Intramolecular Exchange Reactions Research Articles

A nuclear magnetic resonance study of the kinetics of ligand-exchange reactions in uranyl complexes. 4. Intramolecular-exchange reaction of methyl groups of acetylacetonate in UO2(acac)2L with L = Me2S:O, Me2N:COH, and Et2N:COH

A nuclear magnetic resonance study of the kinetics of ligand-exchange reactions in uranyl complexes. 4. Intramolecular-exchange reaction of methyl groups of acetylacetonate in UO2(acac)2L with L = Me2S:O, Me2N:COH, and Et2N:COH

Ultrasonic chemical relaxation mechanisms in protein solution

Reactions of the form −1H+ + HPO42− = −1 + H2PO4− (where −1H+ and −1 represent, respectively, the protonated and neutral forms of a given histidyl residue of a peptide or small protein) are more than usually amenable to study by acoustic techniques. The rate constants and average volume changes for this reaction have been deduced, for a few small proteins (bacitracin, myoglobin, ribonuclease, and hemoglobin), from the acoustic absorption as a function of frequency (0.24–150 MHz), pH, and concentration. The rate constants so deduced are used to estimate the spectrum of relaxation times and relaxation amplitudes associated with intermolecular and intramolecular proton exchange reactions in biological media. It is concluded that the acoustic absorption (between 1 and 10 MHz) reasonably attributable to perturbation of such equilibria is a significant fraction of the absorption observed in intact tissues. Ultrasonic absorption due to perturbation of protein‐protein association equilibria is also discussed as is the possible role of “solvation” equilibria.

Kinetics of the reactions of silicon compounds. Part 10. Kinetics and mechanism of the gas-phase thermal reactions of trichloro-(1,1-difluoroethyl)silane. An intramolecular halogen exchange reaction

The gas-phase thermal isomerisation of trichloro-(1,1-difluoroethyl)silane (I) to chloro-(1,1-dichloroethyl)-difluorosilane (II) is a first-order homogeneous process at 375–416 K and 11–67 mmHg initial pressure. The reaction is unaffected by the presence of the radical inhibitors 2,3-dimethylbut-2-ene and nitric oxide, and it is concluded that the rate-determining step is a unimolecular isomerisation of (I) to dichloro-(1-chloro-1-fluoroethyl)fluorosilane (III), which then undergoes a secondary fast isomerisation to the observed product (II). [graphic omitted], log10k1/s–1=(13.38 ± 0.05)–(127.2 ± 0.4) kJ mol–1/RT ln 10 The data suggest a transition state in which the fluorine atom transfer is more advanced than the chlorine atom transfer. The minor products vinyl chloride and dichlorodifluorosilane are shown to arise from thermal and chemically activated decomposition of the initially formed (II) and/or (III).

Transalkylierung und protonenkatalysierte C-C-Spaltung bei n-Butyl-und n-Pentylbenzol in der Gasphase / Transalkylation and Proton Catalyzed C-C-Cleavage of Gaseous n-Butyl and w-Pentyl Benzenes

Abstract The investigation of several 13carbon and deuterium labelled n-butyl and n-pentyl benzenes demonstrate that chemical ionization (reagent gas: methane) induces specific carbon-carbon bond cleavages of the alkyl group. The extent of competing reaction channels as for instance direct alkene elimination versus dealkylation/reprotonation is analyzed. Partial hydrogen exchange processes between reagent ions and substrate molecules are restricted to the phenyl ring. Intramolecular exchange reactions between the side chain and the aromatic ring which are typical for the open shell molecular ions of alkyl benzenes are not observed for analogous closed shell cations.

Amino acid complexes of platinum(IV). I. Trimethylplatinum(IV) complexes with glycinate, iminodiacetate, n-methyliminodiacetate, nitrilotriacetate, and ethylenediamine-tetraacetate

Reaction between PtMe3(H2O)+ 3 and sodium glycinate gives a series of glycinato complexes, PtMe3(gly)(H2O), [PtMe3(gly)]2, PtMe3(gly)- 2 and PtMe3(gly)2- 3. Variable-temperature PMR has been used to study rapid intramolecular exchange reactions in PtMe3(gly)(D2O) and PtMe3(gly)- 2 in D2O.Iminodiacetate, N-Methyliminodiacetate, and nitrilotriacetate act as tridentate ligands, coordinating through the N- and two O-atoms. The most stable EDTA complex is (Me3Pt)2(EDTA)2-, in which each Pt-atom is coordinated to one N and two O-atoms of bridging EDTA.

