The relative substituent effects of the groups X and CH2X in the meta- nitration of benzene derivatives are discussed in terms of the transmission factor of the methylene bridge. The values of this transmission factor for nine different deactivating groups show a clear division between charged and neutral substituents. The reasons for this division are analysed using a model for the field effect of a dipole based on the substituent effect of positive poles at different distances from the aromatic ring. Some further experimental results concerning deactivation by the –CH2[graphic omitted]H3 and (CH2)2[graphic omitted]H3 substituents are presented. From the complete set of results, it appears that both inductive and field effects contribute to deactivation at the meta-position when the groups X are directly attached to the aromatic ring. The relative importance of the field effect appears much greater for meta-substitution to the substituents CH2X but the inductive effect remains an important factor in determining the para/meta ratio with these substituents.
{"title":"Inductive and field effects in aromatic substitution. Part III. Comparison of the substituents X and CH2X in nitration","authors":"F. Sarlo, G. Grynkiewicz, A. Ricci, J. Ridd","doi":"10.1039/J29710000719","DOIUrl":"https://doi.org/10.1039/J29710000719","url":null,"abstract":"The relative substituent effects of the groups X and CH2X in the meta- nitration of benzene derivatives are discussed in terms of the transmission factor of the methylene bridge. The values of this transmission factor for nine different deactivating groups show a clear division between charged and neutral substituents. The reasons for this division are analysed using a model for the field effect of a dipole based on the substituent effect of positive poles at different distances from the aromatic ring. Some further experimental results concerning deactivation by the –CH2[graphic omitted]H3 and (CH2)2[graphic omitted]H3 substituents are presented. From the complete set of results, it appears that both inductive and field effects contribute to deactivation at the meta-position when the groups X are directly attached to the aromatic ring. The relative importance of the field effect appears much greater for meta-substitution to the substituents CH2X but the inductive effect remains an important factor in determining the para/meta ratio with these substituents.","PeriodicalId":17268,"journal":{"name":"Journal of The Chemical Society B: Physical Organic","volume":"129 1","pages":"719-723"},"PeriodicalIF":0.0,"publicationDate":"1971-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88347612","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 pK value of o-formylbenzoic acid measured by conventional means has been compared with the value derived from observations of the catalytic effect of its anion in the decomposition of nitramide and the mutarotation of glucose. It is concluded that in aqueous solution at 25 °C 93·7% of the acid exists as its cyclic isomer. Measurements of pK values in the temperature range 20–60°C were used to determine the enthalpy of ionization (ΔH= 5·9 kJ mol–1). The temperature-jump relaxation method has been used to study the kinetics and mechanism of the isomerisation.
{"title":"Equilibria and kinetics in the isomerisation of o-formylbenzoic acid","authors":"R. Bell, B. Cox, B. A. Timimi","doi":"10.1039/J29710002247","DOIUrl":"https://doi.org/10.1039/J29710002247","url":null,"abstract":"The pK value of o-formylbenzoic acid measured by conventional means has been compared with the value derived from observations of the catalytic effect of its anion in the decomposition of nitramide and the mutarotation of glucose. It is concluded that in aqueous solution at 25 °C 93·7% of the acid exists as its cyclic isomer. Measurements of pK values in the temperature range 20–60°C were used to determine the enthalpy of ionization (ΔH= 5·9 kJ mol–1). The temperature-jump relaxation method has been used to study the kinetics and mechanism of the isomerisation.","PeriodicalId":17268,"journal":{"name":"Journal of The Chemical Society B: Physical Organic","volume":"11 1","pages":"2247-2250"},"PeriodicalIF":0.0,"publicationDate":"1971-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86413480","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 pyrolysis of 1,2-dichloroethane in a static system has been studied by g.l.c. analysis of the products and by pressure measurements in the temperature range 340–515 °C, surface:volume ratio range (1·32–37·4) cm–1, and with initial pressures from 0·3 to 300 Torr, in reaction vessels coated with pyrolytic carbon films.The major reaction is dehydrochlorination to vinyl chloride, but ethylene is also a primary reaction product. The ethylene yield is very small ( < 2% of the vinyl chloride) under conditions of low surface:volume ratio. It is concluded that the ethylene is produced by a concurrent heterogeneous dechlorination of 1,2-dichloroethane.At low surface:volume ratio the vinyl chloride produced is closely paralleled by the pressure increase and the reaction is found to have a high order (2·4–2·8) and activation energy (73 ± 3 kcal mol–1). The reaction is inhibited by additions of vinyl chloride, ethylene, and propene, and accelerated by added hydrogen chloride, oxygen, and chlorine. The radical-chain mechanism previously suggested by Barton and Howlett is discussed and modified to account for the experimental observations.The pressure–time curves obtained from experiments at high surface:volume ratio indicate that under these conditions the reaction is autocatalytic. The maximum rate corresponds to an order of 1·5 and an activation energy of 33·0 kcal mol–1. It is suggested that the autocatalysis is due to a heterogeneous initiation process involving adsorbed chlorine.
