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Gas-Chromatographic Separation and Estimation of Aliphatic Monocarboxylic Acids with 1Ц5 Carbon Atoms.

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Compound (7) is also produced in 15 "/, yield alongside a
1,2-trimethylenecyclopentadiene on pyrolysis of 2,3-diacetoxybicyclo[3,3,0]octane,b. p. 96-96.5 OC/l mm, n;; =
Received, November Sth, 1964
[Z 858/684 I€]
German version: Angew. Cheni. 77, 42 (1965)
["I The author wishes to thank Dr. Tlierese Bohm-Gossl, DI.
L. Rohrschneider, and Ing. G. Peitscher for the physico-chemical
studies and measurements and their interpretation.
[ I ] W . Sanne and 0. Schlichting, Angew. Chem. 75, 156 (1963);
A . C. Cope, A . C. Haven, F. L. Ramp, and E. R.Trunsbuli, J.
Amer. chem. SOC. 74, 4867 (1952); E. Vogel, 0. Roos, and
K.-H. Disch, Liebigs Ann. Chem. 653, 55 (1962).
[2] G. F. Woods and L . H. Schwartzmann, J. Amer. chem. SOC.71,
1396 (1949); E. R. Lippincott, W . R. Feairheller, and C. E. White,
J . Amer. chem. SOC.81, 1316 (1959); US.-Patent 2707196 (Sept.
28th, 1949/April 26th, 1955), inventor: G. F. Woods; Chem.
Abstr. 50, 2649 (1956); D. E. Evans, J. cham. SOC.(London)
1961, 2566.
[3] W . Ziegenbein, unpublished synthesis;,,A
302 (E - 50880),
288.5 (57240): 276.5 (38050), and 266 m + l(19928) in isooctane.
141 Cf. W. v. E. Doering and W. R . Rotli, Angew. Chem. 75, 27
(1963); Angew. Chem. internat. Edit. 2, 115 (1963); Tetrahedron
19, 715 (1963).
Synthesis and Elucidation of the Structures of
By Prof. Dr.-Ing. F. Asinger, Dr. W. Schafer, and
Dip1.-Chem. H.-W. Becker
lnstitut fur Technische Chemie
der Technischen Hochschule Aachen (Germany)
Elemental sulfur and primary amines react with acetophenone in methanol [I] at room temperature to yield 71,2,3,4,5,6-hexathiocanes ( I )
al kylamino-7-phenyl-8-thioxo[see Table 11. All the hexathiocanes are stable, intensely
Table I . 7-Alkylamino-7-phenyl-8-thioxo-1,2,3,4,5,6-hexathiocan~s( 1 ) .
f Ici
I I P)
yellow, crystalline compounds; they are also formed from
acetophenone imines, sulfur and amines.
The constitution of the hexathiocanes has been proved
unequivocally by degradation experiments with (1.) and by
nuclear magnetic resonance studies of ( l a ) [2]. The N M R
spectrum of ( l a ) [3] contains three proton signals: the signal
from the monosubstituted benzene ring at 6 = -0.1 ppm, the
peak for the secondary amino group a t 6 = 1 . 1 ppm, and the
signal for the methyl protons at 6 = 4.5 ppm, which is split
into a doublet, indicating that the methyl group is directly
adjacent t o the hydrogen atom of the secondary amino group.
Since desulfurizing hydrogenation of (Ze) with Raney nickel
( le}
Angew. Chem. internot. Edit.
Received, Noveniber Sth, 1964
[Z 857/683 IEI
German version: Angew. Chem. 77, 41 (1965)
[I] F. Asinger, W. Schafer, K . Halcour, H . Sam, and H.Triem,
Angew. Chem. 75, 1050 (1963); Angew. Chem. internat. Edit. 3,
19 (1964).
[2] The tentative formulation of ( r e ) at N-n-butyl-l-phenyl2,3,4,5,6,7-hexathiacycloheptan-l-thiocarboxamide(cf. [ I ] p.
1056/p. 25) owing to its solubility in bases and its absorption at
1530 cm-1 must therefore be amended.
[3] We express our gratitude to Dr. Frenzel and Ing. Peitsclier,
Chemische Werke Hiils AG., Marl/Westfalen (Germany), and
to Dr. Kosfeld, lnstitut fiir Physikalische Chemie der Technischen Hochschule Aachen, for measuring and interpreting the
nuclear magnetic resonance spectra.
[41 F. Asinger and K. Halcour, Mh. Chem. 94, 1029 (1963).
[5] Cf. [I], p. 1056/p. 25.
Gas-Chromatographic Separation and Estimation
of Aliphatic Monocarboxylic Acids
with 1-5 Carbon Atoms
By Dr. H. J. Langner [ I ]
Institut fur Lebensmittelhygiene
der Freien Universitgt Berlin (Germany)
Quantitative separation and estimation of formic acid and
acetic acid mixed with aliphatic monocarboxylic acids
containing 3-5 carbon atoms involve considerable difficulties.
