Change in the differential molar free energy of sorption of a methylene group as a function of the length of the chain of an n-alkane under the conditions of GC analysis

1983 ◽  
Vol 32 (5) ◽  
pp. 898-903
Author(s):  
R. V. Golovnya ◽  
D. N. Grigor'eva
Keyword(s):  
Free Energy ◽  
Molar Free Energy ◽  
Gc Analysis ◽  
Methylene Group

Investigation and Analytical Applications of the Reaction of N1-Methylnicotinamide and Active Methylene Containing Drugs

2020 ◽  
Vol 17 ◽  
Author(s):  
Heba A. Elsebaie ◽  
Mervat H. Elhamamsy ◽  
Khaled M. Elokely ◽  
Mohammed A. Eldawy
Keyword(s):  
Quality Control ◽  
Free Energy ◽  
Spectral Analysis ◽  
Quantitative Analysis ◽  
Geometry Optimization ◽  
Fluorescent Product ◽  
Spectrofluorometric Method ◽  
Active Methylene ◽  
Methylene Group

Background: The reaction between N1-methylnicotinamide iodide (NMNI) and the active methylene group containing compounds yields a fluorescent product, which can be used in the quantitative determination of certain drugs. Objective: The objective is to develop, adapt and validate a simple spectrofluorometric method for the quantitative analysis of modafinil 1, budesonide 2, allicin 3 and florfenicol 4. Results: A C4 cyclization pathway was confirmed for the formation of the fluorophore. The spectrofluorometric method showed good linearity (R2= 0.996-0.999) over concentrations of 1-50 ng/mL, 0.5-5 ng/mL, 60-150 pg/mL, and 1-15 ng/mL of the standard solutions of 1, 2, 3, and 4, respectively. Methods: Spectral analysis (elemental analysis, 1H, 13C NMR, MS), computational methods (geometry optimization, Gibbs free energy and pKa calculations) and spectrofluorometric approaches were conducted. Conclusion: The proposed method is simple and suitable for quality control and assurance studies

Investigations of the Reversion of Vulcanized Rubber under Heat

1952 ◽  
Vol 25 (2) ◽  
pp. 241-250 ◽  
Author(s):  
Uma Shankar
Keyword(s):  
Free Energy ◽  
Hydrogen Sulfide ◽  
Methyl Iodide ◽  
Energy Of Activation ◽  
Cross Linking ◽  
Molar Free Energy ◽  
Vulcanized Rubber ◽  
Free Energy Of Activation ◽  
Equilibrium Swelling ◽  
Free Sulfur

Abstract (1) During reversion of a vulcanizate, the breakdown of cross-linkages, including those of polysulfides, predominates over any simultaneous reformation of cross-linkages. (2) The reverting modulus falls exponentially with time. (3) The calculated molar free energy of activation is 33.3 ± 1.7 kcal., irrespective of the temperature or the atmosphere of cure or the composition of the mix, and is sufficient to rupture an —S—S— bond. (4) The degree of cross-linking, estimated from the equilibrium swelling measurements in benzene, falls during reversion. (5) The exclusion of oxygen during curing does not prevent reversion if the temperature is high enough to supply the energy needed to break up the cross-linkages. (6) During reversion in nitrogen, hydrogen sulfide is freely evolved, and the C/H ratio rises above the value for C5H8. (7) Evidence for the formation and breakdown of polysulfides during reversion is provided by an increase in free sulfur and a decrease in combined sulfur during a given cure, and the methyl iodide reaction of the reverted vulcanizates.

The Solubility of Metallic Selenium under Anoxic Conditions

2000 ◽  
Vol 663 ◽  
Author(s):  
Yoshihisa Iida ◽  
Tetsuji Yamaguchi ◽  
Shinichi Nakayama ◽  
Tomoko Nakajima ◽  
Yoshiaki Sakamoto
Keyword(s):  
Free Energy ◽  
Solid Phase ◽  
Equilibrium Constants ◽  
Absorption Spectrometry ◽  
X Ray Diffraction ◽  
Molar Free Energy ◽  
Anoxic Conditions ◽  
X Ray ◽  
Free Energy Of Formation ◽  
Energy Of Formation

ABSTRACTThe solubility of metallic selenium was measured in a mixture of 0.1M-NaCl and 0.05M-N2H4under anoxic conditions (O2 < 1 ppm) by both oversaturation and undersaturation methods. Equilibrium was attained in 40 days. The aqueous selenium species identified were HSe at pH between 5 and 8, and Se42at pH between 10 and 13, by UV-Vis absorption spectrometry. The solid phase was identified as Se (cr) by X-ray diffraction. The equilibrium constants ofSe(cr) + H+ + 2e- = HSe- logK0 = -6.5±0.5 and4Se(cr) + 2e- = Se42- logK0 = -16.8±0.5were determined. The standard molar free energy of formation of HSe- and Se42-was determined to be (37.1±2.9) and (95.9±2.9) kJ/mol, respectively.

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