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Protic and aprotic solvent effects 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 Kamlet-Taft solvatochromic equation. The correlations of the kinetic data were carried out by means of the 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 already known reaction mechanism. The solvatation models for all the investigated acids are suggested and related to their specific structure.

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.

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.

Rate constants for the reaction of diazodiphenylmethane (DDM) with 4-pyrimidinecarboxylic, 6-hydroxy-4-pyrimidinecarboxylic and 5-hydroxyorotic acids were determined in twelve protic solvents at 30 °C using the well known UV-spectrophotometric method. The second order rate contants for the examined acids were correlated using the appropriate solvent parameters by the equation log k = log k0 + af(e) + bs * + cngH were f(e) is the Kirkwood function of relative permittivity [(e-l)/(2e + 1 )], s * is the Taft polar constant for the alkyl group R in the alcohol ROH, and nyH is themumber of hydrogen atoms in the (-position in the alcohol. The results obtained for the investigated acids were compared with the corresponding results for benzoic, 2- and 3-hydroxybenzoic acids and the influence of the structure of the investigated acids on the reactivity in hydroxylic solvents is discussed. It was also possible to evaluate and distinguish the specific and non-specific solvent effects and their influence on the reaction rate. Konstante brzina reakcija diazodifenilmetana (DDM) sa 4-pirimidinkarboksilnom, 6-hidroksi-4-pirimidinkarboksilnom i 5-hidroksiorotinskom kiselinom su određene u dvanaest protičnih rastvarača na 30 °C korišćenjem poznate UV-spektrofotometrijske metode. Konstante brzina reakcija drugog reda su korelisane sa odgovarajućim parametrima rastvarača korišćenjem solvatohromne jednačine u sledećem obliku: k = log k0 + af(e) + bs * + cngH gde je broj f(e) Kirkwood-ova funkcija permittivity [(e-l)/(2e + 1 )] relativne permitivnosti,, s * je Taft-ova konstanta alkil-grupe R alkohola ROH, i nyH je broj (-vodonikovih atoma. Dobijeni rezultati su poređeni sa rezultatima korelacija za benzoevu, kao i 2- i 3-hidroksibenzoevu kiselinu kako bi se diskutovao uticaj strukture ispitivanih kiselina u hidroksilnim rastvaračima na njihovu reaktivnost. Takođe su procenjeni specifični i nespecifični efekti rastvarača i njihov uticaj na brzinu ispitivanih reakcija.

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 three isomeric pyridine mono-carbocylic 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 bymeans of multiple regression analysis. The sign of the equation coefficients were in agreement with the postulated reaction mechanism. The mode of the influences of the solvent is discussed on the basis of the correlation coefficients, taking into account the specific structures of the pyridine mono-carboxylic acid N-oxides. Konstante brzina reakcije između diazodifenilmetana i izomernih piridin-N-oksidkarbonskih kiselina određene u trideset dva protična i aprotična rastvarača na 30 ºC, korišćenjem poznate UV spektrofotometrijske metode, analizirane su u funkciji efekata rastvarača. Vrednosti konstanti brzina su generalno veće za piridin-N-oksid- karbonske kiseline u odnosu na piridin-monokarbonske kiseline, izuzev pikolin-N-oksid-kiseline, a takođe vrednosti konstanti brzina su veće u protičnim rastvarač ima u poređenju sa aprotičnim za obe serije kiselina. Određene konstante brzina su korelisane sa parametrima rastvarača korišćenjem Kamlet-Taft solvatohromne jednačine izvedene metodom višestruke 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, uzimajući u obzir specifičnu strukturu piridin- N-oksid-monokarbonskih kiselina.

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.

