The effect of alkyl substitution on the conformation of intramolecularly hydrogen bonded β-γ (enolic) unsaturated alcohols

The equilibrium between associated (OH ⋯ π) and free OH conformations of β-γ unsaturated alcohols has been found to be highly dependent upon the position of alkyl substitution. Two types of intramolecularly hydrogen bonded conformations can be identified which are separated by a difference in OH stretching frequency of approximately 10 cm⁻¹. The occurence of either conformation is dependent upon methyl substitution at the β carbon and the conformations are mutually exclusive. The intensity ratio of the free and intramolecularly hydrogen bonded OH stretching bands are dependent upon the alkyl chain length and also the primary or secondary nature of the alcohol. In both cases, changes in relative intensity result from steric interactions. Increased alkyl chain length decreases the relative intensity of the intramolecularly hydrogen bonded band, whilst a change from primary to secondary alcohol increases the relative intensity of the intramolecularly hydrogen bonded band.     

Calculations on ionic solvation—V The calculation of partition coefficients of ions

The solvation free energy of an ion in an organic solvent is calculated using our new electrostatic method, and is combined with the hydration free energy to yield the free energy of transfer of the ion from water to the organic solvent. It is shown that for the solvent systems water/1,2-dichloroethane, dichloromethane, chloroform, o-dichlorobenzene, chlorobenzene, and nitrobenzene there is good agreement between the calculated ΔG_t^o values and the free energies for partition of ions, ΔG_p^o = -RTlnP. For organic phases in which water is quite soluble, for example 1-octanol, 1-pentanol, isopentanol, ethyl acetate, and methylisobutylketone, the calculated ΔG_t^o values are always more positive than the observed partition values, ΔG_p^o. It is shown that this effect is due to hydration of the ions in the wet organic phase and by calculations on a solvation model in which an ion in the wet organic phase is surrounded by a layer of water of thickness 3.1 Å (the diameter of a water molecule) it is concluded that in the first group of solvents most ions are unhydrated in the wet organic phase; Cl⁻ is an exception and is partially hydrated. In the second group of wet solvents, all ions are at least partially hydrated, and Cl⁻ is hydrated by a layer of water that must be even thicker than the diameter of a water molecule.     

Influence of solvent structure on the aquation of K‐chloro(diethylenetriamine)(ethylenediamine) cobalt(III) ion in water and mixed aqueous solvents

The aquation of K‐[Co(dien)(en)Cl]²⁺ was followed spectrophotometrically within the temperature range (40–60°C) in water, water–isopropyl alcohol, and water–tert‐butyl alcohol media of varying solvent composition up to 50 and 60 vol% of the organic solvent component respectively. The nonlinear plot of log k vs. D^?1_s was attributed to the differential solvation of the initial and transition states. The variation of ΔH^≠, ΔS^≠, and ΔG^≠ with the mole fraction of the organic component was analyzed and discussed. The isokinetic temperatures were found to be 330 and 317 K for water–isopropyl alcohol and water–tert‐butly alcohol mixtures respectively, indicating that the aquation reaction is entropy controlled. The application of free energy cycle at 25°C for the aquation reaction in both co‐solvents suggests that the transition state is more stable than the initial one. © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 34: 1–6, 2002     

Far-infrared investigation of kaolinite and halloysite intercalates using terahertz time-domain spectroscopy

Two clay minerals from the kaolin group, namely well-ordered kaolinite and poorly ordered halloysite, were investigated by terahertz time-domain spectroscopy (THz-TDS). Both clay samples were used for preparation of their respective intercalates using dimethyl sulfoxide (DMSO) and potassium acetate (KAc) with water. The intercalates were also characterized by X-ray powder diffraction and Fourier transform infrared spectroscopy. The dielectric behaviour of clay samples was investigated in the far-infrared region of 0.2–2.7 THz corresponding to about 6.7–89.9 cm⁻¹. The frequency dependence of the power absorption coefficient revealed clear absorption bands for DMSO intercalates but not for KAc with water. For kaolinite – DMSO intercalate a distinct doublet at 1.70 THz (56.6 cm⁻¹) and 1.88 THz (62.6 cm⁻¹), and for halloysite – DMSO intercalate a single broad band centred around 1.72 THz (57.3 cm⁻¹) were found. These bands are reported for the first time in this type of intercalation substances and indicate the application potential of THz time-domain spectroscopy for use in the investigation and detection of chemical behaviour of molecular species introduced into the interlayer space of layered substances such as clays and clay minerals. Additionally, the qualitative characteristics of observed bands of DMSO intercalates in the THz region reasonably resembled the structural order/disorder of used kaolinite and halloysite samples.     

