A comparison is made of the effects of substituents on the proton and carbon basicities of thiophenoxide ions. The carbon basicities were determined by measurements of the equilibrium constants for formation of 1 : 1 covalently bound addition complexes of the thiophenoxides with 1,3,5-trinitrobenzene. They show a somewhat greater susceptibility to change in substituent than do the proton basicities although the general behaviour pattern is similar. The correlation of the substituent effects by σ° values is discussed.
{"title":"A comparison of substituent effects on the proton and carbon basicities of thiophenoxide ions","authors":"M. R. Crampton","doi":"10.1039/J29710002112","DOIUrl":"https://doi.org/10.1039/J29710002112","url":null,"abstract":"A comparison is made of the effects of substituents on the proton and carbon basicities of thiophenoxide ions. The carbon basicities were determined by measurements of the equilibrium constants for formation of 1 : 1 covalently bound addition complexes of the thiophenoxides with 1,3,5-trinitrobenzene. They show a somewhat greater susceptibility to change in substituent than do the proton basicities although the general behaviour pattern is similar. The correlation of the substituent effects by σ° values is discussed.","PeriodicalId":17268,"journal":{"name":"Journal of The Chemical Society B: Physical Organic","volume":"43 1","pages":"2112-2116"},"PeriodicalIF":0.0,"publicationDate":"1971-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84988442","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The rates of pyrolysis of 1-phenylethyl acetate and 1-(pentafluorophenyl)ethyl acetate have been measured between 330·6 and 409·6 °C. At 625 K the latter undergoes elimination 4·60 times slower than the former in contrast to the value of 7·75 predicted from additivity of the effects of the individual fluorine atoms. This confirms the exalted reactivity of pentafluorobenzene obtained in electrophilic aromatic demetallations (carried out in solution) showing this effect to be independent of solvent influences and also not to arise solely from steric acceleration.
{"title":"Measurement of electrophilic aromatic reactivities via pyrolysis of 1-arylethyl acetates. Part IV. The deactivating effect of the pentafluorophenyl group","authors":"R. Taylor","doi":"10.1039/J29710000255","DOIUrl":"https://doi.org/10.1039/J29710000255","url":null,"abstract":"The rates of pyrolysis of 1-phenylethyl acetate and 1-(pentafluorophenyl)ethyl acetate have been measured between 330·6 and 409·6 °C. At 625 K the latter undergoes elimination 4·60 times slower than the former in contrast to the value of 7·75 predicted from additivity of the effects of the individual fluorine atoms. This confirms the exalted reactivity of pentafluorobenzene obtained in electrophilic aromatic demetallations (carried out in solution) showing this effect to be independent of solvent influences and also not to arise solely from steric acceleration.","PeriodicalId":17268,"journal":{"name":"Journal of The Chemical Society B: Physical Organic","volume":"45 1","pages":"255-257"},"PeriodicalIF":0.0,"publicationDate":"1971-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85941052","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The interactions between potassium methoxide and compounds of the type 2,6-dinitro-4-substituted anilinopropionamides (I) have been studied kinetically over a range of temperatures in methanol. The formation of a Meisenheimer complex is shown to occur with σ-bond formation at the 1-position of the aniline and the reasons for the observation of this path rather than anilino N–H ionization or 3-σ complex formation are discussed.
