the inductive effect of the electron donating groups. From Taft’s approach, it can be concluded that the polar effect slightly dominates over the steric one. Excellent correlation between p<em>K</em><sub>BH</sub><sup>+ </sup>and solvation parameters<em> m* </em>was achieved for formamide, dimethylformamide and diethylformamide. At half- and full-protonation, better correlation was obtained for formamides than for acetamides.</p>

Properties of CMV cation exchange membranes in sulfuric acid media

2006 ◽  
Vol 284 (1-2) ◽  
pp. 67-78 ◽  
Author(s):  
Le Xuan Tuan ◽  
M. Verbanck ◽  
C. Buess-Herman ◽  
H.D. Hurwitz
Keyword(s):  
Sulfuric Acid ◽  
Cation Exchange ◽  
Acid Media

Chlorination of some indole derivatives with ethyl N,N-dichlorocarbamate

1970 ◽  
Vol 48 (3) ◽  
pp. 422-428 ◽  
Author(s):  
J. M. Muchowski
Keyword(s):  
Carboxylic Acid ◽  
Indole Derivatives ◽  
Sole Product

The sole product obtained from the reaction of indole-2-carboxylic acid and ethyl N,N-dichlorocarbamate was 3,3,5-trichlorooxindole (7). In contrast, methyl indole-2-carboxylate gave a mixture of methyl-3,5-dichlorooxindole-3-carboxylate (10) and methyl-3,5,7-trichlorooxindole-3-carboxylate (11), the same products as obtained from the chlorination of methyl indole-3-carboxylate. The structures of these products were confirmed by degradation to known compounds and/or by synthesis, and mechanisms for their formation were suggested.

Improved synthesis of anti-sesquinorbornene

1984 ◽  
Vol 62 (9) ◽  
pp. 1840-1844 ◽  
Author(s):  
Karl R. Kopecky ◽  
Alan J. Miller
Keyword(s):  
Acetic Acid ◽  
Sulfuric Acid ◽  
Carboxylic Acid ◽  
Lead Tetraacetate ◽  
Carboxyl Group ◽  
Silver Acetate ◽  
Benzenesulfonyl Chloride ◽  
Methoxide Ion ◽  
Hydrolysis Of ◽  
Monomethyl Ester

Treatment of methyl hydrogen decahydro-1,4:5,8-exo,endo-dimethanonaphthalene-4a,8a-dicarboxylate with lead tetraacetate in benzene – acetic acid replaces the carboxyl group by an acetoxy group. Hydrolysis of this product with 25% sulfuric acid at 130 °C forms 8a-hydroxydecahydro-1,4:5,8-exo,endo-dimethanonaphthalene-4a-carboxylic acid 10. The reaction between 10 and benzenesulfonyl chloride in pyridine containing triethylamine at 95 °C produces anti-sesquinorbornene 1 in 34% yield. In the absence of triethylamine 1 is converted to the hydrochloride. The iodohydroperoxide of 1 is converted by silver acetate at 0 °C to the diketone in a luminescent reaction. The 1,2-dioxetane could not be isolated. Decahydro-1,4:5,8-exo,exo-dimethanonaphthalene-4a,8a-dicarboxylic anhydride is converted slowly by methoxide ion in methanol at 150 °C to the monomethyl ester which then undergoes demethylation. The isomeric exo,endo anhydride undergoes reaction readily with methoxide ion at 80 °C.

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