Analysis of the rotational structure of the 2ν9 band of HNO3 between 891 and 898 cm−1

Several lines belonging to the 2ν₉ band of nitric acid have been assigned on a spectrum recorded with a tunable diode laser around 895 cm⁻¹. This analysis has led to the determination of the band centre and six rotational constants (A, B, C, Δ_K, Δ_JK, Δ_J) for the vibrational level v₉ = 2. For the transitions involved in the calculation the overall standard deviation is 0.005 cm⁻¹.     

Comparison of two simulation methods to compute solvation free energies and partition coefficients

The thermodynamic integration (TI) and expanded ensemble (EE) methods are used here to calculate the hydration free energy in water, the solvation free energy in 1‐octanol, and the octanol‐water partition coefficient for a six compounds of varying functionality using the optimized potentials for liquid simulations (OPLS) all‐atom (AA) force field parameters and atomic charges. Both methods use the molecular dynamics algorithm as a primary component of the simulation protocol, and both have found wide applications in fields such as the calculation of activity coefficients, phase behavior, and partition coefficients. Both methods result in solvation free energies and 1‐octanol/water partition coefficients with average absolute deviations (AAD) from experimental data to within 4 kJ/mol and 0.5 log units, respectively. Here, we find that in simulations the OPLS‐AA force field parameters (with fixed charges) can reproduce solvation free energies of solutes in 1‐octanol with AAD of about half that for the solute hydration free energies using a extended simple point charge (SPC/E) model of water. The computational efficiency of the two simulation methods are compared based on the time (in nanoseconds) required to obtain similar standard deviations in the solvation free energies and 1‐octanol/water partition coefficients. By this analysis, the EE method is found to be a factor of nine more efficient than the TI algorithm. For both methods, solvation free energy calculations in 1‐octanol consume roughly an order of magnitude more CPU hours than the hydration free energy calculations. © 2012 Wiley Periodicals, Inc.     

Modeling ionomer swelling dynamics of a sulfonated polyphenylene,pentablock copolymers,and nafion

The water swelling behavior of Nafion, sulfonated poly(phenylene) (sPP), and poly[t‐butyl styrene‐b‐hydrogenated isoprene‐b‐sulfonated styrene‐b‐hydrogenated isoprene‐b‐t‐butyl styrene) was studied in order to understand microscopic molecular interactions. Ionomer swelling was modeled using the Flory‐Rehner relationship to predict solvent‐ionomer interaction parameter (χ ₁₂) and effective number of elastically active chains (n ). Water swollen PBC had a decreasing χ₁₂ from 1.146 to 0.516 when its ion‐exchange capacity (IEC) increased from 1.0 to 2.0. Nafion 117 and sPP χ ₁₂ values were 0.93 and 0.807 at an IEC of 0.91 and 1.8. Polymer water uptake was inversely dependent upon n and IEC or sulfonic acid‐group concentration. The following trend was noted for ionomer type, n , and water uptake: PBC‐2.0 (159 wt % and 7.89e‐4 mol/cm³) > sPP (48.6 wt % and 1.40e‐3 mol/cm³) > Nafion 117 (23 wt % and 1.24e‐3 mol/cm³). The ionomer's Gibb's total free change (ΔG_Tot ) due to water swelling for Nafion 117 was ?15.3 J, sPP was ?28.5 J, and PBC‐2.0 was ?53.2 J. An empirical equation was created to estimate a material's total solubility parameter (δ ); and dispersion (δ_d ), dipolar (δ_p ,), and hydrogen bonding (δ_h ) forces. The δ values for Nafion 117, sPP, and PBC‐2.0 were 19.9 (J/cm³)^1/2, 21.3 (J/cm³)^1/2, and 21.0 (J/cm³)^1/2. Idealized swelling within an ionomer due to solvent. Ion domains are comprised of fixed sulfonated acid groups (? SO₃H) along the polymer's backbone. These functional groups provide interaction sites for molecules to diffusion and swell chains. The total change in free energy ΔG is dominated by ΔG_mix that is attributed to hydrogen bonding and the concentration of elastically active chains n , which directly impacts its chemical potential Δμ . © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55 , 435–443     

