Infrared spectroscopic study of conformational properties of short chain poly(oxyethylene)s in methanol and carbon tetrachloride

Begum, Roksana; Sagawa, Tatsuya; Masatoki, Sei

doi:10.1016/s0022-2860(97)00338-4

Cited by 10 publications

(14 citation statements)

References 22 publications

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“…8,15,16,21,23,24 An interesting correlation between the conformations of the C-C bond and the C-O bond has been revealed throughout the experiments; 15,16,21,23,24 when the population of gauche C-C bonds increases the population of gauche C-O bonds decreases and vice versa. The same conformational trends have been observed for longer poly(oxyethylene) chains 6,9,10,[14][15][16][17][18][19]21,24,25 and poly-(oxyethylene)-containing compounds. 26 These experimental findings substantiate the choice of 1,2-dimethoxyethane as a model compound of poly(oxyethylene).…”

Section: Introductionmentioning

confidence: 93%

“…It is well-known that the gauche preference of the C-C bond is enhanced at low temperatures 5,[17][18][19][20][21][22][23][24] and in hydrogen bonding or polar solvents, 6,[8][9][10][14][15][16][17][18][19][20][21][22]24 while the C-O bond has an opposite conformational preference. 8,15,16,21,23,24 An interesting correlation between the conformations of the C-C bond and the C-O bond has been revealed throughout the experiments; 15,16,21,23,24 when the population of gauche C-C bonds increases the population of gauche C-O bonds decreases and vice versa. The same conformational trends have been observed for longer poly(oxyethylene) chains 6,9,10,[14][15][16][17][18][19]21,24,25 and poly-(oxyethylene)-containing compounds.…”

Section: Introductionmentioning

confidence: 99%

“…Therefore, the conformation of 1,2-dimethoxyethane has been extensively studied in all phases and in different solvents to elucidate the conformational behavior of the poly(oxyethylene) chain. Vibrational spectroscopy − and NMR spectroscopy − have been the main experimental methods in these studies.…”

Section: Introductionmentioning

confidence: 99%

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Raman Spectroscopic Study on the Conformation of 1,2-Dimethoxyethane in the Liquid Phase and in Aqueous Solutions

2000

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The conformation of 1,2-dimethoxyethane in the liquid phase and in aqueous solutions was studied by Raman spectroscopy. The conformation-sensitive Raman bands of 1,2-dimethoxyethane, located in the wavenumber region 300−600 cm-1, were analyzed by means of the band decomposition based on normal coordinate analysis. The populations of the conformers of 1,2-dimethoxyethane, their relative energies, and their relative entropies in the liquid phase were estimated and compared with the relevant data for the gas phase of 1,2-dimethoxyethane. The condensed phase effects on the conformation of 1,2-dimethoxyethane were discussed on the basis of the experimental data. The populations of the conformers at 318 K in aqueous solutions with different concentrations were estimated. It was revealed that the populations of the TTT and TGG‘ conformers of 1,2-dimethoxyethane decrease on increasing concentration of water, while the populations of the TGT and TGG conformers increase. The entropies of the less hydrophilic TTT and TGG‘ conformers are higher than the entropies of the more hydrophilic TGT and TGG conformers. This experimental observation suggests that the inverse temperature solubility of poly(oxyethylene) in water originates from the conformational changes of the polymer chain.

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Section: Introductionmentioning

confidence: 93%

Section: Introductionmentioning

confidence: 99%

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Raman Spectroscopic Study on the Conformation of 1,2-Dimethoxyethane in the Liquid Phase and in Aqueous Solutions

2000

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“…Although such observations appear not to have been extensively studied, there are a number of theoretical and experimental publications when similar concentration dependent conformational preferences were reported. [32][33][34] For example, inversion of population distribution of felodipine conformations at increasing concentration in DMSO was observed by Khodov and co-workers in 2014. 33 Using NMR spectroscopy, these authors concluded that conformational preference of felodipine in DMSO is concentration dependent: conformers that dominate in a dilute solution become the least abundant in the saturated one.…”

Section: Concentration Dependent Diastereomeric Preferencementioning

confidence: 99%

Diastereomeric preference of a triply axial chiral binaphthyl based molecule: a concentration dependent study by chiroptical spectroscopies

Dezhahang

Poopari

Hernández

et al. 2014

Phys. Chem. Chem. Phys.

