Hydrolyse und Alkoholyse von Reaktivfarbstoffen: II. Hydrolyse von Monochlortriazin-Farbstoffen. 2. Mitteilung über reaktionsmechanistische Untersuchungen an Reaktivfarbstoffen

• 1 The kinetics of the hydrolysis of three monochlorotriazine reactive dyes have been determined in alkaline buffer solutions at 60°, 80° and 98° (ionic strength I = 0.0625).
• 2 The kinetic results as well as diffusion measurements in aqueous solution indicated that these dyes form aggregates at dye concentrations at 6 · 10^?4, but practically not at 6·10^?6 moles/l.
• 3 The reaction order with respect to hydroxyl ions has been determined. The influence of general base concentration was negligible.

     

Hydrolyse und Alkoholyse von Reaktivfarbstoffen: I. Hydrolyse von Dichlortriazin-Farbstoffen. 1. Mitteilung über reaktionsmechanistische Untersuchungen an Reaktivfarbstoffen

• 1 The kinetics of the hydrolysis of a dichlorotriazine reactive dye have been determined in aqueous buffer solutions at pH values between 8.50 and 13.47, at 24.0° and ionic strength I = 0.625.
• 2 The reaction order with respect to the concentration of the dye and the hydroxyl ions is a complex function of the reaction conditions.
• 3 Only in very dilute solutions the kinetics follow the mechanism postulated by Ackermann and Dussy [4].
• 4 Several types of base catalysis can be detected, depending on conditions (pH, concentrations).

     

Zur Berechnung der Aciditätskonstante von Sorbit aus der Sorbitolysenkinetik von Reaktivfarbstoffen. 4. Mitteilung über reaktionsmechanistische Untersuchungen an Reaktivfarbstoffen

The first acid dissociation constant of sorbitol is redetermined (PK_a = 13.00; 60°).     

Nachbargruppenbeteiligung bei massenspektrometrischen Fragmentierungsreaktionen: Spermin-Derivate. 18. Mitteilung über das massenspektrometrische Verhalten von Stickstoffverbindungen

The mass spectral behaviour of tetraacetyl spermine ( 2 ) has been investigated. The fragmentation reactions are characterized by the neighbouring group participation of the amide nitrogen atoms. Only a few reactions can be explained by usual pathways (α-cleavage, onium reactions). Most of the fragment-ions are formed by neighbouring group participation:

• 1 [M-COCH₃]⁺-Ion.
• 2 Breakdown of one of the two 1,3-diaminopropan moieties: m/e 242, 256, 268. This type of fragmentation is characteristic for all acetylated 1,3-diaminopropan-derivatives e.g. triacetylspermidine.
• 3 Expulsion of a neutral amine: m/e 169.
• 4 S_Ni-type reactions, by which cyclic ions are formed: m/e 100.

     

Abschätzung von Reaktivitäts-Parametern von Nucleophilen auf Graund der Kern-Spin-Spin-Kopplungskonstanten J 1 H-199Hg ihrer Methylquecksilberkomplexe

The value of the nuclcear-spin-coupling-constant J_1H-199Hg of methylmecury compounds CH₃HgL is related to:

• 1 (a) the electrode potential for oxidative dimerisation of L,
• 1 (b) the interatomic distances C-Hg in CH₃HgL,
• 1 (c) the interatomic distances Hg-Hg in L-Hg-Hg-L,
• 1 (d) the energy of dissociation of CH₃HgL into CH₃ and HgL,
• 1 (e) the logarithms of the stability constants of CH₃HgL,
• 1 (f) the logarithms of the relative nucleophilic reactivites of L in S_N2 reactions at a saturated carbon atom
• 1 (g) the proton-bascicity of L (in series of structurally similar ligands, possessing the same ligating atom, as for example carboxylate anions).

Approximately linear correlations were found between J_1H-199Hg and the values of (a), (e), (f), and (g). It is suggested that the value of the nuclear-spin-spin-coupling-constant J_1H-199Hg of CH₃HgL provides a measure of the relative energy of the occupied frontier orbital of the nucleophile L.     

