THE HA ACIDITY FUNCTION AND THE MECHANISM OF AMIDE HYDROLYSIS IN HYDROCHLORIC ACID

1965 ◽  
Vol 43 (8) ◽  
pp. 2328-2335 ◽  
Author(s):  
Keith Yates ◽  
J. C. Riordan
Keyword(s):  
Sulfuric Acid ◽  
Hydrochloric Acid ◽  
Acidity Function ◽  
Rate Data ◽  
High Concentration ◽  
Concentration Region ◽  
Experimental Conditions ◽  
Activity Data ◽  
Amide Hydrolysis ◽  
The Difference

Values of the HA acidity function have been determined for 0–35% hydrochloric acid using a set of amide indicators. The indicator pK values agree with those previously obtained in sulfuric acid. The HA scale decreases less steeply than H0 in the high concentration region, but the difference between the two functions is less marked than in sulfuric acid. The reasons for this are discussed. The values of HA have been combined with available rate and water activity data to obtain information about the mechanism of amide hydrolysis. Eleven sets of rate data, consisting of 64 rate constants obtained under a variety of experimental conditions, give similar hydration parameters for this reaction. The temperature dependence of hydration parameters is discussed.

scholarly journals THE INACTIVATION OF DILUTE SOLUTIONS OF CRYSTALLINE TRYPSIN BY X-RADIATION

1955 ◽  
Vol 38 (5) ◽  
pp. 581-598 ◽  
Author(s):  
Margaret R. McDonald
Keyword(s):  
Sulfuric Acid ◽  
Nitric Acid ◽  
Hydrochloric Acid ◽  
Radiation Effects ◽  
Reaction Yield ◽  
X Rays ◽  
Dilute Solutions ◽  
Experimental Conditions ◽  
Ph Range ◽  
Ph Curve

The proteolytic activity of dilute solutions of clystalline trypsin is destroyed by x-rays, the amount of inactivation being an exponential function of the radiation dose. The reaction yield increases steadily with increasing concentration of trypsin, varying, as the concentration of enzyme is increased from 1 to 300 µM, from 0.068 to 0.958 micromole of trypsin per liter inactivated per 1000 r with 0.005 N hydrochloric acid as the solvent, from 0.273 to 0.866 with 0.005 N sulfuric acid as the solvent, and from 0.343 to 0.844 with 0.005 N nitric acid as the solvent. When the reaction yields are plotted as a function of the initial concentration of trypsin, they fall on a curve given by the expression Y α XK, in which Y is the reaction yield, X is the concentration of trypsin, and K is a constant equal to 0.46, 0.20, and 0.16, respectively, with 0.005 N hydrochloric, sulfuric, and nitric acids as solvents. The differences between the reaction yields found with chloride and sulfate ions in I to 10 µM trypsin solutions are significant only in the pH range from 2 to 4. The amount of inactivation obtained with a given dose of x-rays depends on the pH of the solution being irradiated and the nature of the solvent. The reaction yield-pH curve is a symmetrical one, with minimum yields at about pH 7. Buffers such as acetate, citrate, borate and barbiturate, and other organic molecules such as ethanol and glucose, in concentrations as low as 20 µM, inhibit the inactivation of trypsin by x-radiation. Sigmoid inactivation-dose curves instead of exponential ones are obtained in the presence of ethanol. The reaction yields for the inactivation of trypsin solutions by x-rays are approximately 1.5 times greater when the irradiation is done at 26°C. than when it is done at 5°C., when 0.005 N hydrochloric acid is the solvent. The dependence on temperature is less when 0.005 N sulfuric acid is used, and is negligible with 0.005 N nitric acid. The difficulties involved in interpreting radiation effects in aqueous systems, and in comparing the results obtained under different experimental conditions, are discussed.

