G. Fischer et al. · Synthesis, Properties and Dimerization Study of Isocyanic Acid
23
mass by HR: calcd. 129.0174, found: 129.0165 3.2. Polymerization of HNCO
(–1.0 mmu).
Samples of liquid HNCO in a tube in vacuo were
immersed in baths at 0 (ca. 1 d), 24 (ca. 1 h) and
100 C (ca. min). Upon complete polymerization, the
gas phase IR and mass spectra were recorded. The poly-
mer was extracted with hot water (80 C), and, after re-
moval of the insoluble cyamelide, the filtrate concen-
trated. The collected crystalline material was dried at
110 C. Elemental analysis for residue: Found C 27.8;
N 33.6; H 2.8. Calcd (for cyanuric acid): C 27.9; N 32.6;
H 2.3%.
The peaks at m/z43, 44 and 60 are considered be-
ing isocyanic acid, CO2 and urea, respectively. The
detection of ion m/z103 (probably biuret) supports
in part the decomposition reaction of HNCO.
These results suggest that several polymerization
reactions and the simple decomposition reaction oc-
cur simultaneously. It is remarkable that authentic
cyanuric acid, measured under identical conditions,
exhibits neither a peak at m/z 86, nor at 87, which
is more intense than 1%.
Therefore it can be concluded that m/z 86 or
m/z 87 do not represent fragment ions of cyanuric
acid, but dimerization product of isocyanic acid,
(HNCO)2. This is strongly supported by high res-
olution measurements of the polymer: m/z86.0109
(–0.7 mmu); calcd. for H2N2C2O2 m/z86.0116.
3.3. Spectroscopy
The infrared spectra were obtained using KBr discs for
the solids and a 10 cm cell equipped with KBr windows
for the gases by means of a Perkin-Elmer IR Spectrum
One spectrometer. Raman spectra were recorded on a
Perkin-Elmer 2000 NIR FT-Raman spectrometer. NMR
spectra were recorded both as CDCl3 solutions and neat
HNCO using a JEOL Eclipse 400 instrument. Chemi-
cal shifts are with respect to (CH3)4Si (1H and 13C) and
CH3NO2 (14N, 15N). Mass spectra were obtained with
a Jeol MStation JMS 700 gas inlet system (100 C).
The source was operated at a temperature of 200 C,
and the probe temperature was varied from –40 C up
to room temperature. In the EI mode the electron energy
was 70 eV; in the CI mode alternatively ammonia and
isobutane were used as reagent gases. Elemental analy-
sis was performed with a C,H,N-Analysator Elementar
Vario El.
3. Experimental Section
3.1. Preparation and purification
First method: The preparation of HNCO was carried
out by the reaction of one equivalent of purified anhydrous
potassium or sodium cyanate with two equivalents of dry
stearic acid. The reagents were heated under vacuum but
in contrast to [4] at 130 C. Gaseous HNCO was passed
through a tube filled with P4O10 and collected in a liquid
nitrogen trap. Yield: 70%.
Second method: This is a similar procedure as above,
except using oxalic acid. In this method, which has not
been previously described, the reagents were heated in
vacuo under anhydrous conditions and the reaction prod-
ucts were collected in a liquid nitrogen trap. Repeated
Acknowledgements
We would like to thank Mr. G. Spieß for assisting
trap-to-trap distillation in vacuo reduced the impurities with IR and Raman measurements. Financial support for
(most CO2) to less than 1%. This was estimated by vibra- this work by Norsk Hydro ASA (Oslo), the University of
tional and NMR spectroscopy as well as mass spectro- Munich, the Fonds der Chemischen Industrie and MAN
metry investigations. Yield: 65%.
(Nu¨rnberg) is gratefully acknowledged.
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