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Alkaline hydrolysis rates coefficients for the series of methyl 3-(7-substituted-1-naphthyl) propynoate was calculated in 70%v/v dimethylsulphoxide-water at various temperatures (25,30,40, and 50̊ C). The pKa values of 3-(7-substituted-1-naphthyl) propynoic acid and (E)- 3-(7-substituted-1-naphthyl) propenoic acid calculated in 80%w/w 2-methoxyethanol-water at room temperature (25.0̊ C). logk2 of esterification rate coefficients for 3-(7-substituted-1-naphthyl) propynioc acid and (E)-3(7-substituted-1-naphthyl) propenioc acid with DDM have been measured at 30.0̊ C. Reversed substituent dipolar effects were found in the ionization reaction. In the esterification reaction with DDM the result show similar but reduced substituted effects. Rate retardations was found in the alkaline hydrolysis. It could be result from steric effect or reversal of substituent dipolar effect with a combination of steric effect.

N-heterocyclic carbenes (NHCs), and macrocyclic NHCs in particular, have been applied successfully to the stabilization of high oxidation states on transition metal complexes. This access to high oxidation states has enabled their application in oxidative catalysis including aziridination and epoxidation. However, the number of macrocyclic tetra-NHC ligands is still limited, especially those featuring anionic charge, which is beneficial in this regard. In this manuscript, we report a facile and high yielding synthesis for only the second example of such a dianionic, macrocyclic tetra-NHC ligand. This 16-atom macrocycle has the ring size and charge of a porphyrin but with the increased electron donation of NHCs. Its Fe(II) and Fe(III) complexes are reported, and their reactivities for ligand addition and oxidation were tested. Multiple oxidation catalysis reactions were tested with both the Fe(II) and Fe(III) complexes with reagents such as trimethylamine-N-oxide, oxygen (from air), diazodiphenylmethane, a...

The kinetics of the reaction of benzoic, 2-methylbenzoic, phenylacetic, cyclohex-1-enecarboxylic, 2-methylcyclohex-1-enecarboxylic, and cyclohex-1-eneacetic acids with diazodiphenylmethane was studied at 30, 33, 37, 40, and 45°C in a set of 12 protic and aprotic solvents. The reactions were found to follow the second-order kinetics. The activation energy as well as the activation parameters, such as the standard entropy, the standard enthalpy, and the standard Gibbs energy of the activation, was calculated from the second-order rate constants. The solvent and structural effects on the activation energy and the standard Gibbs energy of activation, for each examined compound, were analyzed. The results of Kamlet–Taft multiple correlation analysis show that the specific solvent–solute interactions play a dominant role in the governing of the reaction. The signs of the equation coefficients support the proposed reaction mechanism.

The rate constants for the reactions of diazodiphenylmethane (DDM) with 2-substituted nicotinic acids in nine aprotic solvents at 30?C were determined. The obtained second order rate constants in aprotic solvents were correlated using the Kamlet?Taft solvatochromic equation in the complete form: log k = log k0 + s?* + a??+ b?. The correlations of the kinetic data were realized by means of multiple linear regression analysis. The obtained results were analyzed in terms of the initial and the transition state of the reaction and compared with previously determined kinetic data for nicotinic acid. The signs of the equation coefficients (s, a and b) are in agreement with the reaction mechanism and the influence of the solvent on the reaction rate is discussed based on the correlation results. The mode of the transmission of the substituent effect is discussed in light of the contribution of solute?solvent interaction to the reactivity of the acid. The substituent effect was additionally analyzed by the Hammett equation, log k = p??+ log k0.

The rate constants for the reaction of 2-substituted cyclohex-1-eneacetic and 2-substituted phenylacetic acids with diazodiphenylmethane were determined in various aprotic solvents at 30°C. To explain the kinetic results through solvent effects, the second-order rate constants of the examined acids were correlated using the Kamlet–Taft solvatochromic equation. The correlations of the kinetic data were carried out by means of multiple linear regression analysis, and the solvent effects on the reaction rates were analyzed in terms of initial and transition state contributions. The opposite signs of the electrophilic and the nucleophilic parameters are in agreement with the well-known mechanism of the reaction of carboxylic acids with diazodiphenylmethane. The quantitative relationship between the molecular structure and the chemical reactivity is discussed, as well as the effect of the molecular geometry on the reactivity of the examined compounds. © 2009 Wiley Periodicals, Inc. Int J Chem Kinet 41: 613–622, 2009

Solvent effects on the reactivity of cycloalkenecarboxylic, cycloalkeneacetic, 2-substituted cyclohex-1-enecarboxylic, 2-substituted benzoic, 2-substituted cyclohex-1-eneacetic, 2-substituted phenylacetic, 2-phenylcyclohex-1-enecarboxylic, 2-phenylbenzoic and 2-phenylacrylic acids with diazodiphenylmethane (DDM) were investigated. In order to explain the kinetic results through solvent effects, the second-order rate constants for the reaction of the examined acids with DDM were correlated using the Kamlet-Taft solvatochromic equation. The correlations of the kinetic data were realized by means of multiple linear regression analysis and the solvent effects on the reaction rates were analyzed in terms of the contributions of the initial and the transition state. The signs of the equation coefficients support the proposed mechanism. Solvation models for all the investigated acids are suggested. The quantitative relationship between the molecular structure and the chemical reactivity is also discussed.

