Kinetics,mechanism, and products of the reaction of diphenylcarbonyl oxide with carboxylic acids

The kinetics of the reactions of acetic, benzoic, formic, oxalic, malic, tartaric, trifluoroacetic, and hydrochloric acids with diphenylcarbonyl oxide Ph₂COO was studied. The carbonyl oxide Ph₂COO was generated by flash photolysis of diphenyldiazomethane Ph₂CN₂ in solutions of acetonitrile and benzene at 295 K. The apparent rate constants of the reaction range from 4.6·10⁸ for (COOH)₂ in MeCN to 7.5·10⁹ L mol^–1 s^–1 for acetic acid in a benzene solution. The reaction mechanism was proposed, according to which at the first stage the carbonyl oxide is reversibly solvated by the solvent. Then the solvated carbonyl oxide reacts with the acid molecule by the mechanism of insertion at the O—H bond.     

Flash Photolysis of Diphenyldiazomethane in the Presence of Organic Sulfides

The flash photolysis of diphenyldiazomethane in acetonitrile, benzene, and n-decane solutions saturated with air resulted in the formation of diphenyl carbonyl oxide Ph₂COO which decayed in combination reactions. In the presence of organic sulfides, the transfer of the terminal oxygen atom of Ph₂COO to the sulfur atom was observed. The kinetics of this reaction was studied. The absolute rate constants (k ₆, dm³ mol^–1 s^–1) of the reactions of Ph₂COO with sulfides at 295 K (acetonitrile as a solvent) varied from 4.1 × 10² (Me₂S) to 8.1 × 10⁴ (Ph₂S). The solvent effect on the reaction kinetics and product composition was studied. The mechanism of the process was discussed.     

Rate Constants for the Reaction of Diphenyl Carbonyl Oxide with Phenols

The kinetics of the reaction of diphenyl carbonyl oxide Ph₂COO with o- and p-substituted phenols is studied by pulse photolysis and high-speed spectrophotometry. The rate constant strongly depends on the phenol structure and ranges from 1.3 × 10³ for ionol to 2.1 × 10⁸ l mol^–1 s^–1 for o-aminolphenol. A U-shaped curve illustrating how the logarithm of the rate constant changes with a change in the Hammett constants (⁰) of the substituents in the aromatic ring is found for the studied compounds. Possible pathways for the reaction of Ph₂COO with phenols are discussed.     

Reaction of the N,N-dimethylamide and methyl ester of 3-phenyl-3-chloro-2-ketopropionic acid with triphenylphosphine

Conclusions The dimethylamide of 3-phenyl-3-chloro-2-ketopropionic acid reacts with Ph₃P to give -(N,N-dimethyloxamoyl)benzyltriphenylphosphonium chloride. In the presence of methanol, this reaction gives dimethyl(phenylpyruvoyl)amide and Ph₃PO.2. The methyl ester of 3-phenyl-3-chloro-2-ketopropionic acid reacts with Ph₃P to give methoxycarbonylstyryloxytriphenylphosphonium chloride, which, upon heating in benzene at reflux, gives methyl -chlorocinnamate and Ph₃PO.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1395–1396, June, 1989.     

Reaction of triphenylantimony and triphenylbismuth withtert-butyl peracetate

Triphenylantimony and triphenylbismuth diacetates, Ph₃M(OAc)₂ (M = Sb, Bi), were obtained in 50–94 % yields by the reaction of triphenylantimony and triphenylbismuth withtert-butyl peracetate in the presence of acetic acid or acetic anhydride (molar ratio 1 1 1) in toluene.tert-Butyl peracetate oxidizes Ph₃M into alkoxides, Ph₃M(OAc)OBu^t, which at the instant of formation are acylated with acetic acid or acetic anhydride to give the corresponding derivatives, Ph₃M(OAc)₂.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 964–967, May, 1995.This study was financially supported by the Russian Foundation for Basic Research (Grant 94-03-08846).     

The effects of cyclodextrin inclusion of the ferrocenemonocarboxylate anion on the kinetics of its oxidation by bis(pyridine-2,6-dicarboxylato)cobaltate(III) in aqueous solution

The effects of -, -, dm-(heptakis(2,6-di-O-methyl)--) and -cyclodextrins (CD) on the kinetics of the electron-transfer reaction of the ferrocenemonocarboxylate anion (FCA^–) with bis(pyridine-2,6-dicarboxylato)cobaltate(III) have been investigated in aqueous solution (0.20 M Na₂HPO₄, pH 9.2) at 25.0°C. Substantial decreases in the rate constants for the electron-transfer reactions were observed upon cyclodextrin inclusion of the reductant, due to an increase in the FCA^0/– reduction potential and to the insulation of the reductant from oxidant. The inclusion stability constants for {FCA·CD}^– were evaluated from the¹H NMR and kinetic data, and the order of the stability constants was found to be -CDdm-CD-CD>-CD.     

