2-Fluorotropone reacts with piperidine in benzene to give 2-piperidinotropone quantitatively. Experiments with 2-fluoro[3,5,7-2H3]tropone show normal substitution of fluorine by the nitrogen atom of piperidine. A kinetic investigation shows (i) that this reaction is of overall second-order (first-order with respect to both reagents) and (ii) that the free energy of activation is 4–5 kcal mol–1 lower than the corresponding values found for 2-chloro-, 2-bromo-, 2-iodo-, and 2-methoxy-tropone. Clearly, the reaction does not follow the isokinetic relationship observed for the other tropones. The behaviour of 2-fluorotropone towards quinuclidine depends on the solvent; in dimethyl sulphoxide, substitution of fluorine by quinuclidine gives 1-{2-[N-oxocyclohepta-1,3,5-trien-1-yl)-piperidin-4-yl]ethyl}-1-azoniabicyclo[2,2,2]octane fluoride at a rate comparable to that for similar reaction of 2-iodo- or 2-chloro-tropone, but in benzene at room temperature 2-fluorotropone does not react with quinuclidine unlike the chloro- or iodo-compound. Under reflux, only intractable tars are obtained.1-Halogeno-2,4-dinitrobenzenes behave similarly; they undergo clean substitution of the halogen atom by protic amines in both dimethyl sulphoxide and benzene. However, the fluoro-compound is unreactive towards quinuclidine whereas under similar conditions the chloro-compound gives 1-{2-[N-(2,4-dinitrophenyl)piperidin-4-yl]ethyl}-1-azoniabicyclo[2,2,2]octane chloride. Under forcing conditions piperidinium 2,4-dinitrophenolate is formed by hydrolysis (due to moisture) of 1-fluoro-2,4-dinitrobenzene. Intramolecular base catalysis by the ‘carbonyl’ oxygen atom is suggested as the basis of the isokinetic relationship in the reactions of the troponoid system with protic amines, and the observed data are consistent with this hypothesis.
{"title":"The reactivity of pseudoaromatic compounds. Part IV. Normal substitutions of 2-substituted tropones by secondary or tertiary amines; abnormal behaviour of 2-fluorotropone","authors":"F. Pietra, F. Cima","doi":"10.1039/J29710002224","DOIUrl":"https://doi.org/10.1039/J29710002224","url":null,"abstract":"2-Fluorotropone reacts with piperidine in benzene to give 2-piperidinotropone quantitatively. Experiments with 2-fluoro[3,5,7-2H3]tropone show normal substitution of fluorine by the nitrogen atom of piperidine. A kinetic investigation shows (i) that this reaction is of overall second-order (first-order with respect to both reagents) and (ii) that the free energy of activation is 4–5 kcal mol–1 lower than the corresponding values found for 2-chloro-, 2-bromo-, 2-iodo-, and 2-methoxy-tropone. Clearly, the reaction does not follow the isokinetic relationship observed for the other tropones. The behaviour of 2-fluorotropone towards quinuclidine depends on the solvent; in dimethyl sulphoxide, substitution of fluorine by quinuclidine gives 1-{2-[N-oxocyclohepta-1,3,5-trien-1-yl)-piperidin-4-yl]ethyl}-1-azoniabicyclo[2,2,2]octane fluoride at a rate comparable to that for similar reaction of 2-iodo- or 2-chloro-tropone, but in benzene at room temperature 2-fluorotropone does not react with quinuclidine unlike the chloro- or iodo-compound. Under reflux, only intractable tars are obtained.1-Halogeno-2,4-dinitrobenzenes behave similarly; they undergo clean substitution of the halogen atom by protic amines in both dimethyl sulphoxide and benzene. However, the fluoro-compound is unreactive towards quinuclidine whereas under similar conditions the chloro-compound gives 1-{2-[N-(2,4-dinitrophenyl)piperidin-4-yl]ethyl}-1-azoniabicyclo[2,2,2]octane chloride. Under forcing conditions piperidinium 2,4-dinitrophenolate is formed by hydrolysis (due to moisture) of 1-fluoro-2,4-dinitrobenzene. Intramolecular base catalysis by the ‘carbonyl’ oxygen atom is suggested as the basis of the isokinetic relationship in the reactions of the troponoid system with protic amines, and the observed data are consistent with this hypothesis.","PeriodicalId":17268,"journal":{"name":"Journal of The Chemical Society B: Physical Organic","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1971-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74143057","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 dimethyl sulphinyldipropionate alone and in the presence of 2,6-di-t-butyl-α-(3,5-di-t-butyl-4-oxo-2,5-cyclohexadiene-1-ylidene)p-tolyloxy (Galvinoxyl) was studied. Results show that radical intermediates capable of initiating oxidations are not produced under these conditions but radicals are formed from dimethyl sulphinyldipropionate in the presence of hydroperoxides. This reaction is probably responsible for the pro-oxidant effects associated with sulphoxides.