Diazodiphenylmethane (DDM) undergoes cycloadditions to 1-substituted buta-1,3-dienes exclusively at the C(3)C(4) bond. At room temperature, the N2 loss from the initially formed 4,5-dihydro-3H-pyrazoles 2 is faster than the cycloaddition and furnishes the vinylcyclopropane derivatives 7 and 9 with structural retention at the C(1)C(2) bond. 2-Substituted butadienes react with DDM at the C(3)C(4) bond to give 12; isoprene, however, affords 3,4/1,2 products in the ratio of 86 : 14. DDM is a nucleophilic 1,3-dipole: 1-Cyanobutadiene reacts 400 times faster than 1-methoxybuta-1,3-diene (DMF, 40°). The log k2 for the additions to six 1-substituted butadienes show a linear correlation with σp (Hammett) and ϱ=+2.9; the log k2 of five 2-substituted butadienes are linearly related to Taft's σI (ϱ=+1.7). The structures of the vinylcyclopropanes 7, 9, and 12 are established by NMR spectra and oxidation. A cyclopropyl carbinyl cation is made responsible for the isomerization of 12, R=Ph, Me, by acetic acid to 4-substituted 1,1-diphenylpenta-1,3-dienes 25 and 29; TsOH at 200° converts 25 further to 9,10-dihydro-9-methyl-10-phenyl-9,10-ethanoanthracene (27). Thermal rearrangement of 7, 9, and 12 at 200–300° produces the 3- or 1-substituted 4,4-diphenylcyclopentenes 30 and 31. These give the same mass spectra as the vinylcyclopropanes, and an open-chain distonic radical cation is suggested as common intermediate. Besides spectroscopic evidence for the cyclopentene structures, hydrogenation and epoxidation are described; NMR data support the trans-attack by perbenzoic acid.

The rate constants for the reaction of 2-methyl-cyclohex-1-enylcarboxylic, 2-phenylcyclohex-1-enylcarboxylic, and 2-methylbenzoic and 2-phenylbenzoic acids with diazodiphenyl-methane were determined in 14 various solvents at 30 ◦ C. To explain the ki- netic results through solvent effects, the second-order rate constants of the examined acids were correlated using the Kamlet-Taft solvatochromic equation. The correlations of the ki- netic data were carried out by means of multiple linear regression analysis, and the solvent effects on the reaction rates were analyzed in terms of initial and transition state contributions. The quantitative relationship between the molecular structure and the chemical reactivity has been discussed, as well as the effect of geometry on the reactivity of the examined molecules. The geometric data of all the examined compounds corresponding to the energy minima in solvent, simulated as dielectric continuum, obtained using semiempirical MNDO-PM3 energy calculations. C

Acids are the most common industrial catalysts but have the disadvantage of requiring post-reaction neutralization and salt disposal. We show the catalytic use of self-neutralizing acids. Carbon dioxide interacts with water and amines to form carbonic acid and carbamates. A similar interaction occurs with alcohols to form alkylcarbonic acids. All three solvent systems provide in situ acid formation for catalysis which can be easily neutralized by removal of carbon dioxide. However, water has poor organic solubility and amines form salts so only alkylcarbonic acids combine good organic solubility with simple neutralization via depressurization. The use of in situ acid also completely eliminates the solid salt wastes associated with many acid processes. To elucidate how to implement these systems in place of a standard acid system we compare the reaction rates of several alkylcarbonic acids with diazodiphenylmethane (DDM). We report also the effect of CO2 pressure on reaction rate of DDM as well as measure the dielectric constant of these systems. Finally, a Hammett plot is used to identify the dominant step in alkylcarbonic acid catalysis.

The rate constants for the reaction of different cycloalkenylcarboxylic, cycloalkenylacetic acids, and phenylacetic acid with diazodiphenylmethane were determined in 12 aprotic solvents at 30°C. In order to explain the kinetic results through solvent effects, the second-order rate constant of the examined acids was correlated using the Kamlet–Taft solvatochromic equation. The correlations of the kinetic data were carried out by means of multiple linear regression analysis, and the solvent effects on the reaction rates were analyzed in terms of initial and transition state contributions. The opposite signs of the electrophilic and the nucleophilic parameters are in agreement with the well-known mechanism of the reaction of carboxylic acids with diazodiphenylmethane. The quantitative relationship between the molecular structure and the chemical reactivity is also discussed. © 2005 Wiley Periodicals, Inc. Int J Chem Kinet 37: 361–367, 2005

Rate constants for the reaction of diazodiphenylmethane with isomeric pyridine carboxylic acids were determined in chosen protic and aprotic solvents at 30 °C, using the well known UV spectrophotometric method. The values of the rate constants of the investigated acids in protic solvents were higher than those in aprotic solvents. The second order rate constants were correlated with solvent parameters using the Kamlet-Taft solvatochromic equation in the form: logk = logk0 + s¶*+ aα + bβ. The correlation of the obtained kinetic data were performed by means of multiple linear regression analysis taking appropriate solvent parameters. The signs of the equation coefficients were in agreement with the postulated reaction mechanism. The mode of the influence of the solvent on the reaction rate in all the investigated acids are discussed on the basis of the correlation results. Konstante brzina reakcije između diazodifenilmetana i izomernih piridin-karbonskih kiselina su određene u odabranim protičnim i aprotičnim rastvaračima na 30 °C, korišćenjem poznate UV spektrofotometrijske metode. Vrednosti konstanti brzina ispitivane reakcije u protičnim rastvaračima imaju veće vrednosti u poređenju sa vrednostima konstanti u aprotičnim rastvaračima. Konstante brzina su korelisane sa parametrima rastvarača korišćenjem Kamlet–Taft jednačine oblika: logk = logk0 + s¶*+ aα + bβ. Korelacije dobijenih kinetičkih rezultata sa odgovarajućim parametrima rastvarača su izvedene metodom višestruke linearne regresione analize. Znak koeficijenata u dobijenim korelacijama je u saglasnosti sa pretpostavLJenim reakcionim mehanizmom. Uticaj rastvarača na vrednosti reakcionih konstanti je diskutovan na osnovu dobijenih korelacionih rezultata.