Novel Photobleachable Deep UV Resists Based on Single Component Nonchemically Amplified Resist System

Summary: Photobleachable deep UV resists were designed by introducing diazoketo groups in polymer side chains. The diazoketo groups undergo the Wolff rearrangement upon irradiation in the deep UV, affording ketenes that react with water to provide base‐soluble photoproducts. The polymers were synthesized by radical copolymerization of 2‐(2‐diazo‐3‐oxo‐butyryloxy)‐ethyl methacrylate, 2‐hydroxyethyl methacrylate, and γ‐butyrolacton‐2‐yl methacrylate. The single component resist showed 0.7 µm line and space patterns using a mercury‐xenon lamp in a contact printing mode.

Scanning electron micrograph of 0.7 µm line and space patterns printed with polymer B at a dose of 70 mJ · cm⁻².     

Determination of primary and secondary solvation numbers and binding constants based on the shift of a proton-transfer equilibrium resulting from hydrogen bonding solvation

We show how the shift in the equilibrium constant K _PT for formation of a proton-transfer adduct in a non-interactive solvent, upon addition of a second, hydrogen-bonding solvent S reveals the nature of the hydrogen bonding solvation process. Data are analyzed for the pentachlorophenoltriethylamine proton-transfer equilibrium in cyclohexane solvent, under-going solvation by the acidic alcohols, 2,2,2-trichloroethanol and 1,1,1,3,3,3-hexafluoro-2-propanol. K _PT vs. [S] data are fitted to a binding isotherm corresponding to two-stage solvation of both the adduct and the free amine. Stoichiometries and binding constants for both primary and secondary solvation of both solvated species are determined as adjustable parameters. Best fits correspond to both the adduct and free amine under-going primary solvation by one alcohol molecule (presumably at the oxygen and nitrogen lone-pairs, respectively) followed by secondary solvation by one to nine additional alcohol molecules, with binding constants ranging from 2100 M^–1, for primary solvation of the adduct by hexafluoro-2-propanol, down to 7 M^–1, for secondary solvation of the amine by trichloroethanol. We speculate that the secondary solvation numbers represent average sizes of hydrogen-bonded alcohol chains, nucleated by the enhanced basicity of the primary-solvation alcohol.     

Interaction of water in polymers: Poly(ethylene‐co‐vinyl acetate) and poly(vinyl acetate)

We studied the interaction of water in poly(ethylene‐co‐vinyl acetate) of various vinyl acetate compositions and poly(vinyl acetate), on the basis of the infrared spectrum of the water dissolved therein. The spectrum shows a very sharp and distinct band at about 3690 cm^?1 (named as A), and less‐sharp two bands around 3640 (B) and 3550 cm^?1 (C), the A band being outstanding especially at a low vinyl acetate composition. As the vinyl acetate composition increases, the A band decreases in intensity relative to the C band, whereas the B band increases contrarily. Analysis of the spectral change has elucidated that one‐bonded water (of which one OH is hydrogen‐bonded to the C?O of an ester group and the other OH is free) and two‐bonded water (each OH of which is hydrogen‐bonded to one C?O) coexist in the copolymer and that two‐bonded water increases in relative population with increasing vinyl acetate composition. Dissolved water is entirely two‐bonded in poly(vinyl acetate), in which C?O groups are densely distributed in the matrix. We proved that dissolved water in polymers is hydrogen‐bonded through one or two OH groups to the possessed functional groups but does not cluster. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 777–785, 2005     