{"title":"Mechanisms of antioxidant action: the pro-oxidant stage in the function of thiodipropionate esters as antioxidants","authors":"C. Armstrong, G. Scott","doi":"10.1039/J29710001747","DOIUrl":"https://doi.org/10.1039/J29710001747","url":null,"abstract":"The thermal decomposition of dimethyl sulphinyldipropionate alone and in the presence of 2,6-di-t-butyl-α-(3,5-di-t-butyl-4-oxo-2,5-cyclohexadiene-1-ylidene)p-tolyloxy (Galvinoxyl) was studied. Results show that radical intermediates capable of initiating oxidations are not produced under these conditions but radicals are formed from dimethyl sulphinyldipropionate in the presence of hydroperoxides. This reaction is probably responsible for the pro-oxidant effects associated with sulphoxides.","PeriodicalId":17268,"journal":{"name":"Journal of The Chemical Society B: Physical Organic","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1971-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75164123","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 stereochemistry of a series of 2-alkoxy-4-methyl-1,3,2-dioxaphosphorinans has been investigated by n.m.r. and dipole-moment studies. For a given alkoxy-group (MeO, EtO, or PriO), the more-stable member of the isomeric pair adopts a chair conformation, having the trans-configuration, with equatorial methyl and axial alkoxy-group. The less-stable isomers, having the cis-configuration, adopt rapidly flipping chair conformations. Configurational stability is solvent dependent.
{"title":"The stereochemistry of 2-alkoxy-4-methyl-1,3,2-dioxaphosphorinans","authors":"C. Bodkin, P. Simpson","doi":"10.1039/J29710001136","DOIUrl":"https://doi.org/10.1039/J29710001136","url":null,"abstract":"The stereochemistry of a series of 2-alkoxy-4-methyl-1,3,2-dioxaphosphorinans has been investigated by n.m.r. and dipole-moment studies. For a given alkoxy-group (MeO, EtO, or PriO), the more-stable member of the isomeric pair adopts a chair conformation, having the trans-configuration, with equatorial methyl and axial alkoxy-group. The less-stable isomers, having the cis-configuration, adopt rapidly flipping chair conformations. Configurational stability is solvent dependent.","PeriodicalId":17268,"journal":{"name":"Journal of The Chemical Society B: Physical Organic","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1971-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75435242","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 methyl 3′- and 4′-substituted 2-benzoylbenzoates in 70%(v/v) dioxan–water at 30 °C. The pKa values of the corresponding acids have been measured in 80%(w/w) 2-methoxyethanol–water at 25 °C. The effects of substitution have been assessed by means of the Hammett equation. Comparison of the reaction constants obtained with those for the reference systems, benzoic acids and their methyl esters, indicates clearly that, in the alkaline hydrolysis of the methyl 2-benzoylbenzoates, the rate-determining step involves direct or pre-equilibrium attack at the keto-carbonyl group.
