Letters to the Editor
Alkyl Carbocation and Free Radical Stability: Father and His Four Children
Резюме. It is very important for the students of undergraduate organic chemistry to understand the stability of carbocation and free radical, as many of the organic reactions proceed through formation of these intermediates. To make this topic interesting and easy to understand, carbocation and free radical have been correlated with one family where father (carbon) is having four children (hydrogens or alkyl groups). In case of carbocation, wife (solvent) also plays an important role for stabilizing her husband. With this example order of the stability of carbocation and free radical has been explained in detail in text.
Keywords: organic chemistry, carbocation, free radical, stability
M.T. Chhabria, S.M. Patel, V.V. Shah, P.S. Brahmkshatriya
Teaching Efficiency
A Test for Scoring the Knowledge in the Reference to the Chemical Elements and Their Compounds in the Teaching Contents for 11th Grade
Резюме. A multiple-choice test has been created for scoring the knowledge and skills of the students in reference to the chemical elements and their compounds in the teaching contents for 11-th grade in chemistry and environmental protection – second level. The properties of the test are studied. The test could be used for specific topics, or end of year control in 11th grade, for training the students for their graduation exams, olympiads, competitions, and as university entrance exams. Two versions of the test are presented, each consisting of 20 questions. The test was performed by 90 high school students in four 11th grade classes of the National High School of Mathematics and Science “Acad. L. Tchakalov” in Sofia.
Keywords: chemistry tests; questions; solutions; test assessment
T.M. Apostolova
Problems
XXXIX International Chemistry Olympiad: Problems with Solutions
Резюме. The paper represents problems (theoretical and practical) of the XXXIX International Chemistry Olympiad and the solutions of theoretical problems. Comments of Bulgarian team presentation are given.
Keywords: International Chemistry Olympiad (IChO), practical exams, theoretical problems and solutions.
D. Tasheva, P. Tsanova
From the Research Laboratories
Synthesis, Coordination and Structure of Mixed Ligand Coper (II) Complexes of Iminodiacetic Acid and Hippuric Acid
Резюме. Mixed ligand copper(II) complexes, Na[Cu(C6H5CONHCH2COO){NH(CH2COO)2}.H2O]H2O and Na[Cu(C6H5CONHCH2COO){NH(CH2COO)2}.H2O] formed with iminodiacetic acid and hippuric acid have been synthesized. The mode of coordination and structural investigations have been done by their elemental analysis, spectral (IR and electronic spectra) and magnetic measurements studies. Iminodiacetic acid acts as a tridentate ligand and the coordination occurs with two carboxylate oxygen atoms and the nitrogen atom. Hippuric acid shows a bidentate behavior coordinating through the carboxylate oxygen atom and the nitrogen of the amido group. The sixth coordination position is satisfied by one water molecule. Thus both the Cu(II) complexes have been suggested to show a six fold octahedral structure.
Keywords: synthesis, coordination, structure, Cu(II) compexes, hippuric acid, iminodiacetic acid
G. Kumar, E.M.R. Kiremire
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