Thermal transformations of urea in ethylene glycol: II. Reaction of isocyanic acid with ethylene glycol associates

Samuilov, A. Ya.; Valeev, A. R.; Balabanova, F. B.; Samuilov, Ya. D.; Коновалов, А. И.

doi:10.1134/s1070428013120014

Cited by 12 publications

(11 citation statements)

References 13 publications

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“…This Table 4. Thermodynamic parameters of activation of tautomerization of carbamate VI into azomethinenol VII in gas phase at 298 K: the non-catalytic and catalyzed by the methanol associates Ia-Ic ALCOHOL ASSOCIATES AS CATALYSTS OF TAUTOMERIC TRANSFORMATIONS has been shown for the alcohols reactions with alkyl- [23] and arylisocyanates [24] as well as isocyanic acid [25]; homo associates of phenol [26] and its mixed associates with methanol [27] are more reactive towards isocyanates than the monomeric alcohols; the same effect has been marked in the case of transesterification reactions [28]. The enhancement of reactivity upon association has been revealed for the hydrogen-bond complexes of amines: homo associates of amines [29] and their hetero associates with alcohols [30] are more reactive towards amides formation from esters as compared to the monomeric amines.…”

Section: Catalysis Of Carbamate-azomethinenol Tautomeric Transformatimentioning

confidence: 99%

Alcohol associates as catalysts of tautomeric transformations

et al. 2015

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The B3LYP/6-311++G(df,p) quantum-chemical simulation has revealed that linear associates of methanol catalyze the ketone-enol, nitro-aci-nitro, and carbamate-azomethinenol tautomeric transformations. All the reactions proceed via the coherent transition states. The catalytic effect is enhanced with the increased alcohol degree of association. The acid-base properties of methanol are changed similarly.

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Section: Catalysis Of Carbamate-azomethinenol Tautomeric Transformatimentioning

confidence: 99%

Alcohol associates as catalysts of tautomeric transformations

et al. 2015

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“…We previously showed that ethylene glycol associates catalyze the decomposition of urea and the reaction of isocyanic acid with ethylene glycol [1,18]. Therefore, there exists the possibility for catalysis by ethylene glycol molecules of all three steps of the transformation of urea into ethylene carbonate.…”

Section: Rupture Of the O-h And C-n Bonds And Formation Of The N-h Anmentioning

confidence: 99%

“…The reactions proceed through pre-and post-reaction complexes and cyclic transition states. The free energy barrier decreases when ethylene glycol molecule or zinc oxide is involved.* For communication II, see [1]. …”

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“…We previously studied the decomposition of urea in ethylene glycol into ammonia and isocyanic acid [18] and the reaction of isocyanic acid with ethylene glycol associates [1]. The third step in this process, the trans-formation of 2-hydroxyethyl carbamate into ethylene carbonate is slow.…”

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“…The non-catalytic unimolecular transformation of 2-hydroxyethyl carbamate (1) (2) in the gas phase at 298 K converted into post-reaction complex 2 · 3, and the latter decomposes into ethylene carbonate (2) and ammonia (3) (Scheme 1). There is a weak intramolecular hydrogen bond between the nitrogen atom and hydrogen atom of the hydroxy group in 1 (Fig.…”

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Thermal transformations of urea in ethylene glycol: III. Transformation of 2-hydroxyethyl carbamate into ethylene carbonate

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A Symmetric Recognition Motif between Vicinal Diols: The Fourfold Grip in Ethylene Glycol Dimer

2016

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Ethylene glycol has atransiently chiral, asymmetric global minimum structure,b ut it favors ah ighly symmetric, achiral dimer arrangement which has not been considered or found in previous quantum-chemical studies.C omplementary FTIR and Raman spectroscopyinsupersonic jets allows for the detection and straightforwarda ssignment of this four-fold hydrogen-bonded dimer,w hich introduces an interesting supramolecular binding motif for vicinal diols and provides astrong case for transient chirality synchronization.Carbohydrates are among the most versatile molecules employed by nature in molecular recognition processes and their biomimetic detection is challenging.[1] When reducing their molecular complexity to am inimum, one naturally arrives at vicinal diols.A mong them, the simplest representative ethylene glycol has even been detected in interstellar space.[2] Ethylene glycol or 1,2-ethanediol is ap articularly valuable model system for the study of multiple hydrogenbonded dimers and carbohydrate interactions, [3] because it allows for av ast range of quantum-chemical options to be explored. Indeed, the question of its preferred dimer structure has been addressed repeatedly by theory, [4][5][6] but not by experimental techniques.B ecause of the torsional flexibility of ethylene glycol, there are several possibilities how the four OH groups of the dimer can engage in hydrogen bonds.None of the previously proposed structures involves more than three hydrogen bonds among these OH groups. [4][5][6][7][8][9][10][11] We present unambiguous combined IR and Raman spectroscopic evidence that ethylene glycol in fact forms an S 4 -symmetric and thus non-polar and achiral dimer with four equivalent hydrogen bonds.U sing Gaussian 09, [12] an extensive search of the intermolecular potential-energy hypersurface at B3LYP-D3(BJ)/6-311 + G(2d,p) level (in short B3LYP) confirms that this structure wins over all triply hydrogen-bonded dimer structures by as ubstantial energy margin.Thet wo lowest monomer structures found at the harmonically zero-point energy-corrected B3LYP level are depicted in Figure 1. They have in common a gauche OCCO backbone,aweakly hydrogen-bonded OH group, and af ree OH group pointing in trans (M) or gauche (M') direction relative to the CÀCb ackbone.T hese monomer conformations are chiral and differ only by 1.4 kJ mol À1 at B3LYP level, making both of them potentially observable in aseeded adiabatic jet expansion. They have been investigated previously in much detail, [13][14][15][16][17][18][19][20][21][22][23][24][25] mostly by microwave spectroscopy, [13][14][15][16][17][18][19][20] and experimental estimates for their energy difference are rather close to our theoretical prediction, with 1.4(4) and 2.5(5) kJ mol À1 . [16,20] In jet experiments,t ypically only Mi so bserved in substantial abundance because of efficient conformational relaxation, [18] whereas at room temperature,M ' is also populated. Donor-acceptor OH torsional tunneling splits the levels by 0.2 and 0.05 cm À1 , respectively. ...

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Thermal transformations of urea in ethylene glycol: II. Reaction of isocyanic acid with ethylene glycol associates

Cited by 12 publications

References 13 publications

Alcohol associates as catalysts of tautomeric transformations

Alcohol associates as catalysts of tautomeric transformations

Thermal transformations of urea in ethylene glycol: III. Transformation of 2-hydroxyethyl carbamate into ethylene carbonate

A Symmetric Recognition Motif between Vicinal Diols: The Fourfold Grip in Ethylene Glycol Dimer

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