Chemistry Reference
In-Depth Information
(3) How may its constants be measured with precision and exactitude?; (4) How
may the best method of purification and the most probable value of the constants of
pure materials be found in the literature?”
22
Trying to address at least the first three of these questions we can collect the
following list of empirical information from Gomberg
s original work (according to
Walden
1924
, 49-52, who not only refers to the original publication, and takes
into account results of other scientists):
(a) triphenylmethyl is unsaturated which is confirmed by the reactions with
oxygen (yielding the peroxide) and iodine (yielding the iodide)
(b) despite its extremely unsaturated character triphenylmethyl seems to have a
double formula in solution (with respect
'
to osmotic molecular mass
determinations)
(c) with compounds containing oxygen like ethers triphenylmethyl builds additive
structures (Walden
1924
, 50:
Molek
ulverbindungen
)
(d) similarly, it yields addition products with nitriles (R-CN)
(e) with “indifferent” solvents (chloroform, carbon disulfide, benzene, toluene)
addition products were built, too
(f) the “free” triphenylmethyl can be considered a basic radical (
basisches
Radikal
) because it has a good electric conductivity in SO
2
solutions
(g) particularly remarkable is the formation of addition products even with totally
saturated hydrocarbons like hexane, heptane, octane, decane, cyclohexane
(h) similar results are obtained with triarylmethyls other than triphenylmethyl
(i) triphenylmethyl is reasonably resistant against hydrogen and water
(j) hydrogen chloride (HCl,
€
in dry benzene) causes a rearrangement
to
p-benzhydryltetraphenyl methane
s product follows
classical observable chemical properties such as color, melting point, and, most
important, the
reactivity
(which is inferred from the change of color, the state of
aggregate, stability, solubility, conductivity, and the like). Additionally, he applies
instrumental devices like the thermometer, the balance, the elementary analysis
apparatus and the photometer. In what can be considered his final and concluding
published statement on the triphenylmethyl story he mentions the following items
as “properties of the free radical”: stability, color, disproportionation, molecular
combinations, irreversible combinations and chemical reactions; Gomberg
1932
,
446-447. However, the reliability of his measurements was very remote from that
usually obtained for stable substances. The cryoscopic molecular weight determi-
nations, for example, varied from 412 to 532, with an average of 477. Hence, there
was no way to conclude that the solid really was “pure” triphenylmethyl which had
a calculated molecular weight of 243. Moreover, the dimer with a theoretical
molecular weight of 486 was closer, but by no means a good match. Despite this
mismatch and the obviously incorrect first claim that the obtained solid was a
According to this list,
the characterization of Gomberg
'
22
Timmermans
1940
,5.
