The kinetics of decarboxylation of uronic acids, polysaccharides, and oxycelluloses

1954 ◽  
Vol 7 (2) ◽  
pp. 157 ◽  
Author(s):  
A Meller
Keyword(s):  
Carbon Dioxide ◽  
Sulphuric Acid ◽  
Side Reaction ◽  
Reaction Scheme ◽  
Main Reaction ◽  
Side Reactions ◽  
Acid Solutions ◽  
First Order ◽  
Constant Rate ◽  
Polyglucuronic Acid

Measurements of the rate of carbon dioxide evolution from sulphuric acid solutions of galacturonic acid have revealed that it follows first-order kinetics, but some carbon dioxide is also formed in a side reaction at a constant rate. Glucuronolactone, polyglucuronic acid, and oxycelluloses decarboxylate in essentially homogeneous sulphuric acid solutions according to a two-step reaction scheme, both steps being kinetically first order. This main reaction is accompanied by side reactions in which carbon dioxide is evolved at an approximately constant rate. Mathematical expressions have been derived and applied to compute the constants of the rate equation for the decarboxylation of materials containing uronic acid.

Oxidation scheme of symmetrically disulphonated naphthidines with cerium(IV) sulphate

1981 ◽  
Vol 46 (3) ◽  
pp. 561-572 ◽  
Author(s):  
Karel Komers
Keyword(s):  
Sulphuric Acid ◽  
Rate Constants ◽  
Oxidation Product ◽  
Side Reaction ◽  
Reaction Scheme ◽  
Second Order ◽  
Intermediate Products ◽  
Stable Intermediate ◽  
Starting Compound ◽  
Oxidation Agent

The author derived theoretical dependences of preasymptotic slopes of the currentless E-t curves (potential of an indicator redox electrode against time) on the number of equivalents, n, of added oxidation agent, assuming a reaction scheme of two consecutive concurrent second-order reactions involving the formation of intermediate products ( a side reaction of the starting compound with the final oxidation product leading to an adduct, which undergoes consecutive bimolecular oxidations leading again to the final product). The dependences enable to determine the type of the relatively stable intermediate products and the ratios of the rate constants. The theory was applied to the oxidation of four symmetrically disulphonated naphthidines with cerium(IV) sulphate in aqueous sulphuric acid and the results were substantiated spectrophotometrically

PENYERAPAN GAS KARBONDIOKSIDA (CO 2 ) DALAM BIOGAS DENGAN LARUTAN Ca(OH)2

EKUILIBIUM ◽  
2015 ◽  
Vol 14 (1) ◽  
Author(s):  
Paryanto Paryanto
Keyword(s):  
Experimental Data ◽  
Carbon Dioxide ◽  
Order Reaction ◽  
First Order Reaction ◽  
Glass Ball ◽  
Carbon Dioxide Content ◽  
First Order ◽  
Constant Rate ◽  
Rate Of Reaction ◽  
Reduce Carbon Dioxide

<p>Abstract: Carbon dioxide content in biogas produced by fermentation is still high. Because of<br />that, biogas need a process purification to reduce carbon dioxide content. In this work, Ca(OH)2<br />solution was contacted with biogas in a column for reducing the CO<br />2<br />content. This research<br />studied the effect of packing type used in absorber column on the rate of CO<br />2<br />reduction. Based<br />on experimental data and modelling, it was found that the reaction between CO<br />2<br />followed first order reaction. The constant of rate reaction was affected by the packing type<br />which using glass ball, plastic pipe, ceramic, wood, and clay roof, the constant rate were 0.781,<br />0.464, 0.916, 0.637, and 0.987 min<br />Keywords: Biogas, CO<br />2<br />, Ca(OH)2<br />-1<br />, respectively.<br />, absorber, rate of reaction</p>

Liquid-Phase Oxidative Degradation of the Damaged or Expired Medicinal Products

2014 ◽  
Vol 1040 ◽  
pp. 327-330 ◽  
Author(s):  
Tatyana Volgina ◽  
Viktor T. Novikov ◽  
Oksana Yu. Fedorova
Keyword(s):  
Carbon Dioxide ◽  
Salicylic Acid ◽  
Sulphuric Acid ◽  
Organic Compounds ◽  
Oxidative Degradation ◽  
Zinc Ions ◽  
Acid Solutions ◽  
Medicinal Products ◽  
Cathode Reduction

