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Experimental Evidence for Kink Formation.

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For working up, the acetonitrile was distilled off through
a Vigreux column; the liquid residue (107 g) distills between
25 and 42"C/0.1 torr without a column. The distillate
(90.5 g) obtained consisted of isobutyric acid 23.6%, amide
( l a ) 28.0%, anhydride (3a) 40.8%, and diacylamine ( 2 a )
7.5%.
Received: April 30,1971 [Z 430 IE]
German version: Angew. Chem. 83,579 (1971)
[l] L. Eberson and K. Nyberg, Acta. Chem. Scand. 18, 1567 (1964); J.
M . Kernprobst, A . Laurent, and E . Laurent-Dieuzeide, Bull. SOC.Chim.
Fr. 1968,3657.
[2] Lactim esters (Houben-Weyl-Miiller: Methoden der organischen
Chemie. Thieme, Stuttgart 1958, Vol. 11/2, p. 580), azalactones(3foubenWeyl-Miiller: Methoden der organischen Chemie. Thieme, Stuttgart
1958, Vol. 11/2, p. 372), phthaliminoanhydride.
131 0.Mumm, H. Hesse, and H. Volquartz, Ber. dtsch. chem. Ges. 48,
388 (1915).
[4] However, amidotriazole enol ester was isolated by H . Bauer et al.
Angew. Chem. 83, 115 (1971); Angew. Chem. internat. Edit. 15, 129
(1971).
The n-alkanol complexes of n-alkylammonium layer
silicatesL6'were used as models. In these compounds the
alkanol molecules and the alkylammonium ions arrange
themselves in bimolecular layers between the silicate
sheets, with the alkyl chains perpendicular to the silicate
layers. Since the distance between the silicate layers
(=basal spacing) can be easily measured by X-ray analysis,
the thickness of the bimolecular interlayer can be determined with high accuracy and the shortening of the alkyl
chains can be directly detected.
i2
c
30
-
Experimental Evidence for Kink Formation
By G. Lagaly and Armin Weiss"]
In the past years some types of movements in polymers
have been interpreted by formation and rearrangements
of kinks and
i. e. special rotational isomers of the
hydrocarbon chains containing gauche bonds (Fig. 1). The
formation of kinks and jogs is mainly concluded from
relaxation propertiesr3 'I. Since by conformational changes from trans to gauche the @gth of the alkyl chain
decreases by a multiple of 1.27 A, kink formation should
become evident by chain length measurements.
In the systems studied so far (polymers and alkanes) kink
formation occurs statistically or in small kink blocks between unaltered alkyl chains. Therefore, hitherto, it has
been impossible to measure the decrease in the chain
length directly. Now, we have succeeded in demonstrating
the shortening of the alkyI chains as a consequence of kink
formation by direct X-ray measurements.
I
I
8
I
I
I
I
I
The basal spacings of the alkanol complexes decrease in
regular steps of 1.1-1.3 8, with increasing temperature.
Fig. 2 shows, as examples, the basal spacings of the n-alkanol
complexes of n-alkylammonium beidellites. (The chain
lengths in the alkanol molecules are equal to the chain
lengths in the alkylammoniurn ions.) The change in the
basal spacings with increasing temperature are reproducible and reversible, but hysteresis is often observed. The
height of the steps corresponds exactly to the shortening
of the alkyl chains as calculated for kink formation.
From these results it can be concluded that simple ("2gl")
kinks are introduced in the alkyl chains with increasing
temperature. The number of kinks per chain, however,
seems to have an upper limit; exceeding this limit, the
structure rearranges to a high temperature form with
drastically reduced basal spacings. It has to be assumed
that this transformation is caused by a rearrangement of
simple 2gl kinks to high order kinks (=jogs). If the temperature is raised still further, additional small steps in the
decrease in the basal spacings are observed.
ali- trans- chain
291 - k i n k
292 - kink
IjOQI
...t t t t t ...
...ttgtgtt ...
... ttgtttstt ...
392 -kink
ljogi
...ttgtgtgt1.
Fig. 1. Some conformations of the aikyi chains with kinks and jogs.
[*] Dr. G. Lagaly and Prof. Dr. Armin Weiss
Institut fur Anorganische Chemie der Universitat
8 Miinchen 2, Meiserstrasse 1 (Germany)
558
The results reported in this paper indicate that kink formation and kink rearrangements have to be considered in
discussions of bimolecular films of long chain alkyl compounds['].
Received: April 8, 1971 [ Z 435 IE]
German version: Angew. Chem. 83,580 (1971)
[I]W Pechhold and S. Blasenbrey, Kolloid-2.2. Polymere 216117,235
(1967); 241, 955 (1970).
[Z] H.Hiissler and H. J . Bauer, Kolloid-2.2. Polymere 230,194 (1969).
[3] W Pechhold, Kolloid-2. 2. Polyrnere 228, 1 (1968).
[4] K . H. Illers, Kolloid-2. 2. Polymere 231,622 (1969).
