Triphenylmethane and derivatives

Organic chemistry assignment

1. MAHARSHI DAYANAND UNIVERSITY Rohtak DEPARTMENT OF PHARMACEUTICAL SCIENCES “ Triphenylmethane & its derivative ”

2. Triphenylmethane Triphenylmethane , or  triphenyl methane , is the hydrocarbon with the formula  (C 6 H 5 ) 3 CH . This colorless solid is soluble in nonpolar organic solvents and not in water. Triphenylmethane is the basic skeleton of many synthetic dyes called  triarylmethane dyes , many of them are  pH indicators , and some display  fluorescence . A  trityl  group in organic chemistry is a triphenylmethyl group Ph 3 C, e.g.  triphenylmethyl chloride  (trityl chloride) and the  triphenylmethyl radical  (trityl radical).

3. Properties Chemical formula Molar mass Density Melting point Boiling point Solubility in water Solubility Acidity C 19 H 16 244.337 g·mol −1 AppearanceColorless solid 1.014 g/cm 3 92 to 94 °C (198 to 201 °F; 365 to 367 K) 359 °C (678 °F; 632 K) Insoluble soluble in dioxane and hexane (p K a )33.3

4. Preparation Heating  diphenylmercury  Hg(C 6 H 5 ) 2 with  benzal chloride  C 6 H 5 CHCl 2 Triphenylmethane can be synthesized by Friedel-Crafts reaction from benzene and chloroform with aluminium chloride catalyst: 3 C 6 H 6  + CHCl 3  → Ph 3 CH + 3 HCl Alternatively, benzene may react with  carbon tetrachloride  using the same catalyst to obtain the  trityl chloride-aluminium chloride  adduct, which is hydrolyzed with dilute acid: 3 C 6 H 6  + CCl 4  + AlCl 3  → Ph 3 CCl·AlCl 3 Ph 3 CCl·AlCl 3  + HCl → Ph 3 CH Synthesis from  benzylidene chloride , prepared from   benzaldehyde and  phosphorus pentachloride , is used as well.

5. Acidity The p K a  is 33.3. Triphenylmethane is significantly more acidic than most other hydrocarbons because the charge is delocalized over three phenyl rings. Steric effects however prevent all three phenyl rings from achieving coplanarity simultaneously. Consequently diphenylmethane is even more acidic, because in its anion the charge is spread over two phenyl rings at the same time. The trityl anion is red. This colour can be used as an indicator in acid-base titrations. The sodium salt can be prepared also from the chloride: (C 6 H 5 ) 3 CCl + 2 Na → (C 6 H 5 ) 3 CNa + NaCl The use of tritylsodium as a strong, non- nucleophilic base has been eclipsed by the popularization of butyllithium and related strong bases.

6. Triarylmethane dyes Examples of triarylmethane dyes are  bromocresol green : And the  nitrogen -bearing  malachite green :

7. References Aug. Kekulé and A. Franchimont (1872)  "Ueber das Triphenylmethan"  (On triphenylmethane),  Berichte der deutschen chemischen Gesellschaft ,  5  : 906–908.   J. F. Norris (1925). "Triphenylmethane". Organic Syntheses.  4 : 81.  doi : 10.15227/orgsyn.004.0081 .   Ronald Breslow and William Chu (1969). "Electrochemical determinations of pK a 's. Triphenylmethanes and cycloheptatriene". Journal of the American Chemical Society.  92  (7): 2165.  doi : 10.1021/ja00710a077 . W. B. Renfrow Jr and C. R. Hauser (1943).  "Triphenylmethylsodium“ .  Organic Syntheses . ;  Collective Volume,  2 , p. 607

8. THANK YOU