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Structure of cyclopentadiene from microwave spectra of several deuterated species
Volume 37, number
STRUCTURE
OF CYCLOPENTADIENE
‘OF SEVERAL
D. DAMIANI,
15 January 1976
CHELIICAL PHYSICS LET-I-ERS
2
DEUTERATED
FROM MICROWAVE
SPECTRA
SPECIES
L. FERRETTI
Laboratorio
di Spett;oscopio
arId Istimro
Clrimico
M&cc/are
“G. Ciomician
de! C.N.R.. JO126 Bologna, Italy
“, Uniwrsifb
di Bologna,
40126
Bologna,
itail-
and E. GALLINELLA Istiruro
di
Received 6
Chimica
August
Fisica,
Universirti
di Moderla, 41100 Moderra,
Italy
1975
The microwave rotational spectra of hexadeuterated, pentadeuterated and of threz different monodeuternted species of cyclopentadiene have been measured. Structural parameters for hydrogen atoms have been deduced from rotational constants of these species. From these structural data for the hydrogens and from those relative to the ring deiermined by Scharpen and Laurie the rs and ro structures have been obtained.
several transitiofis observed by Scharpen and Laurie have been re-measured and the frequencies were found to be in close agreement. Moreover some other
1. Introduction
Therefore
In recent years the structure of the cyclopentadiene molecule has been investigated by several authors, who used different techniques [l-6]. However no complete gas-phase structure has been so far obtained. In particular in the microwave work of Scharpen and Laurie [4] only the r,- structure of the carbon ring was determined. The purpose of the present work is to determine a complete structure of the molecule. Taking into account the Czv symmetry of the moiecule (fig. 1) and the data for the isotopic species given by Scharpen and Laurie, only additional data from three different monodeuterated species are needed in order to obtain the complete rS structure. Therefore ‘Lhe rotational constants of cyclopentadieneId,(CP-ldI,), CP-2111 and CP-34, have been measured. Moreover, CP-db and CP-1,2,3,4,5d5 were also investigated in order to acquiie further data. Since error in the cdordinates of the carbon atoms enhance the errors in the structural parameters of the CH groups, a more accurate set of rotational constants of the 13C species and normal species was needed.
Fig. 1. Schematic asis system.
picture of cyc!openiadiene
in the principal,
265
Volume
37, number
Table I Rotational
CHEMICAL
2
constants
(kIHz:r oi cyclopentadiene
hikleahr
species
and substituted
LETTERS
15 January 1976
species B
A
c 2 0.005
CP.
8426.146
+ 0.007
s225.519
i 0.006
4271.433
cP-1-‘3c
8226.028
i 0.009
8219.434
k 0.007
4217.760
+ 0.006
CP-2-‘3c
5419.949
f 0.006
8040.358
c 0.006
4219.419
f 0.004 2 0.007
cP-3-‘3c
8345.097
k 0.010
8108.662
+_0.007
4219.067
CP-I+ir
8129.894
c 0.006
7859.476
+ 0.005
4145.094
+ 0.004
CP-2dr
8414.008
+_0.006
7591.871
+ 0.006
4091.147
f 0.003
CP-34,
8306.997
k 0.006
7678.059
2 0.004
4090.256
+ 0.003
i 0.009
6607.320
+ 0.005
3444.119
i 0.002
r 0.005
6681.870
k 0.005
3529.283
k 0.004
6608.;80
CPd6
7707.857 -
CP-l,2,3,4,5~j
--
PHYSlCS
transitions
have
been
measured.
The
rotational
con-
stants obtained in this way do not differ from the values reported by Scharp :n and Laurie but the accuracy is improved (table 1). The conversion factor 505379.1 2 3.0 amu .k2 MHz [7] and atomic masses based on 12C = 12.000 were . used throughout all calcuiations.
at dry ice temperature, 51 order to avoid dimerization as well as unwanted isomerization. All spectra were recorded with a Hewlett-Packard 8400-C spectrometer in the frequency range 8-40 GHz, with the Stark cell cooled at dry ice temperature, at pressures !ower th.an 50 mm Hg and using Stark fields up to 3 kV/cm. The transition frequencies are assumed to be accurate within 20.02 MHz.
