Ionic conditions

The elements of bromine azide have been added to steroid olefins. The addition can be rationalized as proceeding through a positive bromonium ion under the ionic conditions of Hassner and Boerwinkle (bromine plus sodium azide and hydrochloric acid in nitromethane-dichloromethane) or Ponsold (A-bromosuccinimide or A-bromoacetamide in chloroform contain-... 

The reactions of bromine with E- or Z-1 -fluoropropene under ionic conditions result in stereospecific anti additions to yield the 15,26 and 1R,25 products, respectively [ftl] (equation 4)... 

Electronic structure methods are aimed at solving the Schrodinger equation for a single or a few molecules, infinitely removed from all other molecules. Physically this corresponds to the situation occurring in the gas phase under low pressure (vacuum). Experimentally, however, the majority of chemical reactions are carried out in solution. Biologically relevant processes also occur in solution, aqueous systems with rather specific pH and ionic conditions. Most reactions are both qualitatively and quantitatively different under gas and solution phase conditions, especially those involving ions or polar species. Molecular properties are also sensitive to the environment. 

From electrophoretic data for SLS micelles under various ionic conditions (22 ), values of 80 for the aggregation number and 23 for the effective charge of the kinetic micelles can be used. This gives the following formula for the eluant total ionic strength. 

The addition of iodine electrophiles, fert-butyl hypoiodite (t-BuOI) in the presence of BF3, acetyl hypoiodite (AcOI), iodine monochloride (IC1) and iodine monobromide (IBr), to 1,3-butadiene gives always, under ionic conditions, mixtures of 1,2- and 1,4-Markovnikov adducts (equation 57). These mixtures are the kinetic products, since rearrangement to the thermodynamically stable products occurs under the appropriate conditions86. 

The method of preparation of the proteins is of great importance. Not only does it affect the amount of polydispersity, but the conformation of the proteins themselves varies depending upon the conditions of preparation. Urea-treated proteins can be renatured if sufficient care is taken to prevent precipitous changes in ionic conditions. Proteins have also been prepared using LiCl which avoids the harsh effects of urea. 

As recognized by Widom [301], the equilibrium stability of the nucleosome creates an apparent paradox because the disassembly and reassembly processes take place under ionic conditions for which some of the nucleosome components... 

Rybenkov, V.V., Vologodskii, A.V., and Cozzarelli, N.R. (1997) The effect of ionic conditions on DNA helical repeat, effective diameter and free energy of supercoiling. Nucleic Acids Res. 25, 1412-1418. 

Initially, the antibodies should be purified prior to prepare the immunoaffinity column. Precipitation with ammonium sulfate, ion-exchange chromatography, gel filtration chraoma-tography or affinity chromatography may be employed with the aim of antibody purification. Activated beads which are coated with bacterial proteins A or G may be used as the support material. Some parameters may be changed for the elution of the sample solution for example the ionic conditions of mobile phase may be changed or chaotropic buffers may be used [11]. 

Collagen fibrils from the dermis of the sea cucumber Cucumaria fron-dosa are aggregated in vitro by the dermal glycoprotein stiparin (Trotter et al., 1996). Under physiological ionic conditions, stiparin appears to be both necessary and sufficient to cause fibrils to aggregate (Trotter et ah,... 

Other alkyl hypohalites usually add to carbon-carbon multiple bonds in a free-radical process.155-158 Ionic additions may be promoted by oxygen, BF3, or B(OMe)3.156-160 While the BF3-catalyzed reaction of alkyl hypochlorites and hypo-bromites gives mainly halofluorides,159 haloethers are formed in good yields but nonstereoselectively under other ionic conditions.156-158 160 In contrast, tert-BuOI reacts with alkenes in the presence of a catalytic amount of BF3 to produce 2-iodoethers.161 Since the addition is stereoselective, this suggests the participation of a symmetric iodonium ion intermediate without the involvement of carbocationic intermediates. 

Free-radical bromination was observed to take place in the presence of oxygen on illumination.249 In a competitive reaction under ionic conditions (CC14, room temperature), cyclohexene reacted 5 times faster than styrene. In contrast, the yield of 1,2-dibromoethylbenzene was 10 times as high as that of 1,2-dibromocyclohex-ane when bromination was carried out in the presence of light. 

An interesting observation of the chlorination of allenes is that besides the addition products, monochlorinated compounds are also formed.252-254 Thus allene gave propargyl chloride, and tetramethylallenes gave 3-chloro-2,4-dimethyl-1,3-pentadiene. Since the reactions were carried out in the presence of oxygen, that is, under ionic conditions, proton loss from the intermediate chloronium ion or 2-chlorocarbocation explains these results. 

Butadiene reacts with chlorine under radical and ionic conditions to give both 1,2- and 1,4-addition products.259 The predominant formation of the trans isomer in radical 1,4-addition [Eq. (6.37)] was explained to result from the predominant transoid form of the starting compound and the configurational stability of the resonance-stabilized allylic radical intermediate ... 

The experimental work was performed at temperatures and/or ionic conditions far from those at which the RNA parameters were measured. Try the -T option to rescale the parameters for temperatures other than 37 °C. 

Regioselective / -fragmentation of the alkoxy radical (17) furnishes the ring-expanded iodide (18) in good yield under HgO-l2-irradiation conditions (Scheme 5).27 Similar transformations could not be accomphshed under ionic conditions. 

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