ORGANIC CHEMISTRY 545 



agree almost exactly with the fluorescent and absorption 

 bands of benzene. The Fraunhofer effect has been observed 

 for some of the bands. This is the first time this has been 

 observed for an organic substance of complex structure. 



ORGANIC CHEMISTRY. By O. L. Brady, D.Sc, F.I.C, University 

 College, London. 



The Structure of Benzene^ — ^The old problem of the structure of 

 benzene and its derivatives has recently been attracting con- 

 siderable attention, but, although many ingenious suggestions 

 have been made, the new methods of attack, with the possible 

 exception of the determination of crystal structure by X-rays, 

 have not contributed very much to our previous knowledge. 

 Most, if not all, of the modern investigators have ignored the 

 dynamical formula for benzene first suggested by Collie twenty- 

 five years ago {Trans. Chem. Soc, 1897, 71, 1013 ; 191 6, 109, 

 561), which has the advantage of combining the static formulae 

 of Kekule, Dewar, Baeyer, and others, and provides a more 

 rational starting-point for further speculation than these other 

 formulae. The use of the hexagon as an ideograph by workers 

 in organic chemistry seems to have led investigators to think 

 that a static formula for benzene is very generally accepted, 

 but to those who have worked with benzenoid derivatives the 

 hexagon symbol has usually conveyed much more than a 

 simple structural formula. 



On the experimental side Ingold {Trans. Chem. Soc, 1922, 

 121, 1 1 33 and 1143) has, by the synthesis of a benzenoid 

 derivative from an alicyclic compound, brought forward support 

 for the bridged ring formula [ii] of Dewar as an intermediate 

 phase between the two forms of the Kekule formula [i] and [iii]. 



-^X 



V/ 



^ 



^%, 



\:^ 



[1] [ii] [iii] 



The benzenoid compound synthesised was orcinol [viii] and was 

 obtained by a Dieckmann condensation brought about by treat- 

 ing ethyl 3-methylcyclobutan-i-one-3-acetate [iv] in ethereal 

 solution with a suspension of finely divided sodium in benzene. 

 The reaction can take place in two ways, resulting in the forma- 

 tion of either a spiran ketone [v] or a bridged ring ketone [vi], 

 but it has been found that the condensation takes the second 

 course. 



