Kinetics and mechanism of the aminolysis of O-ethyl S-aryl dithiocarbonates in acetonitrile

The aminolysis reactions of O-ethyl S-(Z-phenyl) dithiocarbonates (Z=p-CH₃, H, p-Cl, and p-NO₂) with anilines (AN) and N,N-dimethylanilines (DMA) in acetonitrile at 30.0°C are investigated. Relatively small values of β_X (β_nuc,0.4 ca. 0.7) and β_Z (β_lg −0.1 ca. −0.4) for both ANs and DMAs, significantly large k_H/k_D values (1.1 ca. 1.9) involving deuterated anilines, and large negative ρ_XZ values for ANs (−0.56) are interpreted to indicate a concerted mechanism for both ANs and DMAs but with a hydrogen bonded four-center type transition state (TS) for ANs. The relative leaving ability, k(Z=p-NO₂)/k(Z=p-CH₃), is smaller for ANs than for DMAs, especially for a weaker nucleophile (1.9 and 4.7 for AN and DMA, respectively, with X=p-Cl). This suggests that the rate enhancement by the hydrogen-bond formation in the four-center type TS for AN is greater for a weaker nucleofuge (Z=p-CH₃), especially when the nucleophile (X=p-Cl) is weaker. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet: 30: 419–423,1998     

Zum basenkatalysierten H/D-Austausch des acetylenischen Wasserstoffatoms in aromatischen Alkinylverbindungen

On the Base-Catalysed H/D-Exchange of the Acetylenic Hydrogen Atom in Aromatic Alkynyl Compounds H/D-exchange rates for a number of compounds of the general type 1 (X = p-CH₃O, m-CH₃O, p-CF₃, m-CF₃, p-CH₃, p-Cl, H; Z ? O, NH, CH₂) were determined in N-methyl-pyrrolidine (NMP)/D₂O mixtures at 25° (see Table 1). It is shown that the log k values of the H/D-exchange correlate nicely (r = 0.995) with the chemical shift of the acetylenic proton in 1 . Thus, the H/D-exchange rate is given by log k (min^?1) = 2.91 · δ (ppm) - 7.79 for the NMP/D₂O mixture at 25°.     

Influence de la structure sur l'hydrolyse des N-pyrrolylmethylene-2 anilines

Hydrolysis of the imine function of a series of Schiff bases derived from pyrrole-2-carboxaldehyde and substituted anilines (X = H, p-OCH₃, p-OC₂H₅, p-CH₃, p-Cl, p-Br, m-CN, m-NO₂, p-NO₂) was studied in all of the pH ranges. The hydrolysis curves log k_abs (mn^?1) = f(pH) were established in buffered aqueous methanol by polarography or amperometry. The shapes of the curves obtained for pH > 5 indicates that N-pyrrolylmethylene-2 anilines hydrolyse according to the same mechanism as N-benzylidene anilines. The particular stability of these products for pH < 5 permits one to obtain complete hydrolysis curves in acid media. A very good Hammett correlation (k_obs = + 1,73) has been established from the maxima which appear for strong acidity. This stability is interpreted as due to the specific electron-donating effect of the pyrrole nucleus. The influence of the structural parameter X on the morphology of the curves log k_abs = f(pH) and on the hydrolysis mechanism of the imine function is discussed in all of the pH ranges.     

Mass spectra of benzenesulfonylhydrazides

The mass spectrometry of substituted benzenesulfonylhydrazides (X.C₆H₄.SO₂NHNH₂) has been studied, with X = p-CH₃, H, p-CH₃O and p-Br. The intensities of [X? C₆H₄SO₂]⁺ and [X? C₆H₄]⁺ follow the Hammett relationship [In(Z/Z₀) =ρδp⁺] with ρ of 0.375 and 2.37, respectively.     

Kinetics and mechanism of the reaction of para‐chlorophenyl aryl chlorophosphates with anilines in acetonitrile

The kinetics and mechanism of the nucleophilic substitution reactions of p‐chlorophenyl aryl chlorophosphates ( 2 ) with anilines are investigated in acetonitrile at 55°C. Relatively large magnitudes of ρ_X and β_X values are indicative of a large degree of bond making in the TS. Smaller magnitudes of ρ_X (0.20 for X = H) and ρ_XY (?0.30) than those for the corresponding reactions with phenyl aryl chlorophosphates ( 1 ) (ρ_X = 0.54 for X = H and ρ_XY = ?1.31) are interpreted to indicate partial electron loss, or shunt, towards the electron acceptor equatorial ligand (p‐ClC₆H₄O‐) in the bipyramidal pentacoordinated transition state. The inverse secondary kinetic isotope effects (k_H/k_D = 0.64–0.87) involving deuterated aniline (ND₂C₆H₄X) nucleophiles, and small ΔH^? and large negative ΔS^? are obtained. These results are consistent with a concerted nucleophilic substitution mechanism. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 34: 632–637, 2002     

