Bromination of Norbornene: the Question of Bromonium Ions vs. 6,1-Hydride Shift

1971 ◽  
Vol 49 (6) ◽  
pp. 885-903 ◽  
Author(s):  
D. R. Marshall ◽  
P. Reynolds-Warnhoff ◽  
E. W. Warnhoff ◽  
J. R. Robinson
Keyword(s):  
Carbon Tetrachloride ◽  
Complex Mixture ◽  
Radical Mechanism ◽  
Hydride Shift ◽  
Product Composition ◽  
Kinetically Controlled ◽  
Ionic Addition ◽  
Made In

The reaction of norbornene (1) with bromine has been re-investigated and found to give in addition to bromonortricyclene (2) and 2-exo-bromonorbornane (20) a complex mixture of dibromides of which five (15–19) have been isolated and identified. These dibromides have been found to be kinetically controlled products of ionic addition. Apparently dibromide 15 is also formed to some extent in carbon tetrachloride by a radical mechanism. The product composition from the bromine addition has been compared with that of the analogous chlorination and bromofluorination reactions. Degradation of the 2-exo,3-endo-dibromonorbornane from bromination of 5,6-14C-norbornene has shown that this dibromide is formed by two ionic routes: (a) from a bromonium ion 14 (or its equivalent), and (b) from the cation 12 formed by 6,1-hydride shift. Improvements have been made in the first and final steps of the standard norbornene degradation method.

Synthesis and radical decomposition of α-hydroxydiazenes. II. tert-Butylazodiphenylcarbinol

1976 ◽  
Vol 54 (9) ◽  
pp. 1349-1354 ◽  
Author(s):  
Dominic W. K. Yeung ◽  
John Warkentin
Keyword(s):  
Carbon Tetrachloride ◽  
Azo Compounds ◽  
Radical Mechanism ◽  
Chain Decomposition ◽  
Tert Butyl ◽  
Radical Decomposition ◽  
Nitrogen Radicals ◽  
Induced Decomposition ◽  
Hydroxyl Hydrogen

tert-Butylazodiphenylcarbinol (Ph2C(OH)N=NCMe3, 3) decomposes in oxygen-free benzene by the unimolecular radical mechanism characteristic of most azo compounds. In benzene or in carbon tetrachloride, with or without air present, decomposition of 3 is also induced by radicals through abstraction of hydroxyl hydrogen in concert with the formation of nitrogen. Radicals which induce decomposition of 3 include trichloromethyl, tert-butyl, phenylthiyl, tert-butylperoxy and possibly oxygen. The failure of inhibitors like thiophenol to stop chain decomposition of 3 is interpreted in terms of the thermochemistry of induced decomposition.

scholarly journals Photocatalytic Hydrophosphination with Air-Stable and Commercially Available Bis(acetylacetonato)copper(II) (Cu(acac)2)

2020 ◽  
Author(s):  
Steven Dannenberg ◽  
Rory Waterman
Keyword(s):  
Ambient Temperature ◽  
Bond Formation ◽  
Thermal Conditions ◽  
Active Species ◽  
Radical Mechanism ◽  
Water Stability ◽  
Temperature Irradiation ◽  
Highly Effective ◽  
Metal Catalyzed ◽  
Made In

Bis(acetylacetonato)copper(II) (Cu(acac)2, 1), is active for the hydrophosphination of alkenes and alkynes with primary and secondary phosphines. Under thermal conditions, the activity of 1 is comparable to some of the best literature catalysts, but 1 is unique in that set possessing air- and water-stability. However, under ambient temperature irradiation centered at 360 nm, the conversions are remarkable with some reactions complete in minutes and several rarely reported unactivated substrates achieving high conversions within hours. The photocatalytic conditions are critical, and comparison to literature catalysts has been made in which 1 demonstrates superior activity. Initial mechanistic work does not suggest a radical mechanism rather the formation of a copper(I) active species. Hammett analysis indicates that depending on the substrate, either a nucleophilic or insertion-based mechanism may be at work. The enhanced reactivity provided by light also appears to be generalizable to other copper(I) compounds under irradiation, representing a broader phenomenon in metal catalyzed P–C bond formation. This simple, bench-stable, and inexpensive catalyst is highly effective, placing hydrophosphination in the hands of many more synthetic chemists.