Rate konstants for the reaction of eight 5-substituted orotic acids with diazodiphenylmethane (DDM) in dimethylformamide (DMF) were determined at 30 ºC by the known spectrophotometricmethod. The determined rate constants were correlated with the equations: logk2 = ασ1+βσR+h logk2 = ασ1+βσR+ψν+h to detect the presence and investigate the influence of both electrical and steric substituent effects. The obtained results show that the electrical effect (the localized – field and delocalized – resonance) is predominant and that the steric effect, althought present, is releatively small in this reaction. Konstante brzine za reakciju osam 5-spstituisanih orotinskih kiselina sa diazodifenilmetanom (DDM) određene su na 30 ºC u dimetilformamidu (DMF) kao rastvarač u, poznatom spektrofotometrijskim metodom. Konstante brzina ispitivanih reakcija korelisane su sledećim jednačinama: logk2 = ασ1+βσR+h logk2 = ασ1+βσR+ψν+h sa ciljem da se odrede efekti supstituenata. Dobijeni rezultati ukazuju na to da su električni efekti supstituenata (induktivni i rezonantni) preovlađujući, a da su sterni efekti supstituenata, iako su prisutni, u odnosu na njih relativno mali.

The rate constants for the reaction of diazodiphenylmethane with 2-(2-substituted cyclohex-1-enyl)acetic acids and 2-(2-substituted phenyl)acetic acids, previously determined in seven hydroxylic solvents, were correlated using the total solvatochromic equation, of the form logk = logk0 + s?*+ a? + b?, the two-parameter model, logk=logk0 + s?*+ a? and a single parameter model logk = logk0 + b?, where ?*is a measure of the solvent polarity, ? represents the scale of solvent hydrogen bond acceptor basicities and ? 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 and the solvent effects on the reaction rates were analyzed in terms of initial state and transition state contributions.

The rate constants of 2-substituted nicotinic acids in reaction with diazodiphenylmethane (DDM) in eight alcohols at 30 ºC have been determined. In order to explain the obtained results through solvent effects, the second order reaction rate constants (k) of the examined acids were correlated using the appropriate solvent parameters by the equation: logk=logk0 af(ε) + bσ* + cnγH where f(ε) is the measure of solvent ability as a dielectric to stabilize the separation of opposite charges in the activated complex, σ* is the measure of solvent ability to stabilize proton in the initial state and nγH represents the ability of protic solvents to form hydrogen bond with the negative end of the ion-pair intermediate. These constants were correlated also by using solvatochromic equation of the form logk=logk0 + s¶* + aα + bβ where ¶* is the measure of the solvent polarity, α represents the scale of the solvent hydrogen bond donor acidities (HBD) and β represents the scale of the solvent hydrogen bond acceptor basicities (HBA). The correlations of the kinetic data were carried out by means of multiple linear regression analysis. The results obtained for 2-substituted nicotinic acids were compared with the results for ortho-substituted benzoic acid under the same experimental conditions. U ovom radu određene su konstante brzine reakcije esterifikacije 2-supstituisanih nikotinskih kiselina sa supstituentima H, Cl, OH,SCH3 iCH3 u osam alkoholnih rastvarača korišćenjem poznate UV-spektrofotometrijske metode. Dobijeni rezultati konstanti brzina reakcije 2-supstituisanih nikotinskih kiselina kaoiliteraturnih podataka za orto-supstiuisane benzoeve kiseline korelisani su korišćenjem jednačine oblika: logk=logk0 + af(ε) bσ* + cnγH gde f(ε) definiše meru stabilizacije razdvojenih naelektrisanja u prelaznom stanju dielektričnim svojstvima rastvarača, σ* definiše meru stabilizacije karboksilatnog protona rastvaračem polaznog stanja i nγH definiše meru mogućnosti građenja vodonične veze rastvarača sa negativnim krajem jonskog para. Dobijeni rezultati su takođe korelisani korišćenjem solvatohromne jednačine oblika: logk=logk0 + s¶* + aα + bβ gde ¶* predstavlja meru polarnosti rastvarača, α definiše kiselost rastvarača kao donora protona u interakciji građenja vodonične veze (HBD), i β definiše baznost rastvarača kao akceptora protona u interakciji građenja vodonične veze (HBA). Diskutovani su dobijeni rezultati za koeficijente višestruke regresione analize obe jednačine koji su dali zadovoljavajuće zavisnosti korelacija konstanti brzina sa parametrima rastvarača. Dobijeni rezultati su pokazali da su uticaji rastvarača više izraženi kod orto-supstituisanih benzoevih kiselina, nego kod 2-supstituisanih nikotinskih kiselina. Izuzetak je ortho-hidroksi-benzoeva kiselina na koju, zbog izuzetno izraženih vodoničnih veza, rastvarači manje utiču.