{"title":"The pyrolysis of 1,2-dichloroethane","authors":"K. A. Holbrook, R. Walker, W. Watson","doi":"10.1039/J29710000577","DOIUrl":"https://doi.org/10.1039/J29710000577","url":null,"abstract":"The pyrolysis of 1,2-dichloroethane in a static system has been studied by g.l.c. analysis of the products and by pressure measurements in the temperature range 340–515 °C, surface:volume ratio range (1·32–37·4) cm–1, and with initial pressures from 0·3 to 300 Torr, in reaction vessels coated with pyrolytic carbon films.The major reaction is dehydrochlorination to vinyl chloride, but ethylene is also a primary reaction product. The ethylene yield is very small ( < 2% of the vinyl chloride) under conditions of low surface:volume ratio. It is concluded that the ethylene is produced by a concurrent heterogeneous dechlorination of 1,2-dichloroethane.At low surface:volume ratio the vinyl chloride produced is closely paralleled by the pressure increase and the reaction is found to have a high order (2·4–2·8) and activation energy (73 ± 3 kcal mol–1). The reaction is inhibited by additions of vinyl chloride, ethylene, and propene, and accelerated by added hydrogen chloride, oxygen, and chlorine. The radical-chain mechanism previously suggested by Barton and Howlett is discussed and modified to account for the experimental observations.The pressure–time curves obtained from experiments at high surface:volume ratio indicate that under these conditions the reaction is autocatalytic. The maximum rate corresponds to an order of 1·5 and an activation energy of 33·0 kcal mol–1. It is suggested that the autocatalysis is due to a heterogeneous initiation process involving adsorbed chlorine.","PeriodicalId":17268,"journal":{"name":"Journal of The Chemical Society B: Physical Organic","volume":"11 1","pages":"577-582"},"PeriodicalIF":0.0,"publicationDate":"1971-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86512274","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 thermal decomposition of gaseous acetic anhydride has been studied in flow and static apparata between 197 and 370°C. The decomposition, which yields keten and acetic acid only, is homogeneous and unimolecular, k= 1011·27 exp (–134,700/RT) s–1.
