Chemistry Reference
In-Depth Information
Fig. 12.1 Projected
structure of
triphenylmethyl.
The molecule has
a propeller-like shape
Fig. 12.2 Structure of the
(virtual) hexaphenylethane
study” - the fully phenylated ethane. The chemical equation of the chosen reaction
he described was:
2C
6
H
5
ð
Þ
3
C
C1
þ
2Ag
¼
ð
C
6
H
5
Þ
3
C
CC
6
H
5
ð
Þ
3
þ
2AgC1
:
:
Still optimistic in 1900, he wrote: “Moreover, I believe that hexaphenylethane, if it
had been once prepared, would turn out to be a quite stable body [ein ganz
best
¨
ndiger K
¨
rper]” (Gomberg
1900a
, 3160). In 1914, after dozens of articles
and serious discussions with many prominent chemists and contrasting with his
former belief, he stated: “Hexaphenylethane still remains a figment of the imagi-
nation.”
5
This is still true today.
6
In fact, Gomberg found quite fascinating reaction
products, among which - at least in a solution - he assumed the radical
triphenylmethyl (Fig.
12.1
) but neither the dissolved product nor the solid could
be identified by him.
For a long time to come, however, textbooks taught their readers that the isolated
“dimer” of triphenylmethyl simply was the symmetric hexaphenylethane, which
would have the following projected structural formula (Fig.
12.2
)
7
.
However, it remained unclear what exactly the reaction product of Gomberg
s
attempt to bring together two monomers of triphenylmethyl really was until 1968,
when new results suggested a quinoid structure.
8
Crucial for this scientific progress
was the application of nuclear magnetic resonance spectrometry (
1
H-NMR). With
the latter, twenty-five “aromatic”, four “unsaturated or dienic”, and one “saturated”
hydrogen atoms could be differentiated in samples of “Gomberg
'
s” solid (Sykes
'
1986
, 44).
5
Gomberg
1914
, 1156.
6
In his well-known textbook on reaction mechanisms, Peter Sykes states: “Hexaphenylethane has
not, indeed, ever been prepared, and may well be not capable of existing under normal conditions
due to the enormous steric crowding that would be present.” (Sykes
1986
, 301)
7
C.f. Fieser and Fieser
1968
, 410.
8
See Lankamp et al.
1968
. See also Nair et al.
2006
.
