Triaryl Carboniums

Fig. 5. Stmctural interrelationships among diaryl and triaryl carbonium dyes. Pyronine = xanthene (61), R = CH3 is Bindschedler s Green.

Just as interaction of the negative ion with solvent or with a catalyst can promote the ionization, the same is true of the interactions of the carbonium ion. The triaryl carbonium ions discussed so far should all be colored. Reports of colorless but conducting solutions of triarylmethyl derivatives are fairly common and may represent covalently solvated carbonium ions which are not expected to be colorless. For example, a colored solution of the ion XVI in acetic acid slowly fades when it is diluted with methanol containing enough acid to prevent the formation of any "color base. The fading is attributed to the formation of XVII.m... 

Triarylbismuth dilahides, 4 31-33 Triarylbismuthines, 4 26-28 Triaryl carbonium dyes, 9 259-261 Triaryl phosphates, 11 493-494 Triarylpyrazolines, 19 113 Triarylstibines, 3 69 Triarylsulfonium salts, photolysis of,... 

Di- and Triaryl Carbonium and Related Dyes. As a class, these dyes are bright and strong, hut are generally deficient in lightfastness. Consequently, they are used in outlets where brightness and cost-effectiveness. rather than permanence, arc paramount, for example, the coloration of paper. Many dyes of this class, especially derivatives of pyronines Ixamhcnes). arc among the most fluorescent dyes known. 

Alcohols also transfer hydride to carbonium ions. ° In seminal experiments Bartlett demonstrated that isopropyl alcohol as well as other alcohols readily transferred hydride to various triaryl carbonium ions oxidation of the alcohol and reduction of the carbonium ion is the result. 

This ratio clearly varies in the order triaryl carbonium ion < indoles < dialkylanilines < anilines < amides, as expected. 

In order to study spiroconjugation by the u.v. technique, the spiro-fluorene derivatives (485)—(488) have been prepared. They were prepared by the reaction of fluorenone with 2-lithio-3,3 -bithienyl, 4,4 -dilithio-3,3 -bithienyl, 3-lithio-2,3 -bithienyl, and 3,3 -dilithio-2,2 -bithienyl, respectively, followed by electrophilic ring-closure of the intermediate triaryl-carbonium ions by the addition of a drop of hydrochloric acid." ... 

Chromic acid oxidation of olefins can rarely be used for the preparation of oxiranes because they occur as intermediates that rapidly undergo further transformation. From an investigation of the mechanism of oxidation of triaryl-substituted olefins, it was concluded that a carbonium ion or cyclic chromate ester is a possible intermediate. Selective epoxidation of compounds containing conjugated double bonds is attainable by means of chromic-acid oxidation (Eq. 48) 535 Exclusively cis product was obtained from a highly substituted octalin with Na2Cr04, KMn04, or ozone (Eq. 49). ... 

Reactions which almost certainly involve 2-substitution by a carbonium ion are those between pyrrole and a triaryl carbinol, or with xanthydrol in acetic acid. Triaryl chlorides also cause 2-substitution by a carbonium ion... 

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