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Vibrational analysis of some cyclopropyl derivatives
321
Journal of Molecular Structure, 266 (1992) 321-326 Elsevier Science Publishers B.V., Amsterdam
Vibrational
Vlasta
analysis of some cyclopropyl
MohaEek and KreSimir
Ruder BoskoviC Institute,
derivatives
Furit
POB
1016, 41001 Zagreb, Croatia
Abstract Vibrational calculated
frequencies
of various conformers
of dicyclopropylacetylene
CsHlo are
for the first time using the empirical valence force field constructed
of bicyclopropyl
tram and diphenylacetylene
dicyclopropylacetylene
are discussed
molecule.
Possible molecular
from those structures
on the basis of broad bands observed
of
for liquid
state bellow 600 cm-‘. Both for bicyclopropyl tram and gauche conformers the valence force field of cyclopropane served as a starting point. Several bicyclopropyl force constants are found to be conformation
1.
sensitive.
INTRODUCTION The cyclopropane
molecule was the subject
tions, while on bicyclopropyl found valence force field (VFF) of bicyclopropyl acetylene
2.
of numerous normal coordinate
only one was performed for cyclopropane
tram and gauche.
is used to construct
Using force constants
group from diphenylacetylene
calcula-
[l]. In this work new, empirically valence force fields
of bicyclopropyl
[2], VFF for dicyclopropylacetylene
trans and is obtained.
CYCLOPROPANE The equilibrium
geometry
of twenty one non redundant and 12 CCH
angle bending
1.).
of internal
Labeling
of cyclopropane coordinates coordinates)
coordinates
(CP)
was taken from ref.[3].
(3 CC bond stretching, sixteen
is identical
force constants to that in ref.[4].
deviation for C&,H, is 0.3 % and for C,D, 0.8 % indicating between calculated and observed frequencies.
0022-2860/92/$05.00
For the set
6 CH bond stretching are used (see table Relative
standard
a very good agreement
0 1992 Elsevier Science Publishers B.V. All rights reserved
322
16
13
Figure 1: Internal
Table 1. Force constants
No.
3.
coordinates
of cyclopropane.
Force constant
of bicyclopropyl.
(mdyn/A
value
No.
1
I
4.152
9
2
I<,
5.073
10
, mdynlrad,
mdyn A/Tad2)
Force constant
value 0.171
Fir*., ;&,5 FL%,,;&
0.117 -0.071 0.045
3 4
FL,.A.~
0.81 -0.06
11 12
Frrz.,;rc11,6 Fp,,&,~
5
FL,.~;A,,
0.27
13
%,,;P1,1
0.109
H0
6
FL~;P~,,
-0.085
14
~*.I&.,
-0.066
7
&,+,,
0.068
15
Foz.,;ezc?.8
-0.033
8
Fb>,;az,,
-0.112
16
Fpz.,;p2,9
0.064
BICYCLOPROPYL Bicyclopropyl
(BCP)
molecules
in crystal
liquid both trans and gauche conformers
take trans form (see figure l.), while in By electron diffraction measure-
are present.
ments on gas phase, Hagen et al. (ref. 14 in [l]) obtained 48.74” as the equilibrium of dihedral angle &, between two cyclopropyl this study was large (7.3”) we undertook
groups.
calculation
Since the standard of the potential
value
deviation
in
energy Q, of BCP
as a function of 4 by means of atom-atom potential functions of Buckingham type. Parameters of Williams’ IV B potential [5] gave @ with the local minimum at 4 z 41”. Using this value for gauche conformer together with molecular geometry from [6], 42 normal modes of BCP only one torsional
tram
and gauche were obtained.
angle was redundant,
because
Among 43 internal
coordinates
clihedral angle was constructed
as a
superposition of two torsional angles: 7s215 and ~6217. Torsional angle 782,s represents the torsional displacement of the Cs - C’s bond around C2 - Cr bond with respect to Cr - CS bond. Other internal coordinates involve all coordinates of two cyclopropane rings, except that two angle deformations #? and one C - H bond stretching coordinate 1 from each ring are replaced by two LCCC angle bending coordinates 6 and C, - Cz
323
bond stretching
coordinate
Force constants
Ki,s.
added to those of cyclopropane
are
listed in table 2.