Über die Entstehung von α-Keto-carbonium-Ionen bei der säurekatalysierten Hydrolyse von Diazoketonen. (Vorläufige Mitteilung)

Secondary deactivated aliphatic diazo compounds (diazo-ketones R CO CN₂ R′; diazo-esters ROOC CN₂ R′; 1, 1, 1-trifluoro-2-diazopropane) are hydrolysed by the A S_E2 mechanism comprising rate determining protonation of the substrate, followed by decomposition. Product analysis shows that the decomposition of the secondary diazonium ions is monomolecular, without intervention of a nucleophile. The corresponding primary diazo compounds (R CO CHN₂, ROOC CHN₂ and CF₃ CHN₂) are hydrolysed by the A-2 mechanism comprising preequilibrium protonation; the primary diazonium ion reacts with a nucleophile in a bimolecular displacement step. The only exception observed is found in p-nitrophenyl-diazomethane, which follows A S_E2 mechanism. The observations are discussed in terms of the stability of the corresponding secondary resp. primary α-keto-carbonium ions.     

Latent solid‐phase extraction with thermoresponsive soluble polymers

The use of soluble thermoresponsive polymers to sequester or scavenge hydrophobic guest molecules from dilute aqueous solutions on heating is described. In these studies, a homopolymer of N‐isopropylacrylamide was shown to sequester 46–83% of a soluble monochlorotriazine from 0.1–10 ppm aqueous solutions when heating above this polymer's lower critical solution temperature (LCST). Substitution of the reactive piperidine‐containing 20:1 copolymer poly(N‐isopropylacrylamide)‐c‐poly[N‐4‐(acrylamidomethyl)piperidine] for this unreactive polymer led to >98% scavenging of these same triazines when heating above this reactive polymer's LCST. The monochlorotriazine guests studied included the herbicide atrazine and two dye‐labeled analogues of this herbicide. In one case, an atrazine analogue was designed so as to contain a dansyl group for fluorescence analysis. In the second case, an atrazine analogue was labeled with a methyl red group to facilitate visual and spectrophotometric analysis. Atrazine concentrations were measured with liquid chromatography–mass spectrometry. The enhanced efficiency of the reactive piperidine‐containing copolymer scavenger in removing triazines from solution is attributed to covalent bond formation by nucleophilic aromatic substitution of the chlorine of the monochlorotriazines by the piperidine nucleophile on the copolymer. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 6309–6317, 2004     

SN2’ versus SN2 Reactivity: Control of Regioselectivity in Conversions of Baylis–Hillman Adducts

TiCl₄‐induced Baylis–Hillman reactions of α,β‐unsaturated carbonyl compounds with aldehydes yield the (Z)‐2‐(chloromethyl)vinyl carbonyl compounds 5 , which react with 1,4‐diazabicyclo[2.2.2]octane (DABCO), quinuclidine, and pyridines to give the allylammonium ions 6 . Their combination with less than one equivalent of the potassium salts of stabilized carbanions (e.g. malonate) yields methylene derivatives 8 under kinetically controlled conditions (S_N2’ reactions). When more than one equivalent of the carbanions is used, a second S_N2’ reaction converts 8 into their thermodynamically more stable allyl isomers 9 . The second‐order rate constants for the reactions of 6 with carbanions have been determined photometrically in DMSO. With these rate constants and the previously reported nucleophile‐specific parameters N and s for the stabilized carbanions, the correlation log k (20 °C)=s(N + E) allowed us to calculate the electrophilicity parameters E for the allylammonium ions 6 (?19<E <?18). The kinetic data indicate the S_N2’ reactions to proceed via an addition–elimination mechanism with a rate‐determining addition step.     

