• 제목/요약/키워드: phenyl

검색결과 1,806건 처리시간 0.021초

¹H NMR Study of the Inclusion Complexes of Chiral Aromatic Guests with β-Cyclodextrin and Its Derivatives: Discrimination of Aromatic Protons and Chiral Recognition

  • 고광희;박종목
    • Bulletin of the Korean Chemical Society
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    • 제17권11호
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    • pp.1052-1056
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    • 1996

  • The effects of β-CD, Me-β-CD, and biphenyl capped β-CD on 1H NMR spectra of mandelic acid 1, α-methylbenzylamine 2 and 2-phenylpropionic acid 3 were investigated. Enantiomeric recognition was observed for mandelic acid 1 by all the hosts used, for α-methylbenzylamine 2 by β-CD and Me-β-CD, and for 2-phenylpropionic acid 3 by Me-β-CD. In the presence of biphenyl-capped β-CD, ο-, m-, and p-protons of the phenyl groups of the guests are discriminated due to ring current of the capped biphenyl group. The splitting pattern of the phenyl protons indicates that the phenyl group of the guests is inserted into the β-CD cavity from the secondary hydroxyl side and positioned in close proximity to the capped biphenyl ring. The magnitude of the upfield shifts of H3 and H5 protons of β-CD upon binding of guests 1-3 is similar to that caused by ephedrine or pseudoephedrine, suggesting that the substitution at benzylic carbon atom has little effect on the depth of the insertion of the phenyl group into the β-CD cavity and stability of the inclusion complexes.

  • https://doi.org/10.5012/bkcs.1996.17.11.1052 인용 PDF

The Studies on Substituent and Kinetic Solvent Isotope Effect in Solvolyses of Phenyl Chloroformates

  • 구인선;이지선;양기열;강금덕;이익춘
    • Bulletin of the Korean Chemical Society
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    • 제20권5호
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    • pp.573-576
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    • 1999

  • The rate constants and kinetic solvent isotope effects (KSIE, KMeOH/kMeOD) for solvolyses of para-substituted phenylchloroformates in CH3OH, CH3OD, H2O, D2O, 50% D2O-CH3OD were determined at 15.0 and 25.0℃ using conductometric method. Kinetic solvent isotope effects for the solvolyses of para-substituted phenyl chloroformates were 2.39-2.51, 2.21-2.28, and 1.67-1.69 for methanol, 50% aqueous methanol, and water, respectively. The slopes of Hammett plot for solvolysis of para-substituted phenyl chloroformates in methanol, 50% aqueous methanol, and water were 1.49, 1.17 and 0.89, respectively. The Hammett type plot of KSIE, log (KSIE) versus p, can be a useful mechanistic tool for solvolytic reactions. The slopes of such straight lines for para-substituted phenyl chloroformates are almost zero in methanol, 50% aqueous methanol, and water. It was shown that the reaction proceeds via an associative SN2 and/or general base catalysis addition-elimination (SAN) mechanism based on activation parameters, Hammett p values, and slopes of Hammett type plot of KS-IE.

  • https://doi.org/10.5012/bkcs.1999.20.5.573 인용 PDF

Transition-State Variation in the Solvolyses of Phenyl Chlorothionoformate in Alcohol-Water Mixtures

  • 구인선;양기열;강대호;박혜진;강금덕;이익춘
    • Bulletin of the Korean Chemical Society
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    • 제20권5호
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    • pp.577-580
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    • 1999

  • Solvolyses of phenyl chlorothionoformate in water, D2O, CH3OD, 50% D2O-CH3OD, and in aqueous binary mixtures of acetone, ethanol and methanol are investigated at 25.0℃. The Grunwald-Winstein plots of firstorder rate constants for phenyl chlorothionoformate with Ycl (based on 2-adamantyl chloride) show a dispersion phenomenon, and also the extended Grunwald-Winstein plots show a poor correlation for the solvolyses of phenyl chlorothionoformate. The ring parameter (I) has been shown to give considerable improvement when it is added as an hI term to the original and extended Grunwald-Winstein correlations. The dispersions in the Grunwald-Winstein correlations in the present studies are caused by the conjugation between the reaction center and the aromatic ring in the vicinity of the reaction center. This study has shown that the magnitude of l and m values associated with a change of solvent composition leads to predict the SN2 transition state. The kinetic solvent isotope effects determined in deuterated water and methanol are consistent with the proposed mechanism of the general base catalyzed SN2 mechanism.

  • https://doi.org/10.5012/bkcs.1999.20.5.577 인용 PDF

Reactivity of the Biheterocyclic Betaine with the para-Substituted Phenacyl Bromides for the Ring Transformation Reaction

  • Yoo, Kyung-Ho;Kim, Dong-Jin;Kim, You-Seung;Park, Sang-Woo
    • Bulletin of the Korean Chemical Society
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    • 제9권3호
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    • pp.164-166
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    • 1988

  • 7-Dithiocarboxy-3-phenyl-5,6-dihydro imidazo[2,1-b]thiazolium-betaine (2) was prepared by treatment of 3-phenyl-5,6-dihydro imidazo[2,1-b]thiazole (1) with carbon disulfide in acetone at room temperature. On the reaction of 2 with para-substituted phenacyl bromides (4) having the electron withdrawing property by virtue of (+) resonance (R) < (-) inductive (I) or (-) resonance (R), (-) inductive (I) effect, ring transformation product p-substituted-2-[2-[7-(p-substituted benzoyl)-5-thioxo-2,3-dihydro-1H-imidazo[1,2-c] thiazol-1-yl]-2-phenylvinylthio] acetophenone (6) was obtained; however, when R is electron donating grops with (+) resonance (R) > (-) inductive (I) effect the quarternary ammonium salt 7-(p-substituted phenyl) carbonyl methyl-3-phenyl-5,6-dihydro imidazo [2,1-b] thiazolium bromide (8) is formed. The reaction of 2 with unsubstituted-phenacyl bromide (R = H), on the other hand, gives 6a and 8a to the similar ratio, respectively.

  • https://doi.org/10.5012/bkcs.1988.9.3.164 인용 PDF