Synthese von Fluoro-λ5-monophosphazenen und Fluoro-1, 3-diaza-2λ5, 4λ5-diphosphetidinen mittels der Staudinger-Reaktion

Synthesis of Fluoro-λ⁵-monophosphazenes and Fluoro-1,3-diaza-2λ⁵,4λ⁵-diphosphetidines by Means of the Staudinger Reaction 35 Tetrafluoro- and 2 difluorodiaza-diphosphetidines as well as 4 difluoro- and 30 monofluoro-λ⁵-monophosphazenes were prepared by the Staudinger reaction between tervalent phosphorus fluorides, R_nPF_3?n (n = 1, 2; R = R₂N, (CH₂)₅N, O(CH₂)₄N, RO, (CH₂O)₂, alkyl, aryl) and phenylazides, X? C₆H₄N₃ (X = H, 4-CH₃, 4-Cl, 4-Br, 4-NO₂, 3-NO₂). PF₃ does not react with phenylazide The influence of substituents on the structure of the reaction products is discussed. Kinetic measurements allowed to determine the constants λ^P_I of the substituents (CH₂)₅N, O(CH₂)₄N and R(C₆H₅)N (R = CH₃, C₂H₅, n-C₄H₉).     

Novel Copolymers of 4-Fluorostyrene. 10. Some Ring-substituted 2-Phenyl-1,1-dicyanoethylenes

Novel copolymers of trisubstituted ethylene monomers, ring-substituted 2-phenyl-1,1-dicyanoethylenes, RC₆H₂CH=C(CN)₂ (where R is 4-C₆H₅O, 2-C₆H₅CH₂O, 3,4-(C₆H₅CH₂O)₂, 2-C₆H₅CH₂O-3-CH₃O, 3-C₆H₅CH₂O-4-CH₃O, 2-Cl-6-NO₂, 4-Cl-3-NO₂, 5-Cl-2-NO₂) and 4-fluorostyrene were prepared at equimolar monomer feed composition by solution copolymerization in the presence of a radical initiator (ABCN) at 70°C. The composition of the copolymers was calculated from nitrogen analysis, and the structures were analyzed by IR, ¹H and ¹³C-NMR. The order of relative reactivity (1/r ₁) for the monomers is 3,4-(C₆H₅CH₂O)₂(31.0) > 2-C₆H₅CH₂O-3-CH₃O (24.8) > 3-C₆H₅CH₂O-4-CH₃O (15.2) > 4-C₆H₅O (3.1) > 4-Cl-3-NO₂ (1.9) > 2-Cl-6-NO₂ (1.6) > 5-Cl-2-NO₂ (1.5) > 2-C₆H₅CH₂O (1.4). High T_g of the copolymers, in comparison with that of poly(4-fluorostyrene) indicates a substantial decrease in chain mobility of the copolymer due to the high dipolar character of the trisubstituted ethylene monomer unit. Decomposition of the copolymers in nitrogen occurred in two steps, first in the 270-400°C range with residue, which then decomposition in 400–800°C range.     

Reactions of palladium(II) cyclometallated benzylideneaniline Schiff's bases. Some relative rates for the synthesis of ortho-substituted carbomethoxy derivatives via CO insertion

The synthesis and characterisation of the complexes [(p-CH₃C₆H₄NCH($\text{C}{}_6\text{H}{}_3\text{Y))P}$d(OAc)]₂ (II) are reported. These complexes react at very different rates with carbon monoxide in methanol to give the ortho-substituted esters, p-CH₃C₆H₄NCHC₆H₃Y - 2R, R = CO₂CH₃, with electron withdrawing Y substituents slowing the reaction. The ¹³C{¹H} data for II show a linear correlation of δ(C(2)) in the 5′-complexes (Y trans to PdC) with δ(C(4)) of monosubstituted benzene compounds. For Y = 5′-NO₂, 4′-NO₂ and 4′-Cl, the bis complex [{p-CH₃C₆H₄NCH(

is formed in a secondary reaction.     

