• Korean Chemical Engineering Research
• /
• v.57 no.2
• /
• pp.164-171
• /
• 2019

The protonation parameters, dissociation constants ($pK_{BH^+}$) of conjugate acid, slope values (m, ${\phi}$ and $m^*$) and correlation coefficients (r) of hydroxamic acids were determined by Hammett acidity function method, Bunnett-Olsen method and excess acidity method in hydrochloric and perchloric acid solutions. Effect of acid concentration on partition and percentage protonation was also studied. $pK_{BH^+}$ values show that hydroxamic acids do not behave as Hammett bases, but hydroxamic acids behave as weak bases in strong acidic solutions. The values of $pK_{BH^+}$ obtained through Bunnett-Olsen method and excess acidity method were compared with the Hammett acidity function. ChemAxon's MarvinSketch 6.1.5 software was also used for determining $pK_a$, pI and microspecies distribution (%) of hydroxamic acids with pH. Hydrogen donor and acceptor values and logD were also obtained. The results show that N-p-chlorophenyl-4-bromobenzohydroxamic acid has the highest $pK_a$ and lowest logD values. On the contrary, N-phenyl-3,5-dinitrobenzohydroxamic acid has lowest the $pK_a$ and highest logD values.

• Bulletin of the Korean Chemical Society
• /
• v.23 no.5
• /
• pp.758-760
• /
• 2002

• Journal of the Korean Chemical Society
• /
• v.46 no.4
• /
• pp.323-330
• /
• 2002

The protonation equilibrium of 5-substituted 2-furaldehydes is investigated spectrophotometrically in aqueous sulfuric acid at $25^{\circ}C$ and the basicity constants(p$K_{BH+}$) of the substrates is calculated by means of the excess acidity method. The basicity constant of 5-metyl-2-furaldehyde having electron donating group is larger than that of 5- nitro-2-furaldehyde having electron withdrawing group. Difference between the basicity constants(p$K_{BH+}$) of these two compounds was about 3.25 pK unit. The m value which is the degree of solvation of the protonated substrate is similar to that of acetophenone having same protonation site. The dependence of p$K_{BH+}$ on m value shows good linear cor-relation.

• The Korean Journal of Food And Nutrition
• /
• v.9 no.3
• /
• pp.265-270
• /
• 1996

When new told grape with high acidity Is used wine, their sensory scores are decreased. Using three available methods reducing excess acidify In winemaking, they were malo-lactic fermentation, addition of apple pomace and malo-alcohol fermentation. The chemical monponents and sensory evaluation of wine were determined. They were found in pink wine added apple pomace that tatal acidity and malic acid content were 0.76 and 0.484%. Color Intensity (A520+A420) in pink wanes, their valuse were in the range 8.21~9.42, while the value of red wine was 20.92. Browning index and total phenol contents in pink wine, their values were In the range of 1.36∼1.42 and 3,300∼3,800mg 11. The sensory evaluation showed that the pink wine added apple pomace(10%) was highest in taste and total scores (P<0.05), and the taste of wine has improved.

• Proceedings of the Korean Society of Crop Science Conference
• /
• 2017.06a
• /
• pp.236-236
• /
• 2017

Low soil pH causes from $H^+$ rhizotoxicity results in nutrients unavailability in the growing media, inhibits plant growth, development and reduces crop yields. The present study was carried out to reveal morpholophysiological and biochemical responses of wheat (Triticum aestivum L.) to acidity stress. Four wheat varieties viz. BARI Wheat-21, BARI Wheat-25, BARI Wheat-26 and BARI Wheat-30 were used in the study. Eight-day-old seedlings were exposed to different pH levels (3.5, 4.5, 5.5 and 6.5) of growing media. Acidity stress at any level reduced biomass, water, and chlorophyll contents in all the varieties; whereas BARI Wheat-26 showed the least damage. $H^+$ rhizotoxicity also caused oxidative stress through excess production of reactive oxygen species and methylglyoxal which increase lipid peroxidation in all the varieties but the lowest oxidative damage was observed in BARI Wheat-26 due to better performance of the antioxidant defense and glyoxalase systems. Considering the growth, physiological and biochemical attributes BARI Wheat-26 may be considered as acidity stress tolerant, among the variety examined.

• Current Applied Physics
• /
• v.18 no.12
• /
• pp.1480-1485
• /
• 2018

Mesoporous carbon-silica composites supported Pt nanoparticle catalysts (Pt/MCS) were firstly applied to the heterogeneous asymmetric hydrogenation of ethyl 2-oxo-4-phenylbutyrate (EOPB). A series of different silica contents were investigated in the fabrication of this mesoporous material. When the volume of added tetraethyl orthosilicate (TEOS) during the preparation of composites is 8 mL, Pt/MCS-8 holds carbon and silica as the main components and possesses relatively strong acidity, mesoporous structures with micropores, appropriate Pt nanoparticle size and high dispersibility showing by XRD, XPS, TPD, $N_2$ sorption and TEM. These properties cause its good catalytic performance in the heterogeneous asymmetric hydrogenation of EOPB with the enantiomeric excess value and conversion up to 85.6% and 97.8%, respectively.

