The stereospecific solvation of a number of aromatic aldehydes and ketones in benzene is investigated through measurements of molar Kerr constants. It is concluded that there is a strong tendency towards orthogonal association of benzene molecules at the carbonyl groups.
{"title":"Molecular polarisability. Association of some aromatic aldehydes and ketones with benzene","authors":"P. Hopkins, R. Fèvre, L. Radom, G. Ritchie","doi":"10.1039/J29710000574","DOIUrl":"https://doi.org/10.1039/J29710000574","url":null,"abstract":"The stereospecific solvation of a number of aromatic aldehydes and ketones in benzene is investigated through measurements of molar Kerr constants. It is concluded that there is a strong tendency towards orthogonal association of benzene molecules at the carbonyl groups.","PeriodicalId":17268,"journal":{"name":"Journal of The Chemical Society B: Physical Organic","volume":"70 1","pages":"574-576"},"PeriodicalIF":0.0,"publicationDate":"1971-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77723062","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}
Twenty-seven 3- and 4-substituted aryl benzoates have been hydrolysed with sodium hydroxide in ethanol–water (6:4 v/v). The kinetic data are correlated by the Hammett equation with ρ= 1·93. Rate enhancements for para-conjugatively electron-withdrawing substituents (–M) are small, diagnostic of a transition state in which there is at most only slight fission of the aryloxy-carbon bond.
{"title":"Rates of base-catalysed hydrolysis of substituted aryl benzoates","authors":"Z. S. Chaw, A. Fischer, D. A. Happer","doi":"10.1039/J29710001818","DOIUrl":"https://doi.org/10.1039/J29710001818","url":null,"abstract":"Twenty-seven 3- and 4-substituted aryl benzoates have been hydrolysed with sodium hydroxide in ethanol–water (6:4 v/v). The kinetic data are correlated by the Hammett equation with ρ= 1·93. Rate enhancements for para-conjugatively electron-withdrawing substituents (–M) are small, diagnostic of a transition state in which there is at most only slight fission of the aryloxy-carbon bond.","PeriodicalId":17268,"journal":{"name":"Journal of The Chemical Society B: Physical Organic","volume":"43 1","pages":"1818-1819"},"PeriodicalIF":0.0,"publicationDate":"1971-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77739620","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 gas-phase pyrolysis of 1,1-dichlorobutane has been studied at initial pressures of 5–150 Torr between 416 and 460°C. Analysis by g.l.c. shows that the amount of dichlorobutane removed is equal to the pressure increase as would be expected for the elimination (i). The pressure increase was used to determine the first-order rate PrnCHCl2→cis- and trans-EtCHCHCl + HCl (i) constant for this reaction which is expressed by equation (ii), where the error limits are the 95% confidence limits. log10(k/s–1)=(13·68 ± 0·27)–(53,872 ± 715)/4·576T(ii)The observed cis:trans-ratio for the 1-chlorobutene was 1·00 ± 0·02 at these temperatures compared with an equilibrium value of 1·60 ± 0·08 which was found independently. No cis–trans-isomerisation occurred under these conditions.The gas-phase pyrolysis of 1,1-dichloropropane was reinvestigated at pressures of 9–185 Torr between 389·2 and 456·5°C. The observed cis:trans-ratio of the 1-chloropropene produced was 1·20 ± 0·02 under these conditions and cis–trans-isomerisation is negligible. The comparable equilibrium cis:trans-ratio at these temperatures is 1·90 ± 0·08. The pressure change obeys first-order kinetics and the rate constant is expressed by equation (iii) where the error limits are the 95% confidence limits. log10(k/s–1)=(14·32 ± 0·30)–(56,679 ± 821)/4·576T(iii)Both pyrolyses have also been briefly studied in packed reaction vessels. The resulting cis:trans-ratios observed then favour the cis-product olefins.
