Stable Carbonium Ions Research Articles

The specificity and mechanism of the Kober reaction

When estrane derivatives are put through the Kober reaction up to four different chromogens may be obtained. There are three essential features which the molecule must possess simultaneously if a positive Kober reaction is to occur — a double bond or oxygen function in ring D, an oxygen function in ring A and an aromatic ring A. There is a fourth feature — the angular methyl group at Cl3 — which considerably enhances the second stage of the reaction. It is suggested that the reaction is initiated by dehydration at the ring D oxygen function which, with protonation of the double bond so formed and angular methyl migration leads to the formation of a stable carbonium ion in which several adjacent tertiary carbon atoms are involved in delocalization of the positive charge. It has been shown that the pink Kober chromogen is not a polyene or free radical. In at least three of the four Kober chromogens — those absorbing in the visible region — the ground state is more polar than the excited state.

Aryl delocalization vs. neighboring group participation in the stabilization of carbonium ions

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTAryl delocalization vs. neighboring group participation in the stabilization of carbonium ionsPaul G. Gassman and Allison F. Fentiman Jr.Cite this: J. Am. Chem. Soc. 1969, 91, 6, 1545–1546Publication Date (Print):March 1, 1969Publication History Published online1 May 2002Published inissue 1 March 1969https://doi.org/10.1021/ja01034a053RIGHTS & PERMISSIONSArticle Views168Altmetric-Citations28LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (215 KB) Get e-Alerts Get e-Alerts

Stable carbonium ions. LXXIV. Protonated alkoxysilanes and disiloxanes and their cleavage in fluorosulfuric acid-antimony pentafluoide solution

Stable carbonium ions. LXXIV. Protonated alkoxysilanes and disiloxanes and their cleavage in fluorosulfuric acid-antimony pentafluoide solution

Bromination of cyclic olefins. Part I. Critical dependence of carbonium ion stability on coplanarity

The kinetics of bromination of 3-phenylindenes (1), 1,2-dihydro-4-phenylnaphthalenes (2), and 6,7-dihydro-9-phenyl-5H-benzocycloheptenes (3) in methanol at 25° were studied. The rate constants for compounds with various substituents in the phenyl group were correlated in terms of the Hammett equation by use of σ for compounds (2) and σ+ for compounds (3). This difference in the transmission of resonance effects has been interpreted in terms of the geometries of the systems: in compounds (3) the substituted phenyl ring is coplanar with the carbonium ion intermediate, but in compounds (2) the phenyl ring rotates out of this plane. Carbonium ion stability (and therefore the σ value appropriate to a given substituent) is dependent on the amount of p-π overlap between the carbonium ion centre and the aryl ring.

Convenient Method for the Preparations of Carboxylic Thiolester and Acid Anhydride

Abstract The reactions of mercuric carboxylates with bivalent sulfur compounds, such as aralkyl sulfides and mercaptoles, were investigated. When mercuric acetate and aralkyl sulfides were refluxed in benzene, mercury mercaptides and aralkyl acetates were obtained. It was made clear that the reactivity of the sulfides depends on the stability of carbonium ions given by elimination of the mercapto group. Next, it was found that acetic anhydride, benzophenone and mercury phenylmercaptide were obtained in high yields by the equimolar reaction of benzophenone diphenylmercaptole with mercuric acetate. Further, the reaction was extended to the preparative method of carboxylic acid anhydrides from free acids by treating the carboxylic acids with diphenylmercury and the mercaptole. On the other hand, S-phenyl thioacetate, benzophenone and mercury mercaptide were produced in good yields when benzophenone diphenylmercaptole (2 mol) was treated with mercuric acetate (1 mol). Further, it was established that thiolesters were exclusively produced in good yields along with benzophenone and the mercury mercaptide by the reaction of benzophenone diphenylmercaptole or bis (p-chlorophenyl) mercaptole (2 mol) with free carboxylic acids (2 mol) and diphenylmercury (1 mol).

Stable carbonium ions. LXX. Protonated nitroalkanes and nitroaromatic compounds. Cleavage of protonated nitroalkanes (cycloalkanes) to carbonium ions

Stable carbonium ions. LXX. Protonated nitroalkanes and nitroaromatic compounds. Cleavage of protonated nitroalkanes (cycloalkanes) to carbonium ions

Stable carbonium ions. LXIX. Protonation of ureas, guanidines, and biotin in super acid solution

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTStable carbonium ions. LXIX. Protonation of ureas, guanidines, and biotin in super acid solutionGeorge A. Olah and Anthony M. WhiteCite this: J. Am. Chem. Soc. 1968, 90, 22, 6087–6091Publication Date (Print):October 1, 1968Publication History Published online1 May 2002Published inissue 1 October 1968https://doi.org/10.1021/ja01024a027RIGHTS & PERMISSIONSArticle Views335Altmetric-Citations61LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (504 KB) Get e-Alerts Get e-Alerts

Stable carbonium ions. LXVII. Halonium ion formation via 1,4-halogen participation. Five-membered-ring tetramethylenehalonium, 2-methyltetramethylenehalonium, and 2,5-dimethyltetramethylenehalonium ions

Stable carbonium ions. LXVII. Halonium ion formation via 1,4-halogen participation. Five-membered-ring tetramethylenehalonium, 2-methyltetramethylenehalonium, and 2,5-dimethyltetramethylenehalonium ions

Stable carbonium ions. LXIII. Diprotonated aliphatic alkoxy alcohols and their cleavage in strong acid solution. Stable secondary alkoxycarbonium ions

Stable carbonium ions. LXIII. Diprotonated aliphatic alkoxy alcohols and their cleavage in strong acid solution. Stable secondary alkoxycarbonium ions