Table 2. Force constants
of bicyclopropyl
(mdyn/A
, mdynlrad,
value
Force constant
Because
KK
2 3 4
HP1
1.0
1.1
0
0.11
space in table 3.
frequencies
value trans
5
0.73
H,
of limited
vibrational
Force constant
4.6
Hs
A/rad2)
gauche
tram 1
(only those added to CP set). mdyn
6 F~m6w 7 %,s;sv -0.27 8 Fs,.,;s,,, -0.017 9 Fs,s,;s,., 0.008
we compare
bellow 600 cm-’
Table 3. Obs. and talc.
Fh.;~
-0.18 0.04 0.25
only those observed
corresponding
skeletal deformations
bicyclopropyl trans
gauche
0.36 0.2
and calculated
to skeletal deformations.
of bicyclopropyl
(cm-‘).
bicyclopropyl gauche
~
The main difference between our assignment sional frequency.
Spiekermann
20 % solution of BCP in cyclohexane the gauche
conformer,
especially
and that from ref.[I] concerns
et al. [l] attributed
the band observed
to trans conformer.
after inspection
well (more than 100°) around the trans position
for
It is more likely it belongs to
of a, which shows very wide potential 4 = 180”. The appropriate
constant of gauche conformer is empirically found to be 0.11 mdyne A/rad2, for BCP - trans almost unhindered large amplitude motion of cyclopropyl suggested.
the tor-
at 134 cm-’
torsional whereas groups is
324
K 1.3
%
K2&
Figure 2: Internal coordinates of acetylene group which conects two cyclopropyl groups.
4.
DICYCLOPROPYLACETYLENE
At the present no equilibrium structure of dicyclopropylacetylene
(DCPA)
is known.
We calculated potential energy ip for DCPA in the same way as for BCP - it is of the type (1 - cos 4) with the maximum at 4 = 180” (tram-DCPA)
and minimum at 4 = 0”
(cis-DCPA). The energy difference was only w 40 cal/mol or z 14 cm-‘. Equilibrium structure of BCP tram and acetylene group from [7) served for construction of DCP.4 geometry.
Using force constants of BCP-tratu with the (L - L),i,
from -0.06 to -0.14 mdyn/&
constant changed
omitting S - 6 interaction constants between two rings
we transferred the force constants from acetylene group (see table 4.) and obtained 48 fundamentals of various DCPA conformers.
Table 4. Force constants of acetylene group transferred from diphenylacetylene (u&s as in tables 1. and 2.) K1.a
[2].
K2.4
5.958 5.958 0.328
0.14 0.328
0.14 0.328 0.328
As can be seen from the table 5, there is no pure symmetric stretching mode of two CC bonds around the triple bond for the cis conf@ration. Since we assumed H, x 0 for DCPA,
~25
(torsion) was omitted from the table 5.
In figure 3. the dependence of ten lowest calculated vibrations on the value of the dihedral angle 4 is shown.
325 Table 5. Observed (see also [S]) and calculated frequencies of DCPA
., -----AI
A2
,
&
~., stretching CH stretching CHz stretching
VI
3082
3090
uz K3 4
?
3066
0.94 K,,
3015 2248
3035 2277
0.97 K, 0.78 Q + 0.22 KK
triple bond stretch.
us @
1454 1343
1454 1347
0.78 HP 0.73 HP,
CHz bending CHfCH2 bending
w a
1186 1029
1191 1029
0.62 KL + 0.25 H6 0.84 Ha + 0.11 Hs
ring breathing CH2 wagging
us VI0
1001 910
951 915
1.02 Ha + 0.35 Ha, 0.53 KL + 0.40 Ha
CHz rock.fCH bending ring/ CHt deformation
WI YZ
779 642
770 626
1.45 Ha 0.32 Ho + 0.31 H6 + 0.29 KK
CHz twisting skeletal deformation
“I3 v14
390 85
380 89
0.64 H6 + 0.19 KK 0.55 H+ + 0.26 Hs
ring flapping linear bending
VI5
3093 3013
3098 3028
1 .OO K, 0.98 Kt
CH2 CH2
stretching stretching
VI6 W7
0.97 K1
cis.
