• Bulletin of the Korean Chemical Society
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• v.26 no.7
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• pp.1037-1043
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• 2005

Kinetic study on the cleavage of N-methylphthalamic acid (NMPA) in mixed acidic aqueous-acetonitrile solvent reveals the formation of both phthalic anhydride (PAn) (through O-cyclization) and N-methylphthalimide (NMPT) (through N-cyclization). The formation of NMPT varies from $\sim$20% to $\sim$3% with the increase in the content of acetonitrile from 2 to 70% v/v. Pseudo first-order rate constants for the formation of PAn are more than 4-fold larger than those for the formation of NMPT at 2% v/v $CH_3CN$ in mixed aqueous solvents. Pseudo first-order rate constants for alkaline hydrolysis of NMPT reveal a nonlinear decrease with increase in the content of $CH_3CN$ in mixed aqueous solvents.

• Elastomers and Composites
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• v.51 no.3
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• pp.175-180
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• 2016

Influence of amino acidic chemical on properties of maleic anhydride-grafted ethylene-propylene-diene terpolymer/zinc oxide (EPDM-g-MAH/ZnO) composites was investigated. 4-Aminosalicylic acid (ASA), 4-amino-2-methoxybenzoic acid (AMBA), 12-aminolauric acid (ALA), and glutamine (Gln) were employed as the amino acidic chemicals. Though small quantity (0.5 phr) of the amino acidic chemical was added to the EPDM-g-MAH/ZnO composite, the properties were notably changed. By adding the amino acidic chemical, the percent crystallinity and apparent crosslink density were reduced. Order of the percent crystallinity was related to that of the $pK_a$ values of amino acidic chemicals. By adding the amino acidic chemical, the basic tensile properties were on the whole improved. The experimental results were explained by the $pK_a$ values of amino acidic chemicals, change of zinc ionomer formation, and interactions between the additive and EPDM-g-MAH chain.

• Applied Chemistry for Engineering
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• v.20 no.3
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• pp.351-353
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• 2009

Pyrylium fluoroborates undergo a wide range of synthetically useful reactions because of the positive charge. And the electron accepting nature has resulted in their widespread use as sensitizers for photo-induced electron transfer (PET) reactions. In this experiment, 2,6-disubstituted pyrylium fluoroborates are synthesized from the reaction between $3^{\prime}$-chloroacetophenone and excess orthoformate in an acidic medium (acetic anhydride/acid). Synthesized products are confirmed by $^1H-NMR$, FT-IR and TOF Mass spectroscopies. Also, photo-properties are analyzed with an UV-Vis spectrophotometer.

• Polymer(Korea)
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• v.33 no.6
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• pp.530-536
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• 2009

A cycloaliphatic epoxy/acidic anhydride system incorporating short carbon fibers (SCF) and short glass fibers (SGF) was fabricated and thermal/mechanical properties were characterized. At low filler content both SCF- and SGF-reinforced composites showed a similar decrease in coefficient of thermal expansion (CTE), measured by a thermomechanical analyzer, with increasing loadings, above which SCF became more effective than SGF at reducing the CTE. Experimental CTE data for the SCF-reinforced composites is best described by the rule of mixtures at lower SCF contents and by the Craft-Christensen model at higher SCF contents. Storage modulus (E') at $30^{\circ}C$ and $180^{\circ}C$ was greatly enhanced for short fiber-filled composites compared to unfilled specimens, Scanning electron microscopy of the fracture surfaces indicated that the decreased CTE and the increased E' of the short fiber-reinforced composites resulted from good interfacial adhesion between the fibers and epoxy matrix.

• Applied Chemistry for Engineering
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• v.4 no.4
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• pp.785-790
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• 1993

Three ester-type chitin derivatives were synthesized by reacting chitin with acetic anhydride, propionic anhydride and n-butyric anhydride to form acetyl chitin(AC), propionyl chitin(PC) and n-butyryl chitin(BC). Methanesulfonic acid was used as a catalyst. FT-IR spectra and solid state CP/MAS $^{13}C-NMR$ spectra of three chitin derivatives showed that the substituents were mainly incorporated in the $C_6$ position of chitin. The ester-type chititn derivatives were dissolved well in formic acid and swollen in aqueous acidic solution.

