• Title/Summary/Keyword: $19^F NMR$

Search Result 79, Processing Time 0.026 seconds

Effective Synthesis of $\alpha$--Bromo-$\omega$ -fluoroalkane with Analysis of Gas-chromatography (가스크로마토그라피 분석을 통한 $\alpha$-브로모-$\omega$ -플루오로알칸의 효율적 합성)

  • Yu, Kook Hyun
    • Journal of the Korean Chemical Society
    • /
    • v.39 no.5
    • /
    • pp.414-420
    • /
    • 1995
  • $\alpha$-Bromo-$\omega$-fluoroalkanes are synthesized in 19∼55% yields from the reactions of dibromoalkanes with AgF and TBABr in acetonitrile at $82^{\circ}C$ for 20 minutes. The reaction is monitored with gas-chromatography. 1^H$ NMR and $19^F$ NMR-Spectrometer are used for identification of $\alpha$-Bromo-$\omega$-fluoroalkanes, difluoroalkane, fluoroalken and bromoalkene.

  • PDF

19F NMR investigation on the ratio of amorphous to crystal for the binder PVdF in Li ion battery

  • Im, Jong-san;Park, Junghwan;Kim, Kyoung Soo;Jung, Hyunok
    • Journal of the Korean Magnetic Resonance Society
    • /
    • v.23 no.1
    • /
    • pp.1-5
    • /
    • 2019
  • $^{19}F$ NMR experiments were carried out to observe the change of the characteristics of the PVdF binder which is an auxiliary material of the lithium ion battery. PVdF has various crystalline or amorphous phases by thermal treatment. A mixture of cathode and auxiliary materials including PVdF was coated on aluminum foil as an electron collector and then subjected to thermal treatment at various temperatures. The overlapped $^{19}F$ NMR signals obtained from the various phases were separately convoluted into the respective phases, and it was found that there was a relative ratio change of these phases. In addition, the crystal and amorphous phase of PVdF was changed during the vacuum drying, which is the last step of the actual electrode manufacturing. It was observed that the relative amount of amorphous phase, which may affect the flexibility of the electrode or the wettability of the electrolyte, abruptly changes after a certain temperature.

19F NMR Investigation of F1-ATPase of Escherichia coli Using Fluorinated Ligands

  • Jung, Seun-Ho;Kim, Hyun-Won
    • BMB Reports
    • /
    • v.31 no.1
    • /
    • pp.44-47
    • /
    • 1998
  • Asymmetry amongst nucleotide binding sites of Escherichia coli $F_1$-ATPase was examined using $^{19}F$ NMR signal from fluorinated analogs of adenine nucleotides bound to nucleotide binding sites. ADP-$CF_2-{PO_3}^{2-}$ showed no inhibitory effect to $F_1$-ATPase. But ADP-CHF-${PO_3}^{2-}$ (racemic mixture) showed competitive inhibition of $F_1$-ATPase with $K_i$ of $60\;{\mu}m$. ADP-CHF-${PO_3}^{2-}$ shows only negligible binding to $EF_1$ in the absence of $Mg^2+$. With the addition of $Mg^2+$ to the medium, the $^{19}F$ resonance of free ADP-CHF-${PO_3}^{2-}$ disappeared and the new broad resonances appeared. Appearance of more than two new asymmetric resonances following the binding of ADP-CHF-${PO_3}^{2-}$ to $EF_1$ may indicate that at least one of the isomers showed split resonances. This may suggest that the region between ${\alpha}$-and ${\beta}$-phosphate of ADP-CHF-${PO_3}^{2-}$ which is bound to catalytic sites is experiencing a different environment at different sites.

  • PDF

Study on Relative Stability of Geometrically Constrained Cyclopropylcarbinyl Cation by $^{19}$F-NMR Spectroscopy (풀루오르 19-NMR을 이용한 구조적으로 고정된 사이크로프로필카르비닐 양이온의 상대적 안정도의 비교)

  • Jung Hyu Shin;Bo Hyeon Yoon
    • Journal of the Korean Chemical Society
    • /
    • v.29 no.3
    • /
    • pp.213-219
    • /
    • 1985
  • The relative stability as a function of geometry in rigid cyclopropylcarbinyl cations was examined by $^{19}$F-nmr spectroscopy. 8-p-Fluorophenyl-tricyclo[3.3.1.0$^{2,7}$]octane-8-yl-(I), 9-p-fluorophenyl-tricyclo[3.3.1.0$^{2,8}$]nonane-9-yl (II), and 10-p-fluorophenyl-tricyclo[4.3.1.0$^{2,9}$]decane-10-yl cation(Ⅲ) were prepared from the corresponding carbinols in FSO$_3$H-SO$_2$ClF solution at -120$^{\circ}C$. $^{19}$F-nmr data indicate that the symmetrical bisected geometry of cyclopropane ring for ${\sigma}$-conjugation is a very impotant factor in charge delocalization. However, varied orientation of the bond angle ${\theta}$ within the bisected conformation does not affect the charge delocalization into the cyclopropane ring.

