• Applied Biological Chemistry
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• 제41권7호
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• pp.550-555
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• 1998

Fluoro-quinolone carboxilic acid 유도체에서, 탄소-불소간 one bond coupling constants는 위치와 무관하게 249 Hz에서 257 Hz 사이의 값을 갖는데, geminal 및 vicinal coupling constants는 위치에 따라 그 값의 차이가 많이 생긴다. 즉, seminal coupling constants는 6 Hz에서 23 Hz의 값을 보이고 vicinal coupling constants는 1.9 Hz에서 7 Hz의 값을 보인다. 또한 수소-불소간 three bond coupling constants는 9 Hz에서 10.3 Hz의 값을 보이고, four bond coupling constants는 6 Hz에서 8.3 Hz의 값을 보인다.

• 대한방사성의약품학회지
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• 제3권2호
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• pp.129-133
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• 2017

Since carbon-fluorine (C-F) bonds play a key role to improve bioavailability and lipophilicity, they have found commonly in pharmaceuticals, radiopharmaceuticals, agrochemicals, and material science. Advances on the efficient method to introduce fluorine to complex organic molecules are mainly results of development of fluorination reagents and transition metal catalysts. In this mini-review, we want to emphasize two representative nucleophilic fluorinating reagents regarding carbon-fluorine bond formation, which were developed in the mid-2000s.

• 대한방사성의약품학회지
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• 제4권1호
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• pp.11-15
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• 2018

Electrophilic fluorinating reagents are typically efficient for carbon-fluorine (C-F) bonds formation due to their higher reactivity even under mild condition. Thus, they have been playing an important role to improve C-F bonds formation reactions via direct fluorination reaction with electrophilic fluorinating reagents or transition metal catalysis. Advances on the recent fluorination methods are mainly results of $Selectfluor^{TM}$'s capability on facile fluorination. In this mini-review, we describe synthesis and application of four old yet popular electrophilic fluorinating reagents such as N-fluorobenzenesulfonimide (NFSI), N-fluoropyridinium salts, $Selectfluor^{TM}$, and N-fluorosultam.

• 대한방사성의약품학회지
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• 제3권2호
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• pp.122-128
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• 2017

In the 2000s, there has been a significant advance on carbon-fluorine (C-F) bond formation reactions via transition metal mediated or catalyzed methods. Of course, for the past 10 years, transition metal catalysis improves C-F bond formation in terms of practicality and even can be applied to C-18F bond formation reaction. In this mini-review, we summarize various transition metal mediated or catalyzed fluorination reactions, which were developed in the mid-2000s.

• Carbon letters
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• 제5권1호
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• pp.12-17
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• 2004

In this study, the oxyfluorination of PAN-based carbon fibers was undertaken at room temperature using fluorine-oxygen mixtures, and the influence of oxyfluorination on properties was investigated. The surface characteristics of the modified fiber were determined by using X-ray photoelectron spectroscopy (XPS) and dynamic contact angle analyzer. The oxyfluorination of carbon fibers was one of the more effective methods to increase surface wettability by the formation of semicovalent C-F bond and C-O bond depending on reaction conditions. When oxygen mole fraction is increased from 0.5 to 0.9, it is probable that attached fluorine atoms at the surface of the fibers reacted with other components. As increased oxyfluorination time and decreased its pressures, semi-covalent peak is increased at 0.5 of oxygen mole fraction. The total surface free energy of oxyfluorinated carbon fibers decreased with increasing oxygen mole fraction over 0.5. These results indicate that the surface of carbon fibers became much more hydrophilic after the short oxyfluorination. The surface free energy of oxyfluorinated carbon fibers progressively decreased after 10 min treatment. The polar components of surface free energies were however, significantly higher for all oxyfluorinated samples than that for the untreated carbon fiber.

• 대한방사성의약품학회지
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• 제1권2호
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• pp.80-87
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• 2015

Carbon-fluorine (C-F) bonds have been found ubiquitously in pharmaceuticals, radiopharmaceuticals, agrochemicals, and material science due to their unique properties such as thermal and oxidative stability and lipophilicity to improve bioavailability. For the past five years, there have been significant advances in F-18 fluorination of aromatic complex molecules combined with the development of late-stage fluorination reactions. More recently, direct incorporation of F-18 to fluorinated aromatic molecules via borylation of C-F bonds has been developed by Niwa and Hosoya. In this minireview, we will discuss the progress of C-F bondborylation of fluorinated arenes utilizing transition metal catalysts and the impact on the development of F-18 radiotracers for positron emission tomography (PET).

