The Protonation and Indicator Behavior of Some Ionic Azobenzenes in Aqueous Sulfuric Acid

Reeves, Richard L.

doi:10.1021/ja00962a029

Cited by 69 publications

(38 citation statements)

References 7 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Simonds organic reactions in aqueous sulfuric acid media (10) has given a simple formulation for the first (19). For instance, undissociated sulfuric acid molstage of factor analysis, principal factor analysis ecules are kinetically involved in the rearrange-(PFA) (1); Simonds' method has been used to isolate ment of azox~benzenes to hydroxyazobenzenes medium effects from protonation effects in uv- (20); bisulfate ions are involved in some azoxyvisible spectra at different acidities by Edward and naphthalene rearrangements (21) and in the enoliWong (1 1) and others (12). In this paper PFA is zation of acetone (22).…”

Section: Introductionmentioning

confidence: 99%

Resolution of Raman spectra of aqueous sulfuric acid mixtures using principal factor analysis

Cox¹,

Haldna²,

Idler³

et al. 1981

Can. J. Chem.

View full text Add to dashboard Cite

. Can. J. Chem. 59,2591Chem. 59, (1981. Principal factor analysis has been applied to Raman spectra of 26 sulfuric acidlwater mixtures covering the 0-100% H2S04 concentration range. The analysis greatly facilitates the identification of peaks due to different species. The results show that ions and "free" HS0,-ions do not co-exist with undissociated H2S04 molecules in solution and that two water molecules rather than one are required for the first ionization of H2S04. A species with the composition H2SO4.2H2O, assigned a hydrated ion pair structure, reaches maximum concentration at the same medium composition at which free HS0,-, and H2S04 are at concentration minima, about 75% wlw. The only species apparent in the more concentrated solutions are the ion pair and undissociated H2S04, which could be taken to mean that H2S04 is a weaker acid than H30+, but a stronger one than H30+.H20 (or H502+, if this entity has a real existence). Separate peaks due to the postulated H30+.H2S04 (or H5S05+) were not observed. On a applique l'analyse du facteur principal aux spectres Raman de 26 melanges d'acide sulfurique/eau ayant des concentrations en acide sulfurique allant de 0 a 100%. L'analyse facilite grandement I'identification des pics des differentes espbces. Les resultats indiquent que les ions et lesions "libres" HS04-ne coexistent pas avec les molCcules de H2S04 non dissociees en solution et que deux molecules d'eau plut6t qu'une sont necessaires lors de la premiere ionisation du H2S04. Une espece ayant la composition H2S04.2H20 a laquelle on attribue une structure de paire d'ions, atteint la concentration maximum pour la mCme composition moyenne ou HS0,-libre et H2S04 sont une concentration minimum, environ 75% wlw. Dans des solutions plus concentrkes les seules especes apparentes sont la paire d'ions et le H2S04 non dissocie, qui peuvent signifier que H2S04 est un acide plus faible que H30+, mais plus fort que H,0+.H20 (ou H502+ si cette entite existe reellement). On n'a pas observe de pics separ6s provenant du H30+.H2S04 (ou H5S05+) propose.

show abstract

Section: Introductionmentioning

confidence: 99%

Resolution of Raman spectra of aqueous sulfuric acid mixtures using principal factor analysis

Cox¹,

Haldna²,

Idler³

et al. 1981

Can. J. Chem.

View full text Add to dashboard Cite

show abstract

“…It is reasonable to associate the first PC with the effect of the protonation and the second PC with the medium effect, as was mentioned earlier [9]. Table 2 First PC and the sum of the first and second PC for the studied substances.…”

Section: Determination Of Pk Bh+ Valuesmentioning

confidence: 63%

“…, independent of wavelength. When this method is used, which separates the protonation effects from medium effects, the protonation information is contained in q 1 [1,9,10]. The reconstructed spectra using the first principal components (Figure 2-4) intersect at isosbestic points.…”

Section: Resultsmentioning

confidence: 99%

“…The same ionization ratios are obtained directly from the coefficients of the first PC [1,4,9] i.e. the weighting coefficients:…”

Section: Determination Of Pk Bh+ Valuesmentioning

confidence: 99%

“…Various methods have been widely employed to compensate for medium effects, e.g. principal component analysis (PCA) [5], target testing method of factor analysis [6,7], and characteristic vector analysis (CVA) [1,[8][9][10].…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Protonation acidity constants for benzotoluidides in sulfuric acid solutions

Stojković

Anastasova

2006

Open Chemistry

View full text Add to dashboard Cite

Abstract:The 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 BunnettOlsen Method (-pK BH+ = 2.24-2.28). The probable sites of protonation are discussed.

show abstract

Application of Principal Component Analysis in Organic Chemistry

Zalewski¹

1991

Progress in Physical Organic Chemistry

View full text Add to dashboard Cite

The Protonation and Indicator Behavior of Some Ionic Azobenzenes in Aqueous Sulfuric Acid

Cited by 69 publications

References 7 publications

Resolution of Raman spectra of aqueous sulfuric acid mixtures using principal factor analysis

Resolution of Raman spectra of aqueous sulfuric acid mixtures using principal factor analysis

Protonation acidity constants for benzotoluidides in sulfuric acid solutions

Application of Principal Component Analysis in Organic Chemistry

Contact Info

Product

Resources

About