{"title":"Kinetics of thermal decomposition of acetic anhydride in flow and static systems","authors":"P. G. Blake, A. Speis","doi":"10.1039/J29710001877","DOIUrl":"https://doi.org/10.1039/J29710001877","url":null,"abstract":"The thermal decomposition of gaseous acetic anhydride has been studied in flow and static apparata between 197 and 370°C. The decomposition, which yields keten and acetic acid only, is homogeneous and unimolecular, k= 1011·27 exp (–134,700/RT) s–1.","PeriodicalId":17268,"journal":{"name":"Journal of The Chemical Society B: Physical Organic","volume":"69 1","pages":"1877-1878"},"PeriodicalIF":0.0,"publicationDate":"1971-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86420050","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}
D. W. White, G. K. Mcewen, R. D. Bertrand, J. Verkade
The 1H n.m.r. spectra of twenty one 2-substituted 5,5-disubstituted 1,3,2-dioxaphosphorinan-2-ones (2-substituent = CPh3, CMe2·OH, OMe, OBut, NC5H10, Me, Et, Prn, Ph, CH2Ph, Br, Cl, H), many of which were examined at more than one temperature or concentration or in more than one solvent, are shown to be most consistent with the presence of one dominant chair conformer (2-substituent = alkoxy, Br, Cl, H) or with an equilibrium of rapidly interconverting chair conformers (2-substituent = alkyl, aralkyl, phenyl). The assignment of i.r. phosphoryl stretching bands for some of these derivatives is shown to be qualitatively consistent with the 1H n.m.r. results.Predictions of the dispositions of exocyclic substituents based on these 1H n.m.r. and i.r. spectra are made and a classification of 1,3,2-dioxaphosphorinan-2-ones based on the sum of the two J(POCH) values associated with the 4,6-methylene protons is established.
{"title":"Structural implications of nuclear magnetic resonance and infrared investigations on 2-substituted 1,3,2-dioxaphosphorinan-2-ones","authors":"D. W. White, G. K. Mcewen, R. D. Bertrand, J. Verkade","doi":"10.1039/J29710001454","DOIUrl":"https://doi.org/10.1039/J29710001454","url":null,"abstract":"The 1H n.m.r. spectra of twenty one 2-substituted 5,5-disubstituted 1,3,2-dioxaphosphorinan-2-ones (2-substituent = CPh3, CMe2·OH, OMe, OBut, NC5H10, Me, Et, Prn, Ph, CH2Ph, Br, Cl, H), many of which were examined at more than one temperature or concentration or in more than one solvent, are shown to be most consistent with the presence of one dominant chair conformer (2-substituent = alkoxy, Br, Cl, H) or with an equilibrium of rapidly interconverting chair conformers (2-substituent = alkyl, aralkyl, phenyl). The assignment of i.r. phosphoryl stretching bands for some of these derivatives is shown to be qualitatively consistent with the 1H n.m.r. results.Predictions of the dispositions of exocyclic substituents based on these 1H n.m.r. and i.r. spectra are made and a classification of 1,3,2-dioxaphosphorinan-2-ones based on the sum of the two J(POCH) values associated with the 4,6-methylene protons is established.","PeriodicalId":17268,"journal":{"name":"Journal of The Chemical Society B: Physical Organic","volume":"74 1","pages":"1454-1461"},"PeriodicalIF":0.0,"publicationDate":"1971-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83981866","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}
Many data, collected from the literature, support the postulation of two general rules which describe the static and dynamic results of having in a molecule or generating in an intermediate adjacent electron pairs and/or polar bonds. In disagreement with current chemical intuition, structures which contain the maximum number of gauche-interactions between lone electron pairs or polar bonds represent energy minima and, frequently, the lowest minima. The stereochemical implications of the phenomenon are discussed, along with possible physical explanations. It is suggested that partitioning of the total energy of the system into attractive-dominant and repulsive-dominant interactions provides the most helpful framework for the construction of a physical picture of the phenomenon. The total energy and its components can be obtained by ab initio molecular quantum mechanical calculations.The only apparent exception to the phenomenon that has been found corresponds to a polar bond adjacent to two lone pairs (as in the case of two hetero-atoms attached to the same carbon atom). This exception, here termed the Edward–Lemieux effect, has been examined theoretically by an ab initio(Hartree–Fock) calculation using fluoromethanol as a model compound. The calculation has reproduced the Edward–Lemieux effect; the stable conformation has the C–F bond trans to one ‘electron pair’ and gauche to another, and the conformation in which the C–F bond bisects the ‘electron pairs’ is the energy maximum. The partitioning of the total energy into its components of attraction and repulsion and comparison of the results with other systems for which barriers to internal rotation have been obtained by ab initio methods reveals a similarity between fluoromethanol, hydrazine, hydroxylamine, and hydrogen peroxide. An interpretation of this result is provided in which an early suggestion by Lemieux and Chu is supported and the concept of ‘rabbit-ears’ is not.