The rate constants for the reaction of three isomeric pyridine mono-carbo- cylic acid N-oxides with diazodiphenylmethane were determined at 30 oC in thirty two protic and aprotic solvents by the well known UV spectrophotometric method. The rate constants are generally higher than for pyridine mono-carboxylic acids in a similar range of solvents, except for picolinic acid N-oxide, and also higher in protic than in aprotic solvents. The determined rate constants were correlated with solvent parameters using the Kamlet-Taft solvatochromic equation by means of multiple re- gression analysis. The sign of the equation coefficients were in agreement with the postulated reaction mechanism. The mode of the influences of the solvent is discus- sed on the basis of the correlation coefficients, taking into account the specific struc- tures of the pyridine mono-carboxylic acid N-oxides.

The paper reports the tin(II) chloride catalyzed reactions of diazodiphenylmethane with the cis- and trans-1,2-cyclohexanediols and R,S-1,2-propanediol in 1,2-dimethoxyethane and the identification of the monodiphenylmethyl ethers formed. The catalyst is shown to work for both the cis- and trans-cyclohexanediols, but the catalyst is unstable at high reagent concentrations, especially in the case of the trans-isomer. Conditions where catalyst destruction is negligible show that the rate of the reaction with the trans-isomer is larger than with the cis-isomer. The reactions with 1,2-propanediol show small difference between the selectivity for the primary and secondary hydroxyl groups. This is in contrast with the tin(II) chloride catalyzed reactions of diazomethane and diazophenylmethane in methanol with carbohydrates, glycerol and ribonucleosides, where the primary hydroxyl group does not react.

The molecular geometries and the frontier orbital energies of three diazo compounds [diazodiphenylmethane (2), the α-silyl-α-diazoketone 3 and the isomeric 2-siloxy-1-diazoalkene 4], 10 heterophospholes with a PC bond and two heterophospholes with a PN bond were obtained from DFT calculations at the B3LYP/6–311+G** level. The 1,3-dipolar cycloaddition reactivity of diazo compounds 2–4 toward the heterophospholes is discussed on the basis of FMO theory. It is concluded that in most cases, the dominant frontier orbital interaction is between the HOMO(diazo) and the LUMO(heterophosphole), and that the reactivity should decrease in the order­2 >4 >3. The 1,2-thiaphosphole 9 and 1,3-azaphosphole 10 have HOMOs of high energy and, therefore, the HOMO(heterophosphole)–LUMO(diazo) interaction is also important. Among the different types of heterophos-pholes considered here, the 2-acyl-1,2,3-diazaphosphole 5, 3H-1,2,3,4-triazaphosphole 8, 1,2-thiaphosphole 9 and 1,3,4-thiazaphosphole 14 are predicted to have the highest dipolarophilic reactivities. These conclusions are in qualitative agreement with available experimental results. Copyright © 2003 John Wiley & Sons, Ltd.

Novel reactions of various cis-(LC)Mn(CO)4 complexes (LC = a three-electron chelating ligand) with diazodiphenylmethane and 9-diazofluorene allowed the synthesis of a new type of oligomeric polynuc...

A kinetic study of the tin(II) chloride catalyzed reaction of diazodiphenylmethane with ethylene glycol in dimethoxyethane is reported. The preparation and characterization of ethylene glycol monodiphenylmethyl ether, the main product from this reaction, is also reported as well as the preparation of the two diphenylmethyl monoethers of methyl 4,6-O-benzylidene-alpha-D-glucopyranoside. An unexpected relationship between the concentration of ethylene glycol and the pseudo first-order rate constant, k', was observed in these reactions. For low concentrations of ethylene glycol (below 0.06 M), k' increases with increasing concentration of the diol. This trend is reversed for high concentrations of ethylene glycol (from about 0.06 to about 0.2 M). The apparent rate constant was also inversely related to the initial concentration of diazodiphenylmethane for the concentrations investigated. These results make the previously proposed involvement of a 1,3,2-dioxastannolane intermediate very unlikely [Petursson, S.; Webber, J.M. Carbohydr. Res. 1982, 103, 41-52]. The results suggest that more likely intermediates for these reactions involve tin(II) chloride complexes in a dynamic equilibrium with the diol.

Rate constants have been determined for the reactions of diazodiphenylmethane with a number of 6-substituted nicotinic acids and p-substituted benzoic acids in twelve alcohols. Acomparative study was used to evaluate and compare the Hammett r values and solvent effects. Multiple correlations of the log k values for the reactions of 6-substituted nicotinic acids and p-substituted benzoic acids in 12 alcohols with groups of suitable solvent parameters are very successful. The transmission of electronic effects through the pyridine ring system in compared with that in benzene.