The Reactivity of Diphenyl Carbonyl Oxide in Reactions with Alcohols

The reactivities of ten alcohols in the reactions with diphenyl carbonyl oxide Ph₂COO is characterized by the ratio k ^OH ₃₃ /k ₃₁, where k ^OH ₃₃ and k ₃₁are the rate constants of Ph₂COO reactions with an alcohol and diphenyldiazomethane PH₂CN₂, respectively. The values of k ^OH ₃₃ /k ₃₁range between 0.6 × 10^–2for MeOH to 6.0 for iso-PrOH at 70°C in acetonitrile. The donation of electron density to the alcohol hydroxyl group favors the attack of Ph₂COO; that is, Ph₂COO reacts as an electrophile.     

Photochemical reactions of [(η 5-C5H5)Mn(CO)3] with Ph2P(S)(CH2) n P(S)Ph2 [n=1, dppm(S)2; 2, dppe(S)2; 3, dppp(S)2]

Six new complexes, Mn(CO)( ⁵-C₅H₅){Ph₂P(S)(CH₂) _n P(S)Ph₂}] (1a–3a) [(1a), n=1; (2a), n=2; (3a), n=3] and [Mn₂(CO)₄( ⁵-C₅H₅)₂(cis--Ph₂P(S)(CH₂) _n P(S)Ph₂)] (1b–3b) [(1b), n=1; (2b), n=2; (3b), n=3] have been synthesized by the photochemical reaction of [( ⁵-C₅H₅)Mn(CO)₃] with Ph₂P(S)(CH₂) _n P(S)Ph₂ [n=1, dppm(S)₂; 2, dppe(S)₂; 3, dppp(S)₂]. The complexes have been characterized by elemental analysis, mass spectroscopy, f.t.-i.r. and ³¹P–[¹H]-n.m.r. spectroscopy. The spectroscopic studies reveal that coordination of the ligand iscis-chelate bidentate in [Mn(CO)( ⁵-C₅H₅){Ph₂P(S)(CH₂) _n P(S)Ph₂}] (1a–3a) and cis-bridging bidentate between two metals in [Mn₂(CO)₄( ⁵-C₅H₅)₂(cis--Ph₂P(S)(CH₂) _n P(S)Ph₂)] (1b–3b).     

Kinetics of Anodic Dissolution of Gold in Alkali–Cyanide Solutions: Effect of Lead Ions

Effective order of the gold dissolution reaction by cyanide ions, p, transfer coefficient , and exchange current i ₀are measured at constant coverages of the gold surface by lead adatoms, . Constancy of is ensured by maintaining the time period t, during which the electrode is in contact with solution after the renewal of its surface and before taking measurements, constant. Solutions under study contain (0.5–2) × 10^–5M lead acetate, 0.05–0.2 M KCN, 0.1 M KOH, and 0.01 M KAu(CN)₂. With increasing t, quantities p, , and i ₀increase from, respectively, 0.17, 0.1, and 10^–5A dm^–2(in 0.05 M KCN) to p 1.2, 0.45, and i ₀ 10^–4A dm^–2. The increase in psuggests that the limiting stage alters in the presence of lead adatoms: in addition to adsorbed cyanide ions, as is the case with pure alkali–cyanide solutions, it involves cyanide ions located outside the adsorption layer. A feasible mechanism for the acceleration of gold dissolution by lead adatoms is offered.     

Phosphonioethylation of phenylhydrazine and hydroxylamine and selected properties of the resulting derivatives

The reactions of phenylhydrazine and hydroxylamine with (-X-ethyl)triphenylphosphonium salts (X = Ph, Ph₃P⁺Br^–) (1, 2) afforded the corresponding -N-ethyl-substituted triphenylphosphonium salts (3, 4). The reaction of triphenyl(2-phenylhydrazinoethyl)phosphonium bromide 3with an aqueous solution of NaOH in benzene afforded a statistical mixture of the nisand transisomers of 2-(diphenylphosphoryl)acetaldehyde phenylhydrazone. (2-Hydroxyaminoethyl)triphenylphosphonium bromide reacted with sodium methoxide to give O-phosphobetaine.     