{"title":"A theoretical study of the Edward–Lemieux effect (the anomeric effect). The stereochemical requirements of adjacent electron pairs and polar bonds","authors":"S. Wolfe, A. Rauk, L. M. Tel, I. Csizmadia","doi":"10.1039/J29710000136","DOIUrl":"https://doi.org/10.1039/J29710000136","url":null,"abstract":"Many data, collected from the literature, support the postulation of two general rules which describe the static and dynamic results of having in a molecule or generating in an intermediate adjacent electron pairs and/or polar bonds. In disagreement with current chemical intuition, structures which contain the maximum number of gauche-interactions between lone electron pairs or polar bonds represent energy minima and, frequently, the lowest minima. The stereochemical implications of the phenomenon are discussed, along with possible physical explanations. It is suggested that partitioning of the total energy of the system into attractive-dominant and repulsive-dominant interactions provides the most helpful framework for the construction of a physical picture of the phenomenon. The total energy and its components can be obtained by ab initio molecular quantum mechanical calculations.The only apparent exception to the phenomenon that has been found corresponds to a polar bond adjacent to two lone pairs (as in the case of two hetero-atoms attached to the same carbon atom). This exception, here termed the Edward–Lemieux effect, has been examined theoretically by an ab initio(Hartree–Fock) calculation using fluoromethanol as a model compound. The calculation has reproduced the Edward–Lemieux effect; the stable conformation has the C–F bond trans to one ‘electron pair’ and gauche to another, and the conformation in which the C–F bond bisects the ‘electron pairs’ is the energy maximum. The partitioning of the total energy into its components of attraction and repulsion and comparison of the results with other systems for which barriers to internal rotation have been obtained by ab initio methods reveals a similarity between fluoromethanol, hydrazine, hydroxylamine, and hydrogen peroxide. An interpretation of this result is provided in which an early suggestion by Lemieux and Chu is supported and the concept of ‘rabbit-ears’ is not.","PeriodicalId":17268,"journal":{"name":"Journal of The Chemical Society B: Physical Organic","volume":"8 1","pages":"136-145"},"PeriodicalIF":0.0,"publicationDate":"1971-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82838360","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}
Spectra of three [2,2]paracyclophanylene bisnitroxides have been measured. For two of the biradicals the exchange interaction J is much larger than the nitrogen hyperfine splitting and five-line e.s.r. spectra are observed, while for the third the zero-field splitting is so large that its solution spectrum cannot be resolved. Values of the zero-field tensor D for all three biradicals have been evaluated by measuring their spectra in glasses.
{"title":"Nitroxide radicals. Part X. Electron spin resonance spectra of [2,2]paracyclophanylene bisnitroxides","authors":"A. R. Forrester, R. Ramasseul","doi":"10.1039/J29710001645","DOIUrl":"https://doi.org/10.1039/J29710001645","url":null,"abstract":"Spectra of three [2,2]paracyclophanylene bisnitroxides have been measured. For two of the biradicals the exchange interaction J is much larger than the nitrogen hyperfine splitting and five-line e.s.r. spectra are observed, while for the third the zero-field splitting is so large that its solution spectrum cannot be resolved. Values of the zero-field tensor D for all three biradicals have been evaluated by measuring their spectra in glasses.","PeriodicalId":17268,"journal":{"name":"Journal of The Chemical Society B: Physical Organic","volume":"20 1","pages":"1645-1647"},"PeriodicalIF":0.0,"publicationDate":"1971-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88976528","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 conformations of some new indan-1-ols have been assigned from their mode of synthesis and from their n.m.r. spectra. Those with a substituent RCH2 on C-1 show an unexpected correlation between the chemical shifts of the methylene protons and the configuration of the 2,3-substituents.