On the growth of Hg2Cl(1–x)2Brx2 single crystals

1992 ◽  
Vol 7 (9) ◽  
pp. 2507-2510
Author(s):  
N.B. Singh ◽  
E.P.A. Metz ◽  
A. Stewart ◽  
M. Gottlieb ◽  
R. Hopkins ◽  
...  
Keyword(s):  
Single Crystals ◽  
Structural Parameters ◽  
Thermal Conditions ◽  
Mixed Crystals ◽  
Vapor Transport ◽  
High Concentration ◽  
Concentration Region ◽  
Low Concentration ◽  
Mercurous Chloride ◽  
The Difference

Single crystals of mixed mercurous halides Hg2X2 (where X = Cl and Br) were grown by the physical vapor transport process. Structural parameters and optical properties were determined to examine the suitability of mixed crystals for acousto-optic devices. Mixed crystals grown in the low concentration region did not show striations or banding. Crystals grown in the high concentration region showed considerable inhomogeneity in the refractive index. Since we had used identical thermal conditions, inhomogeneity was attributed to the solutal convection caused by the difference in densities of mercurous chloride and bromide vapors. A low concentration of dopant did not change the acoustic velocity of the parent components.

Acid-catalyzed enolization of acetophenone: catalysis by bisulfate ion in sulfuric acid solutions

1986 ◽  
Vol 64 (6) ◽  
pp. 1224-1227 ◽  
Author(s):  
J. R. Keeffe ◽  
A. J. Kresge ◽  
J. Toullec
Keyword(s):  
Aqueous Solution ◽  
Sulfuric Acid ◽  
Acidity Constant ◽  
Acidity Function ◽  
Acid Solutions ◽  
Dilute Aqueous Solution ◽  
Acid Catalyzed ◽  
The Difference ◽  
Carbon Acid ◽  
Sulfuric Acid Solutions

Rates of acid-catalyzed enolization of acetophenone in dilute aqueous solution, measured under conditions where the solvated proton is the only acidic species present, give a hydrogen ion catalytic coefficient, [Formula: see text], that is 35% smaller than the value obtained by X acidity function extrapolation of measurements made in moderately concentrated sulfuric acid solutions. The difference may be attributed to catalysis by bisulfate ion in the sulfuric acid solutions; this is supported by direct measurement of the bisulfate ion catalytic coefficient in dilute sulfuric acid. This revised value of [Formula: see text] leads to new, but only slightly different, values of the keto–enol equilibrium constant for acetophenone in aqueous solution, pKE = 7.96 ± 0.04, the acidity constant for acetophenone ionizing as a carbon acid, [Formula: see text] and the encounter-controlled rate constant for the reaction of acetophenone enol with molecular bromine, k = (3.2 ± 0.4) × 109 M−1 s−1.

Equilibrium protonation of the 1,3,5-trinitrobenzene–phenoxide σ-complex

1976 ◽  
Vol 54 (15) ◽  
pp. 2436-2444 ◽  
Author(s):  
Erwin Buncel ◽  
Walter Eggimann
Keyword(s):  
Sulfuric Acid ◽  
Hydrochloric Acid ◽  
Hydrogen Chloride ◽  
Picric Acid ◽  
Aqueous Media ◽  
Acidity Function ◽  
Acidic Properties ◽  
Aqueous Sulfuric Acid ◽  
Conjugate Acid ◽  
Nitronic Acid

The protonation behavior of the trinitrobenzene–phenoxide σ-complex has been determined in aqueous sulfuric acid, aqueous hydrochloric acid, and ethanolic hydrogen chloride. The conjugate acid of the σ-complex, a nitronic acid, exhibits acidic properties similar to those of picric acid and the cyanocarbon acids. The acidity (pKa) of the nitronic acid has been evaluated with the aid of various acidity function techniques and using the Bunnett–Olsen method. The nitronic acid is ca. 1 pK unit stronger than picric acid. However, both the nitronic acid and picric acid are considerably weaker acids in ethanolic than in aqueous media (ΔpK ca. 4 units). The results provide a preliminary H− acidity function scale for aqueous and ethanolic hydrogen chloride.