Acid-catalyzed decomposition of diazodiphenylmethane (DDM) has been studied in DMSO containing varying amounts of water. The reaction was found to be first-order in DDM and first-order in acid. The Brønsted plot for a series of carboxylic acids is curved with the H+ point falling below the curve defined by the carboxylic acids. In near-anhydrous DMSO, kinetic hydrogen isotope effects (KIEs) are 1.7 and 1.6 for acetic acid and chloroacetic acid, respectively. The chloroacetic acid KIE increases with increasing water concentration, rising to 2.9 at 3.6 M water. As a function of [H2O], kHA for chloroacetic acid shows a sharply defined minimum occurring at 1 M water. This behavior and the water effect on KIE suggest that the carboxylic acid-catalyzed reactions in near-anhydrous DMSO do not use the ASE-2 mechanism attributed to the reaction of DDM in hydroxylic solvents. A mechanism, leading to an azoalkane, is suggested. Either directly or indirectly, this may lead to diphenylcarbene, which would account for the observed products: benzophenone, benzhydrol, and benzhydryl esters. For the H+ catalyzed decomposition of DDM in near-anhydrous DMSO, benzophenone is not found among the products, and we suggest that this reaction does not undergo a change in mechanism and continues to use the ASE-2 mechanism.Key words: decomposition mechanism, kinetics, solvent effect, reaction with carboxylic acids.

The rate coefficients for the esterification of a series of oxocarboxylic acids with diazodiphenylmethane have been determined in ethanol or 2-methoxyethanol at 30.0 °C. These and the rates of reaction with model compounds have been used to estimate the equilibrium constants for ring-chain tautomerism for the oxocarboxylic acids.

The rate constants for the reactions of diazodiphenylmethane (DDM) with 2-substituted nicotinic acids in nine aprotic solvents at 30°C were determined. The obtained second order rate constants in aprotic solvents were correlated using the Kamlet-Taft solvatochromic equation in the complete form: log k = log k0 + sπ*+ a( + bβ. The correlations of the kinetic data were realized by means of multiple linear regression analysis. The obtained results were analyzed in terms of the initial and the transition state of the reaction and compared with previously determined kinetic data for nicotinic acid. The signs of the equation coefficients (s, a and b) are in agreement with the reaction mechanism and the influence of the solvent on the reaction rate is discussed based on the correlation results. The mode of the transmission of the substituent effect is discussed in light of the contribution of solute-solvent interaction to the reactivity of the acid. The substituent effect was additionally analyzed by the Hammett equation, log k = pσ + log k0. Konstante brzine za reakciju diazodifenilmetana (DDM) sa 2-susptituisanim nikotinskim kiselinama u devet aprotičnih rastvarača su određene na 30 °S. Dobijene konstante brzine za reakciju drugog reda su korelisane Kamlet-Taftovom totalnom solvatohromnom jednačinom u obliku: log k = log k0 + sπ*+ a( + bβ. Korelacija kinetičkih podataka izvršena je višestrukom linearnom regresionom analizom. Dobijeni rezultati su analizirani u odnosu na osnovno i prelazno stanje i upoređeni sa ranije određenim vrednostima za nesupstituisanu kiselinu. Znaci ispred koeficijenata u jednačini su u skladu sa pretpostavljenim mehanizmom reakcije. Diskutovan je prenos efekata supstituenata na reakcioni centar uzimajući u obzir doprinos efekata rastvarača na reaktivnost ispitivanih jedinjenja. Efekat supstituenata je dodatno analiziran Hametovom jednačinom: log k = pσ + log k0.

The effects of protic and aprotic solvents on the reactivity of picolinic, nicotinic and isonicotinic acid, as well as of some substituted nicotinic acids, with diazodiphenylmethane (DDM) were investigated. In order to explain the kinetic results through solvent effects, the second-order rate constants for the reaction of the examined acids with DDM were correlated using the Camlet-Taft Solvatochromic Equation. The correlations of the kinetic data were realized by means of multiple linear regression analysis and the solvent effects on the reaction rates were analyzed in terms of the contributions of the initial and the transition state. The signs of the coefficients of the Equation support the already known reaction mechanism. Solvation models for all the investigated acids are suggested and related to their specific structure. U ovom radu analiziran je uticaj protičnih i aprotičnih rastvarača na reaktivnost pikolinske, nikotinske i izonikotinske kiseline, kao i nekoliko supstituisanih nikotinskih kiselina sa diazodifenilmetanom (DDM). Da bi se dobijeni kinetički podaci mogli objasniti pomoću efekata rastvarača, konstante drugog reda za reakciju ispitivanih kiselina i DDM-a su korelisane Kamlet-Taftovom totalnom solvatohromnom jednačinom. Korelacija kinetičkih podataka urađena je višestrukom linearnom regresionom analizom i efekat rastvarača je posmatran sa strane osnovnog stanja, odnosno reaktanata, i prelaznog stanja u reakciji. Aritmetički znaci ispred koeficijenata u jednačini su u skladu sa poznatim mehanizmom ispitivane reakcije. Solvatacioni modeli za sve ispitivane kiseline su predloženi i povezani sa specifičnostima njihovih struktura.

