Radiochemical Studies of Hydrogen Exchange in Organic Compounds

<p>A property of a new or unknown organic compound which must be determined once the empirical formula and molecular weight are known, is the number of active or replaceable hydrogen atoms which the compound contains. These include hydrogen atoms present in amine, hydroxyl, carboxyl and other groups, where the hydrogen is not bound to a carbon atom but to an oxygen, nitrogen or sulphur atom or is in a position where it can ionize. The most general method by which this may be done quantitatively, is the one originally due to Zerewitinoff Zerewitinoff - Berichte 40 2023 (1907) 41 2233 (1908) 42 4802 (1909) 43 3590 (1910) 47 1659 (1914) 47 2417 (1914) and since developed on a micro scale by Roth A. Soltys Mikrochemie 20 107 (1936), Flaschentrager A. Roth Mikrochemie 11 140 (1932), whose method incorporates work by Tschugaeff - Flaschentrager z. Physiol Chem. 146 219 (1923) and the other two authors, and Soltys L. Tschugaeff Berichte 35 3912 (1902), and incorporates many of the latest improvements. This involves the quantatatively evolution of methane from reaction of the Grignard reagent MeMgI on groups such as -SH, -OH, -NH2, -COOH etc., i.e. those groups containing active or replaceable hydrogen atoms. Analysis by this method requires extreme care in technique and exact attention to experimental details. High results are obtained if the solvent or any part of the apparatus contains moisture and the whole determination must be carried out in an atmosphere of nitrogen to avoid reaction of the Grignard reagent with any oxygen present. Low results are obtained if the test solution does not dissolve completely in the chosen solvent and it is essential to carry out a blank prior to each analysis. The proceedure is labourious and painstaking and gives an accuracy of not greater than 5% using 3-5 mgm of organic compound. It also has the disadvantage that the Grignard Reagent will also react with other groups, such as carbonyl, aldehyde, nitrile etc., which may be present. This method cannot be applied to highly water soluble compounds which do not dissolve in ethers or other organic solvents and as the molecular size or complexity of the sample increases, the accuracy of the gasometric reactions becomes less, due to side reactions and incomplete reaction.</p>

Radiochemical Studies of Hydrogen Exchange in Organic Compounds

<p>A property of a new or unknown organic compound which must be determined once the empirical formula and molecular weight are known, is the number of active or replaceable hydrogen atoms which the compound contains. These include hydrogen atoms present in amine, hydroxyl, carboxyl and other groups, where the hydrogen is not bound to a carbon atom but to an oxygen, nitrogen or sulphur atom or is in a position where it can ionize. The most general method by which this may be done quantitatively, is the one originally due to Zerewitinoff Zerewitinoff - Berichte 40 2023 (1907) 41 2233 (1908) 42 4802 (1909) 43 3590 (1910) 47 1659 (1914) 47 2417 (1914) and since developed on a micro scale by Roth A. Soltys Mikrochemie 20 107 (1936), Flaschentrager A. Roth Mikrochemie 11 140 (1932), whose method incorporates work by Tschugaeff - Flaschentrager z. Physiol Chem. 146 219 (1923) and the other two authors, and Soltys L. Tschugaeff Berichte 35 3912 (1902), and incorporates many of the latest improvements. This involves the quantatatively evolution of methane from reaction of the Grignard reagent MeMgI on groups such as -SH, -OH, -NH2, -COOH etc., i.e. those groups containing active or replaceable hydrogen atoms. Analysis by this method requires extreme care in technique and exact attention to experimental details. High results are obtained if the solvent or any part of the apparatus contains moisture and the whole determination must be carried out in an atmosphere of nitrogen to avoid reaction of the Grignard reagent with any oxygen present. Low results are obtained if the test solution does not dissolve completely in the chosen solvent and it is essential to carry out a blank prior to each analysis. The proceedure is labourious and painstaking and gives an accuracy of not greater than 5% using 3-5 mgm of organic compound. It also has the disadvantage that the Grignard Reagent will also react with other groups, such as carbonyl, aldehyde, nitrile etc., which may be present. This method cannot be applied to highly water soluble compounds which do not dissolve in ethers or other organic solvents and as the molecular size or complexity of the sample increases, the accuracy of the gasometric reactions becomes less, due to side reactions and incomplete reaction.</p>

Studying the Chemical Reactivity Properties of Cytosine and its Antiviral Analogues: Zebularine, 5-Aza-Cytosine And 5-Aza-5,6-Dihydro-Cytosine through Density Functional Theory