2. Experimental
CP+ was prepared by deuteroxide-catalyzed hydrogen exchange of cyclopentadiene and D,O in hexamethyl-phosphoric triamide solution [S] . After five successive exchanges the deuterium content of CPd6 obtained was evaluated to be 99.0-99.2% both from the Raman spectrum and from NMR measurements. CP-1,2,3,4,5-d, was prepared by obtaining first pentadeuterocyclopentadienyl-thallium, by the reaction of CPA6 with n2sG4 in a NaOD solution in DzO Then
the thallium
solution
of H2S04
derivative in I-I,0
was hydrolyzed [9]
and the CPxI5
in a dilute was dis-
Wed off. CP-l-d, was obtained in a similar way. Normal cyclopentadiene was used for the preparation of the thallium derivative and a dilute solution cf D2SO4 in D?O with isotopic purity hotter than 99% was employed?or the hydrolysis. The mixture of monodeurerocyclopentadiene CP,141, CP-2-cli and CP-3-d, was obtained by heating [IO], a s&ple of CP-1 dI vapour in a flask under a .prressure of 3 few. nun Hg for several hours. The cyclopentadienes were stored as liquid samples :266.:,,.
_,: ‘,
i:_:_
,.
.,
.’ :
”
3. Spectra Cyclopentadiene is an oblate rotor and deuteration causes a large rotation of the a and b axes in the plane of the carbon ring. However all of the isotopic species except the CP3d, one, show a spectrum due either purely or predominantly to one component of the dipole moment. For the (Y-34, pn = pb as can be deduced from G&intensities of “a” and “6” type spectra. For the CPG, molecule it has been difficult to assign the observed spectrum to the “IS”or the “h” type. In fact the CPB, is a sli&t!y asymmetric oblate rotor {k’= 0.999) and this causes, as is well-known, the “Q" and “b” spectra to be practically coincident. This ambiguity was removed by measuring the dipole mo_ment from the Stark effect. It was found that ‘&e dipole moment assumed an acceptab!e value only if it was computed frcm the Stark coefficients of the “a” type transitions. .. The sole component ~1~of the dipole moment of the CP-di molecule was measured from the Stark displacement of severa! M components of the following transition:
Volume 37, number 3
-2,o
+
2
CHEMICAL PHYSICS LETTERS
1.5 Ja-uary
1576
This value is in good agreement with the value obby Scharpen and Laurie for the normal species. Table 2 lists the observed transitions and the n&sured frequencies for the isotopic species invebrigated. The wiues of the rotational constants for each species (table 1) were obtained by a least squares fitting of the frequencies of each set, in the rigid rotor approximation.
lo,,
3 3;:; 73+221 c- 2,:,
served
The result obtained is: P -/Jo = 0.420 i 0.003 debye. Table 2 Rotational
transition
frequencies
Transition
(MHz) of cyclopentadiene Frequency obs.
CP-la’1
la,1 21,l
Transition
Frequency
obs. - c&z.
obs.
12 004.57
0.00
31,3 +- 1-1,2
28 399.11
i
27 723.63
0.11
31,z
+ 229
34 933.71
32~
+ &,I
37 191.75
II,0
30,3 + 20 2
28 72.5 23
-0.02
31,3 +- 21,2
28 711.45
-0.03
31,2 - 21,~ 32~ - 22,1
36 754.09
32~
m-3-d,
obs. - CA.