Overview of uraemic toxins

2018 ◽  
Author(s):  
Griet Glorieux ◽  
Nathalie Neirynck ◽  
Anneleen Pletinck ◽  
Eva Schepers ◽  
Raymond Vanholder
Keyword(s):  
Patient Outcome ◽  
Biological Effects ◽  
Complex Mixture ◽  
Identification And Characterization ◽  
Organ Dysfunctions ◽  
Important Progress ◽  
Made In

The uraemic syndrome is a complex mixture of organ dysfunctions attributed to the retention of a multitude of compounds that under normal conditions are excreted by healthy kidneys. Although important progress has been made in the identification and characterization of uraemic retention solutes and in the revealing of their pathophysiological effects, this knowledge remains far from complete. Data are discussed on general characteristics of specific uraemic retention solutes, on in vitro and in vivo biological effects and on available observational and interventional studies with respect to their removal and related patient outcome are discussed.

The Chemistry of Laurenene. XVI. Investigation of the Mechanism of a Cationic Rearrangement

1993 ◽  
Vol 46 (8) ◽  
pp. 1163 ◽  
Author(s):  
DB Clarke ◽  
RT Weavers
Keyword(s):  
Rearrangement Product ◽  
Deuterium Label ◽  
Deuterium Labelling ◽  
Hydride Shift ◽  
Product Composition ◽  
Cationic Rearrangement

Some aspects of the mechanism of the acid-induced rearrangement of laurenan-2β-ol have been deduced from deuterium- labelling studies. A key intermediate arises from two pathways, one involving a 1,4- and one a 1,5-hydride shift. Formation of this intermediate is partially suppressed by substitution of the migrating hydrogen by a deuterium. A proposed pathway which involves a 1,3-methyl migration has been disproved, and scrambling and loss of deuterium label has been accounted for in terms of equilibria involving lauren-1-ene and another previously reported rearrangement product. The rearrangement is strongly promoted in dichloromethane, and the product composition is highly solvent-dependent.

The reaction of N,N-dibromobenzenesulfonamide with norbornylene. The occurrence of a hydride shift during an ionic addition to norbornylene

1964 ◽  
Vol 5 (38) ◽  
pp. 2663-2668 ◽  
Author(s):  
A.C. Oehlschlager ◽  
L.H. Zalkow
Keyword(s):  
Hydride Shift ◽  
Ionic Addition

scholarly journals Analysis of Carbon Tetrachloride-Extractable Species from Daxing Bituminous Coal

2020 ◽  
Vol 10 (2) ◽  
pp. 494
Author(s):  
Caixia Jv ◽  
Fenggang Li ◽  
Peng Yan ◽  
Mengmeng Fan ◽  
Linlin Jia ◽  
...  
Keyword(s):  
Carbon Tetrachloride ◽  
Soxhlet Extraction ◽  
Extraction Methods ◽  
The Other ◽  
Radical Mechanism ◽  
Free Radical Mechanism ◽  
Assisted Extraction ◽  
Before And After ◽  
Ultrasonic Assisted ◽  
Extraction Processes

Soxhlet extraction (SE), ultrasonic-assisted extraction (UAE), and microwave-assisted extraction (MAE) were carried out on Daxing coal with carbon tetrachloride. The extracted components were analyzed by GC-MS while the residues of the coal after extractions were analyzed by FT-IR spectroscopy. The obtained IR spectra indicated that the functional groups were barely changed in strength for the coal before and after extractions concluding that the macromolecular structures of coal were not destroyed in the extraction processes. XRD diagrams showed the peak around θ = 47 was totally disappeared by all the three extractions, indicating that the graphite-like structural substances in the coal were totally destroyed in the extraction processes. GC/MS analysis showed that: (1) The SE method extracted the least number of substances from the coal; on the other hand, the extracted compounds are largely chlorinated which can be explained by the free radical mechanism. (2) MAE extracted 75 organic compounds of which 53 are oxygen-containing substances. A small portion of non-alkanes (1.19%) was found, which is in contrast to the other two extraction methods. Moreover, a few biomarker compounds were also identified including hexaoxane, 2-methylcholest-3-ene, 6,9,12-tripropylheptadecane, and 17α-21β-28,30-bisnorhopane. (3) The three extraction methods gave totally different extraction patterns for the same coal, highlighting that the extraction method can dominate the outcome of the extracted products. The mechanisms behind these extraction processes are discussed. This study provides a base for the future choice of the extraction methods in terms of outcomes of the extraction products.

