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Stereochemistry
Published in Michael B. Smith, A Q&A Approach to Organic Chemistry, 2020
No! Specific rotation is a physical property of a molecule that is determined from the interaction of the enantiomers with plane-polarized light. Absolute configuration is the spatial arrangement of atoms around a stereogenic center and prioritizing those atoms is an interpretive property, not a physical property. An enantiomer with a specified absolute configuration could have either a (+) or a (–) specific rotation.What are the sequence rules used to determine absolute configuration?
Effect of chiral monomer containing D(+)-camphoric acid on the optical properties and phase behaviours of side-chain cholesteric liquid crystal polymers
Published in Liquid Crystals, 2021
Ya-Ru Ma, Xue-Song Zhang, Xuan Xie, Yue-Jiao Huang, Xiao-Zhi He, Yue-Hua Cong, Bao-Yan Zhang, Ying-Gang Jia
Fourier transform infrared spectroscopy (FT-IR) was conducted by a PerkinElmer Spectrum One FT-IR spectrometer (PerkinElmer Instruments, USA). 1H NMR spectra (400 MHz) were recorded on a Bruker AV 400 spectrometer in 5-mm o.d. sample tubes. Specific rotation was performed with Autopol IV (Rudolph, USA) polarimeter. All optical activity measurements of PPL series were performed in chloroform with a Na lamp (λ = 589 nm). Differential scanning calorimetry (DSC) was carried out on a Netzsch DSC 204 (Netzsch, Germany) with a flow of dry nitrogen cooling system under the scanning rates of 10°C min−1. A Leica DMRX (Leica, Germany) polarising optical microscope (POM) equipped with a Linkam THMSE-600 (Linkam, UK) hot stage was used to test liquid-crystal properties. XRD measurements were performed with a nickel-filtered Cu-Kα radiation (λ = 0.1542 nm) with a DLAX-3A Rigaku (Rigaku, Japan) powder diffractometer. Thermogravimetric analysis (TGA) measurement is performed by a NETZSCH TGA 209 C thermogravimetric analyser.
Mesomorphic, structural, electro-optic and dynamic properties of lactic acid derivative and its selectively deuterated isotopomers by means of electro-optics, SAXS, 2H-NMR and neutron spin-echo spectroscopy
Published in Liquid Crystals, 2020
Alexej Bubnov, Mario Cifelli, Martin Cigl, Peter Fouquet, Vera Hamplova, Valentina Domenici
Detailed synthetic procedures are described in the following paragraphs. All starting materials and reagents were purchased from Sigma-Aldrich, Acros Organics or Lach-Ner. All solvents used for the synthesis were ‘p.a.’ grade. 1H NMR spectra were recorded on Varian VNMRS 300 instrument (Palo Alto, California, USA); deuteriochloroform (CDCl3) and hexadeuteriodimethyl sulfoxide (DMSO-d6) were used as solvents and signals of the solvent served as internal standard. Chemical shifts (δ) are given in ppm and J values are given in Hz. The purity of final compound was checked by HPLC analysis (high-pressure pump ECOM Alpha; column WATREX Biospher Si 100, 250 × 4 mm, 5 μm; detector WATREX UVD 250). Column chromatography was carried out using Merck Kieselgel 60 (60–100 μm). Enantiomeric purity of chiral compounds was confirmed by chiral HPLC system (chiral column: Daicel Chiralpak AD-3, 150 × 4.6 mm I.D., 3 µm). The specific rotation was measured in CHCl3 solution (c = 0.10 M) using the automatic polarimeter polAAr 3000 (Optical Activity Ltd., Ramsey, UK).
NaClO2-mediated preparation of pyridine-2-sulfonyl chlorides and synthesis of chiral sulfonamides
Published in Journal of Sulfur Chemistry, 2020
Dong Xu, Shiyi Yang, Aijun Gao, Zhanhui Yang
All the chemicals and solvents were used directly as received. TLC analyses were performed on Yantai Chemical Co., Ltd. silica gel GF254 plates with petroleum ether (PE) and ethyl acetate (EA), and the plates were visualized with UV light. Products were purified with column chromatography using Qingdao Ocean Chemical Co., Ltd. silica gel (200-300 mesh) with PE and EA as eluents. Melting points were obtained on a Yanaco MP-500 melting point apparatus and are uncorrected. The specific rotation analysis was measured by Anton Paar MCP200 Polarimeter. IR spectra were taken on a Bruker FT-IR spectrometer on KBr pellets. 1H and 13C spectra were recorded on a Bruker 400 MHz spectrometer as CDCl3 solution with TMS as an internal standard. HRMS data were obtained with an Agilent LC/MS TOF mass spectrometer.