Wyniki wyszukiwania - BazTech

1

Microwave-aided reactions of aniline derivatives with formic acid : inquiry-based learning experiments

Mycak Michael, Doležal Rafael, Bílek Martin, Kolář Karel

Chemistry-Didactics-Ecology-Metrology

|

2022

|

R. 27, NR 1-2

135--151

EN

The synthesis of amides belongs to traditional experimental tasks not only in organic chemistry exercises at universities but also at chemically focused secondary schools or in special practices at general high schools. An example of such a synthesis may be the preparation of acetanilide via reaction of aniline with acetic acid or acetic anhydride. However, both of these reactions are associated with a rather long reaction time and certain hazards that limit their straightforward use in pedagogical practice. Conveniently, the reaction of aniline with acetic acid may be significantly optimised if it is performed under solvent-free conditions in the presence of microwaves, which reduces considerably the reaction time and provides very good yield, compared to traditional heating by a heating nest. In this study, the main pedagogical aim of the experimental design is elucidation of the influence of the structure of the amines on the course of the reaction with formic acid through inquiry-based learning. Specifically, the proposed experiments consist in investigation of the chemical yield achieved in microwave assisted reactions of aniline and its derivatives with formic acid in such a way that is adequate for constructive learning of undergraduate chemistry students. The selected series of amines involves aniline, 4-methoxyaniline, 4-chloroaniline, and 4-nitroaniline. In accordance with the chemical reactivity principles, students gradually realise that the influence of the substituent is reflected in the reaction yield, which grows in the following order: N-(4-nitrophenyl)formamide ˂ N-(4-chlorophenyl)formamide ˂ N-phenylformamide ˂ N-(4-methoxyphenyl)formamide. Therefore, the results of the experiments enable students to discover that stronger basicity of the amine increases the yield of the amide. In order to deepen the students’ chemical knowledge and skills, the concept of the experiments was transformed to support inquiry-based student learning. The proposed experiments are intended for experimental learning in universities educating future chemistry teachers, but they may be also utilised in the form of workshops for students at secondary schools of a general educational nature.

2

Microwave synthesis of sulfanilic acid

Havlíček J., Myška K., Tejchman W., Karásková N., Doležal R., Maltsevskaya N. V., Kolář K.

Chemistry-Didactics-Ecology-Metrology

|

2017

|

R. 22, NR 1-2

93--98

EN

Sulfanilic acid represents an important substance, which is frequently utilized in the industry of azo dyes as well as in drug development of antimicrobials (e.g. of sulfonamides). Students can also meet with such type of compounds in chemistry labs, for example, when they estimate pH by methyl orange indicator or prepare Orange II for textile colouring. Both of these dyes are products of azo coupling of sulfanilic acid as diazonium salt with N,N-dimethylaniline or 2-naphthol, respectively. In the article, we focus on the synthesis of sulfanilic acid as a well-known experiment in the organic chemistry education. The synthesis was modified as the solvent free and microwave assisted experiment under semimicroscale conditions. That experiment is very convenient for the organic chemistry courses in the university or the high school teaching.

PL

Kwas sulfanilowy stanowi ważną substancję, często stosowaną w przemyśle barwników azowych, jak również w produkcji leków przeciwdrobnoustrojowych (np. sulfonamidów). Studenci mogą również spotykać się z takimi związkami w laboratoriach chemicznych, na przykład przy oznaczaniu pH z wykorzystaniem oranżu metylowego lub przy przygotowywaniu Oranżu II dla przemysłu tekstylnego. Oba te barwniki są produktami sprzężenia soli diazoniowych kwasu sulfanilowego odpowiednio z N,N-dimetyloaniliną lub 2-naftolem. W artykule przedstawiono syntezę kwasu sulfanilowego jako przykład dobrze znanego eksperymentu w edukacji chemii organicznej. Syntezę zmodyfikowano jako reakcję bez rozpuszczalników i wspomagano mikrofalowo w warunkach półmikropreparacji. Eksperyment ten powinien być przedstawiany podczas kursów chemii organicznej na uniwersytecie lub w szkole średniej.

3

Microwave synthesis and characterization of non-stoichiometric Mg0.1551Fe1.8966O3

Celik G., Somunkiranoglu S., Kurtulus F.