{"title":"Gas-phase pyrolyses of 1,1-dichlorobutane and 1,1-dichloropropane","authors":"K. A. Holbrook, K. Parry","doi":"10.1039/J29710001762","DOIUrl":"https://doi.org/10.1039/J29710001762","url":null,"abstract":"The gas-phase pyrolysis of 1,1-dichlorobutane has been studied at initial pressures of 5–150 Torr between 416 and 460°C. Analysis by g.l.c. shows that the amount of dichlorobutane removed is equal to the pressure increase as would be expected for the elimination (i). The pressure increase was used to determine the first-order rate PrnCHCl2→cis- and trans-EtCHCHCl + HCl (i) constant for this reaction which is expressed by equation (ii), where the error limits are the 95% confidence limits. log10(k/s–1)=(13·68 ± 0·27)–(53,872 ± 715)/4·576T(ii)The observed cis:trans-ratio for the 1-chlorobutene was 1·00 ± 0·02 at these temperatures compared with an equilibrium value of 1·60 ± 0·08 which was found independently. No cis–trans-isomerisation occurred under these conditions.The gas-phase pyrolysis of 1,1-dichloropropane was reinvestigated at pressures of 9–185 Torr between 389·2 and 456·5°C. The observed cis:trans-ratio of the 1-chloropropene produced was 1·20 ± 0·02 under these conditions and cis–trans-isomerisation is negligible. The comparable equilibrium cis:trans-ratio at these temperatures is 1·90 ± 0·08. The pressure change obeys first-order kinetics and the rate constant is expressed by equation (iii) where the error limits are the 95% confidence limits. log10(k/s–1)=(14·32 ± 0·30)–(56,679 ± 821)/4·576T(iii)Both pyrolyses have also been briefly studied in packed reaction vessels. The resulting cis:trans-ratios observed then favour the cis-product olefins.","PeriodicalId":17268,"journal":{"name":"Journal of The Chemical Society B: Physical Organic","volume":"47 1","pages":"1762-1765"},"PeriodicalIF":0.0,"publicationDate":"1971-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81355714","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. E. Grocock, G. Hallas, J. Hepworth, J. Hudson, D. Ibbitson
Attempts to synthesise 2-dimethylaminobenzylidyne trifluoride (2-trifluoromethyl-NN-dimethyl aniline) have, so far, been unsuccessful. The possible relevance of steric factors and intramolecular hydrogen bonding operative in 2-amino- and 2-methylaminobenzylidyne trifluoride (2-trifluoromethyl- and 2-trifluoromethyl-N-methyl-anline) is discussed by comparing observed and calculated dipole moments of these compounds and by assessing their tendencies to undergo intermolecular hydrogen bonding to dioxan.
迄今为止，合成2-二甲氨基苄酰三氟(2-三氟甲基- nn -二甲基苯胺)的尝试尚未成功。通过比较观察到的偶极矩和计算得到的偶极矩，并通过评估它们与二恶烷发生分子间氢键的倾向，讨论了在2-氨基和2-甲基氨基对三氟化(2-三氟甲基和2-三氟甲基- n -甲基-苯胺)中发生的立体因素和分子内氢键的可能相关性。
{"title":"The ortho-effect in 2-amino- and 2-methylamino-benzylidyne trifluoride, (2-trifluoromethyl- and 2-trifluoromethyl-N-methyl-aniline)","authors":"D. E. Grocock, G. Hallas, J. Hepworth, J. Hudson, D. Ibbitson","doi":"10.1039/J29710000457","DOIUrl":"https://doi.org/10.1039/J29710000457","url":null,"abstract":"Attempts to synthesise 2-dimethylaminobenzylidyne trifluoride (2-trifluoromethyl-NN-dimethyl aniline) have, so far, been unsuccessful. The possible relevance of steric factors and intramolecular hydrogen bonding operative in 2-amino- and 2-methylaminobenzylidyne trifluoride (2-trifluoromethyl- and 2-trifluoromethyl-N-methyl-anline) is discussed by comparing observed and calculated dipole moments of these compounds and by assessing their tendencies to undergo intermolecular hydrogen bonding to dioxan.","PeriodicalId":17268,"journal":{"name":"Journal of The Chemical Society B: Physical Organic","volume":"28 1","pages":"457-459"},"PeriodicalIF":0.0,"publicationDate":"1971-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82346617","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 1H spectra of some five-membered heterocyclic olefins and related compounds are reported and analysed. The observation of some weak, hitherto ignored transitions in the AA′BB′ spectrum of the CH2·CH2 groups removes the deceptive simplicity of the spectrum and gives well determined and non-equal values of Jcis and Jtrans.The mechanisms contributing to the CH·CH couplings in these systems are considered in detail. It is concluded that (a) ring buckle and the known dihedral angle dependence satisfactorily accounts for the values in carbocyclic rings; (b) these contributions plus angle deformations and the orientation of the electronegative substituents account for the values in saturated five-membered heterocyclics. (c) No reasonable combination of these mechanisms provides a quantitative explanation of the large couplings observed in the five-membered heterocyclic olefins investigated.Possible reasons for this are given.
