Total Internal Reflection IR Spectroscopy Research Articles

Composition and Structure of Complexes Formed in Aqueous Solutions of Trifluoroacetic Acid According to IR Spectroscopy Data

The composition and structure of complexes that formed in aqueous solutions of trifluoroacetic acid were studied by frustrated multiple total internal reflection IR spectroscopy (FMTIR). Two types of complexes with a molecular structure formed: trimers CF3COOH · (H2O)2 and cyclic tetramers (CF3COOH)2 · (H2O)2, in which the molecules of the components are arranged in pairs. In the range of acid concentrations from 100% to [H2O]/[CF3COOH] = 1: 1, only these tetramers formed, and all added water was bound into these hydrates. In more dilute solutions (up to [H2O]/[CF3COOH] = 2: 1), CF3COOH · (H2O)2 complexes formed along with tetramers; at a double excess of H2O, the components of the solution were completely bound into these trimers. In dilute solutions (from 0 to 3.6 M CF3COOH), the acid is completely dissociated into H5O 2 + and CF3COO– ions hydrated with water molecules. In the range of medium concentrations (from 3.6 M to [H2O]/[CF3COOH] = 2: 1), the solutions contain both these ions and CF3COOH · (H2O)2 dihydrates. For this range of compositions of the CF3COOH−H2O system, the concentrations of H5O 2 + ions and CF3COOH · (H2O)2 dihydrates were calculated.

A study of muscular tissue of animal origin by reflection-spectroscopy methods

A comparative analysis of the spectral characteristics of the surface of muscular tissue of animal origin (pork) and its main components has been performed by the methods of diffuse reflection electronic spectroscopy (DRES) and frustrated total internal reflection IR spectroscopy. The experiments have shown that the application of the DRES method makes it possible to detect more pronounced changes in the surface optical characteristics of muscular tissue and obtain electronic spectra containing information about the component composition of its main parts under successive extraction of sarcoplasmic materials, myofibrillar proteins of the actomyosin complex, and stroma mucopolysaccharides.

Structure of complexes in the H2SO4—2-pyrrolidone system as determined by IR-spectroscopy and quantum-chemical calculations

Specific features of complexation in solutions of a strong dibasic acid in the H2SO4–2-pyrrolidone (Pyr) system (in the range of compositions of 0–100% H2SO4) are studied using multiple frustrated total internal reflection IR spectroscopy. The conclusions drawn on the structure of the complexes formed in such solutions are confirmed by quantum-chemical calculations of the mPyr · nH2SO4 (m, n = 1, 2) heteroassociates and by comparison of their calculated and measured vibrational spectra. It is found that, in the investigated solutions, four types of acid–base complexes, with various degrees of proton transfer in the OHO bridge, are formed: (AHA)– anions with quasi-symmetric H-bonds, solvated by acid molecules, or entering into the composition of PyrH+ · (AHA)– ion pairs; quasi-ion pairs with incomplete proton transfer to the base molecule of 1: 1 and 2: 2 compositions; and 2Pyr · H2SO4 complexes with two O–H···O bridges of molecular type. The main differences in the mechanisms of the acid–base interactions in the H2SO4–Pyr system as compared to the CH3SO3H–Pyr system result from the participation of two OH-groups of H2SO4 molecule in these interactions. Therefore, two types of quasi-ion pairs and complexes of 2Pyr · H2SO4 composition are formed.

H3O 2 - ions with a strong quasi-symmetrical H-bond and their hydration in aqueous solutions of NaOH and KOH

Ion-molecular interactions in aqueous solutions of NaOH (0–47.8%) and KOH (0–51.95%) are studied by multiple frustrated total internal reflection IR spectroscopy. Interpretation of the spectra and analysis of the spectral data are performed based on the results of DFT calculations (B3LYP/6-31++G(d, p)) of the characteristics of the free and double hydrated H3O2- ion. It is established that the changes in the IR spectra of NaOH and KOH aqueous solutions caused by increasing alkali concentration are due to the formation of H3O2- ions with a strong quasi-symmetrical hydrogen bond and their subsequent hydration by one or two water molecules. The influence of the cation nature on the degree of hydration of H3O2- ions is demonstrated. The equilibrium concentrations of monohydrate (H3O2- ∙ H2O) and dihydrate (H3O2- ∙ 2H2O) are calculated and their IR continuous absorption spectra are isolated.

Plasma chemical modification of polymer surface. Polyethylene terephthalate

Methods of electron microscopy, atomic force microscopy, contact angles, multiple attenuated total internal reflection IR spectroscopy, and X-ray photoelectron spectroscopy were used to study the molecular-chemical, structural and morphological, and energy characteristics of polyethyleneterephthalate (PET) surfaces before and after treatment in plasma of high-frequency air discharge. It is shown that modification of PET surface results in a change in the structural-morphological surface properties and the formation of oxidized near-surface layers. The peel test was used to determine the adhesion characteristics of the substrate with respect to a standard adhesive. It is shown that the decisive role in providing high strength of adhesive joints in the course of plasma chemical modification is played by a significant increase in the surface energy of the substrate, namely its polar component. The kinetics of relaxation of surface characteristics of the substrate are studied in the case of long-term storage under laboratory conditions.

