• Title/Summary/Keyword: Acid-catalyzed hydrolysis

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Determination of Reactivity by MO Theory (ⅩⅧ). An Intermolecular Perturbation Study of the Acid-Catalyzed Hydrolysis of Diformamide$^*$

  • Kwun, Oh-Cheun
    • Bulletin of the Korean Chemical Society
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    • v.1 no.3
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    • pp.109-112
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    • 1980
  • Ultraviolet spectrophotometric investigations were carried out on monoalkylbenzene-iodine systems in carbon tetrachloride. The results reveal the formation of one-to-one molecular complexes. On the basis of the equilibrium constants for these complexes of representative monosubstituted benzenes, the following order of increasing stability is obtained: i-propyl- ${\Delta}$H, ${\Delta}$G and ${\Delta}$S for the interaction of a number of monoalkyl substituted benzenes with iodine have been determined. In general, it can be said that as ${\Delta}$H becomes increasingly negative, corresponding decreases in the ${\Delta}$G and the ${\Delta}$S values are observed, and these variations are linear. The thermodynamic constants become increasingly negative with increasing monoalkyl substitution of the aromatic donor nucleus. The complex bond is therefore weak, and its formation is accompanied by relatively small entropy changes. Thus, analysis of these findings is discussed.

A New Dimeric Lignan from the Stems of Willughbeia edulis

  • Nguyen, Hai Xuan;Do, Truong Nhat Van;Le, Tho Huu;Dang, Phu Hoang;Nguyen, Mai Thanh Thi;Nguyen, Nhan Trung
    • Natural Product Sciences
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    • v.28 no.2
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    • pp.53-57
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    • 2022
  • As part of our continued study on the chemical constituents of Willughbeia edulis stems, a new dimeric lignan named edulignan (1) was isolated from its EtOAc-soluble extract. Based on NMR spectroscopic interpretation, the planar structure of 1 has been suggested to have two 2-substituted 4-chromanone subunits with different stereochemical configurations. In addition, the MS/MS analysis of the products obtained by acid-catalyzed hydrolysis of 1 was supportive of its structure. Unfornatually, the new compound 1 did not show 𝛼-glucosidase inhibitory activity with an IC50 value > 250 𝜇M.

Determination of Reactivities by MO Theory (ⅩⅡ). Nucleophilic Substitution Reactions of N-Acetylpiperidone (MO 理論에 依한 反應性의 決定 (第12報). N-아세틸피페리돈의 親核性 置換反應)

  • Lee Ik Choon;Kim Shi Choon;Lee Suk Kee;Park Dong Whan;Jeon Young Gu
    • Journal of the Korean Chemical Society
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    • v.22 no.6
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    • pp.396-402
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    • 1978
  • MO theoretical studies on the conformation and the acid-catalyzed nucleophilic substitution of N-acetylpyperidone were carried out by EHT, CNDO/2 and the orbital mixing analytical methods. MO calculations show that the most preferred conformation is the half-chair, cis-trans form and the protonation occurs most readily on the acetyl carbonyl oxygen. These results were interpreted in terms of conjugative, electrostatic and steric effect. From orbital mixing analysis, we found also that the reactivity of protonated carbonyl carbon is greatly enhanced due to increase in positive charge (for charge controlled reaction) of the carbonyl carbon atom. Accordingly, the acetyl cleavage will be preferred in the nucleophilic substitution (acid-catalyzed hydrolysis) to the ring cleavage.

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Production of Total Reducing Sugar and Levulinic Acid from Brown Macro-algae Sargassum fulvellum (거대 갈조류 모자반으로부터 환원당과 레불린산의 생산)

  • Jeong, Gwi-Taek
    • Microbiology and Biotechnology Letters
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    • v.42 no.2
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    • pp.177-183
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    • 2014
  • Recently, many biofuels and chemicals converted from renewable resources have been introduced into chemical industries. Sargassum fulvellum is a brown macro-algae, which is found on the seashores of Korea and Japan. In this work, the production of total reducing sugar and levulinic acid from S. fulvellum, using dilute-acid catalyzed hydrothermal hydrolysis and statistical methodology, was investigated. As a result, 15.28 g/l total reducing sugar was obtained under the optimized conditions of $160.1^{\circ}C$, 1.0% sulfuric acid, in 20.2 min. Furthermore, 2.65 g/l levulinic acid was obtained at $189.5^{\circ}C$, 2.93% sulfuric acid, in 48.8 min.