Dialkylsulfate formation in sulfuric acid-seeded secondary organic aerosol produced using an outdoor chamber under natural sunlight

2016 ◽  
Vol 13 (4) ◽  
pp. 590 ◽  
Author(s):  
Jiaying Li ◽  
Myoseon Jang ◽  
Ross L. Beardsley
Keyword(s):  
Sulfuric Acid ◽  
Functional Groups ◽  
Organic Aerosols ◽  
Field Studies ◽  
Organic Aerosol ◽  
Multiphase System ◽  
Experimental Conditions ◽  
Aerosol Acidity ◽  
The Difference ◽  
Volatile Organic Hydrocarbons

Environmental context Laboratory and field studies have both provided evidence for organosulfate formation by esterification of H2SO4 with organic compounds in aerosols. Using an outdoor chamber, the production of dialkylsufate was measured for organic aerosols produced by photooxidation of various hydrocarbons in the presence of H2SO4 aerosol and NOx. The formation of organosulfates influences the decrease of both aerosol acidity and aerosol hygroscopicity. Abstract Secondary organic aerosols (SOA) were produced by the photooxidation of the volatile organic hydrocarbons (VOCs) isoprene, α-pinene and toluene, in the presence of excess amounts of sulfuric acid seed aerosol with varying NOx concentrations using a large, outdoor smog chamber. Aerosol acidity ([H+], μmol m–3) was measured using colorimetry integrated with a reflectance UV-visible spectrometer (C-RUV). The C-RUV technique measures aerosol acidity changes through the neutralisation of sulfuric acid with ammonia and the formation of dialkylsulfate, a diester of sulfuric acid. The concentration (μmol m–3) of dialkylsulfate in aerosol was estimated using the difference in [H+] obtained from C-RUV and particle-into-liquid-sampler ion chromatography (PILS-IC). The yield of dialkylsulfate (YdiOS) was defined as the dialkylsulfate concentration normalised by the concentrations of both the ammonium-free sulfate ([SO42–]free=[SO42–] – 0.5 [NH4+]) and organic carbon. The highest YdiOS appeared in isoprene SOA and the lowest YdiOS in α-pinene SOA. Under our experimental conditions, more than 50% of the total sulfates in sulfuric acid-seeded isoprene SOA were dialkylsulfates. For all SOA, higher YdiOS was observed under higher NOx conditions (VOC (ppb C)/NO (ppb)<15). Among the major functional groups (–COOH, –CO–H, –CHO and –ONO2) predicted to be present using a simple absorptive partitioning model of organic products in the multiphase system (gas, organic aerosol and inorganic aerosol), the concentrations of –CO–H, –CHO and –ONO2 groups were found to be correlated with YdiOS. In particular, a strong correlation was observed between YdiOS and the concentration of alcohol functional groups.

Tem analysis of multiple-energy arsenic implanted and Rta'd silicon

1987 ◽  
Vol 45 ◽  
pp. 246-247
Author(s):  
R.A. Herring
Keyword(s):  
Device Fabrication ◽  
High Concentration ◽  
Tem Analysis ◽  
Defect Clusters ◽  
High Fluences ◽  
Small Defect ◽  
Before And After ◽  
The Matrix ◽  
The Difference ◽  
Factor Type

Rapid thermal annealing (RTA) of ion-implanted Si is important for device fabrication. The defect structures of 2.5, 4.0, and 6.0 MeV As-implanted silicon irradiated to fluences of 2E14, 4E14, and 6E14, respectively, have been analyzed by electron diffraction both before and after RTA at 1100°C for 10 seconds. At such high fluences and energies the implanted As ions change the Si from crystalline to amorphous. Three distinct amorphous regions emerge due to the three implantation energies used (Fig. 1). The amorphous regions are separated from each other by crystalline Si (marked L1, L2, and L3 in Fig. 1) which contains a high concentration of small defect clusters. The small defect clusters were similar to what had been determined earlier as being amorphous zones since their contrast was principally of the structure-factor type that arises due to the difference in extinction distance between the matrix and damage regions.