The Berginization of Raw Rubber

1930 ◽  
Vol 3 (1) ◽  
pp. 33-34
Author(s):  
H. I. Waterman ◽  
R. H. Dewald ◽  
A. J. Tulleners
Keyword(s):  
Carbon Dioxide ◽  
Thermal Decomposition ◽  
Carbon Tetrachloride ◽  
Acetone Extract ◽  
Raw Material ◽  
Compressed Air ◽  
Contact Period ◽  
Made In

Abstract As a raw material for the experiments, a sample of raw rubber, viz., first latex crepe, was used. This was obtained from the Reichskautschukprüfungsanstalt in Delft, where analysis showed the particular sample of crepe contained 93 to 94 per cent rubber hydrocarbon, with the remaining 6 to 7 per cent composed of 2 to 3 per cent acetone extract, 2 to 3 per cent proteins (calculated as protein with factor 6.25) and finally moisture and ash. When dry distilled in the ordinary way, this crepe yielded up to 450° C. about 95 per cent of a yellow oil which was highly unsaturated. The bromine addition number (according to the McIlhiney method) of the distilled benzine (b. p. up to 220° C.) was, with a 3-minute contact period in carbon tetrachloride in darkness, higher than 120. The benzine obtained from the berginization of the raw rubber was far different from this. The experiments were carried out in an agitated autoclave. Five iron balls served as a means of stirring. In each experiment 150 g. of crepe were rolled around the pyrometer tube in the autoclave. Each time before an experiment, the autoclave was evacuated and was charged with hydrogen at 110 kg. per sq. cm. pressure. Two experiments, D6 and D7, were carried out. For comparison 2 similar experiments, D3 and D4, were made in which hydrogen under pressure was not used, in this case the heating being carried out under the pressure of the gases formed by the thermal decomposition. The conditions used in the D3 and D4 experiments were otherwise identical with those of the D6 and D7 experiments. The heating was carried on so that 450° C. was reached as rapidly as possible, at which point the system was maintained for 15 minutes. At the end of this period of heating, the autoclave was cooled rapidly by compressed air. After cooling the gases were drawn off through a previously evacuated spiral receptacle cooled with a carbon dioxide-acetone mixture. Whatever was not condensed in this way was collected in a gas-measuring receiver. After the pressure in the autoclave had fallen to one atmosphere, the autoclave valve was closed, the cold mixture was removed from the spiral, as a result of which the liquid condensed within the spiral evaporated in part.

The Effect of Temperature and Solvent upon the Addition of 4-Chlorobenzenesulfenyl Chloride to cis- and trans-1-Phenylpropene

1972 ◽  
Vol 50 (15) ◽  
pp. 2465-2469 ◽  
Author(s):  
George H. Schmid ◽  
Valeria M. Csizmadia
Keyword(s):  
Thermodynamic Parameters ◽  
Effect Of Temperature ◽  
Kinetic And Thermodynamic Parameters ◽  
Product Composition ◽  
Kinetically Controlled ◽  
The One ◽  
Cis And Trans

The effect of temperature upon the product composition of the addition of 4-chlorobenzenesulfenyl chloride to cis- and trans-1-phenylpropene in 1,1,2,2-tetrachloroethane has been studied. The kinetically controlled product in both cases is the adduct with Markownikoff orientation while the thermodynamically controlled product is the one with the anti-Markownikoff orientation. Kinetic and thermodynamic parameters have been determined for the isomerization of the threo as well as the erythro adducts. The effect of different solvents on the product composition has been studied at 25°. The regioselectivity towards Markownikoff product parallels the increasing acidity and anion solvating ability of the solvent.

scholarly journals Polarisation measurements on basic beryllium acetate and beryllium acetylacetonate

1932 ◽  
Vol 137 (832) ◽  
pp. 372-379 ◽  
Keyword(s):  
Dipole Moment ◽  
Carbon Tetrachloride ◽  
Chemical Analyses ◽  
Melting Points ◽  
Molecular Configuration ◽  
Carbon Tetrachloride Solution ◽  
Physical Measurements ◽  
Beryllium Compounds ◽  
Polarisation Measurements ◽  
Made In

An investigation of organic beryllium compounds is being carried out by one of us (W. R. A.) with a view to obtaining information regarding their molecular configuration and a study of their molecular polarisations suggested itself as a means of deciding whether or not these compounds are spatially symmetrical. No previous attempts appear to have been made to measure the dipole moment of compounds of this type; other physical measurements have been made and will be discussed in a later section. In the present investiga­tion measurements have been made in benzene and carbon tetrachloride solution, but in both solvents the compounds are only sparingly soluble. 2. Purification of Materials . Beryllium Compounds .—Small quantities of basic beryllium acetate and beryllium acetylacetonate were very kindly supplied by Professor G. T. Morgan, F. R. S., and Dr. S. Sugden, and our best thanks are due to them. The melting points of the compounds were in accord with the values quoted at the literature: acetate, m.p. 285° C.; acetylacetonate, m.p. 108-5° C. Micro-chemical analyses, carried out by Dr. Schoeller, in Berlin, gave the following table.

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