{"title":"The n.m.r. spectra and conformations of cyclic compounds part V. Mechanism of CH·CH coupling in heterocyclic compounds","authors":"R. J. Abraham, K. Parry, W. Thomas","doi":"10.1039/J29710000446","DOIUrl":"https://doi.org/10.1039/J29710000446","url":null,"abstract":"The 1H spectra of some five-membered heterocyclic olefins and related compounds are reported and analysed. The observation of some weak, hitherto ignored transitions in the AA′BB′ spectrum of the CH2·CH2 groups removes the deceptive simplicity of the spectrum and gives well determined and non-equal values of Jcis and Jtrans.The mechanisms contributing to the CH·CH couplings in these systems are considered in detail. It is concluded that (a) ring buckle and the known dihedral angle dependence satisfactorily accounts for the values in carbocyclic rings; (b) these contributions plus angle deformations and the orientation of the electronegative substituents account for the values in saturated five-membered heterocyclics. (c) No reasonable combination of these mechanisms provides a quantitative explanation of the large couplings observed in the five-membered heterocyclic olefins investigated.Possible reasons for this are given.","PeriodicalId":17268,"journal":{"name":"Journal of The Chemical Society B: Physical Organic","volume":"11 1","pages":"446-453"},"PeriodicalIF":0.0,"publicationDate":"1971-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82636912","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}
We present a simple method of calculating the effects of geminal substituents upon the differences in shielding between 19F nuclei bonded to sp3 carbon in a variety of compounds. A single experimental parameter is used, the Huggins electronegativity of α-substituents. The method rationalises some hitherto puzzling data, and makes it possible to calculate the chemical shifts (referred to CFCl3 as an arbitrary standard) of 19F nuclei in a variety of molecules containing the elements C, H, N, O, F, Cl, Br, and I; the calculated values (in the absence of long-range interactions) agree with experimental results to within the errors dictated by solvent effects and referencing procedures.
{"title":"The structural dependence of the inductive effect. Part I. The calculation of geminal substituent effects upon fluorine-19 chemical shifts","authors":"L. Phillips, V. Wray","doi":"10.1039/J29710002068","DOIUrl":"https://doi.org/10.1039/J29710002068","url":null,"abstract":"We present a simple method of calculating the effects of geminal substituents upon the differences in shielding between 19F nuclei bonded to sp3 carbon in a variety of compounds. A single experimental parameter is used, the Huggins electronegativity of α-substituents. The method rationalises some hitherto puzzling data, and makes it possible to calculate the chemical shifts (referred to CFCl3 as an arbitrary standard) of 19F nuclei in a variety of molecules containing the elements C, H, N, O, F, Cl, Br, and I; the calculated values (in the absence of long-range interactions) agree with experimental results to within the errors dictated by solvent effects and referencing procedures.","PeriodicalId":17268,"journal":{"name":"Journal of The Chemical Society B: Physical Organic","volume":"65 1","pages":"2068-2074"},"PeriodicalIF":0.0,"publicationDate":"1971-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80991778","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 bromination (in 70% acetic acid at 25°) of a series of 5-(arylmethylenehydrazino)tetrazoles, benzylated in the heteroaromatic ring, are independent of the bromine concentration. The slow step is a syn–anti-isomerisation of the hydrazone. A mechanism involving rotation about the CN bond is favoured in the light of data on the effect of substituents on the rate of isomerisation. The products formed on bromination are hydrazonyl bromides and the replacement of the labile bromine by external and internal nucleophiles is reported.
