Zbigniew Grobelny

Characterization of potassium and sodium-potassium alloy solutions containing metal anions and complexed cations by means of NMR and ESR techniques.

The influence of a complexing agent, kind of solvent and temperature on the stability and ionic composition of potassium and sodium-potassium alloy solutions containing metal anions and complexed cations as well as solvated electrons are discussed basing on the analysis of alkali metal NMR and ESR spectra. Surprisingly it seems that the stability of metal solutions in tetrahydrofuran at ambient temperature is inversely proportional to the durability of K+ complex in the case of five studied ligands. The most stable metal solutions were obtained using 15-crown-5. It was shown that the characteristic blue colour of metal solutions is not connected with the presence of solvated electrons but with metal anions.

Selective cleavage of the linear ether bond in benzyl glycidyl ether and triphenylmethyl glycidyl ether by potassium alkalide as two-electron-transfer reagent

Abstract The linear ether bond was exclusively cleaved in benzyl glycidyl ether and triphenylmethyl glycidyl ether under the influence of K − , K + (15-crown-5) 2 ( 1 ), whereas the strongly strained three-membered oxacyclic ring remained undisturbed. Potassium glycidoxide and benzylpotassium were found as the primary reaction products of benzyl glycidyl ether with 1 . Subsequently, benzylpotassium reacted with benzyl glycidyl ether giving the next potassium glycidoxide molecule and bibenzyl. Benzyl phenyl ether was used as a model compound to explain the mechanism of bibenzyl formation. The reaction of triphenylmethyl glycidyl ether with 1 resulted in potassium glycidoxide and stable triphenylmethylpotassium. After treating with a quenching agent a new glycidyl ether or glycidyl ester was obtained from potassium glycidoxide. These results were found when the reaction occurred at the excess of glycidyl ether. In another case, i.e. at the excess of 1 further reactions took place with the participation of potassium anions and various new compounds were observed in the reaction mixture after benzylation or methylation. Thus, the method of substrates delivery influences the course of studied processes in a decisive way.

Decomposition of the crown ether ring in the reaction of K−, K+(15-crown-5)2 with oxetane

A cleavage of both oxacyclic rings occurs in the reaction of K−, K+(15-crown-5)2 with oxetane in tetrahydrofuran solution. Oxetane ring opening leads to the formation of organometallic compounds, which react with the crown molecule. Potassium methoxide, potassium n-propoxide as well as potassium tetra(ethylene glycoxide) vinyl ether are the main reaction products. It means that crown ether can act both as an activator and as a reagent under studied conditions.

New facts concerning the reaction of K − , K + (15-crown-5) 2 with phenyl glycidyl ether: unexpected formation of potassium cyclopropoxide

Abstract A new mechanism of the reaction of K−, K+(15-crown-5)2 with phenyl glycidyl ether is presented. The linear ether bond is attacked only to a small extent, if at all. As the main reaction path the oxirane bond in the β-position is cleaved, followed by the γ-elimination of potassium phenoxide and the formation of potassium cyclopropoxide. Crown ether ring opening also occurs in reactions with organometallic intermediates.

Study on the initiation step of 2-(9-carbazolyl)ethyl glycidyl ether polymerization by K−, K+ (15-crown-5)2

Abstract Several reactions occur during the initiation of 2-(9-carbazolyl)ethyl glycidyl ether polymerization by K−, K+ (15-crown-5)2. At first the oxirane ring is opened mainly in the β-position. An organometallic intermediate obtained cleaved then the linear ether bond in the substituent and the cyclic one in crown ether. Various potassium alkoxides are finally formed. They are the real initiators of the polymerization. 9-Vinylcarbazole being another reaction product is inactive in this process.

Cleavage of different ether bonds in butyl glycidyl ether and allyl glycidyl ether by K−, K+(15-crown-5)2

Abstract The kind of substituent in alkyl glycidyl ethers affects the course of their reaction with K−, K+(15-crown-5)2. The cyclic oxirane ring is exclusively cleaved in the case of butyl glycidyl ether whereas the presence of the unsaturated allyl group in the glycidyl ether molecule unexpectedly prefers the scission of the linear ether bond. In both the systems organometallic intermediates are formed. They react with crown ether causing its ring opening. Allylpotassium formed from allyl glycidyl ether reacts also with another glycidyl ether molecule; the oxirane ring is opened in this case.

The unusual outcome of the reaction of potassium anions with phenyl glycidyl ether

Abstract The formation of potassium phenolate, potassium hydroxide, propylene and ethylene in the reaction of phenyl glycidyl ehter with the potassium anions has been demonstrated. Evidently, the PHOCH 2 bond is remarkably readily cleaved by the K − ion under these conditions.

Self-decomposition of K−, K+(15-crown-5)2 tetrahydrofuran solution via organometallic intermediates

Abstract Self-decomposition of K − , K + (15-crown-5) 2 tetrahydrofuran solution results in dipotassium tetraethylene glycoxide and ethylene as the main reaction products. Dipotassium triethylene glycoxide, potassium tetraethylene glycoxide vinyl ether, potassium butoxide and potassium ethoxide are found as secondary products of the reaction. Organometallic intermediate compounds formed in the studied process are very reactive and their life-times are short. The mechanism of decomposition reactions is proposed. The course of the process is found to be different from that presented earlier in the literature for the K − , K + (18-crown-6) system.

Electron-transfer processes in the reaction of K−, K+(15-crown-5)2 with carbazole: unexpected formation of metallic potassium

Abstract Transfer of one electron from K − to the aromatic ring occurs in the reaction of K − , K + (15-crown-5) 2 with carbazole giving K° and a radical anion. The latter rapidly decomposes with the liberation of hydrogen and formation of carbazylpotassium. It can also undergo an intramolecular proton-exchange reaction followed by a transfer of the second electron from the part of K° product. That leads to a dianion which then reacts with another carbazole molecule. Finally, carbazylpotassium and 1,4-dihydrocarbazylpotassium are formed.

Structure of poly(propylene oxide) obtained in the presence of K−, K+(15-crown-5)2

Abstract Potassium isopropoxide and potassium tetraethylene glycoxide vinyl ether as well as small amounts of dipotassium tri- and tetraethylene glycoxides are formed in the initiation step of propylene oxide polymerization by K−, K+(15-crown-5)2. Chain transfer reactions occur during the polymerization. Therefore, macromolecules with various starting groups, i.e. with the isopropyl, vinyl, allyl, and propenyl ones, are obtained in the process. The kind of end groups generally depends on the quenching agent used for termination. However, the macromolecules terminated in the chain transfer reactions possess exclusively the hydroxyl end group. The functionality of protonated polymers is equal to about 1.2 as a result of propagation occurring on dipotassium glycoxides.