  • PDF

Structure and Dynamics of Perfluoroalkanes and Their ${\beta}$-Cyclodextrin Inclusion Compounds Investigated by Solid-state $^{19}F$ MAS NMR

  • Tatsuno, Hiroto;Ando, Shinji
    • Proceedings of the Polymer Society of Korea Conference
    • /
    • 2006.10a
    • /
    • pp.305-305
    • /
    • 2006
  • The molecular structure and dynamics of inclusion compounds (ICs) consisting of n-perfluoroalkane (PFA) guests and ${\Box}-cyclodextrin$ (${\Box}-CD$) host were investigated using $^{19}F$ magic angle spinning (MAS) and $^{1}H{\to}^{19}F$ cross polarization (CP) / MAS NMR spectroscopy with the aid of thermal analyses, FT-IR spectroscopy, X-ray diffraction, and $^{1}H{\to}^{19}F$ CP/MAS technique revealed that $C_{9}F_{20}$ molecules included in ${\Box}-CD$ undergo vigorous molecular motion and partly come out of the ${\Box}-CD$ channel above $80^{\circ}C$. In case of $C_{20}F_{42}/{\Box}-CD$, an exothermic peak is observed by differential scanning calorimetry (DSC) at ca. $40^{\circ}C$ which suggests that ${\Box}-CD$ molecules become mobile and commence rearrangements that form more ordered structures at higher temperatures.

  • PDF

Variable Temperature High-Resolution 19F MAS Solid-State NMR Characterization of Fluorocarbon Rubbers

  • Park, Tae-Joon;Choi, Sung-Sub;Kim, Ji-Sun;Kim, Yong-Ae
    • Bulletin of the Korean Chemical Society
    • /
    • v.32 no.7
    • /
    • pp.2345-2350
    • /
    • 2011
  • Variable temperature high-resolution $^{19}F$ magic angle spinning (MAS) solid-state NMR spectroscopy was used to characterize fluorocarbon (FKM) rubbers. The high-resolution spectra of copolymers made from two monomers, vinylidene fluoride and hexafluoropropene, and terpolymers composed of vinylidene fluoride, hexafluoropropene, and tetrafluoroethylene, were obtained using MAS speeds of up to 18 kHz combined with high temperatures of up to 200 $^{\circ}C$ at a magnetic field strength of 9.4 Tesla. From these high resolution solid-state NMR spectra, we were able to assign the spectral peaks and differentiate the copolymer FKM from the terpolymer FKM. We also determined quantitatively the monomer compositions of each FKM rubber.

Fluorine-19 NMR Spectroscopic Studies of Phenyl-fluorinated Iron Tetraarylporphyrin Complexes

  • Song, Byung-Ho;Yu, Byung-soo
    • Bulletin of the Korean Chemical Society
    • /
    • v.24 no.7
    • /
    • pp.981-985
    • /
    • 2003
  • Fluorine-19 NMR solution measurements have been made for various phenyl-fluorinated iron porphyrin complexes. Large chemical shifts for phenyl fluorine signals of iron(III) and iron(II) are observed, and these signals are sensitive to electronic structure. The chemical shift differences in ortho-phenyl fluorine signals between high-spin ferric and low-spin ferric tetrakis(pentafluorophenyl)porphyrins are approximately 40 ppm, whereas the differences are approximately 7 ppm between high- and low-spin states of ferrous tetrakis(pentafluorophenyl)porphyrin complexes. Analysis of fluorine-19 isotropic shifts for the iron(III) tetrakis(pentafluorophenyl) porphyrin using fluorine-19 NMR indicates there is a sizable contact contribution at the ortho-phenyl fluorine ring position. Large phenyl fluorine-19 NMR chemical shift values, which are sensitive to the oxidation and spin states, can be utilized for identification of the solution electronic structures of iron(III) and iron(II) porphyrin complexes.