{"title":"The mechanism of bromination of heterocyclic hydrazones. syn–anti-Isomerisation of 5-(arymethylenehydrazino)-1- and -2-benzyltetrazoles","authors":"J. Tobin, A. F. Hegarty, F. Scott","doi":"10.1039/J29710002198","DOIUrl":"https://doi.org/10.1039/J29710002198","url":null,"abstract":"The rates of bromination (in 70% acetic acid at 25°) of a series of 5-(arylmethylenehydrazino)tetrazoles, benzylated in the heteroaromatic ring, are independent of the bromine concentration. The slow step is a syn–anti-isomerisation of the hydrazone. A mechanism involving rotation about the CN bond is favoured in the light of data on the effect of substituents on the rate of isomerisation. The products formed on bromination are hydrazonyl bromides and the replacement of the labile bromine by external and internal nucleophiles is reported.","PeriodicalId":17268,"journal":{"name":"Journal of The Chemical Society B: Physical Organic","volume":"1 1","pages":"2198-2202"},"PeriodicalIF":0.0,"publicationDate":"1971-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90897584","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 nitrations of o-xylene and biphenyl by nitric acid in aqueous sulphuric acid have been studied. The variation of the rates of nitration with acidity indicates that the nitronium ion is the electrophile in both cases. The ratio of 1,2-dimethyl-3-nitrobenzene to 1,2-dimethyl-4-nitrobenzene formed from o-xylene varies from 0·45 to 1·5 over the range 50–70% sulphuric acid at 25° and becomes constant above 70% sulphuric acid. Possible explanations of these data are proposed and their implications examined. The ratio of 2-nitrobiphenyl to 4-nitrobiphenyl formed from biphenyl is ca. 3·5. This suggests that previous deductions about the nitration of this substrate should be reconsidered.
{"title":"Electrophilic aromatic substitution. Part VIII. Isomer ratios and assignment of mechanism in aromatic nitration. o-xylene and biphenyl","authors":"R. Coombes, L. W. Russell","doi":"10.1039/J29710002443","DOIUrl":"https://doi.org/10.1039/J29710002443","url":null,"abstract":"The nitrations of o-xylene and biphenyl by nitric acid in aqueous sulphuric acid have been studied. The variation of the rates of nitration with acidity indicates that the nitronium ion is the electrophile in both cases. The ratio of 1,2-dimethyl-3-nitrobenzene to 1,2-dimethyl-4-nitrobenzene formed from o-xylene varies from 0·45 to 1·5 over the range 50–70% sulphuric acid at 25° and becomes constant above 70% sulphuric acid. Possible explanations of these data are proposed and their implications examined. The ratio of 2-nitrobiphenyl to 4-nitrobiphenyl formed from biphenyl is ca. 3·5. This suggests that previous deductions about the nitration of this substrate should be reconsidered.","PeriodicalId":17268,"journal":{"name":"Journal of The Chemical Society B: Physical Organic","volume":"9 1","pages":"2443-2447"},"PeriodicalIF":0.0,"publicationDate":"1971-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90105578","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 molecular ions of both 10,10-dimethyl-(Ia) and 10,10-diphenyl-phenoxasilin (Ib) undergo consecutive elimination of the two substituents from position 10, followed by ejection of SiO from the centre ring. The (M– R)+ species in (Ia) fragments by competitive expulsion of CH2O, SiH2O, and SiHO·, which involves complex molecular reorganizations. An abundant m/e 91 (C7H7) peak, generated through C(alkyl)–C(aryl) bond formation, is noted. The unique extrusion of the oxygen bridge in conjunction with two aromatic hydrogen atoms (H2O) from the (M– R)+ peak in (Ib) leads to an abundant even-electron siliconium ion at m/e 255. The expulsion of SiHO· from the (M– R)+ species is also observed in compound (Ib). The elements of dibenzofuran are lost from the molecular ion to give divalent siliconium ions SiR2˙+ in both compounds (Ia) and (Ib).