Rate constants for the reaction of diazodiphenylmethane with cyclohex-1-enylcarboxylic acid and 2-methylcyclohex-1-enylcarboxylic acid were determined in nine aprotic solvents, as well as in seven protic solvents, at 30 ºC using the appropriate UV-spectroscopic method. In protic solvents the unsubsituted acid displayed higher reaction rates than the methyl-substituted one. The results in aprotic solvents showed quite the opposite, and the reaction rates were considerably lower. In order to explain the obtained results through solvent effects, reaction rate constants (k) of the examined acids were correlated using the total solvatochromic equation of the form: log k = log k0 + sπ* + aα + bβ, where π* is the measure of the solvent polarity, α represents the scale of the solvent hydrogen bond donor acidities (HBD) and β represents the scale of the solvent hydrogen bond acceptor basicities (HBA). The correlation of the kinetic data were carried out by means of multiple linear regression analysis and the opposite effects of aprotic solvents, as well as the difference in the influence of protic and aprotic solvents on the reaction of the two examined acids with DDM were discussed. The results presented in this paper for cyclohex-1-enylcarboxylic and 2-methylcyclohex-1-enylcarboxylic acids were compared with the kinetic data for benzoic acid obtained in the same chemical reaction, under the same experimental conditions. . Konstante brzine za reakciju između diazodifenilmetana (DDM) i cikloheks-1-enilkarbonske, kao i 2-methilcikloheks-1-enilkarbonske kiseline su određene u devet aprotičnih i sedam protičnih rastvarača, odgovarajućom UV-spektrofotometrijskom metodom. U protičnim rastvaračima nesupstituisana kiselina je pokazala veće reakcione brzine od supstituisane. Rezultati u aprotičnim rastvaračima su pokazali upravo suprotno i brzine su znatno manje. Da bi se dobijeni rezultati objasnili kroz efekte rastvarača, konstante brzine reakcije (k) su korelisane totalnom solvatohromnom jednačinom oblika: log k = log k0 + sπ* + aα + bβ, gde je π* mera polarnosti rastvarača, α predstavlja skalu baznosti rastvarača kao akceptora protona u vodoničnoj vezi, a β predstavlja skalu kiselosti rastvarača kao donora protona u vodoničnoj vezi. Korelacija kinetičkih podataka je izvršena metodom multiple linearne regresije i razmatrani su suprotni efekti aprotičnih rastvarača, kao i razlika u uticaju protičnih i aprotičnih rastvarača na reakciju dve ispitivane kiseline i DDM-a. Rezultati prikazani u ovom radu za cikloheks-1-enilkarbonsku i 2-methil-cikloheks-1-enilkarbonsku kiselinu su upoređeni sa kinetičkim podacima za benzoevu kiselinu, dobijenim u istoj hemijskoj reakciji pod istim eksperimentalnim uslovima. .

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.

Rate constants have been determined for the reactions of diazodiphenylmethane (DDM) with 3- and 4-pyridineacetic acid, 3- and 4-pyridineacetic acid N-oxide and some meta- and para-substituted phenylacetic acids in twelve alcohols. The determined rate constants, together with literature data, were used for calculation of Hammett ? values in a series of alcohols. Secondary ? constants have been calculated for substituents in meta and para-position of phenylacetic acids not given in literature, and also ? constants for 3N, 3N-O, 4N and 4N-O in pyridineacetic acids, in alcohols used. The transmission of electronic effects through the phenylacetic acid system and pyridineacetic system is compared with that in benzene and pyridine. The multiple correlation of log k values for reaction of above acids in 12 alcohols with group of suitable solvent parameters was very successful.

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 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.

Correlation of the data for the reaction of 11 substituted 4-pyrimidine carboxylic acids with diazodiphenylmethane (DDM) in dimethylformamide (DMF) with calculated atomic charges on the carboxylic group showed that the reaction in this solvent may proceed via a concerted transition state.

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 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.

