Structure of Simpler Organic Compounds. 141 



Of the three carboxyl acids known, therefore, the oriho- 

 phthalic acid can be readily distinguished from the other 

 two. One of the other two can, however, be obtained by 

 a synthetic method, which leaves no doubt as to its con- 

 stitution. When acetone is distilled with concentrated 

 sulphuric acid, it yields a product C 9 H 12 , which behaves 

 like a benzene derivative 



3CH 3 COCH 3 = C.H,(CH 3 ), + 3H,0 



The product is known as mesitylene, and if it is a 

 benzene derivative it would, from its formation from 

 acetone, contain probably three methyl groups which would 

 be in a symmetrical position to one another. If three 

 molecules of acetone are written in such a way as to 

 indicate the method of the withdrawal of water, a picture 

 of the following character is obtained 



-~ 



' H'. \ ,,-N 



% 



It is hardly conceivable that any but a symmetrical 

 derivative could be obtained by such a reaction as the 

 above. Furthermore, when alkyl substitution products 

 of benzene are submitted to oxidation, the alkyl group 

 is oxidized to a carboxyl group. Thus, mesitylene can 

 be oxidized to C 6 H 3 (COOH) 3 . This reaction can be accom- 

 plished in stages, and by regulating the process it is 

 possible to isolate first the substance C 6 H 3 (CH 3 ) 2 COOH, 

 the calcium salt of which on distillation with lime yields 