Nitrogen Trichloride Decomposition in the Presence of Molecular Hydrogen: I. Promotion of Nitrogen Trichloride Decomposition by Molecular Hydrogen Additives Near the Lower Self-Ignition Limit

The promotion of the branched-chain decomposition of nitrogen trichloride by molecular hydrogen additives at room temperature and 20 torr manifests itself in a decrease in the induction period and the acceleration of reactant consumption with an increase in the hydrogen concentration in the NCl₃+ H₂+ He mixtures. The emission spectrum of the H₂+ NCl₃flame contains the intense bands of NCl (b ¹⁺– X ^3–, = 1 – 0, = 0 – 1, and = 0 – 0, where is the vibrational quantum number) and the bands of a hydrogen-free compound. The latter bands can be assigned to electronically excited NCl ₂radicals formed in the H + NCl₃reaction. The calculations restrict the number of elementary reactions favoring promotion. The promotion effect in the system studied should be due to the side reaction of linear branching. The occurrence of the H + NCl₃reaction via two pathways (NHCl + 2Cl and NCl ₂+ HCl) ensures the qualitative agreement between the experimental data and calculation.     

Kinetics and mechanism of chromium(VI) oxidation of L-methionine

The kinetics and mechanism of chromium(VI) oxidation of L-methionine in acidic medium have been studied spectrophotometrically. The reaction proceeds via the formation of a transient intermediate (_max = 410–420 nm) which decomposes by a proton catalyzed pathway. The rate law is:

The hydrolysis and fluoride complexation behavior of Fe(III) at 25°C and 0.68 molal ionic strength

Fe(III) hydrolysis and fluoride complexation behavior was examined in 0.68 molal sodium perchlorate at 25°C. Our assessment of the complexation of Fe(III) by fluoride ions produced the following results: log_F1 = 5.15₅, log_F2 = 9.10₇, log_F3 = 11.96, log_F4 = 13.7₅, where log_Fn = 5.15₅=[FeF _n ^(3-n)+ ][Fe³⁺]^–1[F^–]^–n. The stepwise fluoride complexation constants,FK _n+1, obtained in our work (where log_F K _n+1 =log_Fn) indicate that K _n+1/K _n =0.072±0.01. Formation constants for equilibria, Fe³⁺+nH₂OFe(OH) _n ^(3–n)+ +nH⁺, expressed in the form _n ^* [Fe(OH) _n ^(3-n)+ ][H⁺]ⁿ ,[Fe ³⁺]^-1, were estimated as ₁ ^* = –2.754, and ₂ ^* –7. Our study indicates that the results of previous hydrolysis investigations include very large overestimates of Fe(OH) ₂ ⁺ formation constants.     

Chromium(VI), chromium(V) and chromium(IV) oxidation of 12-tungstocobaltate(II)

The reaction between Cr^VI and 12-tungstocobaltate(II) was carried out in 2.0 mol dm^–3 HCl and followed a simple second order rate law. The reaction was catalysed by hydrogen ion due to the formation of active H₂CrO₄ and was inhibited by chloride ion as, in its presence, conversion of the active species into inactive chlorochromate occurs. Chromium(V) and chromium(IV) were generated in situ by the use of Cr^VI—V^IV or Cr^VI—2-ethyl-2-hydroxybutyric acid and Cr^VI—i-PrOH reactions respectively, and the oxidation of 12-tungstocobaltate(II) by these atypical oxidation states, was also studied. The rate constants for the oxidation of 12-tungstocobaltate(II) by Cr^VI, Cr^V and Cr^IV were found to be in the ratio 1:1.2:5.2 respectively. The ionic strength did not affect the reaction, while decrease in the solvent polarity increased the rate of the reaction. The activation parameters were also determined and the values H , G and S were found to be 52.4 ± 6 kJ mol^–1, 100.8 ± 7 kJ mol^–1, –151.7 ± 10 J K^–1 mol^–1 respectively, supporting the mechanism proposed.     

Ab initio Study of β-lactam antibiotics

Ab initio SCF-MO-LCAO calculations have been performed with a 7s3p/3s GTO basis set for the CH₃O--lactam + OH^– reaction which is related to the mode of action of -lactam antibiotics. The comparison of the present results with the previous ones for -lactam + OH^– and 3-cephem + OH^– shows that the CH₃O substitution has a negligible effect on the amidic bond breaking of -lactam, so that this group probably influences other steps of the antibiotic reactivity of cephaloporins.     