CH2
+ 0.26 HP + 0.11 KK
+O.ll
H4
VIB
1427 1162
1419 1192
0.84 HP 1.47 Ho
CHz CH2
bending twisting
Y9 YO
1093 1052
1087 1057
0.49 HP + 0.27 Ha, 0.85 Ho
CH2 CH2
rock./CH wagging
u21 m2
872 814
909 802
0.95 KL 0.65 Ha + 0.63 Ha<
ring deformation CH2 rock./CH twisting
m3 Y4
518 200
506 221
0.79 H+ + 0.35 H6 0.92 H+ + 0.35 Ha
linear bending skeletal deformation
YB
3093
3098
1.00 K,
CHz
w7
stretching
Y8
3013 1378
3028 141s
0.98 K, 0.84 HP
CHa CHa
stretching bending
w9 “30
1174 1089
1192 1087
1.47 HP 0.49 Ha + 0.28 Hat
CHz CHz
twisting rock.lCH
WI
1050
1057
0.84 Ha
CHz wagging ring deformation CH2
rock.lCH
twisting
twisting
twisting
skeletal deformation
326
3(cm’)_______
_ ____
600 t Figure 3. The dependence of ten lowest calculated bands of DCPA on dihedral angle.
Dashed lines denote peak positions of the observed liquid bands.
300-
Only two
lowest bands were measured on DCPA --
m--_--_A
100: _ _I- _ _
--
vapour (92 cm-’
-----
_ _ _--_----
in far IR and 85 cm-l
in Raman spectrum). The existence of these two linear bending modes is
---
- z
very important for the interpretation of phonon spectra that DCPA displays at low temperatures [9].
0
u)
80
120
160
't'ldeg
Due to the broadness, asymmetry and the overlap of low frequency bands the number of conformers couldn’t be determined.
Acknowledgement We thank Dr.
2. MeiC for initiating this investigation
and Prof.
M. Dakkouri for
providing us with dicyclopropylacetylene.
References [l] M. Spiekermann, B. Schrader, A. de Meijere, W. Liittke, J. Mol. Str. ‘7’7 (1981) 1. (21 G. Baranovit, Thesis, University of Zagreb 1987. [3] W. J. Jones, B. P. Stoicheff, Can. J. Phys. 31(5) (1976) 1377. [4] M. Spiekermann, D. Bougeard, B. Schrader, J. Mol. Struct. 60 (1980) 55. (51 D. Williams, J. Chem. Phys, 4’7(11) (1967) 4680. [6] D. Nijveldt, A. Vos, Acta Cryst. B44 (1988) 281. [7] Th. Koops et al., J. Mol. Struct. 100 (1983) 95. [8] G. Schrumpf, T. Alshuth, J. Mol. Struct., 101 (1983)47.
[9]V. Mohacek, K. Furic, M. Dakkouri, M. Grosser, to be published.
Journal of Molecular Structure, 266 (1992) 321-326 Elsevier Science Publishers B.V., Amsterdam
Vibrational
Vlasta
analysis of some cyclopropyl
MohaEek and KreSimir
Ruder BoskoviC Institute,
derivatives
Furit
POB
1016, 41001 Zagreb, Croatia
Abstract Vibrational calculated
frequencies
of various conformers
of dicyclopropylacetylene
CsHlo are
for the first time using the empirical valence force field constructed
of bicyclopropyl
tram and diphenylacetylene
dicyclopropylacetylene
are discussed
molecule.
Possible molecular
from those structures
on the basis of broad bands observed
of
for liquid
state bellow 600 cm-‘. Both for bicyclopropyl tram and gauche conformers the valence force field of cyclopropane served as a starting point. Several bicyclopropyl force constants are found to be conformation
1.
sensitive.
INTRODUCTION The cyclopropane
molecule was the subject
tions, while on bicyclopropyl found valence force field (VFF) of bicyclopropyl acetylene
2.
of numerous normal coordinate
only one was performed for cyclopropane
tram and gauche.
is used to construct
Using force constants
group from diphenylacetylene
calcula-
[l]. In this work new, empirically valence force fields
of bicyclopropyl
[2], VFF for dicyclopropylacetylene
trans and is obtained.
CYCLOPROPANE The equilibrium
geometry
of twenty one non redundant and 12 CCH
angle bending
1.).
of internal
Labeling
of cyclopropane coordinates coordinates)
coordinates
(CP)
was taken from ref.[3].
(3 CC bond stretching, sixteen
is identical
force constants to that in ref.[4].
deviation for C&,H, is 0.3 % and for C,D, 0.8 % indicating between calculated and observed frequencies.
0022-2860/92/$05.00
For the set
6 CH bond stretching are used (see table Relative
standard
a very good agreement
0 1992 Elsevier Science Publishers B.V. All rights reserved
322
16
13
Figure 1: Internal
Table 1. Force constants
No.
3.
coordinates
of cyclopropane.
Force constant
of bicyclopropyl.
(mdyn/A
value
No.