• Bulletin of the Korean Chemical Society
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• 제27권3호
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• pp.345-354
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• 2006

Ionic liquids are alternative reaction media of increasing interest and are regarded as an eco-friendly alternatives, of potential use in place of the volatile organic solvents typically used in current chemical processing methods. They are emerging as the smart and excellent solvents, which are made of positive and negative ions that they are liquids near room temperature. The nucleophilic substitution reaction is one of the important method for inserting functional groups into a carbon skeleton. Many nucleophilic substitution reactions have been found with enhanced reactivity and selectivity in ionic liquid. In this review, some recent interesting results of nucleophilic substitution reactions such as hydroxylations, ether cleavages, carbon-X (X= carbon, oxygen, nitrogen, fluorine) bond forming reactions, and ring opening of epoxides in ionic liquids are discussed.

• 한국재료학회지
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• 제1권4호
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• pp.214-220
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• 1991

실리콘 산화막을 $CHF_{3/}C_2F_6$ 혼합가스를 사용하여 반응성이온 건식식각을 행할 때 실리콘 표면에 형성되는 잔류막과 손상층을 X-선 광전자 분광기(XPS)와 이차이온 질량 분석기(SIMS)를 사용, 연구하였다. 실리콘, 탄소, 산소 및 불소의 angle-resolved XPS분석기술을 이용한 비파괴적 화학결합상태의 깊이분포 분석을 통하여 잔류막의 표면부에 O-F 결합이 존재하며 잔류막은 주로 탄소와 불소의 결합체인 C-F 플리머로 구성되어져 있고 Si-O, Si-C 및 Si-F 결합 등이 존재함을 알았다. 손상층은 실리콘 표면에서 약 60nm 깊이까지 탄소와 불소의 침투에 의해 형성되어져 있음을 알았다.

• 한국응용과학기술학회지
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• 제28권2호
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• pp.232-239
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• 2011

Fabric fibrous filter has been used in various industrial applications owing to the low cost and wide generality. However, the basic properties of fabric materials often limit the practical utilization including hot gas cleaning. This study attempts to find new coatings of porous fibrous filter media in order to overcome its insufficient thermal resistance and durability. Teflon was one of the plausible chemicals to supplement the vulnerability against frequent external thermal impacts. A foaming agent composed of Teflon and some organic additives was tentatively coated on the glass fiber mat. The present test Teflon foam coated filter was fount to be useful for hot gas cleaning, up to $250^{\circ}C$-$300^{\circ}C$. Close examination using XPS(X-ray Photoelectron Spectroscopy) and Contact angle proved the binding interactions between carbon and fluorine, which implies coating stability. The PTFE/Glass foam coated filter consisted of more than 95% (C-F)n bond, and showed super-hydrophobic with good-oleophobic characteristics. The contact angle of liquid droplets on the filter surface enabled to find the filter wet-ability against liquid water or oil.

• Animal Bioscience
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• 제37권2_spc호
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• pp.396-403
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• 2024

Objective: Monofluoroacetate (MFA) is a potent toxin that blocks ATP production via the Krebs cycle and causes acute toxicity in ruminants consuming MFA-containing plants. The rumen bacterium, Cloacibacillus porcorum strain MFA1 belongs to the phylum Synergistota and can produce fluoride and acetate from MFA as the end-products of dehalorespiration. The aim of this study was to identify the genomic basis for the metabolism of MFA by this bacterium. Methods: A draft genome sequence for C. porcorum strain MFA1 was assembled and quantitative transcriptomic analysis was performed thus highlighting a candidate operon encoding four proteins that are responsible for the carbon-fluorine bond cleavage. Comparative genome analysis of this operon was undertaken with three other species of closely related Synergistota bacteria. Results: Two of the genes in this operon are related to the substrate-binding components of the glycine reductase protein B (GrdB) complex. Glycine shares a similar structure to MFA suggesting a role for these proteins in binding MFA. The remaining two genes in the operon, an antiporter family protein and an oxidoreductase belonging to the radical S-adenosyl methionine superfamily, are hypothesised to transport and activate the GrdB-like protein respectively. Similar operons were identified in a small number of other Synergistota bacteria including type strains of Cloacibacillus porcorum, C. evryensis, and Pyramidobacter piscolens, suggesting lateral transfer of the operon as these genera belong to separate families. We confirmed that all three species can degrade MFA, however, substrate degradation in P. piscolens was notably reduced compared to Cloacibacillus isolates possibly reflecting the loss of the oxidoreductase and antiporter in the P. piscolens operon. Conclusion: Identification of this unusual anaerobic fluoroacetate metabolism extends the known substrates for dehalorespiration and indicates the potential for substrate plasticity in amino acid-reducing enzymes to include xenobiotics.