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Study on the synthesis of novel 5-substituted 2-[2-(pyridyl)ethenyl]-1,3,4-oxadiazoles and their acid-base interactions.

Kudelko A, Jasiak K, Ejsmont K - Monatsh. Chem. (2014)

Bottom Line: A series of novel 5-substituted 2-[2-(pyridyl)ethenyl]-1,3,4-oxadiazoles were efficiently synthesized by cyclocondensation of the appropriate 3-(pyridyl)acrylohydrazides with triethyl orthoesters in the presence of glacial acetic acid.The products were identified by means of spectroscopic methods and their pK A ionization constants were determined.The influence of substituents on the basicity of the pyridine system has been discussed.

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Affiliation: Department of Chemical Organic Technology and Petrochemistry, The Silesian University of Technology, Krzywoustego 4, 44100 Gliwice, Poland.

ABSTRACT

Abstract: A series of novel 5-substituted 2-[2-(pyridyl)ethenyl]-1,3,4-oxadiazoles were efficiently synthesized by cyclocondensation of the appropriate 3-(pyridyl)acrylohydrazides with triethyl orthoesters in the presence of glacial acetic acid. The products were identified by means of spectroscopic methods and their pK A ionization constants were determined. The influence of substituents on the basicity of the pyridine system has been discussed.

No MeSH data available.


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Mentions: Considering the fact that physical properties of compounds are also strongly dependent on their ability to acid–base interactions, the pKA values of 5-substituted 2-[2-(pyridyl)ethenyl]-1,3,4-oxadiazoles 6a–6i were determined (Table 4). The determination of the pKA dissociation constants was performed according to the spectrophotometric method of Albert and Serjeant [61] in 50 % aqueous methanol solution (10−5 M, room temperature) due to the low solubility of the examined compounds in water. The pKA values determined in aqueous methanol solution are lower about 0.6 pKA unit comparing with those determined in aqueous solution which is the result of different ionic products of these solvents. Absorption maxima of the 1,3,4-oxadiazole ions were selected as analytical wavelengths bearing in mind their considerable shifts relative to the maxima of the non-protonated forms. The conducted studies have shown that the 1,3,4-oxadiazol-2-ylethenyl moiety at positions 2, 3, or 4 of the pyridine ring causes an increase in acidity compared to the pKA value of the unsubstituted pyridine (7, Scheme 4) [62].Table 4


Study on the synthesis of novel 5-substituted 2-[2-(pyridyl)ethenyl]-1,3,4-oxadiazoles and their acid-base interactions.

Kudelko A, Jasiak K, Ejsmont K - Monatsh. Chem. (2014)

© Copyright Policy - OpenAccess
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4495023&req=5

Mentions: Considering the fact that physical properties of compounds are also strongly dependent on their ability to acid–base interactions, the pKA values of 5-substituted 2-[2-(pyridyl)ethenyl]-1,3,4-oxadiazoles 6a–6i were determined (Table 4). The determination of the pKA dissociation constants was performed according to the spectrophotometric method of Albert and Serjeant [61] in 50 % aqueous methanol solution (10−5 M, room temperature) due to the low solubility of the examined compounds in water. The pKA values determined in aqueous methanol solution are lower about 0.6 pKA unit comparing with those determined in aqueous solution which is the result of different ionic products of these solvents. Absorption maxima of the 1,3,4-oxadiazole ions were selected as analytical wavelengths bearing in mind their considerable shifts relative to the maxima of the non-protonated forms. The conducted studies have shown that the 1,3,4-oxadiazol-2-ylethenyl moiety at positions 2, 3, or 4 of the pyridine ring causes an increase in acidity compared to the pKA value of the unsubstituted pyridine (7, Scheme 4) [62].Table 4

Bottom Line: A series of novel 5-substituted 2-[2-(pyridyl)ethenyl]-1,3,4-oxadiazoles were efficiently synthesized by cyclocondensation of the appropriate 3-(pyridyl)acrylohydrazides with triethyl orthoesters in the presence of glacial acetic acid.The products were identified by means of spectroscopic methods and their pK A ionization constants were determined.The influence of substituents on the basicity of the pyridine system has been discussed.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemical Organic Technology and Petrochemistry, The Silesian University of Technology, Krzywoustego 4, 44100 Gliwice, Poland.

ABSTRACT

Abstract: A series of novel 5-substituted 2-[2-(pyridyl)ethenyl]-1,3,4-oxadiazoles were efficiently synthesized by cyclocondensation of the appropriate 3-(pyridyl)acrylohydrazides with triethyl orthoesters in the presence of glacial acetic acid. The products were identified by means of spectroscopic methods and their pK A ionization constants were determined. The influence of substituents on the basicity of the pyridine system has been discussed.

No MeSH data available.