• The Korean Journal of Food And Nutrition
• /
• v.22 no.3
• /
• pp.345-351
• /
• 2009

The principal objectives of the experiments in this study were to assess the quality of venison jerky made from Elk deer (female, weight; 380 kg, age; 15 old years) in accordance with various seasoning sauce and mixture fruit extract level. Salinity, saccharinity and acidity values of the seasoning sauces were all high(VJ-1; 3.72%), (VJ-3; 3.95%), (VJ-1; 0.35%). The salinity range of the venison jerky products was 5.65~5.92%, the saccharinity range was 3.75~4.18%, and the seasoning sauce samples resulted in a significant difference in acidity values(p<0.05). Crude protein, fat and ash contents of the venison jerky products satisfied the Korean jerky standard value, but the moisture content range was 36.18~38.59%, and this was also in excess of the jerky standard level. The manufacturing yield was 42.24~44.48%, with VJ-1 at lowest levels followed by VJ-2 and VJ-3. The pH value of VJ-1 was high, but not significantly higher than the other samples(p>0.05). The water activity value range was measured at 0.68~0.71, and the lightness(L) and redness(a) value evidenced marked increases with increased amounts of added sodium nitrite(p<0.05), and the yellowness(b) values did not significantly differ(p>0.05). The overall sensory acceptance scores ranged between 5.53~7.49, in the order VJ-3, VJ-2, VJ-1(p<0.05).

• Journal of the Korean Chemical Society
• /
• v.41 no.2
• /
• pp.63-68
• /
• 1997

Calorimetric measurements have been carried out for the binary mixture between protic, ROH (R=Me, Et) and dipolar aprotic solvents, MeCN,$Me_2CO,\;MeNO_2(or EtNO_2)$in order to investigate the molecular interaction and liquid structure of isodielectric solvents. From the measured partial molar enthalpies of the solutions, excess enthalpies for the mixing process were determined. The hydrogen bond strength between two components decreases in the order of$ROH-ROH>ROH-Me_2CO>ROH-MeCN>ROH-MeNO_2(or EtNO_2)$and the hydrogen bond donor acidity decreases in the order of MeOH>EtOH. From this result, we can conclude that the most important interaction for the formation of binary liquid mixture comes from the specific hydrogen bond.

• Korean Journal of Food Science and Technology
• /
• v.38 no.3
• /
• pp.408-413
• /
• 2006

The domestic grape cultivar Campbell Early has high levels of both malic acid and tartaric acid. Therefore, the processing of wine made from Campbell Early must include decreasing the acidity. Six different methods were tested for reducing excess acidity: traditional vinification, precipitation, cold stabilization, malolactic fermentation (MLF), carbonic maceration and cold fermentation. Wines had higher pH values and lower total acidity than control after all the processing methods except cold stabilization. With regard to the measured organic acid content, the control contained 2,927 ppm tartaric acid, 2,421 ppm malic acid and 486 ppm lactic acid, but the precipitated wine contained 2,346 ppm tartaric acid. The MLF wine contained 828 ppm malic acid and 2,394 ppm lactic acid. Wine after carbonic maceration contained 792 ppm malic acid and cold fermentation decreased the organic acid contents in general. Sensory analysis showed that the carbonic maceration and precipitation methods resulted in wines that were excellent in color, flavor, taste and overall preference.

• Microbiology and Biotechnology Letters
• /
• v.25 no.1
• /
• pp.96-101
• /
• 1997

Among the lactic flora responsible for the development of acidity and characteristic flavor of Kimchi which is a traditional fermented Chiness cabbage. Homofermentative Lactobacillus plantarum is rod-shaped and to be known to ewert major role during later fermentation period. Once this strain establishes main flaora in the Kimchi fermentation process, it gives rise to excess acid production to reduce the taste and quality of Kimchi during storage. As a primary work to increase the keeping quality using virulent Lactobaillus plantarum bacteriophages, it was isolated sucessfully from collected Kimchi samples and their characteristics were studied. The new isolated phage, named SC 921, adsorbed to its host without Ca$^{2+}$, and nearly eliminated at 60$\circ $C of heat treatment for 5 min. This phages were atable at pH 4~ 10 but inactivated below pH 3.0 or pH 11.0 above. The latent period, rise period, and burst size of this phage was 100 min, 120 min, 31$\pm $2pfu/ml, respectively. Electron micrograph showed the phages particles were unusually oval feature of head (dia 80~ 120 nm) without contractile tail.