A high pressure kinetic study was made of the 1,3-dipolar cycloaddition reaction of Ph2CN2 with dimethyl maleate (DMM), dimethyl fumarate (DMF), methyl acrylate (MA), maleonitrile (MN), fumaronitrile (FN), and acrylonitrile (AN) in toluene at 25 °C. The activation volumes (ΔV\eweq) at 1 bar obtained for DMM, DMF, MA, MN, FN, and AN are −23.4±0.5, −22.3±0.2, −19.8±0.4, −21.5±0.6, −21.0±1.1, and −23.9±0.5 cm3 mol−1, respectively. The reaction volume (ΔV) for the reaction between Ph2CN2 and DMM was determined dilatometrically by taking advantage of supersaturation of the cycloadduct in solution; ΔV=−24.5±0.5 cm3 mol−1 and ΔV\eweq⁄ΔV=0.955. The present volumetric information coupled with a kinetic analysis shows that Firestone’s biradical mechanism is not the case; the concerted mechanism is supported. The experimental result is compared with that of a recent ab initio molecular orbital calculation with respect to the activation and reaction volumes.

The rate coefficients for the reaction with diazodiphenylmethane, in ethanol at 30.0°, of a number of substituted indole-2-carboxylic acids, indole-3-carboxylic acids, coumarin-3-carboxylic acids, coumarilic acids, and N-phenylglycines have been determined. The effect of substitution is assessed by use of adapted Hammett and Dewar–Grisdale relations. The relations give good correlations for oxygen-ring heterocyclic systems, and the relative ability of the systems to transmit π-electron effects has been determined. An anomalous perturbing effect appears to operate in the indole-carboxylic acid systems.

The rate coefficients for the reaction with diazodiphenylmethane in methanol, ethanol, isopropyl alcohol, t-butyl alcohol, 2-methoxyethanol, 2-n-butoxyethanol, and ethyl acetate at 30° and the pKa values in 80% 2-n-butoxyethanol–water of a series of 9-substituted 10-anthroic and 8-substituted 1-naphthoic acids have been determined. The effect of substitution has been analyzed by linear free energy relations. The variation in the susceptibilities of the systems to polar substituent effects with the medium are examined. The occurrence of reversed dipolar substituent effects in the reactions of the 1,8-naphthoic acids is detected. The implications of the results for the inductive and field effect models for the transmission of polar effects are discussed.

A series of 9-substituted 10-triptoic acids have been prepared. Their pKa values in 80% 2-methoxy-ethanol–water and 50% ethanol–water at 25° and rate coefficients for esterification with diazodiphenyl-methane in five alcohols at 30° have been measured. The results have been analyzed by linear free energy relations. The π-inductive effect is shown to be unimportant in such systems, while the field effect model can account for the transmission.

The rate coefficients for the esterification with diazodiphenylmethane in ethanol at 30° and the pKa values at 25° of a number of ortho-substituted trans-cinnamic, phenoxyacetic, 3-phenylpropionic, ortho-, meta-, and para-substituted cis-trans-α-phenylcinnamic acids have been determined. The effects of substitution have been assessed by a Hammett-type correlation. A comparison of the transmission of the polar effects of ortho and meta/para substituents indicates the prime importance of the field effect, augmented where possible by a π-inductive effect. A reversed dipolar substituent field effect has been detected for the cis-ortho-substituted cinnamic acids.

1. The reactions are described of hexafluoroacetone with a number of compounds: hydroxylamine, hydrazoic acid, diazodiphenylmethane, some organomagnesium compounds, N-methylated anilines, N,P,P,P-tetraphenylphosphine imine, and ethyl hydrogen benzamidomalonate. 2. The strongly marked electrophilic reactivity of hexafluoroacetone was confirmed. 3. Some reactions of compounds prepared from hexafluoroacetone are described.

Rate coefficients have been determined for the reactions in ethanol at 30° of diazodiphenylmethane with several groups of carboxylic acids. Each group included the parent acid and three nuclear substituted acids. The parent acids were: benzoic, phenylacetic, β-phenylpropionic, phenoxyacetic, and trans-cinnamic acid. The reactions of 3-fluoro- (or chloro-) or 4-methyl-biphenyl-4′-carboxylic, and of 9-X-10-anthroic acids (X = Me, Cl, or Br) were also studied similarly. The Hammett polar susceptibility constant, ρ, has been calculated for each set of reactions. The values of ρ are discussed in terms of transmission of electronic effects through the side-chain by a field effect, and for side-chains conjugated with the ring, by a π-electron effect, both of which are inversely proportional to the first power of the distance of the carbonyl group from the ring.