A novel intramolecular exchange reaction between coordinated nitrosyl and nitro groups in cis-nitrosylnitrobis(dithiocarbamato)iron

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTA novel intramolecular exchange reaction between coordinated nitrosyl and nitro groups in cis-nitrosylnitrobis(dithiocarbamato)ironOliver A. Heperuma and Robert D. FelthamCite this: J. Am. Chem. Soc. 1976, 98, 19, 6039–6040Publication Date (Print):September 1, 1976Publication History Published online1 May 2002Published inissue 1 September 1976https://doi.org/10.1021/ja00435a045RIGHTS & PERMISSIONSArticle Views67Altmetric-Citations22LEARN 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 (259 KB) Get e-Alerts Get e-Alerts

A study of the electron impact‐induced fragmentation of 1,6‐diaminohexane

AbstractThe mass spectrometric behaviour of 1,6‐diaminohexane has been studied with the help of deuterium labelling in every position of the molecule. Extensive intramolecular exchange reactions between the hydrogen atoms of the amino groups and those of the hydrocarbon chain are responsible for the apparent complexity of the fragmentation mode.

Studies on drug metabolism by use of isotopes. XI. Studies on synthesis and physiochemical features of 2H-labeled l-ephedrine on benzene ring (author's transl)

As a fundamental study on the applicability of a drug labeled with deuterium on benzene ring for the human metabolic studies, l-ephedrine [arom.-2H5] was synthesized by a reaction sequence starting with benzene [arom.-2H6]. Infrared (IR), nuclear magnetic resonance (NMR), and mass spectra of l-ephedrine [arom.-2H5] and propiophenone [arom.-2H5] were compared with those of the corresponding nonlabeled compounds. The bands at 700 and 750 cm-1, which appear characteristically in monosubstituted benzene derivatives, disappear completely in the IR spectra of deuterated compounds, and absorptions for the aromatic C-H (3000-3100 cm-1) and aromatic C=C (1600 cm-1 shifted completely to 2280 cm-1 and 1560 cm-1 respectively.The signal for aromatic proton in NMR spectrum is completely lacking in the deuterated samples. From these data, it was concluded that l-ephedrine [arom.-2H5] obtained here does not contain a perceptible amount of hydrogen on its benzene ring. Comparison of mass spectra of deuterated compounds with that of nonlabeled compounds, suggests that an intramolecular exchange reaction between deuterium on the benzene ring and hydrogen on the side chain does occur during the fragmentation process to a small but significant extent.

Studies on drug metabolism by use of isotopes. XII. Quantitative analysis of 22H-labeled compounds on benzene ring by mass spectrometry (author's transl)

Mass spectral problems on the applicability of a drug labeled with deuterium on the benzene ring for the metabolic studies in man were investigated using benzoic acid [arom.-2H5] and hippuric acid [arom.-2H5]. By comparing the mass spectra of deuterated compounds with those of unlabeled analogues, an intramolecular exchange reaction between deuterium on the benzene ring and hydrogen on the side chain was recognized slightly in the phenyl ion and remarkably in the benzoyl ion from the deuterated benzoic acid. However, such an exchange reaction was not observed in any ion from the deuterated hippuric acid. Deuterium radical from the M-CO2+ of labeled hippuric acid was lost during the fragmentation. Moreover, an isotope effect of a few percent was obsirved in the production of the phenyl ion and the C4H3+ ion by examination of the mass spectrum of an equimolar mixture of nonlabeled and labeled compounds. From these results, the molecular ion and the benzoyl ion of benzoic acid, and the benzoyl ion of hippuric acid were chosen as the main peak for quantitative analysis. By comparing the total peak height in the region of the ±1 mass unit of the main peak from deuterated compound with those from protiated counterpart, the former diluted in the order of 100-fold amount of the latter was determined with a precision within 3%.