{"title":"Skeletal rearrangements of siliconium ions in the gas phase: mass spectra of some phenoxasilins","authors":"I. Lengyel, M. Aaronson","doi":"10.1039/J29710000177","DOIUrl":"https://doi.org/10.1039/J29710000177","url":null,"abstract":"The molecular ions of both 10,10-dimethyl-(Ia) and 10,10-diphenyl-phenoxasilin (Ib) undergo consecutive elimination of the two substituents from position 10, followed by ejection of SiO from the centre ring. The (M– R)+ species in (Ia) fragments by competitive expulsion of CH2O, SiH2O, and SiHO·, which involves complex molecular reorganizations. An abundant m/e 91 (C7H7) peak, generated through C(alkyl)–C(aryl) bond formation, is noted. The unique extrusion of the oxygen bridge in conjunction with two aromatic hydrogen atoms (H2O) from the (M– R)+ peak in (Ib) leads to an abundant even-electron siliconium ion at m/e 255. The expulsion of SiHO· from the (M– R)+ species is also observed in compound (Ib). The elements of dibenzofuran are lost from the molecular ion to give divalent siliconium ions SiR2˙+ in both compounds (Ia) and (Ib).","PeriodicalId":17268,"journal":{"name":"Journal of The Chemical Society B: Physical Organic","volume":"55 2 1","pages":"177-181"},"PeriodicalIF":0.0,"publicationDate":"1971-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89697832","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}
Kinetics and activation parameters have been measured for deuteriation at position 6 of 2,3-dihydro-5,7-dimethyl-1,4-diazepinium perchlorate by deuteriosulphuric acid in deuterium oxide, and the data are compared with those for the corresponding deuteriation catalysed by primary phosphate ions. In contrast, protons at positions 5 and 7 in two other diazepines were only slightly affected by dilute deuteriosulphuric acid. In anhydrous deuteriotrifluoroacetic acid protons at positions 5 and 7 were completely unaffected. The relative reactivities of positions 6 and 5 (or 7) are discussed. The ratio of the reactivities is 109 and the difference in activation energies is 61 kJ mol–1.
{"title":"Diazepines. Part XIII. Relative reactivities of positions 5 and 6 in electrophilic substitution reactions of 2,3-dihydro-1,4-diazepinium salts measured by deuterium exchange kinetics","authors":"A. Butler, D. Lloyd, D. R. Marshall","doi":"10.1039/J29710000795","DOIUrl":"https://doi.org/10.1039/J29710000795","url":null,"abstract":"Kinetics and activation parameters have been measured for deuteriation at position 6 of 2,3-dihydro-5,7-dimethyl-1,4-diazepinium perchlorate by deuteriosulphuric acid in deuterium oxide, and the data are compared with those for the corresponding deuteriation catalysed by primary phosphate ions. In contrast, protons at positions 5 and 7 in two other diazepines were only slightly affected by dilute deuteriosulphuric acid. In anhydrous deuteriotrifluoroacetic acid protons at positions 5 and 7 were completely unaffected. The relative reactivities of positions 6 and 5 (or 7) are discussed. The ratio of the reactivities is 109 and the difference in activation energies is 61 kJ mol–1.","PeriodicalId":17268,"journal":{"name":"Journal of The Chemical Society B: Physical Organic","volume":"83 1","pages":"795-797"},"PeriodicalIF":0.0,"publicationDate":"1971-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89788182","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}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：