We have now succeeded in separating and estimating these
acids by gas chromatography in the form of their amyl esters.
About 100 mg of the free acids are weighed into a 10 ml
measuring flask with a standard ground-glass joint, and 3 ml
of diethyl ether, 0.1 ml of boron trifluoride, and an equimolar
(based on the free acids) amount of 1-pentanol are added;
the flask is attached t o a Dimroth condenser 50 cm long and
heated in an air-bath until the first white vapors of BF3
appear. The solution, which contains a quantitative yield
of the amyl esters [2] is cooled t o room temperature and
filled u p t o the mark with ether. The solution is dried
over anhydrous sodium sulfate plus sodium hydrogen
carbonate and is then ready for chromatographic analysis.
The analysis was conducted with a 50 m capillary band
column filled with Apiezon L grease in a Perkin-Elmer F 6/4
H F Fraktometer. The working temperature was 100 "C and
the rate of gas flow was 1 ml of helium per minute. One
microliter samples were injected at a separating factor of
1 : 100.
i b
Fig. 1. Gas chromatogram of the amyl esters of: a = formic acid,
b = acetic acid, c = propionic acid, d = isobutyric acid, e = n-butyric
acid, f = irovaleric acid, g = 2,2,2-trimethylacetic acid, and h = nvaleric acid; i = diethyl ether (solvent).
1 Vol. 4 (1965)
at room temperature affords n-butyl-1-phenylethylamine [4],
the position of the nitrogen atom in the molecule is assured.
Reduction of ( I e ) with hydrogen sulfide in the presence of
amines [ 5 ] yields bis-(2-phenylethyl) polysulfide, and treatment of ( I e ) with sodium methoxide in methanol causes
elimination of elemental sulfur produce 2-n-butylamino-2phenyl-3-thioxothiirane (Z), which can be "resulfurized"
with hydrogen sulfide and sulfur to reform ( l e ) .
No. I
A flame ionization detector was used o n account of the
extremely minute amounts of material to be expected from
biological materials; the detector sensitivity was X : 4 and
R : l . The temperature of the injection block, the detector
leads, and the standard gas outlet was 300 "C.
The recorder was a Siemens Elektronenkompensograph with
a speed of 1 cm/min. By utilizing the complete sensitivity of
the apparatus, quantities of acid down to 0.1 ng (10-10 g) can
be detected; by concentrating the ether solutions (the esters
boil at 110 O C and higher) and by decreasing the separating
factor to 1 :5-1 : 10 amounts down to 10-12 g can be measured. Figure 1 shows a typical gas chromatogram.
A mean error of & 2.5 % was observed in six acetic acid
analyses with samples weighing 100.5-207.9 mg; for ten
injections of 207.0 mg of acetic acid, 207.16 5 0.1 mg was
Received, November 9th, 1964 [ Z 861/687IE]
German version: Angew. Chem. 77, 95 (1965)
[ I ] We are indebted to E. MaZek, Berlin, for carrying out the
[2] Excess amyl alcohol is used for the esterification of biological
material. Amy1 alcohol recurs as an unsymmetrical band between
acetic acid and propionic acid and does not interfere.
A Stable Triradical [*]
By Prof. Dr. Richard Kuhn, Dr. F. A. Neugebauer, and
H. Trischmann
Institut fur Chemie, Max-Planck-Institut
fur Medizinische Forschung, Heidelberg (Germany)
The ease of formation and stability of the verdazyls [l] has
made it possible to secure a compound with t h r e e unpaired
electrons per molecule. 1,3,5-Triformylbenzene was converted vin its trisphenylhydrazone with crystalline benzenediazonium chloride in pyridine into its extremely insoluble
red trisformazan, which decomposes explosively a t 272 to
273 "C.
A suspension of this derivative in dimethylformamide (DMF)
reacted with BaO plus Ba(OH)* and methyl iodide [I] to
form the deep green triradical 1,3,5-tris-(1,5-diphenylverdazyl-3-yl)benzene ( I ) , which contains ten six-membered
rings (7 benzene rings and 3 heterocycles) in conjugation,
and which crystallizes from DMF/methanol as almost black
prisms which decompose at 242-243 "C.
On catalytic hydrogenation over Pd/BaS04 in DMF, ( I )
rapidly absorbs 1.48-1.50 moles of hydrogen (calc. 1.50
moles). Its molar extinction in D M F (E = 12500 at lmax
721 mp) is almost three times as large as that of 1,3,5-triphenylverdazyl (E = 4400 at hmax = 720 mp).