Stable carbonium ions. LXXII. Raman and N.M.R. spectroscopic study of the nortricyclonium ion [protonated tricyclo[2.2.1.02,6]heptane] and its relation to the 2-norbornyl [bicyclo[2.2.1]heptyl]cation. The nature of the stable long-lived norbornyl cation in strong acid solutions

Stable carbonium ions. LXXII. Raman and N.M.R. spectroscopic study of the nortricyclonium ion [protonated tricyclo[2.2.1.02,6]heptane] and its relation to the 2-norbornyl [bicyclo[2.2.1]heptyl]cation. The nature of the stable long-lived norbornyl cation in strong acid solutions

Stable carbonium ions. LXIV. Protonated carbonic acid (trihydroxycarbonium ion) and protonated alkyl (aryl) carbonates and hydrogen carbonates, and their cleavage to protonated carbonic acid and carbonium ions. The possible role of protonated carbonic acid in biological carboxylation processes.

Stable carbonium ions. LXIV. Protonated carbonic acid (trihydroxycarbonium ion) and protonated alkyl (aryl) carbonates and hydrogen carbonates, and their cleavage to protonated carbonic acid and carbonium ions. The possible role of protonated carbonic acid in biological carboxylation processes.

Stable carbonium ions. LIII. Diprotonated aliphatic glycols and their rearrangement in fluorosulfonic acid-antimony pentafluoride solution

Stable carbonium ions. LIII. Diprotonated aliphatic glycols and their rearrangement in fluorosulfonic acid-antimony pentafluoride solution

Stabilities of carbonium ions in solution. I. Calorimetric heats of formation in fluorosulfonic acid antimony pentafluoride mixtures at -60.degree.

Stabilities of carbonium ions in solution. I. Calorimetric heats of formation in fluorosulfonic acid antimony pentafluoride mixtures at -60.degree.

Stable carbonium ions. LIX. Protonated alkyl carbamates and their cleavage to protonated carbamic acids and alkylcarbonium ions.

Stable carbonium ions. LIX. Protonated alkyl carbamates and their cleavage to protonated carbamic acids and alkylcarbonium ions.

Mechanism of the solvolysis of allylic diphenyl phosphates in phenol

The alkylation of phenol by solvolysis of allylic diphenyl phosphates in phenol is shown to be a carbonium ion process, and to be autocatalysed by diphenyl hydrogen phosphate. The products obtained in these solvolyses have been compared with those obtained from the alkylation of phenol by diphenyl hydrogen phosphate and olefins, under comparable conditions. These studies have shown that alkylation on carbon is favoured with more stable carbonium ions, such as tertiary or 3,3-dimethylallyl, while alkylation on oxygen is favoured with secondary carbonium ions. The acid-catalysed rearrangement, to 2-methylcoumaran, of the initial alkylated products of the solvolysis of allyl diphenyl phosphate has been shown to be largely intramolecular.

Stable carbonium ions. LX. Protonated alpha,beta-unsaturated carboxylic acids and their cleavage to alkenyloxocarbonium ions.

Stable carbonium ions. LX. Protonated alpha,beta-unsaturated carboxylic acids and their cleavage to alkenyloxocarbonium ions.

PMR spectroscopic investigation of structures, stabilities, and rearrangement reactions of C4‐C7tertiary carbonium ions in HF‐SbF5

AbstractSolutions in HF‐SbF5 of the tertiary butyl, pentyl, hexyl, methylcyclopentyl and heptyl cations have been investigated by PMR spectroscopy. A variety of procedures, conventional as well as novel ones, for preparing stable solutions of these cations are briefly described.Tertiary hexyl and heptyl cations rearrange rapidly to equilibrium mixtures of the isomeric tertiary hexyl and heptyl cations, respectively. The equilibrium compositions show the differences in thermodynamic stability of isomeric tertiary carbonium ions to be small. Equilibrations effected by a single 1,2‐hydride or methyl shift between equivalent positions have half‐lives of less than 10−3 s at ‐ 60 °C. Rearrangements of the type tert‐2‐methylpentyl to tert‐3‐methylpentyl cation have a half‐life of about 0.1 s at 0° (Eact = ∼ 14 kcal/mole, and Sact = ∼ 0). For these rearrangements a stepwise mechanism by successive hydride, methyl and hydride shifts via secondary carbonium ions is in agreement with the experimental data. Rearrangements of tertiary carbonium ions involving a change in the degree of chain branching (monobranched to linear or to dibranched cations) have half‐lives of the order of 10 s at 0°.

Stable carbonium ions. LVIII. Carbon-13 resonance investigation of protonated carboxylic acids (carboxonium ions) and oxocarbonium ions (acyl cations)

Stable carbonium ions. LVIII. Carbon-13 resonance investigation of protonated carboxylic acids (carboxonium ions) and oxocarbonium ions (acyl cations)

Stable carbonium ions. LII. Protonated esters and their cleavage in fluorosulfonic acid-antimony pentafluoride solution

A series of protonated esters was studied in HSO3F - SbF,-SO. solution . Carbonyl oxygen protonation was observed by nmr spectroscopy with negligible exchange rates . Spectral evidence was found for the exist- ence of isomers of protonated formates . Kinetics of cleavage of a series of protonated methyl esters was studied. Both acyl oxygen and alkyl oxygen cleavage was observed for esters of primary aliphatic alcohols.

Stable carbonium ions. XLIX. Protonated dicarboxylic acids and anhydrides and their cleavage to oxocarbonium ions

Stable carbonium ions. XLIX. Protonated dicarboxylic acids and anhydrides and their cleavage to oxocarbonium ions