The reactivities of 2-substituted cyclohex-1-enylacetic acids with diazodiphenylmethane in eleven alcohols has been investigated. The solvent effect is interpreted in terms of the influence of the relative permittivity on the rate constants. The multiple linear correlation of log k with the Kirkwood function of relative permittivity, Taft σ* value for the alkyl group of the alcohol and the number of γ-hydrogen atoms in the alcohol nγH was highly successful (R= 0.9927). The log k values for the various acids were correlated by using the appropriate form of the extended Hammett equation involving inductive, resonance and steric parameters.The reaction of cyclohex-1-enylacetic acid with diazodiphenylmethane in eleven alcohols shows a good linear free energy relationship with the corresponding reaction of phenylacetic acid (R= 0.9793). The results obtained for 2-substituted cyclohex-1-enylacetic acids were compared with the results for ortho-substituted phenylacetic acids under the same experimental conditions.

The reactivities of 2-substituted cyclohex-1-enecarboxylic acids with diazodiphenylmethane in several alcohols were investigated. The rate data for these acids were correlated with a simple Hammett equation by means of the σp constants. The transmission of polar effects through the double bond, in terms of polar susceptibility constant ρ, has been discussed. For the reactions of a given acid in the various alcohols, the log k and ρ values were correlated through multiple regression on appropriate solvent parameters. The results obtained for 2-substituted cyclohex-1-enecarboxylic acids were compared with the results for ortho-substituted benzoic acids under the same experimental conditions.

Solvent effects on the reactivity of cycloalkenecarboxylic, cycloalke- neacetic, 2-substituted cyclohex-1-enecarboxylic, 2-substituted benzoic, 2-sub- stituted cyclohex-1-eneacetic, 2-substituted phenylacetic, 2-phenylcyclohex-1- enecarboxylic, 2-phenylbenzoic and 2-phenylacrylic acids with diazodiphe- nylmethane (DDM) were investigated. In order to explain the kinetic results through solvent effects, the second-order rate constants for the reaction of the examined acids with DDM were correlated using the Kamlet-Taft solvato- chromic equation. The correlations of the kinetic data were realized by means of multiple linear regression analysis and the solvent effects on the reaction rates were analyzed in terms of the contributions of the initial and the transition state. The signs of the equation coefficients support the proposed mechanism. Solvation models for all the investigated acids are suggested. The quantitative relationship between the molecular structure and the chemical reactivity is also discussed.

The reactivities of 2-substituted cyclohex-1-enylacetic acids with diazodiphenylmethane in eleven alcohols has been investigated. The solvent effect is interpreted in terms of the influence of the relative permittivity on the rate constants. The multiple linear correlation of log k with the Kirkwood function of relative permittivity, Taft σ* value for the alkyl group of the alcohol and the number of γ-hydrogen atoms in the alcohol nγH was highly successful (R= 0.9927). The log k values for the various acids were correlated by using the appropriate form of the extended Hammett equation involving inductive, resonance and steric parameters.The reaction of cyclohex-1-enylacetic acid with diazodiphenylmethane in eleven alcohols shows a good linear free energy relationship with the corresponding reaction of phenylacetic acid (R= 0.9793). The results obtained for 2-substituted cyclohex-1-enylacetic acids were compared with the results for ortho-substituted phenylacetic acids under the same experimental conditions.

The sections in this article are Introduction Phase Transfer Catalysis Background Phase Transfer Catalysis Quaternary Ammonium Salt-catalyzed Reactions PTC Separation and Recycling Using CO2 Near-critical Water Definition Properties Friedel–Crafts Chemistry in NCW Alkylcarbonic Acids Probing Alkylcarbonic Acids – Alkylcarbonic Acids with Diazodiphenylmethane (DDM) Reactions Using Alkylcarbonic Acids Ketal Formation Formation of Diazonium Salts Conclusion Keywords: supercritical fluid; coupling reactions; phase transfer catalysis; acid-catalyzed reactions; supercritical carbon dioxide

Heating of a mixture of N,N′-(thiocarbonyl)diimidazole (= 1,1′-(carbonothioyl)bis[1H-imidazole]; 1) and 2,5-dihydro-1,3,4-thiadiazole 2a or 2b gave the 1,3-dithiolanes 4a and 4b, respectively, via a regiospecific 1,3-dipolar cycloaddition of the corresponding ‘thiocarbonyl methanides’ 3a,b onto the CS group of 1 (Schemes 1 and 2). The adamantane derivative 4b was not stable in the presence of 1H-imidazole and during chromatographic workup. The isolated 1,3-dithiole 5 is the product of a base-catalyzed elimination of 1H-imidazole from the initial cycloadduct 4b. The formation of the S,N-acetal 6 can be rationalized by a protonation of the ‘thiocarbonyl ylide’ 3b followed by a nucleophilic addition of 1H-imidazole. With the diazo compounds 8a–e (Scheme 3) 1 underwent a regiospecific 1,3-dipolar cycloaddition to give the corresponding 2,5-dihydro-1,3,4-thiadiazole derivatives 9, which spontaneously eliminated 1H-imidazole to yield (1H-imidazol-1-yl)-1,3,4-thiadiazoles 10. The structures of 10a and 10d were established by X-ray crystallography. In the case of diazodiphenylmethane (8f), the initial cycloadduct 9f decomposed via a ‘twofold extrusion’ of N2 and S to give 1,1′-(2,2-diphenylethenylidene)bis[1H-imidazole] (11; Scheme 3).