Synthesis of Surface Active Properties of Destructible Surfactants with 1,3-Dioxane (1,3-디옥산을 함유한 분해성 계면활성제의 합성의 및 계면 특성)

  • Kim, Chi-Hoi;Roh, Yun-Chan;Kim, Yu-Ok;Nam, Kie-Dae
    • Journal of the Korean Applied Science and Technology
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    • v.13 no.3
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    • pp.61-71
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    • 1996
  • In acid-catalyzed acetal cyclization of long aliphatic aldehydes($R=n-C_7H_{15}$ ; $n-C_9H_{19}$ ; $n-C_{11}H_{23}$) with 1,1,1-tris(hydroxymethyl)propane, 2-alkyl-5-hydroxymethyl-5-ethyl-1,3-dioxanes were obtained. The final products, sodium 2-alkyl-5-(sulfonatedpropylethermethyl)-5-ethyl-1,3-propanesultion in the presence of sodium hydride. These compounds were a new group of destructible surfactants which were readily hydrolyzed and oxidized in natural water reservoirs. Physical properties of these new compounds involved some surface properties such as Krafft point(Kp), critical micelle concentration(cmc), surface tension of aqueous solutions near cmc(${\gamma}_{min}$), foaming power, emulsion power and hydrolysis properties were determined. The destructible surfactants containing 1,3-dioxane ring were synthesized to about $85{\pm}5.5%$ yield. The cmc values of the compounds by ring method were assumed to $0.5{\sim}5.0{\times}10^{-3}mol/L$ range and surface tensions at cmc were $29.5{\sim}33.0dyne/cm$ respectively at $25^{\circ}C$. The foaming power and foam stability were $170{\sim}230mm$ and $52{\sim}135mm$ respectively at $1{\times}10^{-2}mol/L$, foam was occurred rarely below $1{\times}10^{-3}mol/L$. The emulsion property of liquid paraffin was better than that of soybean oil. For hydrolysis property with ph and time, these compounds were decomposed within about 200minutes at $ph1{\sim}2$. Hopefully these compounds are expected to be a good O/W emulsifier that have decomposability in acid and may be used in the process which do not need foaming.

Kinetic Studies of the Hydrolysis of 1-Arylpyrrole Imine (1-Arylpyrrole Imine의 가수분해 반응의 속도론적 연구)

  • Hak-Soo Lyu;Hee-Ju Chae
    • Journal of the Korean Chemical Society
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    • v.27 no.2
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    • pp.133-141
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    • 1983
  • The kinetics of the acid-catalyzed hydrolysis of a series of 1-aryl-2-pyrrylideneaniline (3) have been studied in 20% MeOH solution using UV spectrophotometer. Substituents in 3 showed a relatively small effect, with hydrolysis facilitated by electron withdrawing group. By obtaing linear plots of $log k_{obs}$ against Hammett ${\sigma}$ constants, it was able to show that substituents had a considerable contribution to the aromaticity of pyrrole compounds. The small positive ${\rho}$ values were consistent with the rate-determining addition of water to the protonated schiff base in the buffer solution of pH 4 to 8, whereas the addition of water to the free imine seemed to be the rate-determining in the solution of acidities greater than pH 8.

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Studies on unknown methylated compounds of non-histone nuclear protein

  • Lee, Hyang-Woo;Hong, Sung-Youl;Kim, Sang-Duk;Paik, Woon-Ki
    • Archives of Pharmacal Research
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    • v.8 no.3
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    • pp.149-157
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    • 1985
  • The HCL hydrolyzate of the non-histone protein fractionated from the rat liver nuclei which have been incubated inthe presence of S-adenosyl-L-[methyl-$^{14}C$ ]-methionine shows at least four unidentified radioactive peaks on a basic amino acid analysis chromatogram. One of these unknown compounds (designated as compound 3) is also formed by the rat liver homogenated with the exogenous addition of an appropriate protein substrate. Since boiled rat liver homogenate or fresh homogenate in the absence of an exogenous protein substrate failed to form compound 3, its formation can be considered to be enzyme-catalyzed. The enzyme which yields compound 3 shows a preference of protein substrate in the order of reductively methylated hemoglobin > native > histone type II-A. The rat enzyme is nuclear in location associated with chromatin, and exhibits the highest activity in the liver among various rat organs. A compound 3-forming enzyme is also present in Neurospora crassa, since endogenous formation of the compound 3 can be demonstrated with the crude extract of this mold. The chemical identity of compound 3 is not yet known. However, it resisted to the following treatments; 6 N HCL and 0.1 N Na NaOH hydrolysis at $110^{\circ}C$, OR L-amino acid oxidase.