{"title":"Reactions of carbonyl compounds in basic solutions. Part II. The mechanism of the alkaline hydrolysis of methyl 2-benzoylbenzoates","authors":"K. Bowden, G. R. Taylor","doi":"10.1039/J29710000145","DOIUrl":"https://doi.org/10.1039/J29710000145","url":null,"abstract":"Rate coefficients have been measured for the alkaline hydrolysis of methyl 3′- and 4′-substituted 2-benzoylbenzoates in 70%(v/v) dioxan–water at 30 °C. The pKa values of the corresponding acids have been measured in 80%(w/w) 2-methoxyethanol–water at 25 °C. The effects of substitution have been assessed by means of the Hammett equation. Comparison of the reaction constants obtained with those for the reference systems, benzoic acids and their methyl esters, indicates clearly that, in the alkaline hydrolysis of the methyl 2-benzoylbenzoates, the rate-determining step involves direct or pre-equilibrium attack at the keto-carbonyl group.","PeriodicalId":17268,"journal":{"name":"Journal of The Chemical Society B: Physical Organic","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1971-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75824761","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 of the osmium(VIII)-catalysed oxidation of glycollic, lactic, and mandelic acids have been investigated in alkaline media. First-order rate plots in chloramine-T were linear up to two half-lives. However, under pseudo-first-order conditions the rate constants showed a slight decrease with increase in chloramine-T concentration. The rate of reaction was independent of α-hydroxy-acid concentration and directly proportional to the osmium-(VIII) and the reciprocal of the hydroxide ion concentrations. The formation of a complex between N-chlorotoluene-p-sulphonamide and osmium(VIII) is rate-determining and is followed by the rapid transfer of a hydride ion from the substrate to this complex.
{"title":"Mechanism of oxidations by chloramine-T. Part I. Oxidation of α-hydroxy-acids","authors":"S. P. Mushran, M. C. Agrawal, B. Prasad","doi":"10.1039/J29710001712","DOIUrl":"https://doi.org/10.1039/J29710001712","url":null,"abstract":"Kinetics of the osmium(VIII)-catalysed oxidation of glycollic, lactic, and mandelic acids have been investigated in alkaline media. First-order rate plots in chloramine-T were linear up to two half-lives. However, under pseudo-first-order conditions the rate constants showed a slight decrease with increase in chloramine-T concentration. The rate of reaction was independent of α-hydroxy-acid concentration and directly proportional to the osmium-(VIII) and the reciprocal of the hydroxide ion concentrations. The formation of a complex between N-chlorotoluene-p-sulphonamide and osmium(VIII) is rate-determining and is followed by the rapid transfer of a hydride ion from the substrate to this complex.","PeriodicalId":17268,"journal":{"name":"Journal of The Chemical Society B: Physical Organic","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1971-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75866502","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}
Oxidation of ethyl mandelate with chromic acid is of the first order with respect to oxidant, ester, and hydrogen ions. The thermodynamic parameters for oxidation have been evaluated. The hydrolysis under similar conditions is slower than oxidation. The main product of oxidation is Ph·CO·CO2Et. The rate of hydrolysis and products rule out the possibility of hydrolysis before oxidation. A mechanism involving C–H bond rupture in the rate-determining step has been suggested.
{"title":"Kinetics of oxidation of ethyl mandelate by chromic acid","authors":"D. Jha, G. V. Bakore","doi":"10.1039/J29710001166","DOIUrl":"https://doi.org/10.1039/J29710001166","url":null,"abstract":"Oxidation of ethyl mandelate with chromic acid is of the first order with respect to oxidant, ester, and hydrogen ions. The thermodynamic parameters for oxidation have been evaluated. The hydrolysis under similar conditions is slower than oxidation. The main product of oxidation is Ph·CO·CO2Et. The rate of hydrolysis and products rule out the possibility of hydrolysis before oxidation. A mechanism involving C–H bond rupture in the rate-determining step has been suggested.","PeriodicalId":17268,"journal":{"name":"Journal of The Chemical Society B: Physical Organic","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1971-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75882470","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 profiles are reported for hydrogen exchange at the 3-position for 2-amino-5-chloropyridine, 5-chloro-2-dimethylaminopyridine, and 2-amino-5-bromopyridine 1-oxide and for exchange at the 5-position for 2-amino-3-methylpyridine.