Effect of cosolvent on the volume of activation for base hydrolysis of tris(1.10‐phenanthroline)‐ and tris (2.2′‐bipyridine)iron(II) complexes

The kinetics of the base hydrolysis of Fe(phen)₃²⁺ and Fe(bipy)₃²⁺ (phen = 1,10‐phenanthroline and bipy = 2,2'‐bipyridine) in some aqueous alcohol mixtures at ambient and elevated pressures (up to 1kbar) have been monitored spectrophotometrically at 25.0°C. For a given pressure, the alcohol cosolvent increases the rate of reaction relative to the reaction in a wholly aqueous medium. In all cases, increasing pressure causes rate retardation and derived volumes of activation for the reactions in aqueous solvent mixtures vary between +15 and +25 cm³ mol⁻¹, indicating that solvation changes of a different magnitude occur upon reaching the transition state from those occurring for the reactions in aqueous medium. Since the reaction has been established earlier to be nucleophilic attack of the incoming hydroxide ion, the volumes of activation signify marked increases in the loss of electrostricted solvent from the vicinities of the hydroxide ion and the iron(II) complex ions. © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 32: 263–270, 2000     

Structural evolution of poly(lactic acid) upon uniaxial stretching investigated by in situ infrared spectroscopy

Structural evolution of poly(lactic acid) (PLA) upon uniaxial stretching was studied with in-situ polarized infrared spectroscopy measurements, and its structural change affected by annealing was also investigated. Band shifting was used to reflect the structural ordering process. It was found that the band at 1302 cm⁻¹ always moves to low wavenumbers before crystallization, indicating the occurrence of intermolecular packing ordering. However, the band at 869 cm⁻¹ shifts to high wavenumbers, which is related to the transition from the amorphous phase to the ordered phase. Interestingly, during stretching, the shifting for the band at 1302 cm⁻¹ always occurs before that for the lower wavenumber band, whereas these two band shifts take place simultaneously under annealing. Based on the different characteristics of the structural evolution under stretching and annealing processes, a critical temperature was found at around 63 °C, which influences the effect weight of kinetic and thermodynamic factors to the crystallization behavior. The effect of the drawing temperature on crystallization and mechanical property of PLA films was also analyzed.     

Revisit to the photocrosslinking behavior of PVA‐SbQ as a water‐soluble photopolymer with anomalously low contents of quaterized stilbazol side chains

The photocrosslinking behavior of poly(vinyl alcohol) (PVA) substituted with 0.1, 0.3, 1.3, and 4.0 mol % of styrylpyridinium (SbQ) (PVA‐SbQs) side chains was reinvestigated. Even‐order derivative spectra of films of PVAs loaded with 0.1 and 0.3 mol % of SbQ revealed the presence of subpeaks owing to vibrational transitions, whereas PVA bearing 1.3 and 4.0 mol % of SbQ displayed a new blue‐shifted band (H‐band) at 328 nm due to H‐aggregation. Changes in derivative spectra disclosed the rapid disappearance of the H‐band of PVA‐SbQs under UV irradiation within exposure doses of 10 mJ cm^?2. On the other hand, the films of the PVA‐SbQs were insolubilized upon UV irradiation at exposure doses of 2 and 3 mJ cm^?2, respectively, leading to the conclusion that the high photosensitivity comes from the photodimerization of H‐aggregate as a ground‐state dimer. Fluorescence measurements implied the presence of J‐aggregate at 386 nm, but the involvement of the J‐aggregation in photocrosslinking was excluded because of its negligible fraction. A photosensitive emulsion of poly(vinyl acetate) emulsified with PVA‐SbQ exhibited similar changes in higher‐order derivative spectra in film and applied to fabricate a stencil for screen printing with aid of an LED‐emitting 375 nm light. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Grain‐Boundary‐Free Super‐Proton Conduction of a Solution‐Processed Prussian‐Blue Nanoparticle Film