{"title":"2,6-Dinitro-4-X-anilino-N-methylpropionamides: reactions with potassium methoxide","authors":"J. Boulton, P. Jewess, N. R. Mcfarlane","doi":"10.1039/J29710000928","DOIUrl":"https://doi.org/10.1039/J29710000928","url":null,"abstract":"The interactions between potassium methoxide and compounds of the type 2,6-dinitro-4-substituted anilinopropionamides (I) have been studied kinetically over a range of temperatures in methanol. The formation of a Meisenheimer complex is shown to occur with σ-bond formation at the 1-position of the aniline and the reasons for the observation of this path rather than anilino N–H ionization or 3-σ complex formation are discussed.","PeriodicalId":17268,"journal":{"name":"Journal of The Chemical Society B: Physical Organic","volume":"161 1","pages":"928-930"},"PeriodicalIF":0.0,"publicationDate":"1971-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85974626","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
An e.s.r. spectroscopic investigation of a wide series of acylarylnitrosamines in several series of solvents has been carried out. In general the signals were either, or both, of two types: those of the PAPN type [ArN(NAr·Acyl)·O·], and in this Chalfont and Perkins' assignment of structure is confirmed, and those of the (phenylazo)oxyl σ-radical type (PhNNO·). These assignments have been established by study of the effect of variation of substituents on the resulting spectra, by theoretical calculations and by computer simulation in selected cases. The constancy of appearance of the (phenylazo)oxyl radical compared with the absence of PAPN in some cases (e.g. mesitylene) but not in others (e.g. benzene) suggests that the former is the more significant chain carrying radical in the decomposition of acylarylnitrosamines in such solvents. It is also concluded that electron transfer involving the diazonium cation and the intermediate arylcyclohexadienyl radical cannot be ruled out as a key step in the decomposition. The identification and mechanistic significance of other signals observed in ether and cumene are discussed.
{"title":"Acylarylnitrosamines. Part I. Electron spin resonance studies relevant to the mechanism of decomposition of acylarylnitrosamines in various solvents","authors":"J. Cadogan, R. Paton, C. Thomson","doi":"10.1039/J29710000583","DOIUrl":"https://doi.org/10.1039/J29710000583","url":null,"abstract":"An e.s.r. spectroscopic investigation of a wide series of acylarylnitrosamines in several series of solvents has been carried out. In general the signals were either, or both, of two types: those of the PAPN type [ArN(NAr·Acyl)·O·], and in this Chalfont and Perkins' assignment of structure is confirmed, and those of the (phenylazo)oxyl σ-radical type (PhNNO·). These assignments have been established by study of the effect of variation of substituents on the resulting spectra, by theoretical calculations and by computer simulation in selected cases. The constancy of appearance of the (phenylazo)oxyl radical compared with the absence of PAPN in some cases (e.g. mesitylene) but not in others (e.g. benzene) suggests that the former is the more significant chain carrying radical in the decomposition of acylarylnitrosamines in such solvents. It is also concluded that electron transfer involving the diazonium cation and the intermediate arylcyclohexadienyl radical cannot be ruled out as a key step in the decomposition. The identification and mechanistic significance of other signals observed in ether and cumene are discussed.","PeriodicalId":17268,"journal":{"name":"Journal of The Chemical Society B: Physical Organic","volume":"85 1","pages":"583-595"},"PeriodicalIF":0.0,"publicationDate":"1971-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76859129","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The n.m.r. spectra of 14 asymmetrically substituted 1,3-dioxans have been examined and their temperature-dependence has provided information on the conformational requirements of the substituents. Thermodynamic parameters for the ring inversion process could be evaluated for six of these molecules.
{"title":"Nuclear magnetic resonance studies of some asymmetrically substituted 1,3-dioxans","authors":"V. Jones, J. Ladd","doi":"10.1039/J29710000567","DOIUrl":"https://doi.org/10.1039/J29710000567","url":null,"abstract":"The n.m.r. spectra of 14 asymmetrically substituted 1,3-dioxans have been examined and their temperature-dependence has provided information on the conformational requirements of the substituents. Thermodynamic parameters for the ring inversion process could be evaluated for six of these molecules.","PeriodicalId":17268,"journal":{"name":"Journal of The Chemical Society B: Physical Organic","volume":"39 1","pages":"567-570"},"PeriodicalIF":0.0,"publicationDate":"1971-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76992779","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Rate constants have been determined for the solvolyses of 5-chloro-2-sulphobenzoic anhydride in five alcohols, 4-bromo-, 4-chloro-, 4-methyl-, and 4-nitro-2-sulphobenzoic anhydride in four alcohols, and 4-iodo-2-sulphobenzoic anhydride in three alcohols, each alcohol containing 6·67% ether. Rate constants for the hydrolysis and deuteriolysis of the 4-methyl compound in 90% dioxan were also obtained. Hammett ρ values and solvent effects are interpreted as indicating a synchronous mechanism with a transition state in which bond forming has proceeded further than bond breaking.