{"title":"The kinetics and mechanism of the electrophilic substitution of heteroaromatic compounds. Part XXV. The acid-catalysed hydrogen-exchange of some 2-aminopyridine derivatives","authors":"A. El-Anani, P. Jones, A. Katritzky","doi":"10.1039/J29710002363","DOIUrl":"https://doi.org/10.1039/J29710002363","url":null,"abstract":"Rate profiles are reported for hydrogen exchange at the 3-position for 2-amino-5-chloropyridine, 5-chloro-2-dimethylaminopyridine, and 2-amino-5-bromopyridine 1-oxide and for exchange at the 5-position for 2-amino-3-methylpyridine.","PeriodicalId":17268,"journal":{"name":"Journal of The Chemical Society B: Physical Organic","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1971-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73242316","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}
Solvent effects on the bathochromic shift in the first π–π* band of aminonitropyridines were examined. They were interpreted in terms of inter- and intra-molecular hydrogen bonding, as well as of transition polarizability which determines solvatochromism. All possible dissociation constants of conjugate acids of amino-, diamino-, nitro-, and aminonitro-pyridines have also been measured at 25°C by spectrophotometric determination of acid–base concentration ratios. The influence of amino- and nitro-groups in the pyridine ring on pKa1 and pKa2 was discussed on the basis of electrical characteristics of substituents and electron availability of reaction site.
{"title":"Ultraviolet absorption and protonation equilibria of amino- and nitro-substituted pyridines","authors":"I. R. Bellobono, G. Favini","doi":"10.1039/J29710002034","DOIUrl":"https://doi.org/10.1039/J29710002034","url":null,"abstract":"Solvent effects on the bathochromic shift in the first π–π* band of aminonitropyridines were examined. They were interpreted in terms of inter- and intra-molecular hydrogen bonding, as well as of transition polarizability which determines solvatochromism. All possible dissociation constants of conjugate acids of amino-, diamino-, nitro-, and aminonitro-pyridines have also been measured at 25°C by spectrophotometric determination of acid–base concentration ratios. The influence of amino- and nitro-groups in the pyridine ring on pKa1 and pKa2 was discussed on the basis of electrical characteristics of substituents and electron availability of reaction site.","PeriodicalId":17268,"journal":{"name":"Journal of The Chemical Society B: Physical Organic","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1971-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73265936","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}
4-Aminomethyleneoxazol-5(4H)-ones are shown to undergo nucleophilic attack at the methylene carbon on the side chain rather than at the ring carbonyl group. Penicillenic acid, formerly reported to react exclusively at the carbonyl, follows this general pattern when intramolecular nucleophilic attack by the thiol group is inhibited, a reaction of possible importance in penicillin carcinogenicity.
{"title":"Nucleophilic attack on 4-aminomethyleneoxazol-5(4H)-ones, a rationalisation of penicillin carcinogenicity","authors":"J. Longridge, D. Timms","doi":"10.1039/J29710000848","DOIUrl":"https://doi.org/10.1039/J29710000848","url":null,"abstract":"4-Aminomethyleneoxazol-5(4H)-ones are shown to undergo nucleophilic attack at the methylene carbon on the side chain rather than at the ring carbonyl group. Penicillenic acid, formerly reported to react exclusively at the carbonyl, follows this general pattern when intramolecular nucleophilic attack by the thiol group is inhibited, a reaction of possible importance in penicillin carcinogenicity.","PeriodicalId":17268,"journal":{"name":"Journal of The Chemical Society B: Physical Organic","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1971-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78447422","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}
Photolysis of 4-phenylbut-1-ene in the gas phase results in the formation of benzylcyclopropane, trans-phenyl-methylcyclopropane, and trans-1-phenylbut-2-ene. By the use of butene, piperylene, and neopentane quenching experiments and by fluorescence measurements, the formation of the products is shown to occur via the triplet manifold and to involve a common vibrationally excited intermediate. In solution 4-phenylbut-1-ene produces no new monomeric compound on excitation in the aromatic absorption band.
{"title":"The photochemistry of 4-phenylbut-1-ene","authors":"K. Salisbury","doi":"10.1039/J29710000931","DOIUrl":"https://doi.org/10.1039/J29710000931","url":null,"abstract":"Photolysis of 4-phenylbut-1-ene in the gas phase results in the formation of benzylcyclopropane, trans-phenyl-methylcyclopropane, and trans-1-phenylbut-2-ene. By the use of butene, piperylene, and neopentane quenching experiments and by fluorescence measurements, the formation of the products is shown to occur via the triplet manifold and to involve a common vibrationally excited intermediate. In solution 4-phenylbut-1-ene produces no new monomeric compound on excitation in the aromatic absorption band.","PeriodicalId":17268,"journal":{"name":"Journal of The Chemical Society B: Physical Organic","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1971-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77256948","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：