Angew. Chem. internat. Edit. 1 Vol. I0 (1971) j No. 8
[5] R. Hosemann, Ber. Bunsenges. Physik. Chem. 74,755 (1970).
[6] G. Lagaly and Armin Weiss, Kolloid-Z. 2. Polymere 216117, 356
(1967); 237, 266, 364 (1970); 238, 485 (1970); 243, 48 (1971).
[7] G . Lagaly and Armin Weiss, Kolloid-Z. 2. Polymere, in press.
Gas chromatographic analysis of acetate composition as a
function of solvolysis time revealed that the kinetic
acetolysis products of ( I ) are the unrearranged acetates
exo-(I), R=Ac, and endo-(I), R=Ac['], but that the
HE
An Energy Surface for Acetolysis via C,H,
Cations from exo-Tetracyclo[3.3.0.02* '.04, 6 ] ~ ~ t 3-yl p-Nitrobenzoate[**]
By WoIfgang Lotsch and Andrew S . Kende"]
We wish to report equilibration and deuterium labeling
studies involving a series of tautomeric C,H, cations
derived from exo-tetracyclo[3.3.0.02*~.04~6]o~t-3-yl
p-nitrobenzoate ( I ) , R =p-nitrobenzoyl[''. These data permit
construction of an energy surface relating the three
distinct carbon skeletons observed in this rearrangement
network.
percentage of tricyclic acetates ( 3 ) , and then of bicyclic
acetates ( 2 ) ,gradually increases as secondary equilibration
of acetates occurs. The 5.5-h mixture is the equilibrium
mixture which can be independently reached starting with
a sample of exo- (I), R =Ac (Table 1).
Table 1. Composition of acetates from e x o - ( I ) , R =p-nitrobenzoyl or
exo-( I), R =Ac.
5
4
H
nitrobenzoyl
2.00
Acetolysis of pure exo-(I), R =p-nitrobenzoyl, in glacial
acetic acid containing an equivalent of sodium acetate gave
after 5.5 h reflux a 93% yield of mixed acetates, purified
by vacuum distillation at 35°C. Preparative gas chromatographyL2'of the distillate yielded 60% of the mixed epimeric acetates (2), 37% of epimeric tricyclic acetates ( 3 ) ,
and ca. 3% of unidentified by-product different from
either exo- or endo-(I), R=acetyl; the presence of more
than 0.1% of either of the latter could have been detected.
The mixture of bicyclic acetates (2) (69% exo and 31%
end^)[^] was saponified and oxidized by chromium trioxide-pyridine complex in methylene chloride[41 to an
unsaturated ketone ( 4 ) ?,:v:
1690 cm-', parent m/e= 120,
identified by TR and NMR comparison with authentic
bicyclo[3.2.1]octa-3,6-dien-2-one~51.
In a similar manner,
the tricyclic acetates ( 3 ) (59% exo and 41% endo)[61were
oxidized to a ketone ( 5 ) ?,::v
1740 cm- m/e= 120. This
ketone was distinguished from the isomeric alternative (6)
by 90-MHz decoupling studies which, inter a h , clearly
demonstrated the 6-Hz vicinal coupling between bridgehead proton H, and one of the bridge protons, HE.
54 38
39 31
53 37
2.00
The mechanism leading from ( I ) to systems (3) and (2)
is further delineated by the fate of deuterated exo- (I),
R=p-nitrobenzoylrE1, on solvolytic rearrangement. The
isolation and oxidation sequence described above converts
the latter to the corresponding deuterated rearrangement
ketones [D1]-(5) and [D,]-(4) which are labeled specifically (Figure 1).
'
-
6
5
2
1
0
r - 1
Fig. 1. NMR spectrum of [D,]-(S) in C,D6 solution, measured in
ppm relative to internal (CH,),Si (not shown) at 90 MHz.
',
[*] Dr. W. Lotsch and Prof. A. S. Kende
University of Rochester, Department of Chemistry
Rochester, New York 14627 (USA)
I**]A. S. K. makes acknowledgment to the donors of the Petroleum
Research Fund, administered by the American Chemical Society, for
partial supporf of this research. The award of a Deutscher Akademischer Austauschdienst Fellowship to W. L. IS gratefully acknowledged.
Angew. Chem. internat. Edit. / Vol. 10 (1971) / No. 8
These data implicate stepwise, stereospecific cleavage
of first one, then the second cyclopropane ring to yield
ultimately the allylic cation of the bicyclic series['].
Moreover, the labeling pattern unambiguously excludes
any degeneracy arising from equilibration of the C,, C,,
and C, bridges in the bicyclic cation despite the availability
of simple 1,2-shifts which would achieve that result.
If our equilibration results are taken in conjunction with
the recent kinetic data obtained by Diaz, Sakaz, and
W i n ~ t e i n [an
~ ] approximate energy diagram for the isomerizations observed in this C,H, network may be con559
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