Electron-impact studies. XCIX—negative ion mass spectrometry of the o-NO2?C6H4?X?C6H5 systems. Aryl hydrogen scrambling and proximity effects

We report the first example of aryl hydrogen scrambling occurring in a molecular anion prior to or accompanying fragmentation, i.e. for the reaction [M]^?· → [M ? H₂NO₂.]^? from o-NO₂? C₆H₄? X? C₆H₅ (X = O or S). Proximity effects occur in these spectra when X = CO, NH, O, or S, and certain of these have been substantiated by ²H and ¹⁸O labelling.     

Novel Copolymers of Styrene. 8. Some Ring-Disubstituted Ethyl 2-Cyano-3-Phenyl-2-Propenoates

Electrophilic trisubstituted ethylenes, ring-disubstituted ethyl 2-cyano-3-phenyl-2-propenoates, RPhCH?C(CN)CO₂C₂H₅ (where R is 3-Br-4-CH₃O, 5-Br-2-CH₃O, 3-F-2- CH₃, 3-F-4-CH₃, 4-F-2-CH₃, 4-F-3-CH₃, 5-F-2-CH₃, 2-Cl-5-NO₂, 2-Cl-6-NO₂, 4-Cl-3- NO₂) were prepared and copolymerized with styrene. The monomers were synthesized by the piperidine catalyzed Knoevenagel condensation of ring-disubstituted benzaldehydes and ethyl cyanoacetate, and characterized by CHN analysis, IR, ¹H and ¹³C-NMR. All the ethylenes were copolymerized with styrene (M₁) in solution with radical initiation (ABCN) at 70°C. The composition of the copolymers was calculated from nitrogen analysis, and the structures were analyzed by IR, ¹H and ¹³C-NMR. The order of relative reactivity (1/r ₁) for the monomers is 5-Br-2-CH₃O (1.02) > 4-Cl-3-NO₂ (0.93) > 3-F-4-CH₃ (0.81) > 2-Cl-6-NO₂ (0.77) > 2-Cl-5-NO₂ (0.71) > 3-Br-4-CH₃O (0.66) > 4-F-3-CH₃ (0.60) > 3-F-2-CH₃ (0.38) > 4-F-2-CH₃ (0.31) > 5-F-2-CH₃ (0.16). Relatively high T_g of the copolymers in comparison with that of polystyrene indicates a decrease in chain mobility of the copolymer due to the high dipolar character of the trisubstituted ethylene monomer unit. Decomposition of the copolymers in nitrogen occurred in two steps, first in the 250–500°C range with residue (2–26% wt.), which then decomposed in the 500–800°C range.     

Cationic polymerization with p-substituted benzyl p-hydroxyphenyl methyl sulfonium salts: Effect of substituents and mechanistic aspects of initiation reaction

Various p-substituted benzyl p-hydroxyphenyl methyl sulfonium salts ( 2 ) were synthesized and their initiator activities were evaluated in bulk polymerization of glycidyl phenyl ether (PGE). The order of the activity was found to be 2b (X = CH₃) > 2a (X = H) ≈ 2c (X = Cl) > 2d (X = NO₂), indicating that the introduction of an electron-donating group enhanced the activity. In Hammett's plots, the logarithm of the ratio of the polymerization rates (log k_x/k_H) was correlated with σ⁺_ρ better than with σ_p and a negative ρ⁺ value (-1.18) was obtained. Reaction of 2a with benzyl mercaptan mainly gave dibenzyl sulfide and p-hydroxyphenyl methyl sulfide. The obtained results seemed to demonstrate that the OH group of the aryl group yielded no proton as initiator for the polymerization, whereas the benzyl group caused the polymerization, which was initiated by the corresponding benzyl cation formed by C? S bond cleavage. © 1993 John Wiley & Sons, Inc.     

Ion Pairing and Salt Structure in Organic Salts through Diffusion,Overhauser, DFT and X‐ray Methods