0.05 0.06 -0.01
32,2
13 638.36
-0.02
0.03
4 a,4 &_ 30,3
36 615.33
-0.06
36 013.72
0.01
36 609.62
-0.03
0.11
40 >4 + 31,3
+ 32 2
10 746.77
53,2
+ 52,3
17 948.05
33,L + 31,2
12 439.67
0.06
-
16 486.70
41,4 “31.3
37.007.59
43,1 c43,2
10 224.71
-0.05 0.04
33,1 -
.64,2 CPdB
65,3
0.04 -0.06
la,1
+Oo,o
10 051.43
0.05
h,l
-
11,o
23 266.11
0.03
$4 rI c42,2
13 136.44
-0.05
&,a
-
IO,I
29 595.70
3.04
52,3 + 52,4
26 896.76
-0.04
30,3
+ 20.2
23 828.48
0.04
%,3
26 909.94
-0.05
31,3 *
21,2
23 828.48
Cl.04
9 584.31
-0.02
31,2 + 21,l
30 157.50
0.01
8 836.43
-0.06
-
51 4
65,1 +65,2 ‘00.0
il,l
20,2 +
II,L
21,2 + lo
I
;?,I
-22
19 736.80
0.02
4op
c
20 687.53
0.08
41,4
+31
3
30 716.69
41,3
<- 31 ,2
37 044.08
-0.06 -0.06
22,1 ‘?I,,
I2 968.58
-0.00
30,3 -
28 371.04
%,z
31,~ + 30 3
19 023.48
3 2,2 +
37 515.48
2, : 1
33,l
+ 32,2
14 276.7 1
4a,4
+31,3
36 61h.21
41,4
+ 30,3
36 627.99 16 672.15
66,O :0,1
6S,l
‘OOC
-0.01 -0.01
+ 22,1
0.07
-0.05
+ 20,2
33 154.31 36 4SO.lS
32~
12 505.22
10 630.66
21,l
CP_3dl
species
“Oa,a
54,1 -54,2
CP-24,
and substituted
11 768.36
0.02 -0.00 0.02 0.01
I0 30 ,3
30 716.69
0.01
42 3 +- 32,~
37 044.08
50,s - 40 4
37 604.92
51,s
37 604.92
0.00
10 537.14
0.00
‘41.4
CP-1,2,3.4,5d5 l1,1.+ 00,o -I,2 - b,l 7
0.00
17 595.71
@.C!O
!I,0
24 552.90
0.05
-0.06
30,3 + 21,z
24 475.68
-0.01
-0.01
31,3
+ 20.2
24 503.77
-0.02
54,l
+53
&,I
+64,2
-0.04
0.05
22,l
-
8 410;29
, 1 I ,I (- 00,o 20,2 +-Ia,1
20 502.13
0.03
74,3 + 73,4
22 892.14
7-I,2 + lo,1
20 577.78
0.02
3-2,l + !l,O
29 011.24
30,n c
20,2
30.3 + &,2
12 397.25
0.01
-0.00
I-7
8 273.15
0.07 0.01 -0.05
76,2 + 75~
17 312.61
0.01
-0.01
76,l - 75,2
8 383.10
0.01
28 468.96
-0.02
%,I
8 801.93
-0.01
28 393.31
-0.01
+ 86,2
267
Volume 31, number 2 4. St&ture
Table4 Structure of cyclopentadiene~?
The coordinates of the atoms in the principal axis system of the normal species (table 3j have been obtained using Kr@tchmann’s equations and the appropriate moments of inertia of the normal and monosubstituted species. By the same method, anci using the moments of inertia of the CPd6 and CP-d, moiecules, the following coordinates of the methylefie deuterium atom in the principal axis system af the CPd6 species were obtained: a = 0.
2 0. b = 1.8724 + 0.0001 c = 0.8840 k 0.0001
= !4
+ IB - lc =
k 0.0014
1.506 r 0.012 1.352 c 0.018 1.474 ? 0.003 1.097 +_0.011 1.077 c 0.008 1.077 r 0.017 103.17 f 1.13 109.29 2 0.66 109.12 I 0.36 106.30 t 1.49 127.15 k 1.37 126.29 i 0.84
O?Distances in A, angles in degrees.
h,L?f.
a.
species of cyclopentadiene -.----_ b
C -
0. zo. 1.2348 k 0.0002 11.1783 i- 0.0001 0.2964 c 0.0003 0.3341 i 0.0001 -0.9726 * 0.0002
0. 0. 0.