Ions with strong symmetric H-bonds and their solvation in aqueous-ethanolic solutions of HCl

Ion-molecular interactions in the HCl-EtOH-H2O system are studied by means of multiple frustrated total internal reflection IR spectroscopy over a wide range of concentrations of the components. It is demonstrated that, in the investigated solutions, the acid is fully bound into ions and uncharged complexes formed by strong symmetric or quasi-symmetric H-bonds. There is a competition between H2O and EtOH molecules during the formation of the (H5C2(H)O…H…O(H)C2H5)+, (H2O…H…OH2)+, and (H2O…H…O(H)C2H5)+ proton disolvates. In dilute solutions of HCl in 2: 1 and 1: 1 EtOH-H2O mixtures, (H2O…H…OH2)+ proton dihydrates are mainly formed, whereas in concentrated HCl solutions, under conditions of a partial solvation of ions by solvent molecules, predominantly (H2O…H…O(H)C2H5)+ mixed proton disolvates arise. In concentrated solutions of HCl in EtOH with low water content, the acid is partially bound into (H5C2(H)O…H+…Cl−) uncharged complexes with the participation of the Cl− anion.

Cation Bridging Studied by Specular Neutron Reflection

The binding of an anionic surfactant onto an anionic surface by addition of divalent ions is reported based on experimental data from specular neutron reflection (NR) and attenuated total internal reflection IR spectroscopy (ATR-IR). Similar measurements using monovalent ions (sodium) do not show any evidence of such adsorption, even though the amount of surfactant can be much higher. This data is interpreted in terms of the so-called bridging mechanism of ion binding.

Chemical composition of the surface of modifying polymers in filled cellulose nitrate composites: An IR study

The surface of modifying polymers in filled cellulose nitrate composites was studied by attenuated total internal reflection IR spectroscopy. The qualitative and quantitative characteristics of the surface structure of butadiene-nitrile and urethane rubbers of various grades and of vinyl polymers were examined. The results were compared to the published IR spectra of the substances in the bulk.

Ion-molecular interactions in solutions of methanesulfonic acid in diethylamine according to IR spectroscopy data

The methanesulfonic acid (MSA)-diethylamine (DEA) binary liquid system is studied over the entire range of compositions at 30°C by using multiple frustrated total internal reflection IR spectroscopy. Solutions with acid: base equimolar ratio contain only 1 : 1 ion pairs. Upon adding the acid, a MSA molecule abstracts an anion from the 1 : 1 complex to produce a protonated DEA and an (H3C(O2)SO…H…OS(O2)CH3)− anion with a strong H bond: (C2H5)2(H)NH+ · OS(O2)CH3− + HOS(O2)CH3 ↔ (C2H5)2(H)NH+ + (H3C(O2)SO…H…OS(O2)CH3)−. This equilibrium is shifted to the left. The 1 : 1 complex is present in solutions even at an significant excess of the acid. To protonate the complex, it is required at least two MSA molecules. Under conditions of an excess of the base, DEA molecules do not solvate the 1 : 1 complex. The solution separates into two phases, composed of (C2H5)2(H)NH+ · OS(O2)CH3− complexes and pure DEA.

Reaction and diffusion in heterogeneous atmospheric chemistry studied by attenuated total internal reflection IR spectroscopy

Download options Please wait... Article information DOI https://doi.org/10.1039/A701767G Article type Paper Download Citation J. Chem. Soc., Faraday Trans., 1997,93, 2741-2746 BibTex EndNote MEDLINE ProCite ReferenceManager RefWorks RIS Permissions Request permissions Reaction and diffusion in heterogeneous atmospheric chemistry studied by attenuated total internal reflection IR spectroscopy A. B. Horn and J. Sully, J. Chem. Soc., Faraday Trans., 1997, 93, 2741 DOI: 10.1039/A701767G To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page. If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given. If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page. Read more about how to correctly acknowledge RSC content. Search articles by author Andrew B. Horn Jessica Sully

Kinetic study of the equilibrium in the methanesulfonic acid-water system

A kinetic study of the hydrolysis of ethyl isovalerate in the methanesulfonic acid-water system from pure water to 60.5% CH3SO3H at 25°C showed that the hydrolysis rate is directly proportional to the concentration of H5O2+ ions determined by IR spectroscopy. The hydrolysis mechanism is the same as in hydrochloric acid and sulfuric acid solutions. Evidence was found for correctness of the measurements of the equilibrium concentrations of molecules and ions in aqueous methanesulfonic acid solutions by multiple frustrated total internal reflection IR spectroscopy. The possibility was demonstrated for an independent measurement of the equilibrium concentrations of H5O2+ ions by a kinetic method in aqueous acid solutions.

A study of the surfaces of films based on cellulose and its mixtures with polymethyl methacrylate using attenuated total internal reflection IR spectroscopy

Attenuated total internal reflection (ATR) IR spectroscopy is used in combination with electron microscopy to study films based on cellulose and mixtures of cellulose with polymethyl methacrylate. The concentrations of the component in the volume and on the surface of the bi-component films differ significantly. The surface in contact with air on the formation of the film shows an excess concentration of cellulose macromolecules compared with the bulk of the specimen, and the surface in contact with the glass shows a higher relative content of polymethyl methacrylate.

The preparation and properties of free films based on epoxydiane and phenol-formaldehyde oligomers

It has been shown by GPC that no chemical reaction occurs between epoxydiane and Bakelite-type (resole) phenol-formaldehyde oligomers when they are heated in ethylcellosolve solution at 120° for 5 hr. Curing the compositions at 200° is accompanied by changes in the infrared spectra in the vibration regions of aliphatic alcohol CO bonds, ester bridges and benzene C = C bonds, related to crosslinking of the oligomers. Using attenuated total internal reflection IR spectroscopy, it was shown that the chemical compositions and the structure of the surface and bulk layers of the polymer are identical. The original oligomers and the films based on them are amorphous to X-rays. The supermolecular structure of the films is globular and the globule size is somewhat increased when the MM of the oligomers increases.