Continuous absorption in the IR spectra of sulfate solutions in 100% sulfuric acid

Кислина, И. С.; Librovich, N. B.; Винник, М. И.

doi:10.1007/bf00956782

Cited by 2 publications

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“…Because no HCl was added (0 titrant equivalent) and almost no H + is present in the solution (pH = 6.27), the acidic water retrieved by IR spectroscopy must be attributed to water in strong interaction with the glycine zwitterion. Excess acidic water has long been estimated by the so-called “continuum of absorption”. − We also reported similar results for IR titrations of phosphoric and malic acids. , This acidic water cannot be attributed to free protons (H + or H 3 O + ) and must be attributed to the solvated solute species. Hence, the aqueous glycine zwitterion spectrum (Figure D z ) must be corrected for its acidic water, as well as for malic acid 27 (see Appendix A).…”

Section: Resultssupporting

confidence: 60%

“…Excess acidic water has long been estimated by the so-called "continuum of absorption". [17][18][19][20][21][22][23][24][25][26] We also reported similar results for IR titrations of phosphoric and malic acids. 7,27 This acidic water cannot be attributed to free protons (H + or H 3 O + ) and must be attributed to the solvated solute species.…”

Section: Resultssupporting

confidence: 54%

“…Many, if not all, aqueous carboxylic acids show low-intensity absorption in the 3000-1800 cm -1 range that many authors call a "continuum of absorption". 1,[17][18][19][20][21][22][23][24][25][26] Several authors who have studied different acids proposed an evaluation of this continuum, each time using different spectral reference positions: 1200, 23 1300, 24 1800, 23,24 1900, 25 1950, 26 2000, 19,22 and 2200 cm -1 . 1,20 Groups led by Maiorov and Librovitch, who studied inorganic acids in water, reported that the continuum of absorption is proportional to "free" hydronium ions (H 3 O + ).…”

Section: Introductionmentioning

confidence: 99%

“…The assignment of the carboxylic acid bands of aqueous organic acids is still a matter of confusion, because of the strong water absorption and the numerous species present. Many, if not all, aqueous carboxylic acids show low-intensity absorption in the 3000−1800 cm -1 range that many authors call a “continuum of absorption”. ,− Several authors who have studied different acids proposed an evaluation of this continuum, each time using different spectral reference positions: 1200, 1300, 1800, , 1900, 1950, 2000, , and 2200 cm -1 . , …”

Section: Introductionmentioning

confidence: 99%

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Infrared Spectroscopy of Aqueous Carboxylic Acids: Comparison between Different Acids and Their Salts

2004

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The attenuated total reflection-infrared (ATR-IR) spectra in the 4800-700 cm -1 range of nine carboxylic acids and their sodium salts in aqueous solutions are obtained and analyzed. Overall, 22 species are studied. Six IR titrations are made with five different acids: acetic acid, malic acid, betaine, glycine, and N,N-((butyloxy)propyl) amino diacetic acid (BOPA). From the spectra of these titrations, the spectra of four types of water (acidic, basic, saline, and pure water) are subtracted, giving spectra with flat baselines without any artificial adjustment. Factor analysis (FA) made on the water-subtracted spectra yield the spectra of the principal species, and their abundances. Titration curves obtained from these precisely fit the theoretical curves and the pK a values in the literature. The remaining water bands that are not subtracted are assigned to water solute close-bound situations. The hydration number varied from 5 to 1, with an average of almost 2 per carboxyl carbonyl group. The IR CO band positions ((16 cm -1 ) are assigned to the different species: 1723 and 1257 cm -1 for the un-ionized acid double and single bonds; 1579 cm -1 for CO 2asymmetric stretch; 1406 cm -1 for CO 2symmetric stretch; and 1094 cm -1 for noncarboxylic ethoxy groups. The OH absorption covers the full region, from 3700 to 1700 cm -1 , in four bands that are ∼220 cm -1 wide. The near-3400 cm -1 band is assigned to solvated water, alcoholic OH, and NH groups, because these are hydrogen-bonded groups. The 3000 and 2600 cm -1 bands are assigned to the carboxyl OH groups that are hydrogen-bonded to other carboxyl groups in the pure acrylic species or to water in the aqueous solutions cases. The 2100 cm -1 band is assigned to a combination band that involves the far-IR absorption. The absorption from 3700 to 1700 cm -1 , which is sometimes called the "continuous absorption", cannot be attributed to the hydronium ion (H 3 O + ), because the acids are not ionized; rather, it results from the strong hydrogen bonds between water and the carboxylic acids.

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Section: Resultssupporting

confidence: 60%

Section: Resultssupporting

confidence: 54%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Infrared Spectroscopy of Aqueous Carboxylic Acids: Comparison between Different Acids and Their Salts

2004

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“…The 3700−1800 cm -1 region is dominated by four weak broad bands situated at 3500, 2930, 2580, and 1995 cm -1 (Figure ). Because of its continuous formation, this diffuse absorption is sometimes referred to as the “continuum of absorbance”. − However, this absorption is associated with the presence of water for two reasons: no H 3 O + is present in the solution, and the absorption in the 3700−1800 cm -1 region is much more intense than in solid malic acid where there is no water (Figure d,d‘). The second derivative technique allowed us to see three very weak bands situated at 2940, 2895, and possibly one at 2840 cm -1 , which we assign to CH 2 antisymmetric and symmetric and CH stretch bands.…”

Section: Resultsmentioning

confidence: 99%

Infrared Spectroscopy of Aqueous Carboxylic Acids: Malic Acid

Ma×

Chapados

2002

J. Phys. Chem. A

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Quantitative infrared (IR) titration of 1.80 M malic acid is presented where factor analysis (FA) was used to obtain the principal species' spectra and their abundances. Three malic species and three water species were obtained. The distribution of the species as a function of pH was made from which their pK a values were determined. The experimental points of the distribution curves correspond to the values calculated from the thermodynamic equilibrium equations. A precise determination of aqueous malic IR bands was obtained from the real spectra of the malic species. The hydrates' hydration numbers were determined to be 2.0 ± 1.0, 3.0 ± 2.0, and 4.0 ± 0.5 for malic acid, mono-, and disodium malate, respectively. The hydrates are stable throughout the pH range where the species are present. The double and single CO stretch bands of malic acid are situated at 1719 and 1272 cm-1, respectively. The antisymmetric and symmetric CO stretch bands of mono- and disodium malate are situated at 1580, 1400 cm-1 and 1563, 1395 cm-1, respectively. Malic acid shows four very broad bands in the 3800−1800 cm-1 region as a continuous absorption assigned to the OH stretch of hydrogen bonded water and alcoholic groups to carboxylic groups. The 2930 and 2580 cm-1 bands, which are far from the 3500 cm-1 band, indicate strong hydrogen bonds. Disodium malate shows one large band at 3320 cm-1 assigned to the OH stretch of solvated water and alcoholic groups. Monosodium malate has the bands of both malic and disodium malate slightly displaced, but with half their intensities.

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Continuous absorption in the IR spectra of sulfate solutions in 100% sulfuric acid

Cited by 2 publications

References 2 publications

Infrared Spectroscopy of Aqueous Carboxylic Acids: Comparison between Different Acids and Their Salts

Infrared Spectroscopy of Aqueous Carboxylic Acids: Comparison between Different Acids and Their Salts

Infrared Spectroscopy of Aqueous Carboxylic Acids: Malic Acid

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