Determination of alcohols in mixtures by 19F NMR spectroscopy using hexefluoroacetone reagent

1982 ◽  
Vol 47 (7) ◽  
pp. 1973-1978 ◽  
Author(s):  
Jiří Karhan ◽  
Zbyněk Ksandr ◽  
Jiřina Vlková ◽  
Věra Špatná
Keyword(s):  
Standard Deviation ◽  
Nmr Spectroscopy ◽  
Standard Method ◽  
Internal Standard ◽  
Internal Standard Method ◽  
Concentration Region ◽  
Experimental Conditions ◽  
Curve Method ◽  
Sample Preparation Procedure

The determination of alcohols by 19F NMR spectroscopy making use of their reaction with hexafluoroacetone giving rise to hemiacetals was studied on butanols. The calibration curve method and the internal standard method were used and the results were mutually compared. The effects of some experimental conditions, viz. the sample preparation procedure, concentration, spectrometer setting, and electronic integration, were investigated; the conditions, particularly the concentrations, proved to have a statistically significant effect on the results of determination. For the internal standard method, the standard deviation was 0.061 in the concentration region 0.032-0.74 mol l-1. The method was applied to a determination of alcohols in the distillation residue from an oxo synthesis.

279 WACSAW: A Statistical and Individually Adaptive Method to Determine Sleep and Wakefulness from Activity

SLEEP ◽  
2021 ◽  
Vol 44 (Supplement_2) ◽  
pp. A111-A112
Author(s):  
Austin Vandegriffe ◽  
V A Samaranayake ◽  
Matthew Thimgan
Keyword(s):  
Time Series ◽  
Optimal Transport ◽  
Activity Patterns ◽  
Adaptive Method ◽  
Wasserstein Distance ◽  
Activity Data ◽  
Commercial Grade ◽  
Movement Data ◽  
The Difference ◽  
Levene Test

Abstract Introduction Technological innovations have broadened the type and amount of activity data that can be captured in the home and under normal living conditions. Yet, converting naturalistic activity patterns into sleep and wakefulness states has remained a challenge. Despite the successes of current algorithms, they do not fill all actigraphy needs. We have developed a novel statistical approach to determine sleep and wakefulness times, called the Wasserstein Algorithm for Classifying Sleep and Wakefulness (WACSAW), and validated the algorithm in a small cohort of healthy participants. Methods WACSAW functional routines: 1) Conversion of the triaxial movement data into a univariate time series; 2) Construction of a Wasserstein weighted sum (WSS) time series by measuring the Wasserstein distance between equidistant distributions of movement data before and after the time-point of interest; 3) Segmenting the time series by identifying changepoints based on the behavior of the WSS series; 4) Merging segments deemed similar by the Levene test; 5) Comparing segments by optimal transport methodology to determine the difference from a flat, invariant distribution at zero. The resulting histogram can be used to determine sleep and wakefulness parameters around a threshold determined for each individual based on histogram properties. To validate the algorithm, participants wore the GENEActiv and a commercial grade actigraphy watch for 48 hours. The accuracy of WACSAW was compared to a detailed activity log and benchmarked against the results of the output from commercial wrist actigraph. Results WACSAW performed with an average accuracy, sensitivity, and specificity of &gt;95% compared to detailed activity logs in 10 healthy-sleeping individuals of mixed sexes and ages. We then compared WACSAW’s performance against a common wrist-worn, commercial sleep monitor. WACSAW outperformed the commercial grade system in each participant compared to activity logs and the variability between subjects was cut substantially. Conclusion The performance of WACSAW demonstrates good results in a small test cohort. In addition, WACSAW is 1) open-source, 2) individually adaptive, 3) indicates individual reliability, 4) based on the activity data stream, and 5) requires little human intervention. WACSAW is worthy of validating against polysomnography and in patients with sleep disorders to determine its overall effectiveness. Support (if any):

scholarly journals Potential Pitfalls in Membrane Fouling Evaluation: Merits of Data Representation as Resistance Instead of Flux Decline in Membrane Filtration