0.
0.8799 c 0.0001
..* 0.
? 0.02 c 0.02 z 0.03 5 0.05 f 0.03
i09.24
109.29 106.33 127.13 126.04
Coordinates (A) of atoms in the principal axis system of normal
II1
r 0.0004 f 0.0005 ? 0.0002 r 0.0003 ? O.OOC4 f o.oolx + 0.03
LCI-C2-C3
TabI_, 3
-Cl. C2 c3
r(C3-H3) LCS-Cl -c2
1.5063 1.3445 1.4682 1.0993 1.0782 1.0797 102.93
K2-C3 -C4 LH-Cl -H LH-C2-C3 LH3-C3-C2
This vaiue can be compared with the corresponding rS va!ues of 0.8799 and 0.8840 obtained for the normal and 46 species, respectively. The rs structure parameters obtained from the coordinates of the atoms a&listed in the first column of table 4. The reported error limiis represent only the cffeet of the estimated error in the rotational constants.
a
r(c1 -C2) r(C2-C3) tic3 -C4) iC1 -Hl) r(C2-H?)
4
In these cases z”cc depends only on the parameters of the methylene hydrogen atom. The mean value and the range of the “c” coordinate calculated in this way from the (possible) species is 0.8774
Parameters
A, A.
Besides these substitutional values, for these isotopic species which have the ring plane coincident with the ab plane, the “6: coordinate of the methylene hydrogen atom can be calculated from the expression for PO: cc
15 January 1976
CHEMICAL PHYSICS LETTERS
1.8939
_c0.0001
H2 2.2046 * 0.0001 .0.6X? _L0.0003 .I13 ‘_ L;34s3.~.o.oooi -0606 i 0.0001
0. 0.
+_0. L 0. * 0.
+ 0. + 0.
A least squares fitting of all experimental rotational constants has been carried out and the structural parameters obtained are shown in the SecGnd column of table 4. By comparing the rS and ‘0 parameters it can be seen that the values obtained by the two methods are coincident within the quoted standard deviations.
5. Conclusions The structural parameters found for the carbon atom ring are in good agreement with the previous ones determined by Scharpen and Laurie. By considering the complete structurai set of CP now obtained, some useful comments can be made by comparison with open-chain structures having similar groups and with the other five-membered ring molecules (table 5). It appears that the methylene group structure is quite similar in propane [ll] , cis-1-butene [ 121 and cyclopentadiene. The two bond lengths for the C=C-Cgroup in cyclopentadiene are very similar to those found in propene 1131 and cis-l-butene. The C2-CJ length irxreases from cyclopentadiene to furar? [I 41 , thiophen [ 15 ] and pyrrole [ 16],, whereas the C3-C4 length decreases in the same order. Tnesc facts support the coxiclusion that the latter compounds are essentially perturbed cis-dienes [5].
Volume 37, number Table 5 Structural
parameters
2
CWMICAL
PHYSICS LETTERS
1.5 Jam&
of related molecules”) Propane 1111
Propene [131
Cis-1 -butene 1121
Cyclepcntadiene
I!uran I141
Thiophnne [ISI
I.501 1.335
1.096
l.OSOb)
1.093
1.099
r(CZ-H2)
1.090
1.cL9:
1.051
1.078
1.078
1.076
r(C3-H3) LCZ-Cl -cs
1.081
1.093 114.5
1.082 102.8
1.077 106.5e)
1.081
1.077 109.8”)
rCCl-HI)
112.4 124.3
UZl-C2-C3
126.1
fC2-C3-C4 LH-Cl-H ~C3-c2-H2 ~C2-c3-H3
106.1
1.362c) 1.361
1.714c’ 1.370
1.465
1.431
1.423
1.37oc) 1.382
1.501 1.336
ric3-C4)
1.505 1.342
Pyrrole 1161
I.526
r(c1 -C2) rtC2-C3)
1976
1.417 0.996d)
109.3
110.6
III.5
107.7
109.3
106.0
112.5
107.4
107.7b) 119.0
105.7 119.0
106.3 !27.1
133.4
128.7
130.8
121.5
119.8
126.0
126.0
123.2
125.5
109.0
105.1
LC’Z-Cl-H
‘) Distances are in A and &es in degrees. b) Assumed. ‘) Heteroatom-C2 distance. d) N-H distance. e) C2-X-C5 angle, X = heteroatom.