Inter- and intramolecular ligand exchange reactions of ruthenium(II) carbonyl porphine complexes with nitrogen bases

To investigate both inter- and intramolecular site exchange in coordinated nitrogenous bases the complexes of tetra( p-isopropylphenyl)porphinato ruthenium carbonyl with4-tert-butylpyridine, 2-methylpyridine, 3,5-dimethylpyrazole, 4,5-dimethylpyridazine, and 3,6-dimethylpyridazine have been studied by total line shape analysis of the variable temperature PMR spectra. Both types of exchange mechanisms have been found in these complexes. All of the complexes undergo intermolecular ligand exchange at rates ranging from ∼0.09 sec −1 (Δ G ≠ ∼ 19 kcal/mol) to 2 × 10 4 sec − (Δ G ≠ ∼ 12 kcal/mol) at 25° for the various complexes, independent of the concentration of excess ligand. Thus the rate determining step is dissociation. The two pyridazine complexes provide the first examples of intramolecular ligand exchange with coordinated nitrogenous bases. The rates at 25° for intramolecular site exchange (∼10 6 and 66 sec −1) are 20–85 times faster than the rates for intramolecular ligand exchange in the same complexes. Within experimental uncertainty there is no intramolecular ligand site exchange in the 3,5-dimethylphyrazole complex. Full kinetic and mechanistic details are discussed.

An Electron Spin Resonance Investigation of the Mechanism of the Intramolecular Cation Migration of Alkali Metal Semiquinone Ion-pairs

A systematic survey of the kinetic characteristics of the intramolecular cation exchange reactions of semiquinone ion-pairs is described. A linear correlation exists between the free energy of activation for the exchange and the strength of the ionic interaction within the ion pair; however, this correlation does not extend to the enthalpy of activation. The significance of the kinetic parameters is discussed in terms of the role solvation plays in determining the course of the exchange process.

Unique intermolecular and intramolecular exchange reactions of hexaborane(10)

Unique intermolecular and intramolecular exchange reactions of hexaborane(10)

Protonation of halogen‐containing benzenes in HF‐SbF5. Part II.: PMR spectra of halotoluenium and halobenzenium ions

AbstractA number of halotoluenes and halobenzenes have been found to give stable benzenium ions in HF‐SbF5. The PMR spectra of these ions are reported. A mixture of all three possible stable cations was obtained with m‐chloro‐ and m‐bromotoluenes; of m‐fluorotoluene only two cations were formed in observable amounts. Likewise, both possible stable m‐dichlorobenzenium ions were observed, but only one m‐difluorobenzenium ion. Reversible line broadenings in the spectra of all these ions, and of 1,3,5‐trichlorobenzenium ion showed the occurrence of rapid intramolecular and/or intermolecular hydrogen exchange reactions at temperatures of 0° C or lower, depending on the cation. In the cases of o‐chloro‐ and o‐fluorotoluenium ions fast exchange reactions lead to coalesced signals at temperatures as low as −40° and 0°, respectively. Protonated fluoro‐benzene and chlorobenzene likewise give coalesced signals at −40°.

Diols and epoxides Communication 8. Reactions of isomeric ?-chloro butanol acetates with potassium hydroxide

1. The reactions of 4-chloro-2-butanol acetate (I) and 3-chloro-1-butanol acetate (II) with potassium hydroxide were investigated. From (I) 1,3-epoxybutane is formed in 80–85% yield, but from (II) the yield of 1,3-epoxybutane is low (about 7%), and propene (about 55%), trans-2-buten-1-ol (about 6%), and 3-buten-1-ol (about 17%) are formed. 2. The course of the transformations of a γ-chloro alkanol acetate under the action of caustic alkali is essentially determined by the structure of the compound. For a system with the chlorine atom in a primary position, the main course is the formation of the β-epoxide by the mechanism of intramolecular nucleophilic exchange. In the case of a compound with the chlorine atom in a secondary position the main course is the formation of an olefin and an oxo compound. These two main processes pass through the intermediate stage of a chloroalkoxide. 3. The two main reactions may be accompanied by bimolecular nucleophilic exchange processes—the formation of a 1,3-diol and unsaturated alcohols. In the case of γ-chloro alkanol acetates, with increase in the order of the carbon atom carrying the chlorine atom the intramolecular nucleophilic exchange reaction is displaced toward 1,4- and 1,2-elimination.

All intramolecular exchange reaction of N,N-dimethylcarbamoylsalicyclic acid

All intramolecular exchange reaction of N,N-dimethylcarbamoylsalicyclic acid

Pyrolysis—Hydrogenation—GLC of poly-α-olefins

Pyrolysis-hydrogenation-GLC experiments on polyethylene, polypropylene, hydrogenated natural rubber, polybutene-1, polyisobutylene, poly-3-methylbutene-1, poly-4-methylpentene-1, polystyrene and poly-α-methylstyrene are discussed with special emphasis on the mechanisms by which the volatile fragments are formed. It is shown that intramolecular hydrogen exchange reactions of the radicals formed on pyrolysis occur mainly with the fifth carbon atom but also with some others. Splitting off of side groups becomes increasingly important as their size increases.