Triphenylmethyl chloride or trityl chloride (TrCl) is a white solid with the chemical formula C19H15Cl. It is an alkyl halide commonly used in organic synthesis to introduce the trityl protecting group. 

Triphenylmethyl chloride is used in the preparation of S-trityl-L-cysteine (STLC), a tight-binding inhibitor of Eg5 that prevents mitotic progression.

Preparation

Triphenylmethyl chloride is commercially available. It may be prepared by the reaction of triphenylmethanol with acetyl chloride, or by the Friedel–Crafts alkylation of benzene with carbon tetrachloride to give the trityl chloride-aluminium chloride adduct, which is then hydrolyzed.

Reference

[1] FONKEN G J. Alkylation of Benzene with Triphenylmethyl Chloride[J]. The Journal of Organic Chemistry, 1963, 28 7: 1909. DOI:10.1021/jo01042a510.

[2] BILL B. SMITH   J. E L. The Behavior of Triphenylmethyl Chloride in Nitromethane[J]. Journal of the American Chemical Society, 1955, 77 6: 1700-1701. DOI:10.1021/ja01611a101.

[3] C. GARDNER SWAIN   Elizabeth E P. Mechanism of Methanolysis of Triphenylmethyl Chloride in Benzene Solution1-3[J]. Journal of the American Chemical Society, 1958, 80 4: 812-819. DOI:10.1021/ja01537a016