高效液相色谱研究丝素亲核基团与一氯均三嗪型活性染料反应动力学

以异丙胺、对甲酚和甲醇分别模拟蚕丝丝素的氨基、酚羟基和醇羟基,应用高效液相色谱分析一氯均三嗪型活性染料与蚕丝丝素的不同亲核基团的反应速率.结果表明:在pH=8～10、70～95 ℃的条件下,染料的酚解总反应速率远大于染料的氨解总反应速率和醇解总反应速率.其中C.I.活性红24 和C.I.活性橙2在pH=9,95 ℃条件下的酚解总速率分别约为其氨解总反应速率的8.5倍和12.5倍,为其醇解总反应速率的23倍和50倍;该两染料的酚解效率分别为47.4和96.3,氨解效率分别为4.6和6.9,醇解效率仅为1左右.通过异丙胺-对甲酚-甲醇混合溶液(1∶ 10∶ 100,V/V)模拟蚕丝与染料的反应,研究一氯均三嗪型活性染料与丝素上亲核基团的反应选择性,推断出一氯均三嗪型活性染料染蚕丝的最适宜条件为pH=8～9,温度85 ℃左右.在此条件下,酚羟基在蚕丝的一氯均三嗪型活性染料染色中起主要作用,氨基起次要作用,而醇羟基的作用甚微.     

Differential-thermoanalytische Untersuchung von einigen Phosphororganischen Verbindungen

The thermal transitions of phosphines, phosphonium salts and esters of phosphorus acids, as well as some reactions of different phosphorus compounds, were studied by DTA.

1. DTA data have been considered for various types of reactions: 1. A→B; 2. A→B+C
2. DTA of reactive mixtures: 1. A+B→C; 2. A+B→C+D

Examples of the use of DTA were shown for studying the processes of isomerization, decomposition, and different regroup reactions of addition, combination, exchange and disintegration. The simple method of DTA allows one to find the optimum conditions of the reactions and to establish their reaction paths.     

Phenolysis and aminolysis of 4‐nitrophenyl and 2,4‐dinitrophenyl S‐methyl thiocarbonates in aqueous ethanol

The reactions of S‐methyl O‐(4‐nitrophenyl) thiocarbonate ( 1 ) and S‐methyl O‐(2,4‐dinitrophenyl) thiocarbonate ( 2 ) with a series of secondary alicyclic (SA) amines and phenols are subjected to a kinetic investigation. Under nucleophile excess, pseudo‐first‐order rate coefficients (k_obs) are obtained. Plots of k_obs against the free nucleophile concentration at constant pH are linear with slopes k_N. The Brønsted plots (log k_N vs. nucleophile pK_a) for the reactions are linear with slope (β) values in the 0.5–0.7 range, in accordance with concerted mechanisms. Comparison of the SA aminolysis of 1 with the same one carried out in water shows that the change of solvent from water to aqueous ethanol destabilizes the zwitterionic tetrahedral intermediate, changing the mechanism from stepwise to concerted. This destabilization is greater than that due to the change from SA amines to quinuclidines. For the phenolysis reactions, the k_N values in aqueous ethanol are smaller than those for the same reactions in water. Considering that the nucleophile is an anion, this result is unexpected because the anion should be more stabilized in the more polar solvent. This result is explained by the facts that the phenoxide reactant has a negative charge that is delocalized in the aromatic ring and the transition state is highly polar. © 2011 Wiley Peiodicals, Inc. Int J Chem Kinet 43: 353–358, 2011     

Neuartige massenspektrometrische Zerfallsreaktionen bei α,ω-disubstituierten Alkanen. 15. Mitteilung über das massenspektrometrische verhalten von stickstoffverbindungen [1]

The mass spectral behaviour of α,ω-disubstituted alkanes and, especially, that of different N-substituted α,ω-diaminoalkanes has been investigated. It was found that the two amino groups which are separated by CH₂-groups can fragment only to a small extent indepently from each other. Yet those fragmentation reactions are predominant in which both functional groups participate. The main reactions of this type are:

• 1 Loss of the N-substituent (R) from the molecular ion, leading to the [M⁺—R]-ions.
• 2 Loss of NH₃, primary or secondary amines from the [M⁺—R]-ion in the case of monodi-, tri- and tetra-substituted diamino compounds respectively.
• 3 α-Cleavage to the non charged nitrogen atom by forming the ions
• 4 S_Ni-type fragmentation.

The mechanisms of these fragmentation patterns were deduced by using D-labelled derivatives, from metastabile peaks and high resolution mass spectrometry. These reactions seem to be typical for disubstituted alkanes.     

