Triphenylmethyl chloride, ionization

The degrees of ionization of triphenylmethyl chloride, di-methoxybenzhydryl chloride, and dimesitylmethyl chloride in liquid... 

One of the most stable carbocation structures is the employing all three rings. Trityl chloride ionizes read-triphenylmethyl cation (trityl cation). In this struc- ily, and can capture an available nucleophile, ture, the positive charge is stabilized by resonance... 

It was mentioned earlier in this chapter that acid amides and nitrocompounds form conducting solutions in liquid ammonia and hydrazine the ionization in these cases is undoubtedly accompanied by, and is associated with, compound formation between solute and solvent. The same is true of triphenylmethyl chloride which is a fair electrolytic conductor when dissolved in liquid sulfur dioxide it also conducts to some extent in nitromethane, nitrobenzene and acetone solutions. In chloroform and benzene, however, there is no compound formation and no conductance. The electrolytic conduction of triphenylmethyl chloride in fused aluminum chloride, which is itself a poor conductor, appears to be due to the reaction... 

It was Meerwein and van Emster who, in 1922, while studying the kinetics of the rearrangement of camphene hydrochloride (1) to isobomyl chloride (2) [Eq. (5.1)], noticed that the reaction rate increased in a general way with the dielectric constant of the solvent. Further, they found that metalhc chlorides such as SbCh, SnCb, FeCb, AlCb, and SbCf (but not BCh or SiCh), as well as dry HCl (all of which promote ionization of triphenylmethyl chloride by the formation of ionized complexes), also considerably accelerate the rearrangement of camphene hydrochloride. Meerwein concluded that the conversion of camphene hydrochloride to isobornyl chloride actually does not proceed by way of migration of the chlorine atom, but by a rearrangement of a cationic intermediate. Thus, the modern concept of carbocation intermediates was born. 

Solution-Phase Ionization of Tropenyl Chloride and Triphenyl-methyl Chloride. Insofar as thermal degradation is concerned, the critical phase in PVC processing occurs in the melt, which may reach temperatures in the vicinity of 200°C (73) over a period of some minutes. The dielectric constant of PVC (3-4 at 25°C, 11-12 at 140°C) (74) is comparable with that of small chlorocarbons (75). Of the organic chlorides whose ionization has been studied in such solvents, tropenyl chloride and triphenylmethyl chloride seem to have received the most attention. 

Triphenylmethyl Chloride. The ionization of triphenylmethyl chloride (Ph3CCl) in 1,2-dichloroethane (dielectric constant of 10.4 at 25°C) (75) has not been measured directly, but an extrapolation from experimental data (76,77) allows the following estimates ... 

Advantage can be taken of the ionizing and dissociating effects produced by a solvent to activate inert molecules and initiate a polymerization. For instance, triphenylmethyl chloride in pure sulfuric acid solution undergoes an instantaneous ionization and produces a triphenylmethylium cation with a characteristic red color ... 

Tetrahydroxylation according to the synthesis of (+)-ll,ll -dideoxyverticillin A (669) (422) led to tetraol 684. Treatment with trifluoroacetic acid in hydrogen sulfide-saturated nitromethane diastereoselectively furnished bisthiohemiaminal 685. Addition of /50-butyryl chloride generated the more stable compound 686. A(-Desulfonylation tmder irradiation (—> 687) followed by hydrazinolysis and sulfenylation of the free thiol furnished bis(triphenylmethandisulfide) derivative 688 in a very good yield. Ionization of the fro-butyryl residues and loss of a triphenylmethyl cation finally led to 689, which was subjected to methanolysis 434) to afford the natural product (+)-chaetocin A (677). 

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