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Elimination of HCl from Gaseous cis- and trans-Chlorostilbene.

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Conversion of Si -0 into Si -N Bonds [l]
By Prof. U. Wannagat, Dr. P. Geymeyer,
and Dip1.-Ing. G. Schreiner
Institut fur Anorganische Chemie
der Technischen Hochschule Graz (Austria)
Silicon-nitrogen compounds are considered - sometimes
mistakenly - t o react with water; they are converted into
silicon-oxygen compounds by alcohols and especially by
acids.
We have now examined the elimination of HCI from cis- and
trans-chlorostilbene (1,2-diphenylchloroethylene)in the vapor
phase on several salt and oxide catalysts. Which mode of
elimination occurs or is favored invariably depends upon the
different reactivities of the two isomers. Both modes of elimination give rise to tolane (diphenylacetylene).
Table 1. The elimination of HCI from cis- and trans-chlorostilbene
on various catalysts.
-
Arrhenius parameters
Catalyst
We found that the reverse of this process occurs when
phenoxysilanes are treated with alkali metal derivatives of
amines.
-/
+ M-N\
-)S1-0-c6H5
+
M
\
/
PSI-N
/
'\
= Li, Na, or
BaC12
CdO
-
f M-G-CsHS
MI@
K
Stoichiometric amounts of the components in 400-500 ml
of petroleum ether o r benzene are heated to boiling for 2-3
hours for molar charges; the N a or K phenoxide formed
precipitates out quantitatively and is then filtered off (LiOC6H5
is best converted with (CH&SiCI into LiCl and (CH3)3SiOCsHs), the SiN compounds being obtained in over 75 %
yield by fractional distillation.
LiN(CzH&, NaN[Si(CH3)312, or KN(C&)2 removes only
one phenoxyl group per Si atom; this limitation does not
hold for NaNH2.
A selection of previously unknown SiN compounds prepared
by this procedure is given in Table 1.
Table I . New Si-N compounds prepared from phenoxysilanes and
substituted alkali amides
I
MnOz
I
,
95-97/1
16212
38-39/13
46-48/1
98-99/2
103/1
Received, December 16th, 1963 [ Z 6291458 1El
German version: Angew. Chem. 76, 99 (1964)
____
111 Communication No. 36 on Silicon Nitrogen Compounds;
Communication No. 31 : H . Biirger and U . Wannagat, Mh. Chem.
94, 761 (1963); Communications Nos. 31-35; Mh. Chem., in
the press.
CaO
Substrate
cistranscistransrisfraiiscisironscis-
E
[kcal/mole
A
(relative)
8
24
1 . 2 1~0 5
4 . 8 109
~
11
2 . 2 X 106
3 . 2 ~108
5.5x 105
ISX 105
$
20
.-
9
8
9
4
%
;;
2
10
9
7
1
8
neutral
t ranscistransristrans-
[*] The rest
OF the material was um
CaClz
A1203
-
10
2 . 6 ~1 0 5
2.1x 105
7 . 8 ~105
5 . 6 104
~
2. I x 105
1 . 4 105
~
-
1 . 4 106
~
Temp.
[ "CI
250
250
250
250
260
260
250
250
283
283
3 50
350
250
250
Yield of [*I
Tolane
Isomer
I %I
[%I
0 frans0 cisI9 trans4 ciso trans- .I cisZ
2 vansI cis- c,
0 trans0 cis24 frans0 cis0 rrans0 cis-
14
5
17
8
:
4
100
8
-
35
26
11
12
41
22
100
0
nged.
As Table 1 shows, the cis-isomer reacts more readily and,
with few exceptions, its activation energy is lower. This
means that both cis- and trans-elimination can occur, but
that cis-elimination is favored.
Isomerization does not occur to any considerable extent on
oxide catalysts, presumably because the HC1 formed (without which isomerization cannot take place) is bound on the
surface of the catalyst. Isomerization does occur o n chlorides,
but it is nevertheless apparent that the cis-isomer reacts directly and more easily.
Measurements were carried out by gas chromatography at
230-430 OC using the pulse technique; the catalyst chamber
was interposed in the carrier-gas train before the chromatography column. The residence time of the chlorostilbene on
the catalyst was about 0.1 sec. The amount of reactant
injected as a saturated acetone solution was 1.0-1.5 pl for
the cis-isomer and 3.0 pl for the trans-isomer; the amount
of catalyst was about 2.5 g.
Received, December 19th, 1963 [Z 631/461 IE]
German version: Angew. Chem. 76, 184 (1964)
[l] The Mechanism of Eliminations on Catalysts, Part 111. Part 11: H. Noller, W. Low,and P. Andrgu, Naturwissenschaften,
in the press.
[2] We thank Dr. G.-M. Schwa6 for his continual interest in
this work, and the Deutsehe Forschungsgemeinschaft and the
Fonds der Chemie for financial support.
Elimination of HCI from Gaseous cis- and
trans-Chlorostilbene [l]
By Dr. P. Andrku, Lic. E. Schmitz, and Dr. H. Noller 121
Physikalisch-Chemisches Institut der Universitat Munchen
(Germany)
The loss of HCI from alkyl halides in the liquid phase is a
irans-or,p-elimination with a n ionic mechanism. Eliminations
o n catalysts have so far been little studied.
Azlactones as 1,3-Dipoles; A New Pyrrole Synthesis
By Prof. Dr. R. Huisgen, Dr. H. Gotthardt,
and Dr. H. 0. Bayer
Institut fur Organische Chemie der Universitat Munchen
(Germany)
When the azlactone ( I ) , R1 = R2 = C6H5, is heated with
dimethyl acetylenedicarboxylate in xylene at 100 OC, dimethyl 2,5-diphenylpyrrole-3,4-dicarboxylate(2) is formed
in 83 yield within 2 hr. Alkaline hydrolysis and decarboxylation of (2) lead to 2,5-diphenylpyrrole.
5-Oxazolones ( 1 ) with either aromatic or aliphatic substituents can be used in this reaction, and the acetylene dicarboxylic ester can be replaced by methyl propiolate. The
same pyrrole derivative (5) is obtained from the azlactones
Angew. Chem. internat. Edit. / Vol. 3 (1964) ] No. 2
135
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elimination, gaseous, chlorostilbene, transp, hcl, cis
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