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We have examined the effects of environmental perturbations, specifically solvents and concentrations, on axial chirality of a recently synthesized axially chiral binaphthyl fluorene based salen ligand, named AFX-155, {[2,2'-(1E,1'E)-(R)-1,1'-binaphthyl-2,2'-diylbis(azan-1-yl-1-ylidene)bis(methan-1-yl-1-ylidene)bis(4-((7-(diphenylamino)-9,9-dihexyl-9H-fluoren-2-l)ethynyl)-phenol)]}. Chirality and dominant conformations of AFX-155 in CDCl3 solvent have been characterized using vibrational absorption (VA) and vibrational circular dichroism (VCD) spectroscopy in combination with DFT calculations. AFX-155 exhibits triple axial chirality: one is at the binaphthyl ring and the other two are related to the axes of chirality along the -C-N bonds where Cs are part of the binaphthyl group. To evaluate solvent and concentration dependence, complementary VA and VCD experiments in both THF-d8 and CDCl3 have been performed, as well as the optical rotatory dispersion (ORD) and electronic CD (ECD) measurements in CDCl3 under much diluted conditions. While the binaphthyl chirality is determined by the synthetic route, the results show that the latter two axial chirality labels of the dominant diastereomers are concentration dependent. Under much diluted conditions, R-binaphthyl, R_intra_HB//R_extra_HB (R-RR) is favoured, whereas R-binaphthyl, S_intra_HB//S_extra_HB (R-SS) is the dominant species in a concentrated solution. This diastereomeric interconversion is found to be independent of the two solvents used. To provide insights into this interesting finding, conformational searches and the related spectral simulations have been carried out at the DFT/B3LYP/6-31G(d) level.

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“…Van Figure 5, At lower temperature ethoxylated oligomers more clearly separated. That the conformational change of an EO chain of PEG in solution depends on its concentration is well known [28,29]. The retention factors of all oligomers increase with increasing temperature from 10 to 40 ~ and then decrease with increasing temperature from 40 to 70 ~ In reversed phase HPLC the Ink of a neutral compound usually decreases linearly with increasing temperature [26,27], but in this case the Van't Hoff plots bend anomalously.…”

Section: Separation Of Leon In Isocratic Eluentmentioning

confidence: 99%

Simultaneous separation of nonionic surfactants and polyethylene glycols by reversed phase high performance liquid chromatography

Kamiusuki¹,

Monde²,

Omae³

et al. 2000

Chromatographia

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The simultaneous separation of polyethylene glycol and its derivatives such as the lauryl alcohol and lauric acid ethoxylate oligomers was carried out by reversed phase high performance liquid chromatography. Branched fluorinated silica gel columns combined with evaporative light scattering detection were used for the characterization of nonionic surfactants. Lauryl alcohol ethoxylate oligomers were separated at 10 ~ with an isocratic eluent according to ethoxylate number and the retention time of the oligomers decreases with increasing ethoxylate number. The Van't Hoffplots of retention factor of lauryl alcohol ethoxylate gave a complex cure, which is anomalous behavior for reversed phase high performance liquid chromatography. The anomalous Van't Holt plots were explained by a partial conformational change from polar to less polar conformers with increasing temperature. The most significant features for the analysis of the lauryl alcohol ethoxylate were the use of acetonitrile as mobile phase and operating temperature. The polyethylene glycol was separated according to ethoxylate number and the retention time of oligomers increased with increasing ethoxylate number. The Van't Hoffplots of retention factor of polyethylene glycol had negative slopes. It was presumed that the polar conformation of the ethylene oxide chain decreased with increasing temperature. The lauryl alcohol ethoxylate and polyethylene glycol were separated simultaneously in gradient elution as a result of the conformational change of the ethylene oxide chain. As a practical example, lauric acid ethoxylate simultaneously separated into free polyethylene glycol, ethoxylate monolaurate and ethoxylate dilaurate in gradient elution.

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Infrared spectroscopic study of conformational properties of short chain poly(oxyethylene)s in methanol and carbon tetrachloride

Cited by 10 publications

References 22 publications

Raman Spectroscopic Study on the Conformation of 1,2-Dimethoxyethane in the Liquid Phase and in Aqueous Solutions

Raman Spectroscopic Study on the Conformation of 1,2-Dimethoxyethane in the Liquid Phase and in Aqueous Solutions

Diastereomeric preference of a triply axial chiral binaphthyl based molecule: a concentration dependent study by chiroptical spectroscopies

Simultaneous separation of nonionic surfactants and polyethylene glycols by reversed phase high performance liquid chromatography

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