Membranes ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 460
Author(s):  
Bastiaan Blankert ◽  
Bart Van der Bruggen ◽  
Amy E. Childress ◽  
Noreddine Ghaffour ◽  
Johannes S. Vrouwenvelder
Keyword(s):  
Membrane Fouling ◽  
Membrane Filtration ◽  
Data Representation ◽  
Strong Impact ◽  
Experimental Conditions ◽  
Permeable Membrane ◽  
Dead End ◽  
Flux Decline ◽  
The Difference ◽  
Filtration Flux

The manner in which membrane-fouling experiments are conducted and how fouling performance data are represented have a strong impact on both how the data are interpreted and on the conclusions that may be drawn. We provide a couple of examples to prove that it is possible to obtain misleading conclusions from commonly used representations of fouling data. Although the illustrative example revolves around dead-end ultrafiltration, the underlying principles are applicable to a wider range of membrane processes. When choosing the experimental conditions and how to represent fouling data, there are three main factors that should be considered: (I) the foulant mass is principally related to the filtered volume; (II) the filtration flux can exacerbate fouling effects (e.g., concentration polarization and cake compression); and (III) the practice of normalization, as in dividing by an initial value, disregards the difference in driving force and divides the fouling effect by different numbers. Thus, a bias may occur that favors the experimental condition with the lower filtration flux and the less-permeable membrane. It is recommended to: (I) avoid relative fouling performance indicators, such as relative flux decline (J/J0); (II) use resistance vs. specific volume; and (III) use flux-controlled experiments for fouling performance evaluation.

scholarly journals Validation of a Method Based on Triglycerides for the Detection of Low Percentages of Hazelnut Oil in Olive Oil by Column Liquid Chromatography

2007 ◽  
Vol 90 (5) ◽  
pp. 1346-1353 ◽  
Author(s):  
Diego L García-González ◽  
María Viera-Macías ◽  
Ramón Aparicio-Ruiz ◽  
Maria T Morales ◽  
Ramón Aparicio
Keyword(s):  
Liquid Chromatography ◽  
Olive Oil ◽  
Carbon Number ◽  
Hazelnut Oil ◽  
Equivalent Carbon Number ◽  
Experimental Conditions ◽  
Mathematical Algorithm ◽  
Relative Standard ◽  
Triglyceride Content ◽  
The Difference

Abstract The difference between theoretical and empirical triglyceride content is a powerful tool to detect the presence of any vegetable oil in olive oil. The current drawback of the method is the separation between equivalent carbon number ECN42 compounds, which affects the reliability of the method and, hence, its cutoff limit. The determination of the triglyceride profile by liquid chromatography using propionitrile as the mobile phase has recently been proposed to improve their quantification, together with a mathematical algorithm whose binary response determines the presence or absence of hazelnut oil. Twenty-one laboratories from 9 countries participated in an interlaboratory study to evaluate the performance characteristics of the whole analytical method. Participants analyzed 12 samples in duplicate, split into 3 intercomparison studies. Statistically significant differences due to the experimental conditions were found in some laboratories, which were detected as outliers by use of Cochran's and Grubbs' tests. The relative standard deviations (RSD) for repeatability and reproducibility were determined following the AOAC Guidelines for Collaborative Studies. The analytical properties of the method were determined by means of the sensitivity (0.86), selectivity (0.94), and reliability (72) for a cutoff limit of 8 (probability 94).

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