References
[I] V. Shomaker and L. Pauling, J. Am. Chem. Sot. 61 (1939) 1769. [2] P.S. O’Sullivan and H.F. xameka, Chem. Phys. Letters 4 (1969) 123. [31 R-C’. Benson and W.H. Flygare, J. Am. Chem. Sot. 92 (1970) 7223. 141 L.H. Scharpen and V.W. Laurie, _I. Chem. Phys. 43 (1965) 2765. I51 F. biomicchioli and G. Del Rc. J. Chem. Sot. B (1S69) 674. 161 C.A. Vera&i, \I. Guidi, hl. Longeri ahd A.h!. Serm, Chem. Phys. Letters 24 (1974) 99. 171 E.R. Coher. and B.N. Taylor, J. Phys. Chem. Ref. Data 2 (1973) 663.
[8l E. Gnllinelln and P. Mirone, Atti Sot. Nat. Mat. Jlodcna 100 (1969) 215;J. Labelled Compounds7 (1971) 183. PI H. hleistcr, Angew. Chem. 69 (19.57) 553. 1101V.A. hlironov, E.V. Sobolev and AX. Elizarova, Doklady Akad. Nnuk SSSR 143 (1962) 1112. [I11 D.R. Lide Jr., J. Chem. Phys. 33 (1968) 1514. (121 S. Kondo, E. Hirofa and Y. hiorino, J. Mol. Spectry. 28 (1968) 471. [I31 D-R. Lide Jr. and D. Christensen, J. Chem. .Phys. 35 (1961) 1374. 1141 B. Bak, D. Christensen, W.B. Dixon, L. Hansen-Nygzard, J. Rastrup-Andersen and %I. Schottlander, J. Mol. Spectry. 9 (1962) 124. [I51 B. Bak, D. Christensen, L. Hansen-Nygaard and J. RnstrupAndersen, J. hIo1. Spectry. 7 (1961) 58. iI61 L. Nygaard, J.T. Nielsen, J. Kirchheiner, G. hlaltesen, J. Rastrup-Ande:sen and G.O. Sorensen, J. Mol. Struct. 3 (1969) 491.
269
STRUCTURE
OF CYCLOPENTADIENE
‘OF SEVERAL
D. DAMIANI,
15 January 1976
CHELIICAL PHYSICS LET-I-ERS
2
DEUTERATED
FROM MICROWAVE
SPECTRA
SPECIES
L. FERRETTI
Laboratorio
di Spett;oscopio
arId Istimro
Clrimico
M&cc/are
“G. Ciomician
de! C.N.R.. JO126 Bologna, Italy
“, Uniwrsifb
di Bologna,
40126
Bologna,
itail-
and E. GALLINELLA Istiruro
di
Received 6
Chimica
August
Fisica,
Universirti
di Moderla, 41100 Moderra,
Italy
1975
The microwave rotational spectra of hexadeuterated, pentadeuterated and of threz different monodeuternted species of cyclopentadiene have been measured. Structural parameters for hydrogen atoms have been deduced from rotational constants of these species. From these structural data for the hydrogens and from those relative to the ring deiermined by Scharpen and Laurie the rs and ro structures have been obtained.