The rate coefficients for the reaction with diazodiphenylmethane in ethanol at 30° and the acid-catalyzed esterification with methanol at 60° of a number of arylaliphatic carboxylic acids and their pKa values in 80% 2-methoxyethanol–water have been measured. Rate coefficients have also been measured for the alkaline hydrolysis in 70% dioxan–water of their 2-diethylaminoethyl esters at 45°. The pKa values and diazodiphenylmethane esterification rate coefficients were also measured for a series of 2-substituted fluorene-9-carboxylic acids. The latter results have been correlated by Hammett equations and the transmission of polar effects in fluorene is discussed. Polar and steric substituent constants are evaluated for the arylaliphatic systems. These values are used to successfully correlate the hydrolysis and ionization reactions using the Taft–Ingold equation.

The rate coefficients for the reaction with diazodiphenylmethane in methanol, ethanol, isopropyl alcohol,t-butyl alcohol, 2-methoxyethanol, 2-n-butoxyethanol, dimethyl sulfoxide, ethyl acetate, and toluene at 30° and the pKa values in water, 50% ethanol–water, and 80% 2-methoxyethanol–water of 18 substituted acetic and propionic acids have been determined. A further 14 acids have been studied to a more limited extent. The effect of substitution has been estimated by linear free energy relations. The reaction constants for the ionization reaction are almost independent of the medium. This is interpreted as being due to the field effect of the proximate polar substituents passing through the molecular cavity almost alone. The occurrence of steric inhibition of solvation causing acid weakening for bulky multi-substitution is confirmed. The reaction constants for the esterification reaction are affected by the solvent. This is attributed to dependence on solvation of the transition state.

The rate coefficients for the reaction with diazodiphenylmethane in ethanol, t-butyl alcohol, and ethyl acetate at 30° and the pKa values in water at 25° of fourteen 3-substituted acrylic acids have been determined. The effect of substitution is assessed by use of linear free energy relations. A definite incremental acid-strengthening effect solely due to cis-substitution is confirmed. This is not a "bulk" steric effect and is due solely to the orientation of substitution. The polar effect of a substituent is found to be approximately the same from the cis- or trans-position. An attempt is made to test the suggested mechanisms for the transmission of the polar effect. In the reactions studied the transmission of the polar effect in 3-substituted acrylic acid and ortho-substituted benzoic acids is approximately twice that of the meta- or para-substituted benzoic acids. This appears to be reasonably accommodated by a significant field effect.

The title reaction is studied with a series of CN- or COOCH3-substituted dipolarophiles. All the reactions obey the second-order rate law. The activation enthalpies and entropies are 44–52 kJ mol−1 and −(129–166) J K−1 mol−1, respectively. The rate constants are insensitive to solvent. The reactivity and product of dimethyl maleate are anomalous.

The magnitude and direction of the electrical effect of tetravalent silicon atoms in organosilicon compounds has not been definitely established. The difference in electronegativity between carbon and silicon on the Pauling scale (+0.7 unit) suggests that silicon should be fairly strongly electron-releasing with respect to carbon. Nonetheless, the low reactivity of trimethylsilylmethyl chloride toward ionizing reagents has been interpreted as indicating that tetravalent silicon atoms are “electronically unsaturated” relative to tetravalent carbon. The possibility exists that silicon atoms may tend to be more electron-attracting than otherwise anticipated since resonance forms involving more than four pairs of electrons in the outer atomic valence shells should be energetically more favorable for silicon than carbon. Actually, strong evidence has been obtained for important contributions of resonance forms involving pentacovalent silicon in the transition states of the displacement reactions of organosilicon halides.

Solvent effects on reaction constant ρ for the dissociation equilibria of several series of organic acids are analysed in terms of three factors, namely, (i) variation in the effective dielectric constant, (ii) variation in the hydrogen-bonding ability of solvents, and (iii) variation in the conformation of the acids. A fourth factor, variation in the charge developed in the transition state of the reaction, is included in the analysis of ρ for reactions between diazodiphenylmethane and several series of carboxylic acids. It is shown that the ρ values for the dissociation equilibria of series of acids in other solvents can be calculated from their ρ values in water.