A porous crystal family has been explored as alternatives of Nafion films exhibiting super‐proton conductivities of ≥10⁻² S cm⁻¹. Here, the proton‐conduction natures of a solution‐processed film of nanoparticles (NPs) have been studied and compared to those of a Nafion film. A mono‐particle film of Prussian‐blue NPs is spontaneously formed on a self‐assembled monolayer substrate by a one‐step solution process. A low‐temperature heating process of the densely packed, pinhole‐free mono‐particle NP film enables a maximum 10⁵‐fold enhancement of proton conductivity, reaching ca. 10⁻¹ S cm⁻¹. The apparent highest conductivity, compared to previously reported data of the porous crystal family, remains constant against humidity changes by an improved water‐retention ability of the film. In our proposed mechanism, the high‐performing solution‐processed NP film suggests that heating leads to the self‐restoration of hydrogen‐bonding networks throughout their innumerable grain boundaries.     

Spectroscopic influences of ion pairing: Infrared matrix isolation spectra of the M+BF−4 ion pair and its chlorine—fluorine analogs

The matrix isolation technique has been combined with the salt/molecule reaction for the study of contact ion pairs in matrices. The infrared spectrum of the Cs⁺BF⁻₄ ion pair shows a splitting of the triply degenerate BF⁻₄ stretching band due to cesium cation perturbation, with a splitting of nearly 200 cm⁻¹. Normal coordinate calculations support a C_3υ model for the anion, and lead to a value of ΔK of 4.1 for Cs⁺, 4.7 for K⁺ and 3.8 for Tl⁺, where ΔK is the difference in BF stretching force constant between the coordinated fluorine and the non-coordinated fluorines. Similar calculations were carried out for the Cs⁺BCl⁻₄ ion pair, and an optimal value of ΔK = 1.6 was obtained.     

The effect of apodization and finite resolution on Fourier transform Raman spectra

The effects that finite resolution and choice of apodization function have on Fourier transform (FT) Raman spectra are illustrated by the 839 cm⁻¹ (ν₁) and 914 cm⁻¹ bands of KMnO₄. FT-Raman spectra were recorded at 0.5, 1, 2, 4, 8, 16 and 32 cm⁻¹ resolution using boxcar, Norton—Beer (strong, medium and weak) and triangular apodization functions at each resolution. The results show the dramatic changes in bandshape that occur as the ratio (resolution/true full width at half height of band) increases. The changes were measured in terms of the full width at half height of the band, the height of the band, the area of the band and the bandshape (expressed as a sum of Lorentzian and Gaussian lines). At a given resolution the degree to which each of these characteristics is affected is strongly dependent on the choice of the apodization function.     

DFT and Raman spectroscopy of porphyrin derivatives: Tetraphenylporphine (TPP)

Raman spectrum of the meso tetraphenylporphine (TPP) deposited onto smooth copper surface as thin film were recorded in the region 200–1700 cm⁻¹. To investigate the effect of meso-phenyl substitution rings on the vibrational spectrum of free base porphyrin, we calculated Raman and infrared (IR) spectra of the meso-tetraphenylporphine (TPP), meso tetramethylporphine (TMP), copper (II)porphine (CuPr) and free base porphine (FBP) at the B3LYP/6-311+G(d,p) level of the density functional theory (DFT). The observed Raman spectrum of the TPP is assigned based on the calculated its Raman spectrum in connection with the calculated spectra of the TMP, CuPr and FBP by taking into account of their corresponding vibrational motions of the Raman modes of frequencies. Results of the calculations clearly indicated that the meso tetraphenyl substitution rings are totally responsible for the observed Raman bands at ∼1593, 1234 and 1002 cm⁻¹. The calculated and observed Raman spectra also suggested that the observed Raman band with a medium intense at 962 cm⁻¹ might result from the surface plasmon effect. Furthermore, the observed Raman bands with medium intense at ∼334 and ∼201 cm⁻¹ are as results of the dimerization or aggregation of the TPP or would be that related to intramolecular interaction. We also calculated IR spectra of these molecules at same level of the theory. To investigate the solvent effect on the vibrational spectrum of porphine, the Raman and IR spectra of the TPP and FBP are calculated in solution phase where water used as solvent. The results of these calculation indicated that there is no any significant effect on the vibrational spectrum of the TPP.     

