Carbonium salts

The degree of dissociation is a = pic = 1 - qlc. We now consider the three special cases shown in Table 3. In order to ascertain which, if any, of the two approximations may be valid, we need to examine the magnitudes of K, Ky and c which are relevant to the systems under discussion. To determine a value of K which will be relevant to polymerizing systems, we need the dissociation constant of a carbonium salt with a large anion, in a solvent of e about 10, at 25 °C. The only relevant information is Longworth and Mason s value of K for triphenylmethyl perchlorate in ethylene dichloride [53], and values of K for two quaternary ammonium perchlorates [140] (see Table 4). 

Wien a little concentrated hydrochloric acid is added the green solution becomes yellow, because now the trichloride is formed and the influence of the second benzene ring is also suppressed, so that the (yellow) fuchsonimine type is formed. All triphenylmethane dyes dissolve in concentrated sulphuric acid with an orange-yellow colour exactly like triphenylcarbinol itself (carbonium salts, Kehrmann). By diluting the solution with water a colourless solution of the tri-acid benzenoid carbinol salt can be obtained. 

The formation from neutral substances (triphenylcarbinol) of coloured, salt-like reaction products which are more or less easily decomposed by water is a phenomenon called halochromism . The halo-chromic salts of triphenylcarbinol are regarded as carbonium salts this follows at once from the above discussion. A quinonoid formula, by which various authors explain the colour, seems less probable. Recently the attempt has been made to attribute complex formulae to the carbonium salts (Hantzsch), in accordance with Werner s scheme for ammonium salts. Such formulae express the fact that, in the ion, the charge is not localised at the methane carbon atom, but spread over the field of force of the whole radicle. The simplest carbonium salt of the group, the yellow perchlorate (K. A. Hofmann), would accordingly have the following structural formula ... 

The infra-red spectra of the trimethyl, dimethyl- and dimethylethyl-carbonium salts in excess antimony pentaduoride are shown in Figs. 4a, b, and c. The IRTRAN cells used are not transparent below 770 cm , thus obscuring the 650 cm SblY absorption which would, however, be overlapped by the solvent SbFs absorption. The broad, intense absorption band which appears in all the spectra near 1550 cm is present in the solvent spectrum. It was found to be dependent on the purity of the SbFs, but the nature of the impurity was not established. It should also be mentioned that Deno found an intense absorption at 1533 cm in cyclohexenyl cations thus, secondary carbonium ions formed from the reaction with olefins (which arise from deprotonation) could add to this broad absorption. 

The two most active compounds in this series are 5-[4-(2-diethylaminoethyl-amino)-l-naphthylazo] uracil (XLa) and 5-(4-amino-l-naphthylazo)uracil (XLb), (ANU). In mice infected with the Puerto Rican strain of S. mansoni, compound (XLa) causes an 82—100 per cent reduction in live worms when administered in the diet at 167—489 mg/kg per day for 14 days [334], whereas ANU (XLb) causes a 73—100 per cent reduction at 221—804 mg/kg per day for the same period [335]. These compounds are reported to be more effective than either lucanthone hydrochloride [334, 336] or the tris-(p-aminophenyl)carbonium salts [334—337]. Substitution of the amino groups at other positions in the... 

A seemingly minor technical problem, the ability of triphenylmethyl to pick up virtually any solvent as solvent of crystallization, occupied Gomberg for some time and led him into consideration of then fashionable structures involving tetravalent oxygen, which were later abandoned. Another sidetrack, more serious in view of the absence of a useful theory, was caused by experiments based on the known fact that triphenylchloromethane showed salt-like conductivity in solution in liquid SO2 It was thus definitively established that there are carbonium salts in the true sense of the definition applied to salts. When triphenylmethyl was dissolved in liquid SO2, it was found that it too conducted the electric current quite well. " How should one explain this strange phenomenon, a hydrocarbon behaving like an electrolyte ... 

This reaction can be used to explain some of the observations of the present work. The carbonium ion has a high affinity for the OH" ion, as illustrated by a pKh = 11 (23). The carbonium salt will thus hydrolyze readily ... 

In an indirect way the caprolactam salts may be formed by heating caprolactam solutions or suspensions of certain neutral or only slightly basic salts which are able to decompose to strong bases (82, 83, 86, 87, 91, 93). This effect can be reached by using alkali salts of carboxylic acids tending to decompose by decarboxylation. Alkali carbonates (7, 10, 13, 17, 28, 44, 45, 60, 65, 82—84, 87, 91, 102), alkali salts of carbonic monoalkyl esters, phenylacetic acid and other similar salts (62, 86, 89, 93, 102) are converted by decarboxylation into strongly basic carbonium salts or metal derivatives of amines or alcohols... 