1
I
4.152
9
2
I<,
5.073
10
, mdynlrad,
mdyn A/Tad2)
Force constant
value 0.171
Fir*., ;&,5 FL%,,;&
0.117 -0.071 0.045
3 4
FL,.A.~
0.81 -0.06
11 12
Frrz.,;rc11,6 Fp,,&,~
5
FL,.~;A,,
0.27
13
%,,;P1,1
0.109
H0
6
FL~;P~,,
-0.085
14
~*.I&.,
-0.066
7
&,+,,
0.068
15
Foz.,;ezc?.8
-0.033
8
Fb>,;az,,
-0.112
16
Fpz.,;p2,9
0.064
BICYCLOPROPYL Bicyclopropyl
(BCP)
molecules
in crystal
liquid both trans and gauche conformers
take trans form (see figure l.), while in By electron diffraction measure-
are present.
ments on gas phase, Hagen et al. (ref. 14 in [l]) obtained 48.74” as the equilibrium of dihedral angle &, between two cyclopropyl this study was large (7.3”) we undertook
groups.
calculation
Since the standard of the potential
value
deviation
in
energy Q, of BCP
as a function of 4 by means of atom-atom potential functions of Buckingham type. Parameters of Williams’ IV B potential [5] gave @ with the local minimum at 4 z 41”. Using this value for gauche conformer together with molecular geometry from [6], 42 normal modes of BCP only one torsional
tram
and gauche were obtained.
angle was redundant,
because
Among 43 internal
coordinates
clihedral angle was constructed
as a
superposition of two torsional angles: 7s215 and ~6217. Torsional angle 782,s represents the torsional displacement of the Cs - C’s bond around C2 - Cr bond with respect to Cr - CS bond. Other internal coordinates involve all coordinates of two cyclopropane rings, except that two angle deformations #? and one C - H bond stretching coordinate 1 from each ring are replaced by two LCCC angle bending coordinates 6 and C, - Cz
323
bond stretching
coordinate
Force constants
Ki,s.
added to those of cyclopropane
are
listed in table 2.
Table 2. Force constants
of bicyclopropyl
(mdyn/A
, mdynlrad,
value
Force constant
Because
KK
2 3 4
HP1
1.0
1.1
0
0.11
space in table 3.
frequencies
value trans
5
0.73
H,
of limited
vibrational
Force constant
4.6
Hs
A/rad2)
gauche
tram 1
(only those added to CP set). mdyn
6 F~m6w 7 %,s;sv -0.27 8 Fs,.,;s,,, -0.017 9 Fs,s,;s,., 0.008
we compare
bellow 600 cm-’
Table 3. Obs. and talc.
Fh.;~
-0.18 0.04 0.25
only those observed
corresponding
skeletal deformations
bicyclopropyl trans
gauche
0.36 0.2
and calculated
to skeletal deformations.
of bicyclopropyl
(cm-‘).
bicyclopropyl gauche
~
The main difference between our assignment sional frequency.
Spiekermann
20 % solution of BCP in cyclohexane the gauche
conformer,
especially
and that from ref.[I] concerns
et al. [l] attributed
the band observed
to trans conformer.
after inspection
well (more than 100°) around the trans position
for
It is more likely it belongs to
of a, which shows very wide potential 4 = 180”. The appropriate
constant of gauche conformer is empirically found to be 0.11 mdyne A/rad2, for BCP - trans almost unhindered large amplitude motion of cyclopropyl suggested.
the tor-
at 134 cm-’
torsional whereas groups is
324
K 1.3
%
K2&
Figure 2: Internal coordinates of acetylene group which conects two cyclopropyl groups.
4.
DICYCLOPROPYLACETYLENE
At the present no equilibrium structure of dicyclopropylacetylene
(DCPA)
is known.
We calculated potential energy ip for DCPA in the same way as for BCP - it is of the type (1 - cos 4) with the maximum at 4 = 180” (tram-DCPA)
and minimum at 4 = 0”
(cis-DCPA). The energy difference was only w 40 cal/mol or z 14 cm-‘. Equilibrium structure of BCP tram and acetylene group from [7) served for construction of DCP.4 geometry.
Using force constants of BCP-tratu with the (L - L),i,
from -0.06 to -0.14 mdyn/&
constant changed
omitting S - 6 interaction constants between two rings
we transferred the force constants from acetylene group (see table 4.) and obtained 48 fundamentals of various DCPA conformers.
Table 4. Force constants of acetylene group transferred from diphenylacetylene (u&s as in tables 1. and 2.) K1.a
[2].
