scholarly journals THE SYNTHESIS OF 1,3-DIMETHYL-6,7-DIMETHOXY-3,4-DIHYDROISOQUINOLINE FROM METHYLEUGENOL : APPLICATION OF RITTER REACTION FOR DIRECTLY CYCLIZATION

2010 ◽  
Vol 6 (3) ◽  
pp. 286-291 ◽  
Author(s):  
M. Farid Rahman ◽  
Elvina Dhiaul Iftitah
Keyword(s):  
Sulphuric Acid ◽  
Room Temperature ◽  
Acid Catalyst ◽  
Empirical Method ◽  
Low Energy ◽  
Ritter Reaction ◽  
Experimental Laboratory ◽  
Semi Empirical

The synthesis of 1,3-dimethyl-6,7-dimethoxy-3,4-dihydroisoquinoline from methyleugenol with application of Ritter reaction for directly cyclization was presented. This research was carried out in 2 steps : (1) Determination of intermediate stability that undergo in the reaction by using hyperchem version 6 with AM 1 semi empirical method, and (2) Synthesis of dihydroisoquinoline from methyleugenol and acetonitrile with acid catalyst (H2SO4) in the laboratory. The result of AM 1 calculation found that generally, the intermediate encourage the formation dihydroisoquinoline product, had low energy were compared with the intermediate in other product. Therefore, the dihydroisoquinoline product was easily formed. The result of experimental laboratory found that dihydroisoquinoline could be synthesed from methyleugenol and acetonitrile in the presence sulphuric acid under reflux in 74,92% yields. In despite, the minor product was formed with amount 6,74%. While the reaction at room temperature gave dihydroisoquinoline in poor yield about 11,42%.   Keywords: stability of intermediate, dihydroisoquinoline, Ritter reaction

scholarly journals Determination of plasma temperature by a semi-empirical method

2004 ◽  
Vol 34 (4b) ◽  
pp. 1673-1676 ◽  
Author(s):  
F. O. Borges ◽  
G. H. Cavalcanti ◽  
A. G. Trigueiros
Keyword(s):  
Plasma Temperature ◽  
Empirical Method ◽  
Semi Empirical

scholarly journals Effect of Unwanted Guest Molecules on the Stacking Configuration of Covalent Organic Frameworks: A Periodic Energy Decomposition Analysis

2020 ◽  
Author(s):  
A.D. Dinga Wonanke ◽  
Mathew Addicoat
Keyword(s):  
Guest Molecule ◽  
Dispersion Model ◽  
Critical Role ◽  
Decomposition Analysis ◽  
Empirical Method ◽  
Low Energy ◽  
Energy Decomposition Analysis ◽  
Energy Decomposition ◽  
Guest Molecules ◽  
Semi Empirical

Elucidating the precise stacking configuration of a covalent organic framework, COF, is critical to fully understand their various applications. Unfortunately, most COFs form powder crystals whose atomic characterisations are possible only through powder X-ray diffraction (PXRD) analysis. However, this analysis has to be coupled with computational simulations, wherein computed PXRD patterns for different stacking configurations are compared with experimental patterns to predict the precise stacking configuration. This task is often computationally challenging firstly because, computation of these systems mostly rely on the use of semi-empirical methods that need to be adequately parametrised for the system being studied and secondly because some of these compounds possess guest molecules, which are not often taken into account during computation. COF-1 is an extreme case in which the presence of the guest molecule plays a critical role in predicting the precise stacking configuration. Using this as a case study, we mapped out a full PES for the stacking configuration in the guest free and guest containing system using the GFN-xTB semi-empirical method followed by a periodic energy decomposition analysis using first principle DFT. Our results showed that the presence of the guest molecule leads to multiple low energy stacking configurations with significantly different lateral offsets. Also, the semi-empirical method does not precisely predict DFT low energy configurations, however, it accurately accounts for dispersion. Finally, our quantum-mechanical analysis demonstrates that electrostatic-dispersion model suggested Hunter and Sanders accurately describe the stacking in 2D COFs as oppose to the newly suggested Pauli-dispersion model.