several transitiofis observed by Scharpen and Laurie have been re-measured and the frequencies were found to be in close agreement. Moreover some other
1. Introduction
Therefore
In recent years the structure of the cyclopentadiene molecule has been investigated by several authors, who used different techniques [l-6]. However no complete gas-phase structure has been so far obtained. In particular in the microwave work of Scharpen and Laurie [4] only the r,- structure of the carbon ring was determined. The purpose of the present work is to determine a complete structure of the molecule. Taking into account the Czv symmetry of the moiecule (fig. 1) and the data for the isotopic species given by Scharpen and Laurie, only additional data from three different monodeuterated species are needed in order to obtain the complete rS structure. Therefore ‘Lhe rotational constants of cyclopentadieneId,(CP-ldI,), CP-2111 and CP-34, have been measured. Moreover, CP-db and CP-1,2,3,4,5d5 were also investigated in order to acquiie further data. Since error in the cdordinates of the carbon atoms enhance the errors in the structural parameters of the CH groups, a more accurate set of rotational constants of the 13C species and normal species was needed.
Fig. 1. Schematic asis system.
picture of cyc!openiadiene
in the principal,
265
Volume
37, number
Table I Rotational
CHEMICAL
2
constants
(kIHz:r oi cyclopentadiene
hikleahr
species
and substituted
LETTERS
15 January 1976
species B
A
c 2 0.005
CP.
8426.146
+ 0.007
s225.519
i 0.006
4271.433
cP-1-‘3c
8226.028
i 0.009
8219.434
k 0.007
4217.760
+ 0.006
CP-2-‘3c
5419.949
f 0.006
8040.358
c 0.006
4219.419
f 0.004 2 0.007
cP-3-‘3c
8345.097
k 0.010
8108.662
+_0.007
4219.067
CP-I+ir
8129.894
c 0.006
7859.476
+ 0.005
4145.094
+ 0.004
CP-2dr
8414.008
+_0.006
7591.871
+ 0.006
4091.147
f 0.003
CP-34,
8306.997
k 0.006
7678.059
2 0.004
4090.256
+ 0.003
i 0.009
6607.320
+ 0.005
3444.119
i 0.002
r 0.005
6681.870
k 0.005
3529.283
k 0.004
6608.;80
CPd6
7707.857 -
CP-l,2,3,4,5~j
--
PHYSlCS
transitions
have
been
measured.
The
rotational
con-
stants obtained in this way do not differ from the values reported by Scharp :n and Laurie but the accuracy is improved (table 1). The conversion factor 505379.1 2 3.0 amu .k2 MHz [7] and atomic masses based on 12C = 12.000 were . used throughout all calcuiations.
at dry ice temperature, 51 order to avoid dimerization as well as unwanted isomerization. All spectra were recorded with a Hewlett-Packard 8400-C spectrometer in the frequency range 8-40 GHz, with the Stark cell cooled at dry ice temperature, at pressures !ower th.an 50 mm Hg and using Stark fields up to 3 kV/cm. The transition frequencies are assumed to be accurate within 20.02 MHz.
2. Experimental
CP+ was prepared by deuteroxide-catalyzed hydrogen exchange of cyclopentadiene and D,O in hexamethyl-phosphoric triamide solution [S] . After five successive exchanges the deuterium content of CPd6 obtained was evaluated to be 99.0-99.2% both from the Raman spectrum and from NMR measurements. CP-1,2,3,4,5-d, was prepared by obtaining first pentadeuterocyclopentadienyl-thallium, by the reaction of CPA6 with n2sG4 in a NaOD solution in DzO Then
the thallium
solution
of H2S04
derivative in I-I,0
was hydrolyzed [9]
and the CPxI5
in a dilute was dis-
Wed off. CP-l-d, was obtained in a similar way. Normal cyclopentadiene was used for the preparation of the thallium derivative and a dilute solution cf D2SO4 in D?O with isotopic purity hotter than 99% was employed?or the hydrolysis. The mixture of monodeurerocyclopentadiene CP,141, CP-2-cli and CP-3-d, was obtained by heating [IO], a s&ple of CP-1 dI vapour in a flask under a .prressure of 3 few. nun Hg for several hours. The cyclopentadienes were stored as liquid samples :266.:,,.
_,: ‘,
i:_:_
,.