K2.4
5.958 5.958 0.328
0.14 0.328
0.14 0.328 0.328
As can be seen from the table 5, there is no pure symmetric stretching mode of two CC bonds around the triple bond for the cis conf@ration. Since we assumed H, x 0 for DCPA,
~25
(torsion) was omitted from the table 5.
In figure 3. the dependence of ten lowest calculated vibrations on the value of the dihedral angle 4 is shown.
325 Table 5. Observed (see also [S]) and calculated frequencies of DCPA
., -----AI
A2
,
&
~., stretching CH stretching CHz stretching
VI
3082
3090
uz K3 4
?
3066
0.94 K,,
3015 2248
3035 2277
0.97 K, 0.78 Q + 0.22 KK
triple bond stretch.
us @
1454 1343
1454 1347
0.78 HP 0.73 HP,
CHz bending CHfCH2 bending
w a
1186 1029
1191 1029
0.62 KL + 0.25 H6 0.84 Ha + 0.11 Hs
ring breathing CH2 wagging
us VI0
1001 910
951 915
1.02 Ha + 0.35 Ha, 0.53 KL + 0.40 Ha
CHz rock.fCH bending ring/ CHt deformation
WI YZ
779 642
770 626
1.45 Ha 0.32 Ho + 0.31 H6 + 0.29 KK
CHz twisting skeletal deformation
“I3 v14
390 85
380 89
0.64 H6 + 0.19 KK 0.55 H+ + 0.26 Hs
ring flapping linear bending
VI5
3093 3013
3098 3028
1 .OO K, 0.98 Kt
CH2 CH2
stretching stretching
VI6 W7
0.97 K1
cis.
CH2
+ 0.26 HP + 0.11 KK
+O.ll
H4
VIB
1427 1162
1419 1192
0.84 HP 1.47 Ho
CHz CH2
bending twisting
Y9 YO
1093 1052
1087 1057
0.49 HP + 0.27 Ha, 0.85 Ho
CH2 CH2
rock./CH wagging
u21 m2
872 814
909 802
0.95 KL 0.65 Ha + 0.63 Ha<
ring deformation CH2 rock./CH twisting
m3 Y4
518 200
506 221
0.79 H+ + 0.35 H6 0.92 H+ + 0.35 Ha
linear bending skeletal deformation
YB
3093
3098
1.00 K,
CHz
w7
stretching
Y8
3013 1378
3028 141s
0.98 K, 0.84 HP
CHa CHa
stretching bending
w9 “30
1174 1089
1192 1087
1.47 HP 0.49 Ha + 0.28 Hat
CHz CHz
twisting rock.lCH
WI
1050
1057
0.84 Ha
CHz wagging ring deformation CH2
rock.lCH
twisting
twisting
twisting
skeletal deformation
326
3(cm’)_______
_ ____
600 t Figure 3. The dependence of ten lowest calculated bands of DCPA on dihedral angle.
Dashed lines denote peak positions of the observed liquid bands.
300-
Only two
lowest bands were measured on DCPA --
m--_--_A
100: _ _I- _ _
--
vapour (92 cm-’
-----
_ _ _--_----
in far IR and 85 cm-l
in Raman spectrum). The existence of these two linear bending modes is
---
- z
very important for the interpretation of phonon spectra that DCPA displays at low temperatures [9].
0
u)
80
120
160
't'ldeg
Due to the broadness, asymmetry and the overlap of low frequency bands the number of conformers couldn’t be determined.
Acknowledgement We thank Dr.
2. MeiC for initiating this investigation
and Prof.
M. Dakkouri for
providing us with dicyclopropylacetylene.
References [l] M. Spiekermann, B. Schrader, A. de Meijere, W. Liittke, J. Mol. Str. ‘7’7 (1981) 1. (21 G. Baranovit, Thesis, University of Zagreb 1987. [3] W. J. Jones, B. P. Stoicheff, Can. J. Phys. 31(5) (1976) 1377. [4] M. Spiekermann, D. Bougeard, B. Schrader, J. Mol. Struct. 60 (1980) 55. (51 D. Williams, J. Chem. Phys, 4’7(11) (1967) 4680. [6] D. Nijveldt, A. Vos, Acta Cryst. B44 (1988) 281. [7] Th. Koops et al., J. Mol. Struct. 100 (1983) 95. [8] G. Schrumpf, T. Alshuth, J. Mol. Struct., 101 (1983)47.
[9]V. Mohacek, K. Furic, M. Dakkouri, M. Grosser, to be published.