A method of oxidative mineralization of the salicylic acid and its derivatives as well as medicinal products containing salicylic acid as the active ingredient was investigated. Destruction of the organic compounds is possible both in the electrolyte under the oxidant, electrochemically formed in situ in the sulphuric acid solutions, and at the anode so. Simultaneously, at the cathode, reduction of the zinc ions, contained in a number of medicinal products, is possible. Final products of the oxidation are simple non-toxic organic compounds, carbon dioxide, and water. This process is the most effective in the 40% sulphuric acid at the current density of 0.5–0.8 A/cm2 and the temperature of 30–50 °C.

The catalytic oxidation of ethylene on palladium films

1962 ◽  
Vol 270 (1341) ◽  
pp. 219-231 ◽  
Keyword(s):  
Acetic Acid ◽  
Acetic Anhydride ◽  
High Pressures ◽  
Kinetic Studies ◽  
Side Reaction ◽  
Reaction Scheme ◽  
Zero Order ◽  
Main Reaction ◽  
Rate Of Reaction ◽  
Low Pressures

The oxidation of ethylene has been studied on evaporated films of palladium in the temperature range 50 to 140 °C, and products were analyzed by means of a mass spectrometer. The main reaction was complete oxidation to carbon dioxide and water, but trace amounts of acetic anhydride and acetic acid were formed by a side reaction. Kinetic studies showed that the reaction was zero order with respect to the pressure of oxygen, first order in ethylene at low pressures but zero order at high pressures, and progressively poisoned by the two minor products. The activation energy associated with the initial rate of reaction was 14 kcal/mole. A number of subsidiary experiments were carried out including the oxidation of acetaldehyde at 77 °C which occurred rapidly producing acetic anhydride and some acetic acid. A reaction scheme was developed which accounted for the detailed kinetic behaviour of the oxidation of ethylene and possible mechanisms are discussed

Studies in polymerization - VII. The polymerization of N -carboxy-α-amino acid anhydrides

1954 ◽  
Vol 223 (1155) ◽  
pp. 495-520 ◽  
Keyword(s):  
Carbon Dioxide ◽  
Amino Acid ◽  
Reaction Scheme ◽  
Positive Temperature Coefficient ◽  
Positive Temperature ◽  
First Order ◽  
Molecular Weights ◽  
Rate Determining Step ◽  
Acid Anhydrides ◽  
Kinetics Of

The kinetics of the polymerization of the N -carbonic anhydrides of DL-leucine, DL-phenylalanine and sarcosine in nitrobenzene solution have been studied. When preformed polymer is used as initiator, and in the complete absence of water, the first two anhydrides polymerize at rates which show first-order dependence on the monomer (anhydride) and initiator con­centrations. The reaction of the sarcosine derivative, however, while first order in monomer, is very nearly second order in initiator, and is strongly catalyzed by carbon dioxide. This latter effect is attributed to the substituted carbamic acids formed by interaction of carbon dioxide and bases in the system. Other acids have been shown to be catalysts for the reaction. The observations are consistent with a reaction scheme (5) in which a complex is formed reversibly from the monomer and a base; this complex may then decompose with evolution of carbon dioxide by routes involving base or acid catalysis. The polymerizations of the DL-leucine and DL-phenylalanine carbonic anhydrides are simple cases of this reaction mechanism in which the formation of the complex is the rate-determining step. This difference explains the lower order of these reactions in the initiator concentration, the absence of catalysis, and also the observation that unlike the formation of polysarcosine these polymerizations have a positive temperature coefficient. When the dimethylamide of an amino-acid is used as initiator the first stage of the reaction is faster than the subsequent stages involving polymers, since the initiator is a stronger base than the polymers. The kinetics for these reactions have been worked out, and shown to agree with experiment. The tertiary bases pyridine and quinoline when quite pure have been shown to be ineffective as initiators of the polymerization of sarcosine carbonic anhydride. Initiation by water and amino-acids is discussed. The molecular weights and molecular weight distribution are not affected by the presence of acid catalysts. The distribution for a reaction in which the first step has a rate different from that of the subsequent ones has been calculated.

