Cations triphenylmethane

Through the presence of aromatic or pseudoaromatic groups in the molecule (tetraphenylborate and related derivatives, the tetraphenyl-arsonium ion, cationic triphenylmethane dyes, complexes of o-phenanthroline with divalent nickel or ion, where the hydrophobicity is increased by further substitution by a hydrophobic group on the pseudoaromatic nucleus). 

In presence of polyamines the maximum of light absorption of indicated triphenylmethane dyes displaces on 10-30 nm, for azo dyes the shift of the band reaches 50-80 nm. The greatest difference of light absorption of associates and reagents is watched for BKM at pH 5,05, for BPR at pH 4,20, for CPR in an interval pH 5,05-5,45. At these pH dyes are anions, it promotes interaction with a cationic surface-active substance. The ratios between polymer and BKM, BPR, CPR are established by spectroscopy method, its equal 1 20, 1 20 and 1 30 accordingly. 

The mechanism of reaction with steroids has not been elucidated. Various nonquantitative reactions occur simultaneously. Cyclopentenyl cations have been postulated as intermediates which condense with anisaldehyde to yield colored compounds [4]. It is probable that triphenylmethane dyes are also formed with aromatic compounds. 

One of the most typical examples demonstrating the importance of the hydro-phobic contribution may be alkaline-fading reactions of triphenylmethane dyes, which take place between dye cations and hydroxyl ions to form carbinols167. ... 

Mechanisms depending on carbanionic propagating centers for these polymerizations are indicated by various pieces of evidence (1) the nature of the catalysts which are effective, (2) the intense colors that often develop during polymerization, (3) the prompt cessation of sodium-catalyzed polymerization upon the introduction of carbon dioxide and the failure of -butylcatechol to cause inhibition, (4) the conversion of triphenylmethane to triphenylmethylsodium in the zone of polymerization of isoprene under the influence of metallic sodium, (5) the structures of the diene polymers obtained (see Chap. VI), which differ. both from the radical and the cationic polymers, and (6)... 

Derivatives of triphenylmethane were among the earliest synthetic colorants, and are still in demand where bright, intense colours are needed without the necessity for outstanding fastness to light and chemical reagents. Basic dyes of this type, as well as other cationic dyes, are suitable for dyeing conventional acrylic fibres, on which they show better fastness properties than on natural fibres. The photodegradation of triphenylmethane dyes has been reviewed [42]. 

The reaction of thiobenzamide and sulfur dichloride is reported to give 3-methyl-4-phenyl-l,2-dithiazetinium chloride (Scheme 137). This salt forms a trityl cation with triphenylmethane, establishing its highly electrophilic nature. However, the analysis is poor (>1.3% off for Cl, N and S) and no other structural proof is provided (70JOU394). 

Oxidation of the ring system in thiins has also been achieved with hydride acceptors such as triphenylmethyl cations, and results in high yields of thiopyrylium salts. This is far more efficient than the disproportionation reactions discussed above, as the only byproduct is triphenylmethane. The reaction will be discussed in the section on synthesis. 

Because the molecule upon oxidation acquires a double positive charge, it will take up two anions. On the other hand, a typical triphenylmethane dye might undergo the reaction taking up an anion, but giving up a cation in the process. Prototype A should... 

Product formation was interpreted in terms of transalkylation of substituted triphenylmethanes. Protonation at the ipso position of the substituted phenyl ring to form arenium ion 64 followed by the C—C bond breaking yields the diphenylmethyl cation, which alkylates benzene or is stabilized by hydride transfer (Scheme 5.30). The protonated intermediate 64 is highly unstable when the ring has an electron-withdrawing substituent. Consequently, its transformation is extremely slow and the primary product triphenylmethane can be isolated. 

Fig. 5.15. Fluorescence quantum yields of bridged and unbridged triphenylmethane dyes in glycerol as a function of temperature/viscosity.211 Not only cationic dyes show the strong fluorescence quenching for lower viscosities, but it is also present for neutral species as shown by the fuchsone DMAF.

Diphenylmethane and triphenylmethane dyes are monomethine dyes with two or three terminal aryl groups, of which at least one, but preferably two or three, are substituted by a donor group para to the methine carbon atom. The most important donor is the amino group. Important dyes belonging to this class include the well-known malachite green (12) [9] and crystal violet (13) [10], which are some of the oldest synthetic cationic dyes ... 

Most of the chromophore systems common in dye chemistry (nitro, azo, anthraquinone, triphenylmethane, and azomethine) are currently used [37,39, pp. 526-533], Disperse, cationic (basic), and anionic (acidic) dyes are employed. 

Ortho-adduct formation is an unlikely complication in transfer of hydride to substituted 9-phenylfluoren-9-yl cations from triphenylmethane, or 4,4 -dimethoxydiphenylmethane (Bethell et al., 1981). The log of the rates correlated with a+ constants, giving p-values of 2.44 when triphenylmethane is the donor and 3.02 when the diphenylmethane was the" donor. They also correlate with the difference in pA R+ between the product and acceptor carbocation. There does not seem to be a simple pattern of reactivity in the... 

Finally, two or three amino or dimethylamino groups in the /jara-position stabilize trityl cations so efficiently that the associated nonionized neutral compounds are no longer able to exist at all but heterolyze quantitatively to salts. These salts include, for example, the well-known triphenylmethane dyes malachite green and crystal violet ... 

The triphenylmethyl cation reacts with the THF to form triphenylmethane and a protonic acid. We believe that this acid is the true initiator and that its reaction with THF may be slow. This can account in part for the deviations in DP. As Bawn and co-workers pointed out, in the case of the SbCl6 gegenion transfer reactions are probably also important and result in low DP s. 

Also with heterocyclic monomers, simple cations are attached to the atom with the highest electron density in the valence sphere, i. e. to the heteroatoms. The reactions of more complicated carbocations are evidently of greater complexity. The triphenylmethyl cation separates a hydride ion from tetrahydrofuran, producing triphenylmethane and an oxonium ion... 

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