The paramagnetic susceptibility pefl/pB of ( I ) - calculated
for three non-coupled unpaired electrons it should be
9 = 3 - was measured with the magnetic balance and was
found to be 2.96 k 0.06 at 298 OK, 2.97 at 195 "K, and 3.02
a t 77'K. Its ESR spectrum - like that of 1,3,5-triphenylverdazyl - extends over 50 gauss [2]. The fact that the
hyperfine structure of ( I ) is not resolved - in contrast to
that of 1,3,5-triphenylverdazyl with 9 lines at 6-gauss intervals in intensity ratios of 1:4: 10: 16: 19: 16: 10:4: 1 - is
considered to be due to interaction between the spins of the
free electrons.
The measurements revealed that the three unpaired electrons
in the n-electron system of the triradical are practically free
from coupling ( t t t ) in the magnetic field of over 3000
gauss used.
In contrast to the biradicals porphyrindin [3] and nitrosoindigo [4] whose paramagnetism decreases with decreasing
temperature, the electrons in the triradical ( I ) remain unpaired down to 77'K, although mesomeric forms of a
zwitterionic monoradical can be written in which the spin
concentration of the substance would be reduced to onethird (' ).
Received, November 1 lth, 1964 [Z 860/686IE]
German version: Angew. Chem. 77, 43 (1965)
[*I Communication No. 5 onverdazyls; - Communication No. 4:
Angew. Chem. 76, 691 (1964); Angew. Chem. internat. Edit. 3,
762 (1964); - Communication No. 3: Angew. Chem. 76, 230
(1964); Angew. Chem. internat. Edit. 3, 232 (1964).
[ I ] R. Kuhn and H.Trischmann, Angew. Chem. 7 5 , 294 (1963);
Angew. Chern. internat. Edit. 2, 155 (1963); Mh. Chem. 95, 457
[2] We express our thanks to Prof. Dr. K . H. Hausser for carrying
out and interpreting the electron spin resonance measurements.
[3] R. Kuhn and H . Katz, Angew. Chern. 46,478 (1933); E . Miiller
and I . Miiller-Rodlof, Liebigs Ann. Chem. 521, 81 (1936).
[4] R. Kuhn and W. Bfau, Liebigs Ann. Chem. 615, 99 (1958).
The Crystal Structure of Nitrogen Selenide
By Dr. H. Barnighausen, Dipl.-Chem. T. von Volkmann, and
Prof. Dr. J. Jander [l]
Chemisches Laboratorium der Universitat FreiburglBrsg.
and Anorganisch-Chemisches Laboratorium
der Technischen Hochschule Munchen (Germany)
In continuation of our studies on the crystal structure of
nitrogen selenide [2], we have now succeeded in interpreting
its three-dimensional Patterson synthesis. The resultant
structural model - which is presently being refined - gave a
reliability index of 13 % for the 536 X-ray diffraction lines
observed and therefore seems sufficiently well established.
Nitrogen selenide consists of discrete N4Se4 molecules.
Although nitrogen sulfide N4S4 [3] and N4Se4 are not
isotypic, there is great similarity between the molecular
geometries of the two compounds. Thus, for example, as in
N4S4, the nitrogen and selenium atoms in N4Se4 are in a n
alternating sequence and assume the boat form of a strongly
puckered eight-membered ring, whose symmetry can be
described in good approximation by the symbol 42 m. The
four nitrogen atoms in the eight-membered ring almost form
a square with N-N distances of 2.82 A, and the four selenium
atoms are situated at the corners of a slightly deformed tetrahedron. The distances between selenium atoms separated by a
nitrogen atom are 2.97 8, on the average, while those situated
diagonally opposed in the eight-membered ring are only 2.76 8,
apart. This distance is very much shorter than the efiective
diameter of selenium atoms held together by van der Waals
forces. It follows that the molecule must be subject to a
strong geometric strain, which may afford an explanation
for the tendency of nitrogen selenide to explode. The average
value for the length of the Se-N bonds is 1.80 8, and thus
corresponds roughly to the sum of the respective covalent
radii [r(Se) + r(N) = 1.14 + 0.7= 1.84 A]. The N-Se-N bond
angle is 103 and the Se-N-Se bond angle is 11 I '.
The arrangement of the N4Se4 molecules in the crystal
lattice is approximately that of a hexagonal closest packing.
The hexagonal pseudo-cell has the lattice constants a M 10 8,
and c w 5.9 8, and i s oriented in such a way relative to the
monoclinic unit cell that the c axis coincides with the direction
[712], and the hexagonal basis lies approximately in the (TI 1)
plane, which is the main limiting surface of the platelet single
crystals. The c/a ratio of 1.7 agrees well with the theoretical
value of 1.633 for hexagonal closest packing. However, the
base of the pseudo-cell has a considerable deformation, which
is most probably due to relatively strong intermolecular
Angew. Chem. internat. Edit. / Vol. 4 (1965) / No. I
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acid, monocarboxylic, separating, 1ц5, aliphatic, atom, chromatography, gas, estimating, carbon
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