The reactivities of 2-(4-substituted phenyl)-cyclohex-1-enecarboxylic acids, 2-(4-substituted phenyl)-benzoic acids, and 2-(4-substituted phenyl)-acrylic acids with diazodiphenylmethane in various solvents were investigated. To explain the kinetic results through solvent effects, the second-order rate constants of the examined acids were correlated using the Kamlet–Taft solvatochromic equation. The correlations of the kinetic data were carried out by means of multiple linear regression analysis, and the solvent effects on the reaction rates were analyzed in terms of initial and transition state contributions. The signs of the equation coefficients support the proposed reaction mechanism. The solvation models for all investigated carboxylic acids are suggested. The quantitative relationship between the molecular structure and the chemical reactivity is discussed, as well as the effect of geometry on the reactivity of the examined molecules. © 2010 Wiley Periodicals, Inc. Int J Chem Kinet 42: 430–439, 2010

As a part of the research of solvent influence on the reactivity of organic compounds the reaction of carboxylic acids with diazodiphenylmethane(DDM) was chosen as a model. Rate constants for acids of various structure: cycloalken e carboxylic and cycloalken e acetic with a differen t number of carbon atoms in the ring, were determined in a wide range of protic and aprotic solvents. The influe nce of the moleculars structure and solvent properties on the kinetics and mechanism of the reaction of carboxylic acids with DDM was discussed... U cilju proučavanja uticaja rastvarača na reaktivnost organskih molekula odabrana je kao model reakcija karbo ksi lnih kiselina sa diazodifenilmetanom (DDM). Odredjene su konstante brzina za karbo ksilne kiseline sa cikličnim ugljovodničnim nizom, različite strukture, sa različitim brojem ugljenikovih atoma u prstenu, u nizu protičnih i aprotičnih rastvarača. Diskutov an je uticaj strukture molekula kiseline i svojstava rastvarača na kinetiku i mehanizam reakcije karbo ksilnih kiselina i diazodifenilmetana...

In connection with a study of the transmission of polar effects through ring double bonds, double bonds in open chain systems and delocalized double bonds, the reactivity of 2-(4-phenylsubstituted)-α,β-unsaturated carboxylic acids with diazodiphenylmethane in ethanol was investigated. The rate data for 2-(4-phenylsubstituted)-cyclohex-1-ene carboxylic acids, 2-(4-phenylsubstituted)-benzene carboxylic acids, cis-3-and 4-substituted and trans-3- and 4-substituted cinnamic acids were correlated with a simple Hammett equation by means of the σp and σm constants and with an extended Hammett equation to detect the presence or absence of steric effects as well as the composition of the electrical effect. The transmission of polar effects through the different double bonds was discussed in terms of the polar susceptibility constant δ and steric interaction of the phenyl and carboxylic group.

Rate constants for the reaction of six possible diazine monocarboxylates with diazodiphenylmethane (DDM) in ethanol, and also for the hydrolysis of the corresponding methyl carboxylate esters, have been determined at four selected temperatures. Correlations with sums of the Hammett σ constants for ring nitrogens treated as substituents, which are fairly satisfactory for the reaction with DDM at 30 °C (ρDDM= 0.64, log k0=–1.54, r= 0.92, s= 0.12) and for ester hydrolysis (ρEH= 2.28, log k0=–3.36, r= 0.94, s= 0.36) are, however, excellent for the intercorrelation of the two reaction series (ρDDM/ρEH= 0.34, r= 0.99, s= 0.12). The reactivity of ortho- and para-diazine dicarboxylates in the reaction with DDM, in ethanol and dimethylformamide, has been investigated and compared with the corresponding reactions of ortho- and para-benzene- and pyridine-dicarboxylates.

The rate coefficients for the alkaline hydrolysis of a series of 2′- and 4′-substituted 2-methoxy-carbonyldiphenylacetylenes and (Z)-2-methoxycarbonylstilbenes have been determined in 70%(v/v) dimethyl sulphoxide–water at both 30.0 and 50.0 °C and at 24.0, 30.0, 40.0, and 50.0 °C, respectively. The pKa values of (Z)-2′- and -4′-substituted 2-carboxystilbenes have been measured in 80%(w/w) 2-methoxyethanol-water at 25 °C. The rate coefficients for the esterification of the corresponding acids with diazodiphenylmethane have been measured at 30.0 °C. For the diphenyl-acetylene system, normal substituent effects are observed from both the 2′- and 4′-position. A trans-mission coefficient for polar effects of ca. 0.2 has been calculated for both positions. The evidence, including the carbonyl stretching frequencies of the esters, indicates an s-trans conformer for the 2′-substituted 2-methoxycarbonyldiphenylacetylenes. For the (Z)-stilbene system, normal substituent effects are observed from both the 2′- and 4′-position. Transmission coefficients for polar effects, with regard to both the 2′- or 4′-position and the reaction studied, vary between 0.2 and 0.7. This appears to arise from the conformers available to the (Z)-2′- and -4′-substituted 2-carboxystilbenes.