Treating entropy and conformational changes in implicit solvent simulations of small molecules

Implicit solvent models are increasingly popular for estimating aqueous solvation (hydration) free energies in molecular simulations and other applications. In many cases, parameters for these models are derived to reproduce experimental values for small molecule hydration free energies. Often, these hydration free energies are computed for a single solute conformation, neglecting solute conformational changes upon solvation. Here, we incorporate these effects using alchemical free energy methods. We find significant errors when hydration free energies are estimated using only a single solute conformation, even for relatively small, simple, rigid solutes. For example, we find conformational entropy (TDeltaS) changes of up to 2.3 kcal/mol upon hydration. Interestingly, these changes in conformational entropy correlate poorly (R2 = 0.03) with the number of rotatable bonds. The present study illustrates that implicit solvent modeling can be improved by eliminating the approximation that solutes are rigid.     

Vibrational spectroscopic study of syngenite formed during the treatment of liquid manure with sulphuric acid

Syngenite (K₂Ca(SO₄)₂·H₂O), formed during treatment of manure with sulphuric acid, was studied by infrared, near-infrared (NIR) and Raman spectroscopy. C_s site symmetry was determined for the two sulphate groups in syngenite (P2₁/m), so all bands are both infrared and Raman active. The split ν₁ (two Raman+two infrared bands) was observed at 981 and 1000 cm⁻¹. The split ν₂ (four Raman+four infrared bands) was observed in the Raman spectrum at 424, 441, 471 and 491 cm⁻¹. In the infrared spectrum, only one band was observed at 439 cm⁻¹. From the split ν₃ (six Raman+six infrared) bands three 298 K Raman bands were observed at 1117, 1138 and 1166 cm⁻¹. Cooling to 77 K resulted in four bands at 1119, 1136, 1144 and 1167 cm⁻¹. In the infrared spectrum, five bands were observed at 1110, 1125, 1136, 1148 and 1193 cm⁻¹. From the split ν₄ (six infrared+six Raman bands) four bands were observed in the infrared spectrum at 604, 617, 644 and 657 cm⁻¹. The 298 K Raman spectrum showed one band at 641 cm⁻¹, while at 77 K four bands were observed at 607, 621, 634 and 643 cm⁻¹. Crystal water is observed in the infrared spectrum by the OH-liberation mode at 754 cm⁻¹, OH-bending mode at 1631 cm⁻¹, OH-stretching modes at 3248 (symmetric) and 3377 cm⁻¹ (antisymmetric) and a combination band at 3510 cm⁻¹ of the H-bonded OH-mode plus the OH-stretching mode. The near-infrared spectrum gave information about the crystal water resulting in overtone and combination bands of OH-liberation, OH-bending and OH-stretching modes.     

Subtraction of atmospheric water contribution in Fourier transform infrared spectroscopy of biological membranes and proteins

The contribution of the absorption of H₂O vapor in the IR spectrum of proteins Interferes with the analysis of the shape of amide I and II bands and prevents correct assignments to be performed, in particular after Fourier self-deconvolution of the spectra Mathematical treatments of the spectra have previously been proposed to subtract the water vapor contribution from the sample spectrum. Here we propose to take advantage of the intrinsic bandwidth difference existing between the absorption bands of the water vapor and these of the liquid or solid sample. When a nominal resolution of 8 or 4 cm⁻¹ is chosen, atmospheric water bands are broad and rather featureless. The subtraction coefficient applied may vary by about 50% according to the operator. Conversely, when the spectrum of the same sample in the same conditions is recorded with a nominal resolution of 0.5 cm⁻¹, subtraction coefficients are exactly evaluated by integration and the visual evaluation can not be mistaken by more than 5%. The very sharp features arising from imperfect matching between the atmospheric water band shapes in the reference and in the sample spectrum completely disappear if the difference spectrum is now convoluted to a final resolution of 4 cm⁻¹. Incidence of the subtractions obtained at different resolutions on the evaluation of protein secondary structure is evaluated.