Solvent-free,catalyst-free aza-Michael addition of cyclohexylamine to diethyl maleate: Reaction mechanism and kinetics

The aza-Michael reaction is the addition of an amine to an electron deficient C=C double bond. This reaction is also used in the synthesis of precursors of polymeric networks. In this study, we paid attention to the kinetics and mechanism of the aza-Michael addition of cyclohexylamine (CHXA) to diethyl maleate (DEM) performed as a solvent-free, catalyst-free reaction and to concurrent reactions. In situ Raman spectroscopy, NMR spectroscopy and gas chromatography/mass spectrometry have shown the occurrence of three simultaneous reactions: (i) the aza-Michael addition of CHXA to DEM leading to diethyl 2-(cyclohexylamino)succinate, (ii) isomerization of DEM to diethyl fumarate (DEF), and (iii) the aza-Michael addition of CHXA to DEF formed by the reaction (ii). All of these reactions proceed with third order kinetics, first order in DEM or DEF and second order in CHXA. We propose a kinetic model that allows kinetic constants to be estimated. Furthermore, a numerical solution of the set of differential equations confirms the expected kinetic equations of reactions (i) and (ii) and gives values of rate constants comparable to the estimated ones. A DFT mechanistic study illustrates the structure of the reaction intermediates and transition states of all reactions and explains the contribution of the second amine molecule in the reaction mechanism.     

Preliminary study to prepare a reference material of toluene metabolite – o-cresol and benzene metabolite-phenol – in human urine

The candidate reference material (RM) was prepared by freeze-drying pooled urine samples obtained from healthy persons occupationally exposed to toluene. Homogeneity testing yielded no significant differences of urinary concentrations of o-cresol and phenol in 15 randomly selected units of RM. Stability testing showed no significant changes of concentrations of the above analytes over a period of 6 months. Property (pre-certified) values of phenol and o-cresol concentrations and their uncertainties (9.06±0.47 mg l⁻¹ and 1.03±0.06 mg l⁻¹, respectively) were estimated from results of a small-scale interlaboratory comparison in which two laboratories participated using four different analytical methods.     

Darstellung neuer Indandion-Analoga, 6. Mitt.: Sulfonierung des Indandion-Analogons aus Diphensäureanhydrid und Phenylessigsäure

Zusammenfassung Durch Behandlung des aus Phenylessigsäure und Diphensäureanhydrid synthetisierten Indandion-Analogons1 mit Oleum wurden Salze von zwei Monosulfosäuren (4 a und5 a) hergestellt. Die IR- und UV-Spektralanalyse sowie einige chemische Umwandlungen deuten darauf hin, daß die Sulfogruppe in4 a die 6- und in5 a die 6'-Stellung einnimmt. Aus der Sulfosäure4 erhielt man nach Behandlung mit SOCl₂ das Sulfochlorid (7), das mit Ammoniak leicht in das entsprechende Sulfonamid (8) übergeht.

---

Preparation of new indandione analogues, VI.: Sulfonation of the indandione analogue from diphenic anhydride and phenylacetic acid

After treatment with oleum of the indandion analogues1 obtained from phenylacetic acid and diphenic anhydrid, the salts of two monosulfo derivates (4 a and5 a) were isolated. The UV and IR spectra, as well as some chemical conversions point out that the sulfo group in4 a is at the 6 position and at 6' position in5 a.From the sulfonic acid4 and SOCl₂ the sulfochloride7 was obtained, which at the action of NH₃ gave easily the corresponding sulfonamide (8).

---

---

5. Mitt: Mh. Chem.100, 2024 (1969).     

Beitrag zur ascorbinometrischen Cer(IV)-Bestimmung

Zusammenfassung Es wird ein Verfahren zur Titration von Cer(IV)-salz mit Ascorbinsäuremaßlösung unter Verwendung von Variaminblau B als Indicator beschrieben. Die erhaltenen Werte stimmen mit den Ergebnissen der Titration mit Eisen(II)-ammoniumsulfatmaßlösung überein. Ein Nachteil der ascorbinometrischen Methode liegt in der leichten Oxydierbarkeit (Titerunbeständigkeit) der Ascorbinsäuremaßlösung.Es ist uns eine angenehme Pflicht, Herrn Prof. Dr. Erdey für die Überlassung von Variaminblau B zu danken.     

Reference material “total protein in human urine”

Two batches of a reference material (RM) “total protein in human urine” were prepared for quality assurance in the determination of human urinary proteins. The material was prepared by freeze-drying of a pooled urine sample obtained from healthy volunteers. Protein concentrations in both batches were within physiological values, close to their upper limit. Interlaboratory comparisons conducted in 26 laboratories using the standard operation procedures elaborated for six of the most frequently employed methods (biuret, Bradford, Exton, Lowry, Pesce, and Watanabe) revealed that the results obtained by the individual methods were significantly different due to various reaction mechanisms involved. It was therefore necessary to certify the mean values and their uncertainties individually for each method. These operationally defined certified or information values are valid only when the prescribed standard operation procedures are strictly followed.     

Ein neues Verfahren zur Darstellung von Dibenzo [c,e] azocinen

Zusammenfassung Unter der Einwirkung von Polyphosphorsäure gehen Monoxime von Di- und Triketonen mit einem 7gliedrigen Ring (3 und8) in die Dibenzo[c, e]azocine4 bzw.9 über. Die Struktur der neuen Azocine wurde durch Elementar-, IR- und NMR-Analyse und einige chemische Umwandlungen bestätigt.

---

A new method for preparation of dibenzo [c, e]azocines

Monoximes of di- and triketones containing a 7membered ring (3 and8) gave upon treatment with polyphosphoric acid the corresponding dibenzo[c, e]azocines (4, 9). The structure of the new azocines was confirmed by elementary analyses, IR-and NMR-spectrometry as well as by some chemical transformations.

     

High-order above-threshold ionization in a laser field: Influence of the ionization potential on the high-energy cutoff

High-energy above-threshold ionization by a strong linearly polarized laser field is analyzed using the strong-field approximation and the quantum-orbit formalism. An analytical formula for the cutoff is derived. The maximal electron kinetic energy is 10.007U _P + 0.538I _P. The first term with the ponderomotive energy U _P is equivalent to the known classical cutoff law, while the second term is a new result and depends on the ionization potential I _P. The validity of this formula is confirmed by comparison with the numerical results for the high-energy electron spectra.     

Divergence of the backward Euler method for ordinary stochastic differential equations

Numerical Algorithms - This paper is based on the analysis of the backward Euler method for stochastic differential equations. It is motivated by the paper (Hutzenthaler et al. Proc. R. Soc. A 467,...