The rate constants for the reaction of 2-substituted cyclohex-1-enecarboxylic acids and the corresponding 2-substituted benzoic acids with diazodiphenylmethane were determined in various aprotic solvents at 30 ºC. In order to explain the kinetic results through solvent effects, the second order rate constants of the reaction of the examined acids were correlated using the Kamlet-Taft solvatochromic equation. The correlations of the kinetic data were carried out by means of multiple linear regression analysis and the solvent effects on the reaction rates were analyzed in terms of the contributions of the initial and transition state. The signs of the equation coefficients support the proposed reaction mechanism. The quantitative relationship between the molecular structure and the chemical reactivity is discussed, as well as the effect of geometry on the reactivity of the examined molecules. Konstante brzine za reakciju 2-supstituisanih cikloheks-1-enkarboksilnih i odgovarajućih 2-supstituisanih benzoevih kiselina sa diazodifenilmetanom su određene u nizu različitih aprotičnih rastvarača na temperaturi od 30 °S. Da bi se kinetički rezultati objasnili pomoću efekata rastvarača, dobijene konstante brzine reakcije drugog reda su korelisane Kamlet-Taftovom solvatohromnom jednačinom. Korelacije kinetičkih podataka su dobijene pomoću metode višestruke linearne regresione analize i efekti rastvarača su posebno analizirani u odnosu na osnovno i prelazno stanje. Aritmetički znaci ispred koeficijenata solvatohromnih parametara rastvarača odgovaraju pretpostavljenom mehanizmu ispitivane reakcije. Takođe je proučavan kvantitativni odnos molekulske strukture i reaktivnosti, kao i efekat geometrije molekula ispitivanih jedinjenja na njihovu reaktivnost.

The rate constants for the reaction of twenty-two N-(substituted phenylmethylene)- m- and -p-aminobenzoic acids with diazodiphenylmethane were determined in absolute ethanol at 30 °C. The effects of substituents on the reactivity of the investigated compounds were interpreted by correlation of the rate constants with LFER equations. The results of quantum mechanical calculations of the molecular structure together with experimental results gave a better insight into the effects of structure on the transmission of electronic effects of the substituents. New σ constants for substituted benzylideneamino group were calculated. Konstante brzina reakcija između dvadeset dve N-(supstituisane fenilmetilen)-m- i -p-aminobenzoeve kiseline i diazodifenilmetana određene su u apsolutnom etanolu na 30 °C. Efekti supstituenata na reaktivnost ispitivanih jedinjenja su interpretirani korelacijom reakcionih konstanti pomoću LFER jednačina. Rezultati kvantno-mehaničkih računanja molekulske strukture zajedno sa eksperimentalnim rezultatima omogućili su bolje razumevanje uticaja strukture na prenos elektronskih efekata supstituenata. Izračunate su nove σ konstante za supstituisane benzilidenamino grupe.

The rate constants for the reaction of diazodiphenylmethane with 1-cyclopentenecarboxylic, 1-cycloheptenecarboxylic, cyclopent-1-enylacetic and cyclohept-1-enylacetic acids were determined in eight alcohols at 30 ºC using the appropriate UV-spectroscopic method. In order to explain the kinetic results through solvent effects, the second order rate constants of the examined acids were correlated using a total solvatochromic equation, of the form: log k = A0+ s¶*+aα+ bβ, where ¶* is a measure of the solvent polarity, βrepresents the scale of solvent hydrogen bond acceptor basicities and β represents the scale of solvent hydrogen bond donor acidities. The correlations of the kinetic data were carried out by means of multiple linear regression analysis. The opposite sings of the electrophilic and the nucleophilic parameters are in agreement with the well-known reaction mechanism. The results presented in this paper were compared with the kinetic data for 1-cyclohexenecarboxylic and cyclohex-1-enylacetic acids obtained under the same experimental conditions. Konstante brzina za reakciju između diazodifenilmetana (DDM) i 1-ciklopentenkarbonske, 1-cikloheptenkarbonske, ciklopent-1-enilsirćetne i ciklohept-1-enilsirćetne kiseline su određene u osam alkoholnih rastvarača na 30 ºC odgovarajućim UV-spektrofotometrijskim metodom. Da bi se dobijeni kinetički rezultati objasnili kroz efekte rastvarača konstante brizna reakcije (k) su korelisane totalnom solvatohromnom jednačinom oblika: log k = A0+ s¶*+aα+ bβ, gde je ¶* mera polarnosti rastvarača, βpredstavlja skalu baznosti rastvarača kao akceptora protona u vodoničnoj vezi, a αskalu kiselosti rastvarača kao donora protona u vodoničnoj vezi. Korelacija kinetičkih parametara je izvršena metodom višestruke linearne regresione analize. Suprotni znaci uz elektrofilni i nukleofilni parametear u saglasnosti su sa izvedenim mehanizmom reakcije. Rezultati prikazani u ovom radu su upoređeni sa kinetičkim podacima za 1-cikloheksenkarbonsku i cikloheks-1-enilsirćetnu kiselinu, dobijenim pod istim eksperimentalnim uslovima.

The pKa values of a series of 2′- and 4′-substituted-biphenyl-2-carboxylic acids have been determined in 80%(w/w) 2-methoxyethanol-water at 25 °C. The rate coefficients for the esterification of these acids with diazodiphenylmethane have been measured in 2-methoxyethanol at 30 °C. The transmission of polar effects from the 4′-position is normal and the transmission coefficient is ca. 0.4. However, for the normally electron-withdrawing substituents at the 2′-position, reversed dipolar substituent effects are observed in both reactions. The reactivity studies indicate that the conformation of the 2,2′-disubstituted-biphenyl system appears to be close to that having orthogonal aryl groups.