• KSBB Journal
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• v.11 no.2
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• pp.186-192
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• 1996

The effects of chemical modification on the enzymes' stability in polar organic solvents were studied with subtilisin Carlsberg in dimethylformamide-water mixtures as a model system. Three out of nine lysine residues of subtilisin Carlsberg were coupled to either trimellilic or pyromellitic anhydrides thereby, for each lysine residue modified, resulting in the net replacement of one basic amino group by two or three acidic carboxyl groups, respectively. In water at 60$^{\circ}C$, both trimellitic and pyromellitic anhydride-modified subtilisin Carlsberg showed increased thermostability by 2.6 times and 1.6 times, respectively, as compared to that of unmodified enzyme. In 70% dimethylformamide at 25$^{\circ}C$, however, only pyromellitic acrid was shown to enhance the stability of subtilisin Carlsberg by 5.5 times increasing the half life time of irreversible inactivation from 4.9hr for unmodified enzyme to 27.8hr for modified enzyme.

• KSBB Journal
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• v.25 no.3
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• pp.251-256
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• 2010

A novel method to prepare polyester from wastepaper through liquefaction and crosslinking stages was studied. At the first stage, the liquefaction of wastepaper was carried out in the presence of ethylene glycol under acidic conditions. The factors that affect on liquefaction yield were found to be reaction time, temperature, and acid concentration, and their ranges were 60~120 minutes, $150{\sim}170^{\circ}C$, and 2~4%, respectively. The optimum condition was found to be 100 minutes, $160^{\circ}C$, and 3% sulfuric acid concentration, and the liquefaction yield at this condition was 67%. At the second stage, polyester was prepared from the liquefied wastepaper obtained at the optimum liquefaction condition by crosslinking with succinic anhydride. The effect of reaction time and carboxylic group/hydroxyl group ratio on crosslinkage were investigated at conditions covering 30~50 minutes of reaction time and 1.5~2.5 of carboxylic group/hydroxyl group ratio. The crosslinkages of polyester prepared were 80~90%, which were almost same regardless of reaction conditions.

• Applied Chemistry for Engineering
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• v.1 no.1
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• pp.91-99
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• 1990

For-${\alpha}$-APM was efficiently prepared by the reaction of For-Asp anhydride and Phe-OMe in methylethylketone, $CH_3CN$, and in water. The selective recovery of For-${\alpha}$-APM from the resulting For-${\alpha}$-APM and For-${\beta}$-APM mixture was possible via repetitive extraction at constant pH of 4.00. The oxidative deformylation was successfully performed by using several oxidants including $H_2_O2$/THF, sodium percarbonate, and $H_2_O2$/HCl/MeOH giving APM in high yields. The efficiency of the oxidative deformylation was raised in acidic condition for all the deformylation reactions.

• Korean Journal of Food Science and Technology
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• v.47 no.2
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• pp.217-223
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• 2015

We investigated the emulsifying properties of barley octenyl succinic anhydride (OSA)-${\beta}$-glucan, such as changes in the fat globule size and zeta-potential as influenced by pH or the addition of NaCl. Additional experiments to fabricate a suitable co-surfactant system were also performed. We found that the fat globule size in OSA-${\beta}$-glucan emulsions increased upon lowering the pH (i.e., under acidic conditions) or increasing the NaCl concentration. These results were confirmed through microscopic observation. Co-surfactant hydrophilic Tween 20 was found to be suitable for the OSA-${\beta}$-glucan emulsion, which facilitated the formation of smaller fat globules and enhanced the creaming stability when it was added in >0.2 wt% concentration. From the results of the surface load of OSA-${\beta}$-glucan in emulsions, Tween 20 addition enhanced the stability probably by the co-adsorption of the two surfactants at the droplet surface.

• Microbiology and Biotechnology Letters
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• v.35 no.1
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• pp.26-29
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• 2007

Tautomycetin (TMC), which is produced by Streptomyces sp. CK4412, is a novel activated T cell-specific immunosuppressive compound with an ester bond linkage between a terminal cyclic anhydride moiety and a linear polyketide chain bearing an unusual terminal alkene. Antifungal activity against Aspergillus niger and TMC productivity assayed by HPLC using culture extracts from Streptomyces sp. CK4412 grown on solid medium adjusted at various pH were measured. The cells cultured at acidic pH (pH 4-5) medium exhibited much stronger antifungal activity as well as higher TMC productivity than those cultured at neutral pH medium, implying that the acidic pH-shock should be an efficient strategy to induce the productivity of secondary metabolites in Streptomyces culture.