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Characterization of the Interaction of Sulfiredoxin (Srx1) with a Vacoular Protein $\alpha$-Mannosidase (Ams1) in Saccharomyces cerevisiae (설피리독신과 알파-만노시다제 간의 단백질 결합 특성에 관한 고찰)

  • Barando, Karen P.;Kim, Il-Han
    • The Journal of Natural Sciences
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    • v.17 no.1
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    • pp.13-29
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    • 2006
  • Most redox-active proteins have thiol-bearing cysteine residues that are sensitive to oxidation. Cysteine thiols oxidized to sulfenic acid are generally unstable, either forming a disulfide with a nearby thiol or being further oxidized to a stable sulfinic acid, which have been viewed as an irreversible protein modification. However, recent studies showed that cysteine residues of certain thiol peroxidases (Prxs) undergo reversible oxidation to sulfinic acid and the reduction reaction is catalyzed by sulfiredoxin (Srx1). Specific Cys residues of various other proteins are also oxidized to sulfinic acid ($Cys-So_2H$). Srxl is considered one of the oxidant proteins with a role in signaling through catalytic reduction of oxidative modification like in the reduction of glutathionylation, a post-translational, oxidative modification that occurs on numerous proteins. In this study, the role of sulfiredoxin in cellular processes, was investigated by studying its interaction with other proteins. Through the yeast two-hybrid system (Y2HS) technique, we have found that Ams1 is a potential and novel interacting protein partner of Srxl. $\alpha$-mannosidase (Ams1) is a resident vacuolar hydrolase which aids in recycling macromolecular components of the cell through hydrolysis of terminal, non-reducing $\alpha$-D-mannose residues. It forms an oligomer in the cytoplasm and under nutrient rich condition and is delivered to the vacuole by the Cytoplasm to Vacuole (Cvt) pathway. Aside from the role of Srxl as a catalyst in the reduction of cysteine sulfenic acid groups, it may play a completely new function in the cellular process as indicated by its interaction with Ams1 of the yeast Saccharomyces cerevisiae.

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Microstructure and Properties of Organic-Inorganic Hybrids(PDMS/SiO$_2$) Through Variations in Sol-Gel Processing (졸-겔공정의 변수조절을 통해 제조된 유기-무기복합체 (PDMS/SiO$_2$)의 미세구조와 특성)

  • Eun, Hui-Tae;Hwang, Jin-Myeong
    • Korean Journal of Materials Research
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    • v.11 no.2
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    • pp.94-103
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    • 2001
  • SiO$_2$ and PDMS/SiO$_2$ xerogels which are derived PDMS into TEOS have been synthesized by sol-gel process and controlled pore size and distribution through 2 step acid/base catalyzed processes using HCI and NH$_4$OH as a catalyst. In HCl catalyzed SiO$_2$ and PDMS/SiO$_2$ xerogels, pH and gellation time of xerogel were 2.3~2.5 and 12~13 days, respectively, and the shape of xerogel was identified to pellet type and column type. Under acidic condition of final reaction solution, the hydrolysis rate is accelerating, resulting in long gel times. The shape of xerogel is pellet type. In contrast, under less acidic condition, the condensation rate is accelerating, resulting in shorter gel times and the shape of xerogel is column type. The surface area and average Pore size were changed 400$\rightarrow$600($\m^2$/g) and 15$\rightarrow$28$\AA$, respectively, depending to the increase of the mole ratio of HCl/NH$_4$OH, and represented uniform pore size distribution. It is that all the alkoxide groups are hydrolyzed by HCl after the first step and the condensation rate is enhanced by NH$_4$OH. The regular backbone structures of silica are formed at low temperature and the uniform pores are produced by heat treatment.

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Mechanism of the Hydrolysis of Phenyl N-(p-chlorobenzoyl)Chloroformimidate Derivatives in Acid Media (산성용액 중에서 Phenyl N-(p-chlorobenzoyl)chloroformimidate 유도체의 가수분해 반응 메카니즘)

  • Nack-Do Sung;Young-Gu Cheun;Ki-Sung Kwon;Tae-Rin Kim
    • Journal of the Korean Chemical Society
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    • v.31 no.4
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    • pp.352-358
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    • 1987
  • Rate constants for the hydrolysis of para-substituted phenyl N-(p-chlorobenzoyl)chloroformimidate (I) derivatives in 1 : 4 dioxane-water at $25^{\circ}C$ have been determined. Rate data, substituent effect $(\rho\>{\rho}^+)$, product analysis and MO calculation indicate that the uncatalyzed reaction proceeds through an $S_N1$ mechanism involving the formation of azocarbonium ion (II) below pH 3.0, and the base-catalyzed reaction proceeds through an $S_N2$ mechanism via transition state (III) above pH 4.0. The relative stability of four peri planar conformational isomers were (E-ap) > (Z-ap) > (E-sp) > (Z-ap), respectively, and the most stable stereo structures shows that the Y-substituted phenyl group $(C_6H_4-Y)$ occupy vertical $(90^{\circ})$ position on the plane of the benzimidochloroformyl group in (E-ap) conformer. The nucleophilic substitution of water molecule occurs by sigma attack to the activatived azomethine carbon atom of (I) derivatives.

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