Chemistry Reference
In-Depth Information
TABLE 20.1 - Polyynes in mol%
Data from HPLC-DAD analysis
RUN 1
from CaC
2
Cu(I)/Cu(II)
RUN 2
from CaC
2
Cu(I)/Cu(II)
RUN 3
from CaC
2
Cu(I)/Cu(II)
RUN 4
from CaC
2
Cu(II)
RUN 5
from CaC
2
Cu(I)
ARC
None
Cu species
POLYYNE
C
6
H
2
20.3
56.8
48.7
67.4
80.9
83.3
C
8
H
2
61.2
35.8
49.1
31.2
18.7
15.6
C
10
H
2
14.8
6.6
2.2
1.2
0.4
1.1
C
12
H
2
2.9
0.7
Traces
0.2
0.0
0.0
C
14
H
2
0.6
0.1
0.0
0.0
0.0
0.0
C
16
H
2
0.2
0.0
0.0
0.0
0.0
0.0
100
100
100
100
100
100
total conc.
0.01mM 85.5mM
53.4mM
97.7mM
56.1mM
28.7mM
15 times with pure heptane and 25 microL were injected. The diodes of the
detector were set at 202, 225, 250, 295 and 350 nm. Use was made of a C-8
column for the separation under isocratic conditions with a mobile phase of
acetonitrile/water 80:20 vol/vol (see
Chapter 8
for further details). Polyynes
were identified on the basis of their retention times and on the basis of their
characteristic electronic absorption spectra (see Chapter 8).
20.2.3 S
TABILITY OF
P
OLYYNES IN
C
ONCENTRATED
S
OLUTIONS
All the solution reported in Table 20.1 on standing, even when left in closed
glass flasks in the dark or in diffuse light, leave a thick brown deposit on the
walls and at the bottom of the flask resembling cork for its color and its
consistency. There are no doubts that the precipitate is the result of a
crosslinking reaction. The brown material can be recovered by decantation
of the solution. It is insoluble in all common solvents and the FT-IR spec-
trum in KBr is as follows (absorption peaks in cm
1
): 3294 (s), 2956 (sh),
2929 (m), 2859 (mw), 2180 (m) 2100 (mw), 1773 (sh), 1714 (sh), 1617 (s),
1384 (ms), 1213 (s), 1122 (s), 978 (sh), 877 (w), 757 (w), 662 (mw).
20.3 RESULTS AND DISCUSSION
One of the drawbacks of the synthesis of the polyynes with the submerged
carbon arc is the simultaneous formation of a mixture of PAHs (polycyclic
aromatic hydrocarbons) and soot (see Chapter 8). Apparently the PAHs
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