.,
.’ :
”
3. Spectra Cyclopentadiene is an oblate rotor and deuteration causes a large rotation of the a and b axes in the plane of the carbon ring. However all of the isotopic species except the CP3d, one, show a spectrum due either purely or predominantly to one component of the dipole moment. For the (Y-34, pn = pb as can be deduced from G&intensities of “a” and “6” type spectra. For the CPG, molecule it has been difficult to assign the observed spectrum to the “IS”or the “h” type. In fact the CPB, is a sli&t!y asymmetric oblate rotor {k’= 0.999) and this causes, as is well-known, the “Q" and “b” spectra to be practically coincident. This ambiguity was removed by measuring the dipole mo_ment from the Stark effect. It was found that ‘&e dipole moment assumed an acceptab!e value only if it was computed frcm the Stark coefficients of the “a” type transitions. .. The sole component ~1~of the dipole moment of the CP-di molecule was measured from the Stark displacement of severa! M components of the following transition:
Volume 37, number 3
-2,o
+
2
CHEMICAL PHYSICS LETTERS
1.5 Ja-uary
1576
This value is in good agreement with the value obby Scharpen and Laurie for the normal species. Table 2 lists the observed transitions and the n&sured frequencies for the isotopic species invebrigated. The wiues of the rotational constants for each species (table 1) were obtained by a least squares fitting of the frequencies of each set, in the rigid rotor approximation.
lo,,
3 3;:; 73+221 c- 2,:,
served
The result obtained is: P -/Jo = 0.420 i 0.003 debye. Table 2 Rotational
transition
frequencies
Transition
(MHz) of cyclopentadiene Frequency obs.
CP-la’1
la,1 21,l
Transition
Frequency
obs. - c&z.
obs.
12 004.57
0.00
31,3 +- 1-1,2
28 399.11
i
27 723.63
0.11
31,z
+ 229
34 933.71
32~
+ &,I
37 191.75
II,0
30,3 + 20 2
28 72.5 23
-0.02
31,3 +- 21,2
28 711.45
-0.03
31,2 - 21,~ 32~ - 22,1
36 754.09
32~
m-3-d,
obs. - CA.
0.05 0.06 -0.01
32,2
13 638.36
-0.02
0.03
4 a,4 &_ 30,3
36 615.33
-0.06
36 013.72
0.01
36 609.62
-0.03
0.11
40 >4 + 31,3
+ 32 2
10 746.77
53,2
+ 52,3
17 948.05
33,L + 31,2
12 439.67
0.06
-
16 486.70
41,4 “31.3
37.007.59
43,1 c43,2
10 224.71
-0.05 0.04
33,1 -
.64,2 CPdB
65,3
0.04 -0.06
la,1
+Oo,o
10 051.43
0.05
h,l
-
11,o
23 266.11
0.03
$4 rI c42,2
13 136.44
-0.05
&,a
-
IO,I
29 595.70
3.04
52,3 + 52,4
26 896.76
-0.04
30,3
+ 20.2
23 828.48
0.04
%,3
26 909.94
-0.05
31,3 *
21,2
23 828.48
Cl.04
9 584.31
-0.02
31,2 + 21,l
30 157.50
0.01
8 836.43
-0.06
-
51 4
65,1 +65,2 ‘00.0
il,l
20,2 +
II,L
21,2 + lo
I
;?,I
-22
19 736.80
0.02
4op
c
20 687.53
0.08
41,4
+31
3
30 716.69
41,3
<- 31 ,2
37 044.08
-0.06 -0.06
22,1 ‘?I,,
I2 968.58
-0.00
30,3 -
28 371.04
%,z
31,~ + 30 3
19 023.48
3 2,2 +
37 515.48
2, : 1
33,l
+ 32,2
14 276.7 1
4a,4
+31,3
36 61h.21
41,4
+ 30,3
36 627.99 16 672.15
66,O :0,1
6S,l
‘OOC
-0.01 -0.01
+ 22,1
0.07
-0.05
+ 20,2
33 154.31 36 4SO.lS