Voltammetric study of the oxidation of quercetin and catechin in the presence of cyanide ion

The reaction of electrochemically generated o-benzoquinones from oxidation of quercetin and catechin as Michael acceptors with cyanide ion as nucleophile has been studied using cyclic voltammetry. The reaction mechanism is believed to be EC; including oxidation of catechol moiety of these antioxidants followed by Michael addition of cyanide ion. The observed homogeneous rate constants (k _obs) for reactions were estimated by comparing the experimental voltammetric responses with the digitally simulated results based on the proposed mechanism. The effects of pH and nucleophile concentration on voltammetric behavior and the rate constants of chemical reactions were also described.     

Katalytische Effekte bei den Reaktionen von 2, 4-Dinitrofluorbenzol mit Benzylamin und N-Methylbenzylamin in Benzol. 6. Mitteilung über nucleophile aromatische Substitutionsreaktionen

• (1) The rates of reaction of 2,4-dinitrofluorobenzene with benzylamine and with N-methylbenzylamine have been measured in benzene solution, with and without the addition of pyridine or 1, 4-diaza-bicyclo[2.2.2]octane (DABCO) as catalyst.
• (2) Both reactions are catalyzed by the reacting amine, by pyridine and by 1, 4-diaza-bicyclo[2.2.2]octane.
• (3) Whereas the dependence on base concentration is linear in the case of N-methyl-benzylamine, the rate constants are curvilinearly related to base concentration in the reaction with benzylamine. Steric effects are shown to be responsible for this different behaviour, which is easily understood in terms of the two-step intermediate mechanism (eq.1) for nucleophilic aromatic substitutions.
• (4) Part of the pyridine catalysis has to be attributed to a medium effect, as can be shown directly in the reaction involving benzylamine.
• (5) The sensitivity of both reactions to base catalysis is much greater than that of the reaction of piperidine with 2, 4-dinitrofluorobenzene, but is found to be considerably smaller than in the reaction of p-anisidine with the same substrate, thus suggesting a correlation between the basicity of the reacting amine and the sensitivity of the reaction to base catalysis.

     

Kinetics of Hydride Abstractions from 2‐Arylbenzimidazolines

The rates of the hydride abstractions from the 2‐aryl‐1,3‐dimethyl‐benzimidazolines 1a – f by the benzhydrylium tetrafluoroborates 3a – e were determined photometrically by the stopped‐flow method in acetonitrile at 20 °C. The reactions follow second‐order kinetics, and the corresponding rate constants k₂ obey the linear free energy relationship log k₂(20 °C)= s(N+E), from which the nucleophile‐specific parameters N and s of the 2‐arylbenzimidazolines 1a – c have been derived. With nucleophilicity parameters N around 10, they are among the most reactive neutral C? H hydride donors which have so far been parameterized. The poor correlation between the rates of the hydride transfer reactions and the corresponding hydricities (ΔH⁰) indicates variable intrinsic barriers.     

Bildung und Eigenschaften von Acylphosphanen. VI. Synthese von Alkyl- und Arylbis (trimethylsilyl)- sowie Alkyl und Aryltrimethylsilyphosphanen

Syntheses and properties of Acylphyosphanes. VI. Syntheses of Alkyl- or Arylbis (trimethylsilyl)- and Alkyl- or Aryltrimethylisilyphosphanes Methods for the preparation of alkyl-or arylbis (trimethylsily)-and alkyl-or aryltrimethylsilyphosphanes are described.

• 1 Primary phosphanes used for the syntheses of the title compounds were prepared by known methods (reduction with LiAlH₄).
• 2 Alkyl- and arylbis(trimethylsily) phosphanes are obtained from the corresponding dilithium phosphides (primary phosphanes and methyllithium) and trimethylchlorosilane or from lithiumbis (trimethylsilyl) phosphide and alkyl halides.
• 3 Suitable syntheses for alkyl-or aryltrimethylsilylphosphanes are the reactions of alkyl-and aryllithiumphosphides with trimethylchlorosilane or of alkyl- and arylbis (trimethylsily) phosphanes with methanole. The reaction between phenylbis (trimethylsilyl)phosphane and water was studied in detail and the formation of trimethylsilanole was proved by ¹H-n.m.r. spectroscopy.

The reactions of lithiumtrimethylsilyphosphides and 2,2-dimethylpropionyl chloride yield (2,2- dimethylpropionyl) trimethylsilylphosphanes (keto forms).     

