Phase-transfer catalysis in the chemistry of tetrazoles

In this review we discuss results obtained in the development of methods for the synthesis of tetrazoles and tetrazolium salts together with studies of alkylation, acylation, and imidoylation of tetrazole and 5-substituted tetrazoles under conditions of phase-transfer catalysis.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 754–761, June, 1992.     

Infrared and Raman spectroscopic investigation of Eu3+-doped mono and Di-urethanesil hybrid siliceous materials

The general features of two series of sol-gel derived materials, designatedurethanesils (Ut), have been investigated by infrared and Raman spectroscopies with the goal of elucidating the chemical environment of the Eu³⁺ cations. The host frameworks of the two families of ormolytes studied have been represented by m-Ut(350) and d-Ut(300), where m stands for mono, d stands for di, 350 and 300 are the average molecular weights of the organic precursors (poly(ethylene glycol) methyl ether, PEGME, and poly(ethylene glycol), PEG, respectively). The hybrid matrix of the mono-xerogels is composed by a siliceous backbone bonded by means of urethane linkages (-NHC (=O)O-) to pendant methyl end capped oligopolymer chains with approximately 7 oxyethylene units, whereas that of the di-xerogels is based on a siliceous network grafted through urethane groups to both ends of poly(oxyethylene) segments containing about 6 (OCH₂CH₂) repeat units. Both classes of materials have been doped with europium triflate (Eu(CF₃SO₃)₃). The doped samples have been identified by m-Ut(350)_nEu(CF₃SO₃)₃ and d-Ut(300)_nEu(CF₃SO₃), where n is the molar ratio of (OCH₂CH₂) repeat units per Eu³⁺ ion. Materials with n ranging from ∞ to 5 have been analyzed. The spectral data obtained provide evidence that the cations begin to coordinate to the ether oxygen atoms of the oligopolymer chains at n=40 in the mono-urethanesils and at n=10 in the di-urethanesils. In mono-urethanesils samples with n>40 and in di-urethanesils materials with n>10, the Eu³⁺ coordinate exclusively to the carbonyl oxygen atoms of the urethane linkages. Paper presented at the 8th EuroConference on Ionics, Carvoeiro, Algarve, Portugal, Sept. 16–22, 2001.     

Mark Grigor'evich Krein

Obituary

Mark Grigor'evich Krein     

Tetrachlorosilane-Sodium Azide System in the Synthesis of Tetrazole-Containing Amino Acid Derivatives

Treatment of N-acetyl-(RS)-phenylalanine and N-acetyl-(RS)-leucine methyl esters with the system tetrachlorosilane-sodium azide leads to formation of tetrazole-containing amino acid derivatives. The latter can be converted into -substituted 5-methyl-1-tetrazolylacetic acids and the corresponding bis-tetrazoles.     

Synthesis and Acidity of 5-Phenyltetrazol-2-ylalkanoic Acids and the Corresponding 5-(5-Phenyltetrazol-2-ylalkyl)tetrazoles

We have obtained 5-phenyltetrazol-2-ylalkanoic acids and their derivatives containing terminal nitrile, amide, and tetrazol-5-yl groups. Tetrazolylalkanoic acids with two (pK _a 4.93) and three (pK _a 5.45) bridging methylene groups are weaker acids than the corresponding ditetrazoles pK _a 4.68 and 5.29 respectively). However, the acidity of 5-phenyltetrazol-2-ylacetic acid (pK _a 3.12), is higher than acidity of the corresponding ditetrazole (pK _a 3.27).     

Linear polynuclear tetrazole-containing compounds

Linear polynuclear tetrazole-containing compounds were synthesized. Alkylation of 5-[-(5-phenyl-2-tetrazolyl)alkyl]tetrazoles with ethyl bromoacetate and chloroacetamide gave the corresponding esters and amides. Treatment of the latter with tetrachlorosilane-sodium azide afforded compounds containing three tetrazole rings linked through polymethylene bridges. Acid ionization constants of the products possessing an NH-tetrazole ring (pK _a = 2.9–3.2) and the corresponding carboxylic acids (pK _a = 2.9–3.1) in aqueous methanol were determined by potentiometric titration.Translated from Zhurnal Organicheskoi Khimii, Vol. 40, No. 10, 2004, pp. 1580–1586.Original Russian Text Copyright © 2004 by Morozova, Komissarov, Esikov, Zubarev, Malin, Ostrovskii.     

Heat effects and rates and molecular mechanisms of water sorption by perfluorinated polymer materials bearing functional groups

The heat effects and the rates and equilibrium quantities of H₂O vapour sorbed and desorbed on polymeric perfluorinated materials (functional groups -SO₃H, -SC₃Na, -SO₃K) and on material treated with FeCl₃ solution as sorbent were investigated.Sorbed H₂O may be completely desorbed in vacuum at 443 K. The material bearing -SO₃H has maximum sorption affinity: the molar heat of -SO₃H wetting is close to that of H₂SO₄ wetting. The differential heat of sorption decreases from 68 kJ mol^–1 atn0(n=H₂O/-SO₃H) to 45 kJ mol^–1 atn5, but not below the heat of H₂O condensation. The -SO₃H samples sorb H₂O vapour in the presence of liquid H₂O at 293 K up ton=17. The -SO₃K material has minimum affinity for H₂O: the equilibrium quantity sorbed in room air is less by a factor of 4 than that for the -SO₃H material. The spatial arrangement of H₂O molecules near the sulpho groups is considered.     

Catalytic decomposition of ozone over cupric oxide catalysts

Kinetic regularities of the catalytic decomposition of ozone over IC-12-1 and ICT-12-9 cupric oxide catalysts in wetted gases have been studied. These catalysts are suggested to be effective for ozone decomposition.

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-12-1 -12-9 . .

     

Tetrazoles. 24. Preparation of 1,4-dimethyl- and 2,4-dimethyl-5-aryl-tetrazolium salts

Alkylation of 1-methyl-5-aryltetrazoles with dimethyl sulfate leads to the formation of 1,4-dimethyl-5-aryltetrazolium ion salts. Alkylation of isomeric 2-methyl-5-aryltetrazoles also apparently takes place at the N(4) atom. 1-Methyl-5-aryltetrazoles display greater reactivity with respect to methylation than the isomeric 2-methyl-5-aryltetrazoles. 1,4-Dimethyl-5-aryltetrazolium methylsulfate salts isomerize upon heating to give the more stable 2,4-dimethyl-5-aryltetrazolium ion salts.For Communication No. 22, see Ref. [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 502–506, April, 1988.