Journal of Achievements in Materials and Manufacturing Engineering

|

2014

|

Vol. 65, nr 1

5--9

EN

Purpose: of this study is clearly different synthesis method (microwave method) of non-stoichiometric magnesium iron oxide using in broad area such as high frequency magnets, data storage systems and especially cancer treatment. Design/methodology/approach: Analytically magnesium oxide and iron (III) oxide weighed an appropriate molar ratio and homogenized in an agate mortar. The mixture placed into a porcelain crucible to heat in microwave oven. After the material was exposed to microwave irritation, it was taken from the oven, and then homogenized again. Then, final product was ready to analyse. Powder X-ray Diffractometer (XRD) was used to determine crystal structure of the product. FTIR spectrum was taken to support the functional groups. Thermo gravimetric-differential thermal analysis (TG/DTA) was carried out to identify thermal character. Morphological properties and semi-quantitative analyse of the sample was performed by Scanning electron microscope/ Electron disperse (SEM/EDX). Findings: The XRD patterns show that the product is Mg0.1551Fe1.8966O3 (ICSD 51171). The first time synthesized material is crystallized in hexagonal system with unit cell parameters a=5.0490, b=5.0490, c=13.7890 Å and space group R-3c. The other supporting methods confirm the crystal structure. Non-stoichiometric Mg0.1551Fe1.8966O3 (ICSD 51171) was synthesized by microwave method completely different from literature for the first time. The characterization was mainly based on powder X-ray diffraction pattern. Also, thermal behaviour and morphology were determined. Research limitations/implications: The synthesis method has some disadvantages such as low repeatability, non-uniform product etc. We tried to minimize these negative aspects in our research and succeeded. Practical implications: The compound can be used to reduce side-effects of drugs for cancer treatment, and find broad usage area in that treatment. For his reason, magnesium iron oxide has practical applications. Originality/value: The originality of the paper is first time microwave synthesis of Mg0.1551Fe1.8966O3. In the literature, the magnesium iron oxide was synthesized so many times by different conventional routes. But, as far as we know cheap, clean and short-term synthesis route has not been used before.

4

A new method for the preparation of solvatochromic 5-(5-X-6-hydroxynaphthyl-2)-7H-indolo[1,2-a]quinolinium merocyanines

Sawicka M.J., Soroka J.A., Gąsiorowska M.

Polish Journal of Chemical Technology

|

2010

|

Vol. 12, nr 1

17-22

EN

A new method for the preparation of 7H-indolo[1,2-a]quinolinium solvatochromic dye precursors has been investigated. 5-(6-Hydroxynaphthyl-2)-7,7-dimethyl-7H-indolo[1,2-a]quinolinium perchlorate, 5-(5-bromo-6-hydroxynaphthyl-2)-7,7-dimethyl-7H-indolo[1,2-a]quinolinium perchlorate and 5-(5-nitro-6-hydroxynaphthyl-2)-7,7-dimethyl-7H-indolo[1,2-a]quinolinium perchlorate were obtained via demethylation of the corresponding 5-(5-X-6-methoxynaphthyl-2)-7,7-dimethyl-7H-indolo[1,2-a]quinolinium salts. The application of pyridinium hydrochloride in the demethylation of the methoxy perchlorates allowed to obtain the products with the almost quantitative yield in a very short time, especially when the reaction was carried out using microwave irradiation.

5

Microwave-assisted boration of potato starch

Staroszczyk H.

Polimery

|

2009

|

T. 54, nr 1

31-41

EN

Granular potato starch was successfully borated with boric acid and sodium tetraborate decahydrate (borax) in a microwave-assisted solid state reaction. Products of starch boration reached (dependently on the conditions of the process) the maximal value of the degree of esterification (DE) equal to 0.27 when boric acid was applied, and 0.18 when borax was used. DTA, TG, DTG and FT-IR methods revealed that boration of starch provided boron esters or borate complexes. High-pressure size exclusion chromatography (HPSEC), DSC and X-ray diffraction showed that although the boration of starch caused changes in its macrostructure, the thermal stability of borated starch was enhanced even by 20°C when compared with native product, with larger stability exhibited by complexes than by esters. The thermal stability of the borated starch increased with an increase in DE. After modification, granularity of starch was retained, as was indicated by the scanning electron microscopy.

PL

Ziarnistą skrobię ziemniaczaną boranowano za pomocą kwasu borowego i dziesięciowodnego tetraboranu sodu (boraksu) w reakcji wspomaganej mikrofalami. Określono wpływ stosunku skrobia:czynnik borujący oraz czasu trwania i mocy naświetlenia na stopień estryfikacji (DE) produktów (tabela 1). Maksymalna osiągnięta wartość DE w próbkach skrobi boranowanej H3BO3 wyniosła 0,27, a boranowanej boraksem 0,18. Wyniki uzyskane metodami DTA, TG, DTG oraz FT-IR (rys. 2-8) wykazały, że produkty boranowania stanowiły estry oraz kompleksy (Schemat A). Na podstawie wyników badań z zastosowaniem wysokociśnieniowej chromatografii żelowej (HPSEC) (rys. 1), DSC (rys. 9 i 10), oraz dyfraktometrii promieni X (rys. 11, 12) ustalono, że chociaż skrobia miała zmienione właściwości fizykochemiczne (tabele 1 i 3) i jej struktura krystaliczna była zaburzona, to stabilność termiczna tak zmodyfikowanej skrobi wzrosła nawet o 20°C w stosunku do skrobi natywnej. Stabilność ta zależała od wartości DE - zwiększała się wraz z jej wzrostem (tabela 2). Ziarnista struktura skrobi po reakcji boranowania została zachowana, co stwierdzono metodą SEM (rys. 13).

6

Zastosowanie promieniowania mikrofalowego w chemii

Nowak I., Kowalska S.

Analityka : nauka i praktyka

|

2007

|

nr 4

4-10