Nucleophilic substitution reactions of diethyl 4‐nitrophenyl phosphate triester: Kinetics and mechanism

The reactions of diethyl 4‐nitrophenyl phosphate ( 1 ) with a series of nucleophiles: phenoxides, secondary alicyclic (SA) amines, and pyridines are subjected to a kinetic study. Under excess of nucleophile, all the reactions obey pseudo‐first‐order kinetics and are first order in the nucleophile. The nucleophilic rate constants (k_N) obtained are pH independent for all the reactions studied. The Brønsted‐type plot (log k_N vs. pK_a nucleophile) obtained for the phenolysis is linear with slope β=0.21; no break was found at pK_a 7.5, consistent with a concerted mechanism. The Brønsted‐type plots for the SA aminolysis and pyridinolysis are linear with slopes β=0.39 and 0.43, respectively, also suggesting concerted processes. The concerted mechanisms for the latter reactions are proposed on the basis of the lack of break in the Brønsted‐type plots and the instability of the hypothetical pentacoordinate intermediates formed in these reactions. © 2011 Wiley Periodicals, Inc. Int J Chem Kinet 43: 708–714, 2011     

Chemie von α-Aminonitrilen. 12. Mitteilung. Sondierungen über thermische Umwandlungen von α-Aminonitrilen

Chemistry of α-Amino Nitriles

1 11. Mitteilung: [1].

. Exploratory Experiments on Thermal Reactions of α-Amino Nitriles The paper extends a previously published report [4] on chemical properties of α-amino nitriles and of members of the C₃H₄N₂ ensemble (Scheme 1) as observed in experiments carried out under non-aqueous conditions. The reactions investigated and the observations made are summarized in some detail in the English footnotes (*) referring to Schemes 1–17 and Fig. 1.     

Electrophilic Reactivities of Azodicarboxylates

The kinetics of the reactions of the azodicarboxylates 1 with the enamines 2 have been studied in CH₃CN at 20 °C. The reactions follow a second‐order rate law and can be described by the linear free energy relationship log k₂(20 °C)=s(N+E) (E=electrophilicity parameter, N=nucleophilicity parameter, and s=nucleophile‐specific slope parameter). With E parameters from ?12.2 to ?8.9, the electrophilic reactivities of 1 turned out to be comparable to those of α,β‐unsaturated iminium ions, amino‐substituted benzhydrylium ions, and ordinary Michael acceptors. While the E parameters of the azodicarboxylates 1 determined in this work also hold for their reactions with triarylphosphines, they cannot be used for estimating rate constants for their reactions with amines. Comparison of experimental and calculated rate constants for cycloadditions and ene reactions of azodicarboxylates provides information on the concertedness of these reactions.     

Über Chalkogenolate. 166. Umsetzungen von Hydrazin mit Kohlenstoffdisulfid 5. Versuche zur Darstellung von Estern der 1,2-Hydrazin-bis(dithiocarbonsäuren) [1]

On Chalcogenolates. 166. Reactions of Hydrazine with Carbon Disulfide. 5. Attempts to Prepare Esters of 1,2-Hydrazine-bis(dithiocarboxylic Acids) Possible reactions to synthesize esters of 1,2-hydrazine-bis(dithiocarboxylic acids) are described:

• 1 The reaction of K₂[S₂C? NH? NH? CS₂] with H₃CI preponderantly forms 2,5-dimethylthio-1,3,4-thiadiazole Ia and a small quantity of bis(methylthio)-ketazine II (formula see ?Inhaltsübersicht”?).
• 2 Hydrazine reacts with Cl? CS? SC₂H₅ to give exclusively compound Ib
• 3 The reaction between K₂[S₂C=N? NH? CS? SCH₃] and H₃CI yields 94% compound Ia and 6% compound II
• 4 K₂[S₂C=N? NH? CS? SCH₃] reacts with C₆H₅? CH₂Br to form a mixture containing 25% dibenzyl sulfide, 15% 2,5-dibenzylthio-1,3,4-thiadiazole I e, and 60% 2-methylthio-5-benzylthio-1,3,4-thiadiazole I d

The compounds Ia , Id and II have been characterized by means of diverse spectroscopic methods. The mechanism of the formation of compounds I has been discussed.