Triphenylchloromethane

Preparation and Properties of Triphenylchloromethane (SECTION 488).—(a) Attach to a 500-cc. flask by means of a stopper a small drying tube containing anhydrous calcium chloride. Provide a beaker containing cold water into which the flask can be sunk up to the neck and held in place by a wire. Add to the flask 31 grams of carbon tetrachloride, 78 grams of benzene, and 28 grams of anhydrous aluminium chloride in the form of lumps. 

The next day filter off the crystals by suction. Disconnect the flask from the pump, add 25 cc. of petroleum ether and in a few minutes draw off the liquid adhering to the crystals. Repeat the washing with another 25 cc. portion of petroleum ether. Spread the crystals on a paper to dry and weigh them. 

Triphenylchloromethane melts at 109°-1110. It can be crystallized from boiling ligroin, in which it is readily soluble hot and difficultly soluble cold. Since triphenylchloromethane is decomposed when heated with water, anhydrous solvents should be used. The compound can be obtained in a very pure condition by recrystallizing it from the boiling acetyl chloride. The yield of the material obtained is 60 per cent of the theoretical. By distilling off the solvent from the first crystallization, and adding to the residue 50 cc. of petroleum ether, an additional quantity of 

—If the dark red oil which separates at first in the reaction is decomposed at once by water, benzophenone chloride, (CeHs CCL, is obtained. This red oil, which is a molecular compound of benzophenone chloride and aluminium chloride, reacts on standing with more benzene and is converted into a substance of the composition (CeHs CCl.AlCL, which is a crystalline solid. Water decomposes this addition-product into its constituents. 

Preparation of Triphenylmethane from Triphenylchloromethane.—When the addition-product of triphenylchloromethane and aluminium chloride is treated with ether, the halogen atom in the former is replaced by hydrogen. 

To prepare triphenylcarbinol from triphenylchloromethane, boil the latter with excess of water for 10 minutes. Filter off the resulting triphenylcarbinol, dry between filter papers, and recrystallise from carbon tetrachloride or alcohol m.p. 162°. The yield is almost quantitative. 

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If pure triphenylchloromethane and freshly prepared sodium amalgam are used, the yield of sodium triphenyl-methide should be almost quantitative but is usually 0 15 mol per htre (1). The reagent should be used as soon as possible after its preparation. 

Triphenylchloromethane (C3Hj)3CCl is readily hydrolysed by warm water to triphenylcarbinol, thus providing an alternative method for the preparation of the latter. The former is conveniently obtained by the reaction between carbon tetrachloride and benzene in the presence of anhydrous aluminium ehloride ... 

The aeetyl chloride eonverts any triphenylcarbinol which may be present into triphenylchloromethane ... 

Benzene reacts with carbon tetrachloride ia the presence of anhydrous aluminum chloride to give triphenylchloromethane no tetraphenjlmethane is formed (20). At elevated temperatures, carbon tetrachloride attacks siUca gel forming a siUcon oxychloride (21). 

A polymer-supported version of our optimal ligand was also developed [52]. Its preparation involves attachment of aziridine carbinols to polymer-bound triphenylchloromethane (Scheme 40). This polymer-bound ligand 53 was almost equally effective in the enantioselective addition of diethylzinc to aromatic and aliphatic aldehydes with ee s ranging from 77-97% for the latter type of substrate [52]. It is of practical interest that this polymer-supported ligand could be reused without losing much of its efficiency. 

Thus for hydrolysis in 50% aqueous acetone, a mixed second and first order rate equation is observed for phenylchloromethane (benzyl chloride, 10)—moving over almost completely to the SV1 mode in water alone. Diphenylchloromethane (11) is found to follow a first order rate equation, with a very large increase in total rate, while with triphenylchloromethane (trityl chloride, 12) the ionisation is so pronounced that the compound exhibits electrical conductivity when dissolved in liquid S02. The main reason for the greater promotion of ionisation—with consequent earlier changeover to the SW1 pathway in this series—is the considerable stabilisation of the carbocation, by delocalisation of its positive charge, that is now possible ... 

Triphenylcarbinol has been obtained by the reaction between phenylmagnesium bromide and benzophenone,1 methyl benzoate, or phosgene 8 by action of phenylsodium upon benzophenone, benzoyl chloride, ethyl chlorocarbonate, or ethyl benzoate 4 by hydrolysis of triphenylchloromethane 5 and by oxidation of tri-phenylmethane.6... 

The yield of triphenylchloromethane depends very much upon the quality of the aluminum chloride used. Fresh commercial resublimed aluminum chloride, in powder form, has been used in the preparation described. 

The product may be stored satisfactorily in ordinary screw-top bottles, provided that they are well sealed with paraffin or some similar material. Triphenylchloromethane is slowly hydrolyzed to triphenylcarbinol by the moisture of the air. Partially hydrolyzed triphenylchloromethane may be purified by recrystallization from one-third its weight of benzene containing 5-25 per cent of acetyl chloride. The product is washed with ligroin containing a little acetyl chloride. 

The filtration should be rapid. Triphenylchloromethane is hydrolyzed by moisture in the air. 

A technical grade of acetyl chloride may be used, since the presence of small amounts of acetic acid does not interfere. The acetyl chloride serves to convert into triphenylchloromethane any triphenylcarbinol which may be present. 

Successful O-alkylation of the Ag salt of phenylnitroacetonitrile with CH3I (12) and triphenylchloromethane (13) was documented (Scheme 3.6, Eqs 1 and 2). 

The reaction is applied preparatively to triphenylchloromethane, p. 346. Finally, the alkyl halides have also acquired extraordinary importance as starting materials for the Grignard reaction, discussed on pp. 337 ff. 

We might expect that the reaction would lead to the formation of tetraphenylmethane from benzene and carbon tetrachloride in the presence of aluminium chloride, but this is not so. In this case the fourth Cl-atom remains in the reaction product. Triphenylchloromethane (C6H5)3CC1 has acquired extraordinary importance because, when applied in the Wurtz reaction, it made possible the discovery of the first free organic radicle (Gomberg, 1900). Compare p. 352. 

The Triphenylmethyl Ion.—A solution of triphenylchloromethane in a dissociating solvent conducts the electric current (Walden). Since, on electrolysis, triphenylmethyl is liberated at the cathode, it follows... 

The triphenylmethyl ion is also, very probably, present in the orange-yellow products of the salt and complex salt type which are produced from triphenylcarbinol with concentrated sulphuric acid and from triphenylchloromethane with metallic chlorides (ZnCl2, A1C13, SnCl4, SbCl6). 

Experiment.—Dissolve a few granules of triphenylcarbinol or of triphenylchloromethane in 0-5 c.c. of concentrated sulphuric acid by rubbing with a glass rod. Add a little water the deep orange-yellow solution is completely decolorised. Simultaneously the unchanged carbinol is precipitated. 

In the same way the above-mentioned complex salts of triphenylchloromethane are readily decomposed by water. In both cases a hydrolysis occurs which causes the triphenylmethyl ion to lose its charge, and the carbinol to be re-formed. 

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