January, 1913. 



KNOWLEDGE. 



39 



synthetic rubber had ever been obtained by Tilden, 

 years before he had himself begun to experiment 

 with this object, need not cause much surprise; 

 more especially as all organic chemists look with 



CH 



CH, 



CH 



CH 



CH 



Sahatier and 

 Senderens. 



CH, 



CH 



CH 2 



CH 2 



CH, 



CH, 



OH 



Phenol. 



NHiOCtCHjh.CO.NH, 



Amide of adipic acid. 



CH 



OH 



HCIO 



NH.,.(CH.,) 4 .NH, 



Tetramethylene 

 diamine. 



CH,I+KOH 



>■ 



Ag,0 



(CH,), 



HO' 



>N.CH,.CH,.CH.,.CH.,.N 



# 



(CH,), 



heat. 



OH 



which have been suggested as a starting point may 

 be mentioned : — 



(1) Coal Tar. (2) Carbohydrates such as starch, 

 sugar or wood. (3) Petroleum. (4) Turpentine oils. 



We will deal with methods 

 of obtaining isoprene or bu- 

 tadiene from these sources, 

 taking each in turn. Dr. 

 Fritz Hofmann, of the firm 

 of Fr. Bayer, of Elberfeld, 

 chose coal-tar as his starting 

 point, and worked out a 

 method of producing both 

 isoprene and butadiene in 

 quantity from this substance. 

 To produce butadiene, 

 first of all phenol is isolated 

 from coal-tar and 

 then is converted 

 by the following 

 series of opera- 

 into buta- 

 (See Table 



COOH CH, 



COOH 



~> 



Adipic Acid. 



I(CH,) 3 . N-(CH,) 4 -N(CH 3 ) :i I 



■> CH, = CH-CH = CH>+2N(CH,),+2H.,0. 



Butadiene. 



CH, 



I 



c 



Table 8. 



grave suspicion on the labours of their fellow-workers. 



However, Figure 29 will set the matter at rest ; 

 for therein is shown a photograph of Sir William 

 Tilden's actual sample of synthetic rubber, which 

 was obtained by the complete polymerisation of 

 isoprene obtained by him no less than thirty years 

 ago. The liquid isoprene had taken about twenty years 

 to spontaneously solidify into rubber of good quality ! 

 This fact settles all argument about the matter, and 

 there are still a great many 

 people who distinctly remember 

 him showing a sample of syn- 

 thetic rubber, at a meeting of 

 the Birmingham Philosophical 

 Society on May 18th, 1892, 

 the paper being published in 

 the Chemical News, Vol. LXV., 

 page 265 (1892). 



After the foregoing remarks 

 it will be seen that the com- 

 mercially successful production 

 of synthetic rubber depends 

 entirely upon the possibility 

 of producing cheaply the hydro- 

 carbons, butadiene and isoprene 

 — for both yield excellent 

 rubbers. 



It must be obvious that the 

 materials we start with 



tions 

 diene. 

 8.) 

 If, 



however, 



isoprene is re- 

 quired, it also is obtained from coal tar by isolating 

 paracresol from it and then treating it to the series 

 of reactions shewn in Table 9. 



The /3-Methyltetramethylene diamine thus pro- 

 duced is converted into isoprene by heating it with 

 caustic potash, water, methyl alcohol, and methyl 

 chloride, CH 3 C1, in an autoclave for twelve hours at 

 100° C, whereby the compound C1(CH 3 ) 3 N.CH 2 . 

 CH(CH 3 ).CH 2 CH a .N(CH. s ) 3 Cl is produced. This 



raw 



must not only be very cheap 

 but must also be obtainable in 

 practically unlimited quantity, 

 if we are to produce a synthetic 

 rubber capable of competing 

 in any way with natural rubber. 

 Among the raw materials 



HC 



HC 



CH 



Sabatitr and 

 r* H Senderens. 



c 



I 



OH 



jiJ-Cresol from 

 coal-tar. 



CH, 



I 

 CH 



CH, CH, 



CH, CH, 



CH 



I 

 OH 



CH, 



I 

 CH 



CH, 



CH, 



CH, 

 I 

 NH,— CH,— CH-CH,— CH,— NH, 



/3-Methyltetramethylene diamine 



COOH CH, 



COOH 



/3'Methyladipic 

 acid. 



CH S 

 I 

 /CH— CH, 



? H * CH, 



I 

 CO.NH, CO.NH: 



Amide of /3-Methyl- 

 adipic acid. 



Table 9. 