Energetic Control of Redox-Active Polymers Towards Safe Organic Bioelectronic Materials

2019 ◽  
Author(s):  
Alexander Giovannitti ◽  
Reem B. Rashid ◽  
Quentin Thiburce ◽  
Bryan D. Paulsen ◽  
Camila Cendra ◽  
...  
Keyword(s):  
Molecular Oxygen ◽  
Organic Semiconductors ◽  
Side Reaction ◽  
Semiconducting Polymers ◽  
Side Reactions ◽  
Redox Active ◽  
Donor Acceptor ◽  
Electrochemical Devices ◽  
Biological Environment ◽  
Device Operation

<p>Avoiding faradaic side reactions during the operation of electrochemical devices is important to enhance the device stability, to achieve low power consumption, and to prevent the formation of reactive side‑products. This is particularly important for bioelectronic devices which are designed to operate in biological systems. While redox‑active materials based on conducting and semiconducting polymers represent an exciting class of materials for bioelectronic devices, they are susceptible to electrochemical side‑reactions with molecular oxygen during device operation. We show that this electrochemical side reaction yields hydrogen peroxide (H<sub>2</sub>O<sub>2</sub>), a reactive side‑product, which may be harmful to the local biological environment and may also accelerate device degradation. We report a design strategy for the development of redox-active organic semiconductors based on donor-acceptor copolymers that prevent the formation of H<sub>2</sub>O<sub>2</sub> during device operation. This study elucidates the previously overlooked side-reactions between redox-active conjugated polymers and molecular oxygen in electrochemical devices for bioelectronics, which is critical for the operation of electrolyte‑gated devices in application-relevant environments.</p>

scholarly journals A Novel Stoichio-Kinetic Model for the DPPH• Assay: The Importance of the Side Reaction and Application to Complex Mixtures

Antioxidants ◽  
2021 ◽  
Vol 10 (7) ◽  
pp. 1019
Author(s):  
Lucrezia Angeli ◽  
Sebastian Imperiale ◽  
Yubin Ding ◽  
Matteo Scampicchio ◽  
Ksenia Morozova
Keyword(s):  
Antioxidant Activity ◽  
Kinetic Model ◽  
Rate Constant ◽  
High Resolution Mass Spectrometry ◽  
Sinapic Acid ◽  
Side Reaction ◽  
Main Reaction ◽  
Dpph Assay ◽  
Best Fitting ◽  
The Common

The 2,2-diphenyl-1-picrylhydrazyl (DPPH•) assay is widely used to determine the antioxidant activity of food products and extracts. However, the common DPPH• protocol uses a two-point measurement and does not give information about the kinetics of the reaction. A novel stoichio-kinetic model applied in this study monitors the consumption of DPPH• by common antioxidants following the second order reaction. The fitting of such decay yields the rate constant k1, which describes the main reaction between antioxidants and DPPH•, and the rate constant k2, which is attributed to a slower side reaction considering the products generated between the transient radicals (AO•) and another molecule of DPPH•. The model was first applied to antioxidant standards. Sinapic acid, Trolox and ascorbic and chlorogenic acids did not show any side reaction. Instead gallic, ferulic and caffeic acids achieved the best fitting with k2. The products of the side reaction for these compounds were confirmed and identified with high-resolution mass spectrometry. Finally, the kinetic model was applied to evaluate the antioxidant activity of eight herbal extracts. This study suggests a new kinetic approach to standardize the common DPPH• assay for the determination of antioxidant activity.

The role of surface crystalline heterogeneities in the electrooxidation of carbon monoxide adsorbed on Rh(111) electrodes in sulphuric acid solutions

1997 ◽  
Vol 432 (1-2) ◽  
pp. 1-5 ◽  
Author(s):  
Roberto Gómez ◽  
JoséM. Orts ◽  
Juan M. Feliu ◽  
Jean Clavilier ◽  
Lorena H. Klein
Keyword(s):  
Carbon Monoxide ◽  
Sulphuric Acid ◽  
Acid Solutions
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