Solvent effects on the reactivity of pyridine and pyridine-N-oxide carboxylic acids and p-substituted benzoic acids in their reaction with diazodiphenylmethane (DDM) in alcohols have been investigated and the rate constants interpreted by Hammett parameters using multiple regression analysis; the influence of solvents on the reactivity of these acids with DDM has not been reported previously.

The rate constants for 10 trans-substituted beta-aroylacrylic acids in their reaction with diazodiphenylmethane (DDM) were determined in ethanol at 30 degrees C. The intention was to study the transmission of electronic effects of substituents on the phenyl nuclei to the carboxylic group reaction center, through the -C(=O)-CH=CH-group. The obtained rate constants were analyzed with the classical Hammett equation and the extended Hammett and Taft equation. It was possible, using Taft's relationship, to effect the separation of the overall polar effect into inductive and resonance components. The pattern of transmission through the observed conjugated system has been discussed. Conformational variations caused by variable substituents in an aromatic ring were calculated using the MNDO-AM I semiempirical method. The inclusion of a calculated conformational effect considerably improves the regression.

The reactions of bis-cyclomanganated 2,3-diphenylquinoxaline with diazodiphenylmethane and 9-diazofluorene allowed the formation of a new oligomeric and dinuclear manganospiralene and the ready preparation of a pentacyclic helix comprising two (eta 5-fluorenyl)Mn(CO)3 fragments, whose helicity can be locked upon one-dimensional linear coordination to silver cation.

The mutual solubility of carbon dioxide and alcohols over a wide range of temperature and pressure provides a useful and tunable medium for reactions and separations. For many years, researchers have used alcohols as cosolvents in supercritical CO2, and recently CO2-swollen alcohols have been used for antisolvent crystallization and as mobile phases for chromatography. However, little consideration has been given to chemical interaction between the alcohols and CO2. We have confirmed that such an interaction does exist and can create an acidic environment. By isolating reaction products we have demonstrated that alcohol−CO2 complexes react similarly to carboxylic acids with diazodiphenylmethane, a compound typically used to evaluate acid strengths. Our evidence indicates that the behavior of CO2−alcohol systems is comparable to that of CO2−water systems, where carbonic acid is formed.

The pKa values of a series of 2′- and 4′-substituted-biphenyl-2-carboxylic acids have been determined in 80%(w/w) 2-methoxyethanol-water at 25 °C. The rate coefficients for the esterification of these acids with diazodiphenylmethane have been measured in 2-methoxyethanol at 30 °C. The transmission of polar effects from the 4′-position is normal and the transmission coefficient is ca. 0.4. However, for the normally electron-withdrawing substituents at the 2′-position, reversed dipolar substituent effects are observed in both reactions. The reactivity studies indicate that the conformation of the 2,2′-disubstituted-biphenyl system appears to be close to that having orthogonal aryl groups.

The principles of linear free energy relationships were applied to the 1 H nmr and 13 C nmr chemical shifts induced by substituents in three isomeric trans-pyridineacrylic and substituted trans-cinnamic acids. The data for the carboxy proton chemical shift correlated well with the simple Hammett equation. Taft's dual substituent parameter equation was used for the interpretation of the balance of the inductive and resonance effects through the ethylenic bond for the C α and C β 13 C nmr shift. Using the nuclear Overhauser method, the conformation of the carboxylic group in 2-pyridineacrylic acid was determined, and its unexpected behaviour in both 1 H nmr chemical shifts;and in the previously studied reaction with diazodiphenylmethane was interpreted by the increased electron density in the π-electronic system favoured by the orbital symmetry of the part of the acid molecule

The reaction between diazodiarylmethanes and triphenylphosphine has previously been shown to be an elementary biphilic reaction in which each reactant behaves simultaneously as both electrophile and nucleophile. Frontier molecular orbital considerations provide a basis for relating structure and reactivity. Diazodiphenylmethane, however, is an order of magnitude more reactive than expected, and substituents in the phenyl groups of the diazoalkane enhance the reaction rate, whether they are electron-withdrawing or electron-releasing, giving rise to a U-shaped Hammett correlation. Evidence is now presented that the substituent effect cannot arise from disturbance of simple energy matching of the frontier molecular orbitals of the two reactants, but rather results from conformational changes in the diazo-compound on passing from the reactant to the transition state. This evidence comprises (i) the linearity of Hammett plots for the effects of substituents in triphenylphosphine on the reactivity towards diazodiphenylmethane, and (ii) a comparison of the reactivity of diazodiphenylmethanes bearing two substituents of opposite polar effect when these are present in the same and in different aromatic groups.

The reactivities of a series of 18 (E)-α-4-substituted phenyl-β-(3N and 4N)pyridineacrylic acids, with a wide range of substituent effects, were investigated in their reaction with diazodiphenylmethane, in dimethylformamide at 30°C, by the known spectrophotometric method. The Hammett equation in its original form has been applied to the results, using the sum of substituent constants from the both aromatic nuclei, but the overall correlation was only fair. Better insight into the transmission of substituent effects was obtained using Taft's Dual Substituent Parameter (DSP) method, where it was possible to distinguish the contributions from the inductive and resonance effects of the substituents