Patent GB-309031-A (GB)
Title: A process for preparing thymol
IPC: C07C39/06
Filed: 1929-03-28
Abstract: 309,031. Rheinische Kam<p>fer-rabrilt I Gres. April 3, 1928, [Convention date]. I Addition to 320,215. ' Thymol and its isomers; sulphonated thymol and thymol isomers; phosphoric and other esters of pitopylated m-cresols; sulpho-chlorides and li phospho-chlorides of propylated m-cresols.-Thymol is produced from propylated or isopropylated derivatives of m-cresol or from 1n-cresol and multiprop<y>lated m-cresol in a manner analogous to that det-cribed in the parent Specification and I in Specification 308,681, by first converting the propylated m-cresol into a substitution compound containing an eleetronegative atom or group, or an addition compound with a salt, treating this product to cause a migration of the propyl group a.s described in the Specifications above refefred to, and then splitting off the substituent or addition group, the thymol being separated from the bye-products, which are then further treated to obtain more thymol. Compounds mentioned ss suitable a,re the sulphonic acids, phosphoric acid esters, other acid esters, and their chlorides. Tn the examples, (1) isopropyl m.-cresyl ether of boiling point 196-197‹ C. is treated with sulphuric acid, the temperature rising to 80-100<0> C., isomerization occurring spontaneously: on cooling the stilpboi)ated products crystallize out, and may be hydrolyzed in known ways, but preferably the Hydrolysis is effected by treating the crude reaction mixture by dilution with water and distillation with superheated steam at 120-160‹ C., the first fraction being thymol, and the second an isomer of melting point 114‹ C. and boiling point 245-246‹ C., which is then treated as described in Example 3 to obtain more thymol; (2) propyl m-cresyl ether of boiling-point 210.6‹ C. is sulphonated, the sulphonation product being converted into sulphonated thymols by heating for an hour to 90-100‹ C., after which the product is hydrolyzed ; (3) 3-oxy-1-methyl-x-propyl or - isopropyl benzene of melting point 114‹ C. and boiling' .point 345-246‹ C. is sulphonated at 90-- 100‹ C. and isomerized by further heating at the same temperature, preferably in an autoclave; the hydrolysis is effected as described above; (4) isopropyl m-cresyl ether is heated to 130‹ C. with phosphorus pentoxide, yielding the esters, a migration of the isopropyl group taking place, the ester mixture being then saponified and the thymols separated by distillation; (5) 3.oxy-1-methylx-propyl or -isopropyl benzene of melting-point 68-69‹ C. and boiling-point 228-229‹ C. is heated to 210-280‹ C. for 5-10 hours, preferably in an autoclave with phosphorus pentoxide or with meta-phosphorio acid containing phosphorus pentoxide, the products being obtained as in the preceding example; (6) 3-oxy-1-methyl-.1epropyl or -isopropyl benzene of melting-point 68-69‹C. and anhvdrous aluminium chloride are. heated to 50-60‹ C. in a.n inert solvent such as carbon disulphide, a compound of the type C6H3.CH3.C3H7.O-Al2Cl4 being produced with evolution of hydrochloric acid; this compound is heated far several hours to 60-90‹ C. in a closed vessel, preferably in an inert solvent such as carbon disulphide to produce isomerization, the produet, being then hydrolyzed with water and fractionally distilled; (7) molecular quantities of. Incresol and of m-CTesol diprolylated or di-isopropylated in the nucleus are sulphonated at 90-100‹ C. in an autoclave, isomerization being effected by further heating at the same temperature ; (8) molecular quantities of m-cresol and propyl thymol ether are sulphonated and treated as in the previous example. Specifications ! 200.151, 294,238, 298,600 and 325,856 also are referred to.