Pulsed gradient spin‐echo (PGSE) diffusion characteristics for a) the new [brucinium][X] salts 6 a – f [ a : X=BF₄^?; b : X=PF₆^?; c : X=MeSO₃^?, d : X=CF₃SO₃^?; e : X=BArF^?; f : X=PtCl₃(C₂H₄)^?], b) 4‐tert‐butyl‐N‐benzyl analogue, 7 and c) the aryl carbocations (p‐R‐C₆H₄)₂CH 9 a (R=CH₃O) and 9 b (R=(CH₃)₂N), (p‐CH₃O‐C₆H₄)_xCPh_3?x⁺ 10 a – c (x=1–3, respectively) and (p‐R‐C₆H₄)₃C⁺ 11 (R=(CH₃)₂N) and 12 (R=H) all in several different solvents, are reported. The solvent dependence suggests strong ion pairing in CDCl₃, intermediate ion pairing in CD₂Cl₂ and little ion pairing in [D₆]acetone. ¹H, ¹⁹F HOESY NMR spectra (HOESY: heteronuclear Overhauser effect spectroscopy) for 6 and 7 reveal a specific approach of the anion with respect to the brucinium cation plus subtle changes, which are related to the anion itself. Further, for carbocations 9 – 12 , (all as BF₄^? salts) based on the NOE results, one finds marked changes in the relative positions of the BF₄^? anion. In these aryl cationic species the anion can be located either a) very close to the carbonium ion carbon b) in an intermediate position or c) proximate to the N or O atom of the p‐substituent and remote from the formally positive C atom. This represents the first example of such a positional dependence of an anion on the structure of the carbocation. DFT calculations support the experimental HOESY results. The solid‐state structures for 6 c and the novel Zeise's salt derivative, [brucinium][PtCl₃(C₂H₄)], 6 f , are reported. Analysis of ¹⁹⁵Pt NMR and other NMR measurements suggest that the η²‐C₂H₄ bonding to the platinum centre in 6 f is very similar to that found in K[PtCl₃(C₂H₄)]. Field dependent T₁ measurements on [brucinium][PtCl₃(C₂H₄)] and K[PtCl₃(C₂H₄)], are reported and suggested to be useful in recognizing aggregation effects.     

Magnetisch nichtäquivalente Methylenprotonen in einigen 2-substituierten 1,3-Benzodioxanen

Zusammenfassung Die magnetische Nichtäquivalenz der Methylenprotonen in 2-R-Benzo-1,3-dioxanen, mit R=C₆H₅,o-ClC₆H₄,m-ClC₆H₄,p-ClC₆H₄,o-BrC₆H₄,m-BrC₆H₄,p-BrC₆H₄,o-NO₂C₆H₄,m-NO₂C₆H₄,p-NO₂C₆H₄,o-CH₃OC₆H₄,m-CH₃OC₆H₄,p-CH₃OC₆H₄, -Naphthyl, -Naphthyl, -Thienyl und -Thienyl, wurde in (CD₃)₂CO, CDCl₃, CCl₄, CS₂ und C₆D₆ untersucht.

---

Magnetic non equivalent methylenic protons of some 2-substituted 1.3-benzodioxanes

The magnetic non equivalence of the methylenic protons in 2-R-1.3-benzodioxanes, with R=C₆H₅,o-ClC₆H₄,m-ClC₆H₄,p-ClC₆H₄,o-BrC₆H₄,m-BrC₆H₄,p-BrC₆H₄,o-NO₂C₆H₄,m-NO₂C₆H₄,p-NO₂C₆H₄,o-CH₃OC₆H₄,m-CH₃OC₆H₄,p-CH₃OC₆H₄, -naphthyl, -naphthyl, -thienyl and -thienyl were studied in (CD₃)₂CO, CDCl₃, CCl₄, CS₂ and C₆D₆.

     

Water Soluble Gold(I)‐diacetyl‐1,3,5‐triaza‐7‐phosphaadamantane‐arylazoimidazole Complexes: Synthesis and Spectroscopic Study

Reaction of [Au(DAPTA)(Cl)] with RaaiR’ in CH2Cl2 medium following ligand addition leads to [Au(DAPTA)(RaaiR’)](Cl) [DAPTA＝diacetyl-1,3,5-triaza-7-phosphaadamantane, RaaiR’＝p-R-C6H4-N＝N- C3H2-NN-1-R’, (1—3), abbreviated as N,N’-chelator, where N(imidazole) and N(azo) represent N and N’, respectively; R＝H (a), Me (b), Cl (c) and R’＝Me (1), CH2CH3 (2), CH2Ph (3)]. The 1H NMR spectral measurements in D2O suggest methylene, CH2, in RaaiEt gives a complex AB type multiplet while in RaaiCH2Ph it shows AB type quartets. 13C NMR spectrum in D2O suggest the molecular skeleton. The 1H-1H COSY spectrum in D2O as well as contour peaks in the 1H-13C HMQC spectrum in D2O assign the solution structure.     

