Enantioselective Raman spectroscopy (esR) for distinguishing between the enantiomers of 2-butanol

Rullich, Claudia C.; Kiefer, Johannes

doi:10.1039/c8an00705e

Cited by 12 publications

(8 citation statements)

References 41 publications

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“…The C═O stretching at 1795 cm À1 is different from the position of 1735 cm À1 in Figure S6C, which could be attributed to the formation of isomers (eg, pentanoic acid 1-methylpropyl ester). 52,53 The characteristic band of hydroxyl groups (-OH) from 2-butanol appears in the range from 3200 to 3500 cm À1 (see Figure S6B), 54 which is overlapped with the hydroxyl groups from water. 55…”

Section: In-situ Electrochemical Raman Studymentioning

confidence: 99%

Electrochemical conversion of valeric acid on carbon‐based materials

Gong

Shen

2022

Intl J of Energy Research

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Converting carboxylic acids into value-added products by electrochemical processes is of great interest. In this work, the electrochemical conversion of valeric acid (VA) on carbon materials including glassy-carbon (GC) electrodes and carbon-paper (CP) electrodes was studied. Owing to the porous structure, CP electrodes showed superior performance relative to GC electrodes. The surface properties of CP electrodes were modified via electro-oxidation processes. The structures of the CP electrodes were characterized by scanning electron microscopy, X-ray diffraction pattern, X-ray photoelectron spectroscopy spectra, and Raman spectra. It was found that the electrochemical activation process had more pronounced effects on electro-oxidation of VA than H 2 O. The onset potential of VA oxidation on electrochemically activated CP electrodes was negatively shifted and the current density was significantly improved. The products of VA oxidation by CP electrodes were determined by gas chromatography-mass spectra. VA was mainly transformed into 2-butanol, butyl valerate, and pentanoic acid 1-methylpropyl ester. The conversion of VA, Faraday efficiency, and product selectivity were determined. The optimal CP electrode exhibited the largest values of product selectivity (85.0%) and VA conversion (13.0%). In-situ Raman spectra were recorded to study the mechanism of VA oxidation on the CP electrodes. The oxidation of VA by CP electrodes follows the non-Kolbe route and the corresponding pathway was proposed.

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Section: In-situ Electrochemical Raman Studymentioning

confidence: 99%

Electrochemical conversion of valeric acid on carbon‐based materials

Gong

Shen

2022

Intl J of Energy Research

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“…for the on-line monitoring of synthesis processes of chiral drugs [120]. The approach was recently advanced with an automatized polarization-resolved Raman setup and coupled with chemometric analysis [119,121] which enabled enantiomeric differentiation of butan-2-ol [120,121]. Also, the enantiomeric fractions of the chiral molecule (5,6)-diphenyl-morpholin-2-one could be determined [119].…”

Section: Raman Optical Activity and Enantioselective Raman Spectroscomentioning

confidence: 99%

Recent advances in nano-photonic techniques for pharmaceutical drug monitoring with emphasis on Raman spectroscopy

Knebl

Frosch

2019

Nanophotonics

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Innovations in Raman spectroscopic techniques provide a potential solution to current problems in pharmaceutical drug monitoring. This review aims to summarize the recent advances in the field. The developments of novel plasmonic nanoparticles continuously push the limits of Raman spectroscopic detection. In surface-enhanced Raman spectroscopy (SERS), these particles are used for the strong local enhancement of Raman signals from pharmaceutical drugs. SERS is increasingly applied for forensic trace detection and for therapeutic drug monitoring. In combination with spatially offset Raman spectroscopy, further application fields could be addressed, e.g. in situ pharmaceutical quality testing through the packaging. Raman optical activity, which enables the thorough analysis of specific chiral properties of drugs, can also be combined with SERS for signal enhancement. Besides SERS, micro- and nano-structured optical hollow fibers enable a versatile approach for Raman signal enhancement of pharmaceuticals. Within the fiber, the volume of interaction between drug molecules and laser light is increased compared with conventional methods. Advances in fiber-enhanced Raman spectroscopy point at the high potential for continuous online drug monitoring in clinical therapeutic diagnosis. Furthermore, fiber-array based non-invasive Raman spectroscopic chemical imaging of tablets might find application in the detection of substandard and counterfeit drugs. The discussed techniques are promising and might soon find widespread application for the detection and monitoring of drugs in various fields.

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“…These limitations present water and ethanol as the most common solvents, making them less relevant for detecting chirality in organic crystals. A few methods are known for enantiomeric differentiation in their solid form such as second harmonic generation, CD, and vibrational CD. , However, some of the mentioned methods are time-consuming, expensive, experimentally complicated, require molecular labeling or addition of chemical agents, and eventually turn out to be impractical in terms of time-resolution for process monitoring …”

Section: Introductionmentioning

confidence: 99%

“…There are recent reports where the Raman enhancement technique is used for enantiomeric discrimination in solution, which requires special sample preparation. Moreover, these reports make use of asymmetries of C–H, C–S–C, and G and D bands of graphene rather than a chiral molecule. ,, A detailed comparison of different types of Raman studies conducted toward enantiomeric discrimination can be found in the Supporting Information section under Table S1.…”

Section: Introductionmentioning

confidence: 99%

“…This includes asymmetrical excitation and collection of the signal and passing it through a polarizer placed before the spectrometer. Some theoretical framework on the polarization phenomena with respect to the laser and Raman signal propagation in optically active samples is proposed elsewhere. ,, Our work is the first to experimentally distinguish between d and l enantiomers in the solid form using a straightforward Raman measurement with no sample preparation.…”

Section: Introductionmentioning

confidence: 99%

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Identification of Enantiomers Using Low-Frequency Raman Spectroscopy

2022

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Distinguishing between D and L enantiomers is of important scientific interest, especially for the pharmaceutical industry. Enantiomeric differentiation in the solid form is repeatedly presented as a challenge in the research community. Raman spectroscopy is a nondestructive tool, widely used for the characterization of different materials by probing their vibrational modes. The low-frequency region of the Raman spectrum reveals lattice-level interactions and global fluctuations in the molecule. Lower frequencies correspond to vibrations arising from weaker bonds and long-range interactions and hence are very susceptible to polarization changes. This work presents low-frequency Raman (LFR) spectroscopy as a facile technique to identify enantiomers. The optical setup of conventional Raman spectroscopy is engineered such that the excitation and collection geometries use an asymmetrical focal cone. In addition, a half-wave retarder is added to the excitation path and a Glan−Taylor polarizer is added to the collection path, and these modifications allow us to select the polarization plane for both excitation and collection geometries. The asymmetry in the foci when using a polarized beam for excitation provides different intensities of the collected signal for each polarization plane. In a calibrated system, one can define the chirality of an analyte by comparing the intensity of the LFR signal along orthogonal sets of polarization planes. For nonchiral molecules, the spectral intensity is always higher in the co-polarized plane when compared to the orthogonally depolarized plane, as expected. This contrast in the intensity of Raman spectra serves as a distinct tool for identifying enantiomers.

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Enantioselective Raman spectroscopy (esR) for distinguishing between the enantiomers of 2-butanol

Cited by 12 publications

References 41 publications

Electrochemical conversion of valeric acid on carbon‐based materials

Electrochemical conversion of valeric acid on carbon‐based materials

Recent advances in nano-photonic techniques for pharmaceutical drug monitoring with emphasis on Raman spectroscopy

Identification of Enantiomers Using Low-Frequency Raman Spectroscopy

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