{"title":"The mechanism of acyl sulphonate reactions. Part II. Solvolyses of a series of 4- and 5-substituted 2-sulphobenzoic anhydrides in hydroxylic solvents","authors":"R. Laird, M. Spence","doi":"10.1039/J29710000454","DOIUrl":"https://doi.org/10.1039/J29710000454","url":null,"abstract":"Rate constants have been determined for the solvolyses of 5-chloro-2-sulphobenzoic anhydride in five alcohols, 4-bromo-, 4-chloro-, 4-methyl-, and 4-nitro-2-sulphobenzoic anhydride in four alcohols, and 4-iodo-2-sulphobenzoic anhydride in three alcohols, each alcohol containing 6·67% ether. Rate constants for the hydrolysis and deuteriolysis of the 4-methyl compound in 90% dioxan were also obtained. Hammett ρ values and solvent effects are interpreted as indicating a synchronous mechanism with a transition state in which bond forming has proceeded further than bond breaking.","PeriodicalId":17268,"journal":{"name":"Journal of The Chemical Society B: Physical Organic","volume":"17 1","pages":"454-456"},"PeriodicalIF":0.0,"publicationDate":"1971-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83587461","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The rates of oxidation by chromic acid in acetic acid of a series of bicyclo[2,2,1]heptan-2-ols with symmetrical exo-5,6-substituents (1,2-benzene and 1,8-naphthalene) have been measured. Rates of oxidation were found to be determined largely by the degree of nonbonded interactions in the ground state of the molecules except in the case of endo-norbornan-2-ol with an endo-naphthalene 5,6-substituent. The α-deuterium isotope effect for oxidation of this substrate (3·7) indicated that both chromate ester formation and elimination were involved in the rate limited step but that in other cases ester elimination alone was rate controlling.
{"title":"Chromic acid oxidation of polycyclic alcohols","authors":"R. Baker, T. Mason","doi":"10.1039/J29710000988","DOIUrl":"https://doi.org/10.1039/J29710000988","url":null,"abstract":"The rates of oxidation by chromic acid in acetic acid of a series of bicyclo[2,2,1]heptan-2-ols with symmetrical exo-5,6-substituents (1,2-benzene and 1,8-naphthalene) have been measured. Rates of oxidation were found to be determined largely by the degree of nonbonded interactions in the ground state of the molecules except in the case of endo-norbornan-2-ol with an endo-naphthalene 5,6-substituent. The α-deuterium isotope effect for oxidation of this substrate (3·7) indicated that both chromate ester formation and elimination were involved in the rate limited step but that in other cases ester elimination alone was rate controlling.","PeriodicalId":17268,"journal":{"name":"Journal of The Chemical Society B: Physical Organic","volume":"5 1","pages":"988-993"},"PeriodicalIF":0.0,"publicationDate":"1971-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85513928","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The mass spectra of all three nitrophenyl(phenyl)methanes (nitrodiphenylmethanes) show an M–OH species produced directly from the molecular ion. In the case of the 2-isomer this arises almost entirely by the expected interaction between the ortho-substituents. Deuterium labelling shows that, for the 4-isomer, the hydrogen atom lost in the hydroxyl radical originates primarily in the aromatic ring bearing the nitro-substituent and a mechanism is suggested to account for this. The formation of the M–17 ion may be followed by loss of a second hydroxy-group. Discrepancies in the conclusions drawn from a study of the molecular ion region of two deuteriated analogues of 2-nitrodiphenylmethane highlight the danger of relying on evidence from the spectrum of a single labelled compound to confirm a suspected fragmentation mode. The mass spectra of some related compounds are also discussed.