Zebularine, 5-aza-cytosine and 5-aza-5,6-dihydro-cytosine are structurally similar to cytosine, but their biological functions are rather different. Cytosine can be methylated which is a gene lesion that can cause human disease. On the contrary, zebularine and 5-aza-cytosine are inhibitors of DNA methylation. 5-aza-5,6-dihydro-cytosine is specifically designed to induce lethal mutagenesis in HIV for its structurally variability. Here, theoretical research into their chemical properties through density functional theory is reported. Molecular hardness and molecular electronic surface potential were analysed. Compared to cytosine, the main reason for the inability of methyl addition of zebularine is the reduced nucleophilicity of C5 atom. The lack of a hydrogen atom at N5 atom in 5-aza-cytosine is responsible for the incomplete reaction of methyl transfer. Variability of 5-aza-5,6-dihydro-cytosine is responsible for the mutagenesis treatment by paring with guanine or adenine with its different tautomers. Aspect of these chemical reactivities can be accounted for the distinctive biological functions of these molecules.

Completion of Partial Reaction Equations

We present a deep-learning model for inferring missing molecules in reaction equations. Such an algorithm features multiple interesting behaviors. First, it can infer the necessary reagents and solvents in chemical transformations specified only in terms of main compounds, as often resulting from retrosynthetic analyses. The completion with necessary reagents ensures that reaction equations are compatible with deep-learning models relying on a complete reaction specification. Second, it can cure existing datasets by detecting missing compounds, such as reagents that are essential for given classes of reactions. Finally, this model is a generalization of models for forward reaction prediction and retrosynthetic analysis, as both can be formulated in terms of incomplete reaction equations. We illustrate that a single trained model, based on the transformer architecture and acting on reaction SMILES strings, can address all three points.<br><br>Workshop paper at the Machine Learning for Molecules Workshop at NeurIPS 2020.<br>

Completion of Partial Reaction Equations

We present a deep-learning model for inferring missing molecules in reaction equations. Such an algorithm features multiple interesting behaviors. First, it can infer the necessary reagents and solvents in chemical transformations specified only in terms of main compounds, as often resulting from retrosynthetic analyses. The completion with necessary reagents ensures that reaction equations are compatible with deep-learning models relying on a complete reaction specification. Second, it can cure existing datasets by detecting missing compounds, such as reagents that are essential for given classes of reactions. Finally, this model is a generalization of models for forward reaction prediction and retrosynthetic analysis, as both can be formulated in terms of incomplete reaction equations. We illustrate that a single trained model, based on the transformer architecture and acting on reaction SMILES strings, can address all three points.<br><br>Workshop paper at the Machine Learning for Molecules Workshop at NeurIPS 2020.<br>

Effect of Fuel Stage Proportion on Flame Position in an Internally-Staged Combustor

To study the effect of fuel stage proportion on flame position and combustion characteristics of the internally-staged combustor, a detailed numerical investigation is performed in the present paper. The prediction method of flame position is established by analyzing the variations of the distribution of intermediate components and the turbulent flame speed. Meanwhile, the flame position is simulated to verify the accuracy of the prediction method. It is demonstrated that the flame position prediction model established in this paper can accurately predict the flame position under different fuel stage proportions. On this basis, special attention is paid to analyze the variation of velocity field, temperature field, distribution of intermediate components and emissions under different fuel stage proportions. As the proportion of pilot fuel stage increases slightly, the mass fraction of fuel at the combustor dome increases. In addition, the combustion characteristics change significantly with the increase in the proportion of pilot stage fuels. The flame moves downstream and the high temperature area increases as the proportion of pilot fuel increases. In particular, when the proportion of pilot stage reaches 3%, the highest flame temperature is generated due to the most concentrated reaction area, resulting in the largest emission of NOx. At the same time, due to the most complete reaction, the minimum CO emission is produced. When the proportion of pilot fuel stage reaches 1%, the NOx emission is the lowest, and the highest CO emission is generated due to the incomplete reaction.

DILUTE CAUSTIC AND WATER COMPARISONS AS SOLVENTS IN THE REMOVAL OF ACIDIC GASES FROM COMBUSTION EXHAUST STREAM OF A BOILER.

