19,6 Cole: Dissociation of Hexaphenylethane 685 
Lewis’s nomenclature will be used in a few cases where it is 
desired to emphasize the supposed electron positions. 
The normal structure of hexaphenylethane is accordingly the 
following : 
H H H H 
1(5') !(•*'> \(4) 1(5) 
C C Ph Ph C — C 
(6')/' ^ (5') l(/) I (2) ( 3 )/' ^ (6) 
A. H — C C — C — C — C C H 
\ / I I \ '/ 
C — C Ph Ph C — ■ C 
| (7') |(tf') | (fi) | (7) 
II H H H 
(All the phenyl groups have the same structure as those given 
in detail.) 
The three strongly negative phenyl groups attached to carbon 
atom ( 1 ) draw six of its shell electrons away from the kernel. 
Consequently the remaining two electrons, namely those shared 
by carbon atoms ( 1 ) and ( 2 ), are held very firmly by the kernel 
of ( 1 ) . Similarly these two electrons are held very firmly by 
the kernel of carbon atom ( 2 ). It therefore follows from the 
Lewis-Langmuir theory of valence that hexaphenylethane can- 
not possibly dissociate without a rearrangement of one or more 
of the phenyl groups. This conclusion is thoroughly substan- 
tiated by the experimental evidence that dissociation of this and 
similar compounds does not occur without color. The chromo- 
phoric nature of the quinoid form of the benzene ring has long 
been established. The reason for the formation of a quinoid ring 
is generally that electrons are pulled toward two atoms connect- 
ed to para or ortho carbon atoms. In the case under discussion 
it is evident that the strong pull of electrons toward one atom 
attached to each ring [carbon atoms ( 1 ) and ( 2 )~\ is sufficient 
under certain conditions to cause rearrangement and consequent 
dissociation. 
In nonionizing solvents such as benzene, rearrangement and 
dissociation occur symmetrically. One electron between C ( 3 ) 
and C (-4) is pulled to a position between C ( 2 ) and C (5), 
resulting in a quinoid ring in which C ( 6 ) lacks one electron. 
The electrons shared between C ( 1 ) and C ( 2 ) are now no longer 
held firmly by C ( 2 ), which momentarily has nine electrons in 
its shell. Therefore C ( 1 ) and C ( 2 ) separate symmetrically, 
each retaining one electron of the shared pair. A double bond 