A semi-empirical approach for determination of low-energy gamma-emmiters in sediment samples with coaxial Ge-detectors

2004 ◽  
Vol 61 (2-3) ◽  
pp. 361-366 ◽  
Author(s):  
E.G San Miguel ◽  
J.P Perez-Moreno ◽  
J.P Bolivar ◽  
R Garcı́a-Tenorio
Keyword(s):  
Empirical Approach ◽  
Low Energy ◽  
Sediment Samples ◽  
Energy Gamma ◽  
Semi Empirical

A semi-empirical method for the determination of the spatial distribution of channeled ions

1983 ◽  
Vol 77 (1-2) ◽  
pp. 79-87 ◽  
Author(s):  
K. Beck ◽  
K. Kopitzki ◽  
G. Krauss ◽  
G. Mertler
Keyword(s):  
Spatial Distribution ◽  
Empirical Method ◽  
Semi Empirical

scholarly journals Determination of organic phosphorus in samples of peat soils

1955 ◽  
Vol 27 (1) ◽  
pp. 104-115
Author(s):  
Armi Kaila ◽  
Oili Virtanen
Keyword(s):  
Sulphuric Acid ◽  
Room Temperature ◽  
Phosphorus Content ◽  
Organic Phosphorus ◽  
Peat Soil ◽  
Acid Extraction ◽  
Peat Soils ◽  
Alkali Extraction ◽  
Mineral Soils

Attention was paid in the present paper to the fact that the precision of the values obtained by different methods for the total organic phosphorus in soil cannot be very high. Even the variation caused by the treatment of the extracts and connected with the colorimetric estimation of phosphate in the solution makes it impossible to report the results more accurately than by 10—20 ppm organic P, at least if routine analyses are in question. Although the somewhat modified methods of Dean, Wrenshall and Dyer,. Pearson, and Mehta et al. yielded equal results for the organic phosphorus content of the respective mineral soils and of most of the peat soils analyzed, the treatment with cold alkali in the Wrenshall and Dyer procedure apparently failed to extract the organic phosphorus from two peat samples as quantitatively as the treatment with hot alkali in the other methods. On the basis of this observations a new modification of the method of Wrenshall and Dyer was proposed. It consists of an extraction of 1-g sample with 25 ml of 4 N sulphuric acid at room temperature for 18 hours, followed by washing with water and two successive extractions with 100 ml of 0.5 N sodium hydroxide, the first of them for 18 hours at room temperature, the second for 4 hours at 90°C. This method was found to extract from 40 peat soil samples on the average about 97 per cent of the total phosphorus dissolved by the Kjeldahl digestion and about 9 per cent more organic phosphorus than the method of Pearson. Experiments concerning the ignition and acid extraction procedures indicated that the method of Ghani was not suitable for the determination of organic phosphorus in the twelve samples analysed. The extraction with sulphuric acid showed no marked differences between the increase in the soluble phosphorus due to the ignition when the ratio of extraction was varied from 1:40 to 1:200, and the extractant from 0.2 N acid to 5 N acid. The results obtained for 40 peat samples by ignition for one hour at 600°C and extraction of the ignited and untreated samples with 0.2 N sulphuric acid in a ratio of 1:100 for half an hour were on the average 8 per cent higher than those given by the proposed acid-alkali extraction. The total organic phosphorus content of soil may probably be somewhat higher than the figure yielded by the acid-alkali extraction and slightly lower than the value obtained by the ignition method. For the present, the most reliable result seems to be found in the average of the data given by these two methods.

scholarly journals Line broadening of SO2 and CO2 volcanic activity gases in the Earth’s atmosphere

2018 ◽  
Vol 62 ◽  
pp. 02010
Author(s):  
Anna S. Dudaryonok ◽  
Nina N. Lavrentieva ◽  
Nikolai A. Lavrentiev
Keyword(s):  
Carbon Dioxide ◽  
Quantum Number ◽  
Room Temperature ◽  
Rotational Quantum Number ◽  
Energy Difference ◽  
Empirical Method ◽  
Line Broadening ◽  
Wide Range ◽  
Line Widths ◽  
Semi Empirical

Calculations of the CO2-broadening coefficients of sulfur oxide lines by the semi-empirical method [Mol. Phys. 102 (2004) 1653] and averaged energy difference method [Atmosph. Ocean. Optics 28 (2015) 403] are presented. In this work, 41 lines are considered, the rotational quantum number J varies from 14 to 51. Calculations of the line widths are carried out for room temperature (296 K), and also for the temperature range typical for the Ears atmosphere. There is good agreement with the literature data. The carbon dioxide lines broadening coefficients induced by nitrogen, nitrogen oxide, carbon monoxide and carbon dioxide at room temperature (T = 296 K) are obtained for a wide range of the rotational quantum number J (up to 100). The temperature exponents are calculated for every line widths. The calculations were performed by a semi-empirical method, based on the semiclassical impact theory of line broadening and modified by introducing additional correction factor whose parameters can be determined by fitting the broadening or shifting coefficients to the experimental data.

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