Reactivity of the carbocation generated in the photolysis of 1,2,2,4,6-pentamethyl-1,2-dihydroquinoline toward azide ion

The reaction of the azide ion with the carbocation generated in the photolysis of 1,2,2,4,6-pentamethyl-1,2-dihydroquinoline in methanol was studied by pulse (conventional and laser) and steady-state photolysis techniques. The adduct of the azide ion was characterized by ¹H NMR spectrum. Experimental results were interpreted taking into account a competition between the addition of methanol and azide ion to the carbocation. The rate constants for the reaction of the azide ion with the carbocation (k _Az) were measured at 2—48 °C in a wide range of [N₃ ^–]₀ concentrations from 2·10^–7 to 0.1 mol L^–1 at different ionic strengths () of the solution. The resulting k _Az values are more than an order of magnitude lower than those for diffusional-controlled reactions and vary from 3.2·10⁸ ( = 0) to 4.5·10⁶ L mol^–1 s^–1 ( = 0.8 mol L^–1) in the presence of NaClO₄ (18 °C). The activation energy of addition of the azide ion to the carbocation is 21 kJ mol^–1, which is by 12 kJ mol^–1 lower than the activation energy of the reaction of the carbocation with methanol. The features of the reaction under study are discussed from the viewpoint of the structures of carbocations generated in the photolysis of dihydroquinolines.     

Kinetics and mechanism of the reaction betweencis-dichlorobisbipyridineruthenium(II) and nitric acid in water-methanol solutions

Summary The kinetics of the reaction betweencis-dichlorobisbipyridineruthenium(II) and nitric acid have been investigated spectrophotometrically in the 25°–40° range in the presence of 0.03 to 0.2 mol dm^–3 HNO₃. The reaction proceeds with the stepwise formation of monoaqua and diaqua products. Only the formation of the monoaqua intermediate was followed as this species could not be obtained in a pure state. Aquation proceeds through a dissociative process. The second order rate constants are 11.8 (25°), 17.5 (30°); 30.0 (35°) l mol^–1 s^–1. Activation parameters are H 52±3 kJ mol^–1; S–108±8 JK^–1 mol^–1.     

Kinetics and mechanism of the reaction between bis 4-(2-pyridylazo) resorcinol ferrate(II) complex and cyanide ion

Summary Cyanide ion reacts with [Fe(Par)₂]^2–,i.e. Par=4-(2-pyridylazo)resorcinol to form a 113 mixed cyanocomplex. The reaction has been studied spectrophotometrically at 720 nm _max, pH=11.5±0.02, and I=0.1 M (NaClO₄) at 25±0.1°C. The order with respect to cyanide varies from one to two at high and low cyanide concentrations respectively. The rate constants for respective reactions are k₁=(6.1±0.3)×10^–2 M^–1 s^–1, k₂=(12.6±1.0) M^–2 s^–1. The reverse reaction does not occur at a measurable rate even in presence of a large excess of Par. These observations suggest that [Fe(Par)₂]^2– forms a mixed [FePar(CN)₃]^3– complex in presence of an excess of cyanide ion. The activation parameters for the reaction have been calculated and used to support a three step mechanism consistent with these results. The effect of ionic strength tends further support to the mechanism.     

A study by pulse radiolysis of the radiation-chemical transformation of aqueous solutions of hydrazine in the presence of oxygen

It is shown by pulse radiolysis that in aqueous solutions of hydrazine containing oxygen the radical N₂H₃ reduces oxygen to O₂ ^– at pH > 7 (k 3·10⁹ dm³· mole^–1·sec^–1), while this reaction does not occur for the protonated form N₂H₄ ⁺ at pH < 7 (k, 5·10⁶ dm³·mole^–1·sec^–1). The rate constants for the disappearance of O₂ ^– have been determined in the pH range from 4 to 12. Rate constants have been calculated for the reaction of O^– with N₂H₄ [k=(1.6 ±0.2)·10⁹ dm³·mole^–1·sec^–1] and of O₃with N₂H₄ [k=(1.2 ±0.2)·10⁶ dm³· mole^–1·sec^–1].Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 341–345, February, 1991.     

Kinetics and mechanism of distribution of Am(III) and Eu(III) between thenoyltrifluoroacetone-triphenylarsine oxide mixture in chloroform and aqueous nitrate medium

The kinetics of distribution of Am(III) and Eu(III) between thenoyltrifluoroacetone (HTTA) and triphenylarsine oxide (Ph₃AsO) mixture in chloroform and aqueous nitrate medium has been investigated using a stirred Lewis cell at ionic strength of 0.1M. The effect of the concentration of HTTA, Ph₃AsO, H⁺ and NO ₃ ^– on the rate of distribution of Am(III) and Eu(III) was studied. The results were interpreted by reaction mechanisms where the rate-determining steps are the parallel reactions of Am(OH)²⁺ or Eu(OH)²⁺ with one HTTA molecule and one Ph₃AsO molecule in the aqueous medium. The values at 25 °C of the rate constantk _HLL (HL=HTTA andL=Ph₃AsO) are 1.6±0.3·10⁶M^–2·s^–1 and 2.3±±0.3·10⁸M^–2·s^–1 for Am(III) and Eu(III), respectively.