This work focused on the comparative analyses between the use of dilute caustic with a composition of 1.84% and using water alone (pH=7) that have the potential to remove SO2 completely from the exhaust flue gas of a combustion system and H2S in the incomplete reaction scenario. Two reaction pathways were utilized for the study, the complete combustion pathway as well as the incomplete combustion pathway. ASPEN HYSYS 8.6, a process simulation software, was used to simulate conditions with PENG-ROBINSON utilized as the vapour-liquid equilibrium (VLE) data prediction tool of the software. For the complete combustion pathway, a complete removal of SO2 was achieved using caustic while with the same conditions, utilizing water as solvent achieved a reduction of 90%. For the incomplete combustion pathway, using caustic gave about 53% removal efficiency for H2S while the water only showed a poor 16% increase of H2S. The study recommended the use of the dilute caustic for the following reasons; it gave a better removal percentage than using water alone, the use of the caustic will not contribute to caustic corrosion because of the low composition of the dilute caustic that will be used in the absorber, the choice of the caustic was also observed to be economical. Keywords: Caustic, Absorption, Emission, Simulation, Combustion, Solvents.

Dilute caustic and water comparisons as solvents in the removal of acidic gases from combustion exhaust stream of a boiler

This work focused on the comparative analyses between the use of dilute caustic with a composition of 1.84% and using water alone (pH=7) that have the potential to remove SO2 completely from the exhaust flue gas of a combustion system and H2S in the incomplete reaction scenario. Two reaction pathways were utilized for the study, the complete combustion pathway as well as the incomplete combustion pathway. ASPEN HYSYS 8.6, a process simulation software, was used to simulate conditions with PENG-ROBINSON utilized as the vapour-liquid equilibrium (VLE) data prediction tool of the software. For the complete combustion pathway, a complete removal of SO2 was achieved using caustic while with the same conditions, utilizing water as solvent achieved a reduction of 90%. For the incomplete combustion pathway, using caustic gave about 53% removal efficiency for H2S while the water only showed a poor 16% increase of H2S. The study recommended the use of the dilute caustic for the following reasons; it gave a better removal percentage than using water alone, the use of the caustic will not contribute to caustic corrosion because of the low composition of the dilute caustic that will be used in the absorber, the choice of the caustic was also observed to be economical. Keywords: Caustic, Absorption, Emission, Simulation, Combustion, Solvents.

GAS AND SATURATION IN A GAS CONDENSATE RESERVOIR

This work focused on the comparative analyses between the use of dilute caustic with a composition of 1.84% and using water alone (pH=7) that have the potential to remove SO2 completely from the exhaust flue gas of a combustion system and H2S in the incomplete reaction scenario. Two reaction pathways were utilized for the study, the complete combustion pathway as well as the incomplete combustion pathway. ASPEN HYSYS 8.6, a process simulation software, was used to simulate conditions with PENG-ROBINSON utilized as the vapour-liquid equilibrium (VLE) data prediction tool of the software. For the complete combustion pathway, a complete removal of SO2 was achieved using caustic while with the same conditions, utilizing water as solvent achieved a reduction of 90%. For the incomplete combustion pathway, using caustic gave about 53% removal efficiency for H2S while the water only showed a poor 16% increase of H2S. The study recommended the use of the dilute caustic for the following reasons; it gave a better removal percentage than using water alone, the use of the caustic will not contribute to caustic corrosion because of the low composition of the dilute caustic that will be used in the absorber, the choice of the caustic was also observed to be economical. Keywords: Caustic, Absorption, Emission, Simulation, Combustion, Solvents.

DILUTE CAUSTIC AND WATER COMPARISONS AS SOLVENTS IN THE REMOVAL OF ACIDIC GASES FROM COMBUSTION EXHAUST STREAM OF A BOILER.

This work focused on the comparative analyses between the use of dilute caustic with a composition of 1.84% and using water alone (pH=7) that have the potential to remove SO2 completely from the exhaust flue gas of a combustion system and H2S in the incomplete reaction scenario. Two reaction pathways were utilized for the study, the complete combustion pathway as well as the incomplete combustion pathway. ASPEN HYSYS 8.6, a process simulation software, was used to simulate conditions with PENG-ROBINSON utilized as the vapour-liquid equilibrium (VLE) data prediction tool of the software. For the complete combustion pathway, a complete removal of SO2 was achieved using caustic while with the same conditions, utilizing water as solvent achieved a reduction of 90%. For the incomplete combustion pathway, using caustic gave about 53% removal efficiency for H2S while the water only showed a poor 16% increase of H2S. The study recommended the use of the dilute caustic for the following reasons; it gave a better removal percentage than using water alone, the use of the caustic will not contribute to caustic corrosion because of the low composition of the dilute caustic that will be used in the absorber, the choice of the caustic was also observed to be economical. Keywords: Caustic, Absorption, Emission, Simulation, Combustion, Solvents.