{"title":"The mass spectra of nitrophenyl(phenyl)methanes: the formation of an M–17 ion from the meta- and para-isomers","authors":"G. Robinson, C. Thomas, J. Vernon","doi":"10.1039/J29710001273","DOIUrl":"https://doi.org/10.1039/J29710001273","url":null,"abstract":"The mass spectra of all three nitrophenyl(phenyl)methanes (nitrodiphenylmethanes) show an M–OH species produced directly from the molecular ion. In the case of the 2-isomer this arises almost entirely by the expected interaction between the ortho-substituents. Deuterium labelling shows that, for the 4-isomer, the hydrogen atom lost in the hydroxyl radical originates primarily in the aromatic ring bearing the nitro-substituent and a mechanism is suggested to account for this. The formation of the M–17 ion may be followed by loss of a second hydroxy-group. Discrepancies in the conclusions drawn from a study of the molecular ion region of two deuteriated analogues of 2-nitrodiphenylmethane highlight the danger of relying on evidence from the spectrum of a single labelled compound to confirm a suspected fragmentation mode. The mass spectra of some related compounds are also discussed.","PeriodicalId":17268,"journal":{"name":"Journal of The Chemical Society B: Physical Organic","volume":"112 1","pages":"1273-1282"},"PeriodicalIF":0.0,"publicationDate":"1971-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72857830","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In strong aqueous base, pH > 11, the catalysed chlorination of nitroethane (N) obeys the rate law, v=k[N]0[ClO–][OH–]–1. These kinetics are consistent with a rate-determining attack of either hypochlorite on the nitronic acid (A)kA= 1·8 × 108 l mol–1 s–1, or hypochlorous acid on nitronate (C–)k8≃ 1·5 × 105 l mol–1 s–1, at 25°C. A rationale is provided for the fact that the usual second-order kinetics for deprotonation of N do not apply to this halogenation of a nitro-alkane.
在pH为bbbb11的强水中，硝基乙烷(N)的催化氯化反应遵循v=k[N]0[ClO -][OH -] - 1的速率规律。这些动力学与25℃下次氯酸对硝酸(a)kA= 1·8 × 108 l mol-1 s-1或次氯酸对硝酸(C -)k8≃1·5 × 105 l mol-1 s-1的速率决定作用相一致。通常的N去质子化的二级动力学不适用于硝基烷烃的卤化，这一事实提供了一个基本原理。
{"title":"Inverse kinetic dependence on hydroxide in the reaction of hypochlorite with nitroethane","authors":"R. Lii, Sidney I. Miller","doi":"10.1039/J29710002271","DOIUrl":"https://doi.org/10.1039/J29710002271","url":null,"abstract":"In strong aqueous base, pH > 11, the catalysed chlorination of nitroethane (N) obeys the rate law, v=k[N]0[ClO–][OH–]–1. These kinetics are consistent with a rate-determining attack of either hypochlorite on the nitronic acid (A)kA= 1·8 × 108 l mol–1 s–1, or hypochlorous acid on nitronate (C–)k8≃ 1·5 × 105 l mol–1 s–1, at 25°C. A rationale is provided for the fact that the usual second-order kinetics for deprotonation of N do not apply to this halogenation of a nitro-alkane.","PeriodicalId":17268,"journal":{"name":"Journal of The Chemical Society B: Physical Organic","volume":"7 1","pages":"2271-2272"},"PeriodicalIF":0.0,"publicationDate":"1971-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73137451","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
M. Abraham, D. Dodd, Michael D. Johnson, E. Lewis, R. O'Ferrall
Recent criticisms of well established mechanistic interpretations of isotopic exchange reactions of organomercury-(II) compounds have been shown to be erroneous by consideration of three-dimensional potential-energy surfaces, which show the several possible reaction paths. The method provides a clear understanding of the principle of microscopic reversibility as applied to symmetrical organometallic exchange reactions.
{"title":"Microscopic reversibility and the symmetrical isotopic exchange reactions of organometallic compounds","authors":"M. Abraham, D. Dodd, Michael D. Johnson, E. Lewis, R. O'Ferrall","doi":"10.1039/J29710000762","DOIUrl":"https://doi.org/10.1039/J29710000762","url":null,"abstract":"Recent criticisms of well established mechanistic interpretations of isotopic exchange reactions of organomercury-(II) compounds have been shown to be erroneous by consideration of three-dimensional potential-energy surfaces, which show the several possible reaction paths. The method provides a clear understanding of the principle of microscopic reversibility as applied to symmetrical organometallic exchange reactions.","PeriodicalId":17268,"journal":{"name":"Journal of The Chemical Society B: Physical Organic","volume":"53 1","pages":"762-766"},"PeriodicalIF":0.0,"publicationDate":"1971-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76625367","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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