Effets de micelles cationiques sur l'hydrolyse alcaline d'acetanilides a groupe acyle active par des substituants electro-attracteurs

Micellar effects of CTAB upon the alkaline hydrolysis of CF₃-CO-N(CH₃)C₆H₅, CHCl₂-CO-N(CH₃)C₆H₄X and CH₂Cl-CO-N(CH₃)C₆H₄X, (X=p-OCH₃H,p-Cl) are reported. Variations of k_obs, and of kinetic order of the reaction with respect to HO^? ion, are interpreted as an acceleration of HO^?-catalyzed steps, and a decrease of catalysis by water for decomposition of tetrahedral intermediates; these two effects oppose each other in HO^? and H₂O catalyzed steps. Differences between micellar and DMSO effects suggest a very small local concentration of HO^? ions in micelles.     

Thermal reactions of ethane-d6–acetylene and D2–acetylene mixtures behind shock waves

A study of the thermal decomposition of an acetylene–ethane-d₆ mixture indicates that the rate constant for hydrogen abstraction from acetylene by methyl is more than 20 times less than for abstraction from ethane. Isotopic exchange is initiated by a rapid reaction between product D atoms and C₂H₂. A series of experiments involving the reactions of a D₂–acetylene mixture indicated that a molecular exchange process was also occurring, and it was shown that d[C₂HD]/dt = k[D₂]^0.7[C₂H₂]^0.3, effective activation energy = 15.8 kcal/mol. This mechanism made an insignificant contribution to isotope exchange in C₂H₂–C₂D₆ mixtures.     

A dipole moment study of n-trimethyl-ammoniobenzamidates and n-benzoyliminodimethylsulphur(iv)

Analysis of the dipole moments of N-trimethylammoniobenzamidates Me₃N⁺-N^?COC₆H₄X, with X = H, p-F, p-Cl or p-NO₂, and of N-aroyliminodimethylsulphur(IV) Me₂SNCOC₆H₄X (X = H and p-NO₂) shows that, as solutes, these compounds exist in the syn conformation. Models are proposed for N-trimethylammonio-orthochloroben-zamidate and N-orthocyanobenzoyliminodimethylsulphur(IV). The (Me₃N⁺-N^t-) and (SN) dipole moments, and the (N-CO) and (SN-CO) mesomeric moments, are derived and discussed.     

An Efficient and Highly Stereoselective Synthesis of CIS-1-Acetyl-2-Aryl-6,6-Dimethyl-5,7-Dioxo-Spiro-[2,5]-4,8-Octadiones and β,γ-Trans-β-Acetyl-γ-Aryl-Butyrolactones

Acetylmethyltriphenylarsonium bromide 6 in the presence of potassium carbonate and trace water reacted with 2,2-dimethyl-l,3-dioxa-5-substituted-benzylidene-4,6-dione 2 at room temperature to give cyclopropane derivatives cis-l-acetyl-2-aryl-6,6-dimethyl-5,7-dioxospiro-[2,5]-4,8-octadiones 7 (X=p-CH₃, p-Cl, H, p-NO₂) or β,γ-trans-β-acetyl-γ-aryl-γ-butyrolactones 8 (X=p-CH₃O, p-N(CH₃)₂, 3′,4′-OCH₂O-) with good yield and high stereoselectivity.     

Hydrolyse acide du p-nitrophényl-diazométhane dans les mélanges H2O?D2O: analyse des effets isotopiques

The velocity of the hydrogen ion catalysed hydrolysis of p-nitrophenyl-diazo-methane (I) has been measured in H₂O? D₂O mixtures, giving an isotopic α_i = 0.49. The product isotope effect r = 5.1, determined from product analyses, combined with the (overall) solvent isotope effect k_H/k_D = 2.81, yields the primary kinetic isotope effect (k_H/k_D)^I = 3.8, and the secondary kinetic isotope effect (k_H/k_D)^II = 0.75. The CICH₂COOH-catalysed hydrolysis of I in H₂O? D₂O mixtures gave a straight-line plot of k_n/k_H versus the atomic fraction n of deuterium. With four carboxylic acids, as catalysts, values of about 4.3 for the kinetic (overall) isotope effects were observed.     

Kinetics and mechanism of dimerization of arylmercurials

The kinetics of dimerization of arylmercurials XC₆H₄HgCl (X ? H, p-CH₃, m-CH₃, p-Cl, m-OCH₃, m-CO₂C₂H₅, and o-OCH₃) in the presence of [ClRh(CO)₂]₂ was studied in hexamethylphosphoramide (HMPA). The experimental rate law obtained is ?d[ArHgCl]/dt=k[ArHgCl]². The kinetic parameters of these reactions have been reported, and the variation, therein, has been explained on the basis of steric effect of substituents. The apparent activation energy E is linearly proportional to pre-exponential factor lnA. A most plausible mechanism has been proposed on the basis of experimental results. © 1993 John Wiley & Sons, Inc.