{"title":"Conformational analysis of indan-1-ols","authors":"M. Hiscock, G. Porter","doi":"10.1039/J29710001631","DOIUrl":"https://doi.org/10.1039/J29710001631","url":null,"abstract":"The conformations of some new indan-1-ols have been assigned from their mode of synthesis and from their n.m.r. spectra. Those with a substituent RCH2 on C-1 show an unexpected correlation between the chemical shifts of the methylene protons and the configuration of the 2,3-substituents.","PeriodicalId":17268,"journal":{"name":"Journal of The Chemical Society B: Physical Organic","volume":"18 1","pages":"1631-1634"},"PeriodicalIF":0.0,"publicationDate":"1971-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91528316","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}
Symmetrically bifurcate three-centre hydrogen bonding, N–[graphic omitted], was found in the symmetrical cis,cis-form of several bis-(β-acylvinyl)amines, [R1C(O)CR2CR3]2NH. The alternative cis,trans–s-cis and cis,trans–s-trans-structures were also detected in amounts depending on the size of the R-alkyl substituent, the solvent, and its concentration. The data do not prove conclusively that the hydrogen bond is truly symmetrically forked.
{"title":"Symmetrically bifurcate hydrogen bonding. Part I. Bis-(β-acylvinyl)-amines","authors":"J. Dąbrowski, Z. Świstun","doi":"10.1039/J29710000818","DOIUrl":"https://doi.org/10.1039/J29710000818","url":null,"abstract":"Symmetrically bifurcate three-centre hydrogen bonding, N–[graphic omitted], was found in the symmetrical cis,cis-form of several bis-(β-acylvinyl)amines, [R1C(O)CR2CR3]2NH. The alternative cis,trans–s-cis and cis,trans–s-trans-structures were also detected in amounts depending on the size of the R-alkyl substituent, the solvent, and its concentration. The data do not prove conclusively that the hydrogen bond is truly symmetrically forked.","PeriodicalId":17268,"journal":{"name":"Journal of The Chemical Society B: Physical Organic","volume":"27 6","pages":"818-821"},"PeriodicalIF":0.0,"publicationDate":"1971-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91404979","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 coefficients have been measured for the alkaline hydrolysis of a comprehensive series of methyl 2-acyl- and 2-aroyl-benzoates and closely related esters in 70%(v/v) dioxan–water at several temperatures. The entropies and enthalpies of activation have been evaluated. The effect of substitution in the 2-acyl system has been correlated with the steric substituent parameter, Es. The relative rates of hydrolysis, activation parameters, substituent effects, solvent isotope, and solvent effects have been used to delineate the importance and extent of neighbouring-group participation by the keto- or formyl-carbonyl groups in the alkaline hydrolysis of the esters under study.
{"title":"Reactions of carbonyl compounds in basic solutions. Part III. The mechanism of the alkaline hydrolysis of methyl 2-aroyl- and 2-acylbenzoates and related esters","authors":"K. Bowden, G. R. Taylor","doi":"10.1039/J29710000149","DOIUrl":"https://doi.org/10.1039/J29710000149","url":null,"abstract":"Rate coefficients have been measured for the alkaline hydrolysis of a comprehensive series of methyl 2-acyl- and 2-aroyl-benzoates and closely related esters in 70%(v/v) dioxan–water at several temperatures. The entropies and enthalpies of activation have been evaluated. The effect of substitution in the 2-acyl system has been correlated with the steric substituent parameter, Es. The relative rates of hydrolysis, activation parameters, substituent effects, solvent isotope, and solvent effects have been used to delineate the importance and extent of neighbouring-group participation by the keto- or formyl-carbonyl groups in the alkaline hydrolysis of the esters under study.","PeriodicalId":17268,"journal":{"name":"Journal of The Chemical Society B: Physical Organic","volume":"50 1","pages":"149-156"},"PeriodicalIF":0.0,"publicationDate":"1971-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83145765","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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