Figure 5 Structures and examples of nomenclature for phosphonium and carbonium salt-based reagents. Rules of nomenclature dictate that the latter be named as modified ureas see text for revised structures "ino" indicates a ring linked at the nitrogen atom.

Many papers have been published concerning the structure of the active centers in anionic and cationic ring-opening polymerization reactions of oxacyclic monomers. Recently, attention has been paid in our laboratory to the influence of the structure of complex carbonium salt initiators, especially of the dioxolanyllum salts used for initiating the cationic polymerization reactions of trioxane, tetrahydrofuran and dioxolane, on the course of the polymerization ( ). 

In order to examine the behaviour of Eq. (6) we need to define likely values of c/K and fi. For reasons which will be explained later, values of c greater than about 10 5 M need not be considered for carbonium polymerisations, and a useful lower limit is probably about 10 10 M. As far as K is concerned, in solvents such as ethylene and methylene dichloride, whose D.C. lies between ca. 9 and 16, according to the temperature, the evidence (6, 7, 8, 9) shows that under these conditions the dissociation constants of trityl salts are in the range 10 4 to 10 5 M. This is the only information which we have on the dissociation constants of carbonium salts, and it is of little direct relevance to the likely dissociation constants of ion-pairs involving... 

The idea of carbonium ions is quite old in organic chemistry. Olah has traced the early history (15). In 1902 Von Baeyer wrote of carbonium salts in explaining the deep color formed when triphenylmethyl chloride was dissolved in sulfuric acid. Carbonium ions as reaction intermediates were proposed by Meerwein in 1922, and much used by Ingold, Hughes, and others in England soon thereafter. F. C. Whitmore in the USA from 1932 on showed how carbonium ions as reaction intermediated could explain the acid-catalyzed reactions of alkylation, polymerization, and isomerization. His studies were summarized in a review article in 1948 ( ). More recently, of course, there have been many spectroscopic studies of stable carbonium ions formed in highly acidic solutions at low or moderate temperatures, as, for example, in the works of N. C. Deno and G. A. Olah. 

Amides and carbamates undergo analogous alkylation reactions with dienyl carbonium salts (A. J. Liepa, personal communication) as do purines and pyrimidines (I. D. Jenkins, unpublished). Another useful application of dienyl carbonium salts is in the synthesis of 2,4-dienylphosphonic acid derivatives through a facile Arbusov reaction with phosphites [Eqs. (114) and (115) (Birch et a ., 1975)]. This type of compound would be difficult to synthesize by normal procedures. 

Carbonium salts s. Azulenium salts, Garboxonium —, Cyclopropenium —, Triphenylcarbonium — Carbon monoxide (s. a. 

Carbonium salts and cation radicals 1,2-Divinyloxyethane CHCI3... 

Details of the manufacture of polytetrahydrofuran have not been disclosed. Because of the stability of the 5-membered ring in tetrahydrofuran, combinations of Lewis acids with water are not very effective initiators. More active cationic initiators are preformed carbonium salts (e.g., (C6Hs)3C SbCl6") and oxonium salts (e.g., (C2H5 )30 BF4"). The mechanism of reaction is thought to be fundamentally similar to that given above (Section 8.4.5) for the polymerization... 

A mixture of ClCHjSMe and SbClj contains the chloro-sulphonium salts ClCHjSciMe SbClj" and CljCHSciMe SbCl , and not the carbonium salts, as previously claimed. However, MeS Clj SbCl is formed from CljCSMe. 

Synthesis of Derivatives of Thionocarboxylic Acids.—Thiono-esters are obtained by the reaction of dialkoxycarbonium ions with NajS or anhydrous NaHS in acetonitrile (Scheme 6). Cyclic carbonium salts from 1,2- or 1,3-diols give monothiono-esters of these diols. The tetrahedral intermediates in this process may be alkylated to give... 

D yachkovskii. Polymerization of ethylene in the presence of macromolecular carbonium salts of complex catalyst components, Kompleks. Metalloorgan. Katalizatory Polimeriz. Olefinov. Chernogolovka 1980 66 Chem. Abstr. 85 43768 (1981). 

TiCl5"R3C -(C2H5)3Al2Cl3 R,C = carbonium salt (C2H,0)3TiCl-C2H5AlCl2 (BuO)4Ti-(C2H,),Al... 

Monothioacyl disulfides Tris(alkylthio)carbonium salts Trithiocarbonic acid esters Trithiocarbonates 5 Trithioorthocarboxylic — Orthotrithiocar-boxylic — 20... 

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