32~
12 505.22
10 630.66
21,l
CP_3dl
species
“Oa,a
54,1 -54,2
CP-24,
and substituted
11 768.36
0.02 -0.00 0.02 0.01
I0 30 ,3
30 716.69
0.01
42 3 +- 32,~
37 044.08
50,s - 40 4
37 604.92
51,s
37 604.92
0.00
10 537.14
0.00
‘41.4
CP-1,2,3.4,5d5 l1,1.+ 00,o -I,2 - b,l 7
0.00
17 595.71
@.C!O
!I,0
24 552.90
0.05
-0.06
30,3 + 21,z
24 475.68
-0.01
-0.01
31,3
+ 20.2
24 503.77
-0.02
54,l
+53
&,I
+64,2
-0.04
0.05
22,l
-
8 410;29
, 1 I ,I (- 00,o 20,2 +-Ia,1
20 502.13
0.03
74,3 + 73,4
22 892.14
7-I,2 + lo,1
20 577.78
0.02
3-2,l + !l,O
29 011.24
30,n c
20,2
30.3 + &,2
12 397.25
0.01
-0.00
I-7
8 273.15
0.07 0.01 -0.05
76,2 + 75~
17 312.61
0.01
-0.01
76,l - 75,2
8 383.10
0.01
28 468.96
-0.02
%,I
8 801.93
-0.01
28 393.31
-0.01
+ 86,2
267
Volume 31, number 2 4. St&ture
Table4 Structure of cyclopentadiene~?
The coordinates of the atoms in the principal axis system of the normal species (table 3j have been obtained using Kr@tchmann’s equations and the appropriate moments of inertia of the normal and monosubstituted species. By the same method, anci using the moments of inertia of the CPd6 and CP-d, moiecules, the following coordinates of the methylefie deuterium atom in the principal axis system af the CPd6 species were obtained: a = 0.
2 0. b = 1.8724 + 0.0001 c = 0.8840 k 0.0001
= !4
+ IB - lc =
k 0.0014
1.506 r 0.012 1.352 c 0.018 1.474 ? 0.003 1.097 +_0.011 1.077 c 0.008 1.077 r 0.017 103.17 f 1.13 109.29 2 0.66 109.12 I 0.36 106.30 t 1.49 127.15 k 1.37 126.29 i 0.84
O?Distances in A, angles in degrees.
h,L?f.
a.
species of cyclopentadiene -.----_ b
C -
0. zo. 1.2348 k 0.0002 11.1783 i- 0.0001 0.2964 c 0.0003 0.3341 i 0.0001 -0.9726 * 0.0002
0. 0. 0.
0.
0.8799 c 0.0001
..* 0.
? 0.02 c 0.02 z 0.03 5 0.05 f 0.03
i09.24
109.29 106.33 127.13 126.04
Coordinates (A) of atoms in the principal axis system of normal
II1
r 0.0004 f 0.0005 ? 0.0002 r 0.0003 ? O.OOC4 f o.oolx + 0.03
LCI-C2-C3
TabI_, 3
-Cl. C2 c3
r(C3-H3) LCS-Cl -c2
1.5063 1.3445 1.4682 1.0993 1.0782 1.0797 102.93
K2-C3 -C4 LH-Cl -H LH-C2-C3 LH3-C3-C2
This vaiue can be compared with the corresponding rS va!ues of 0.8799 and 0.8840 obtained for the normal and 46 species, respectively. The rs structure parameters obtained from the coordinates of the atoms a&listed in the first column of table 4. The reported error limiis represent only the cffeet of the estimated error in the rotational constants.
a
r(c1 -C2) r(C2-C3) tic3 -C4) iC1 -Hl) r(C2-H?)
4
In these cases z”cc depends only on the parameters of the methylene hydrogen atom. The mean value and the range of the “c” coordinate calculated in this way from the (possible) species is 0.8774
Parameters
A, A.
Besides these substitutional values, for these isotopic species which have the ring plane coincident with the ab plane, the “6: coordinate of the methylene hydrogen atom can be calculated from the expression for PO: cc
15 January 1976
CHEMICAL PHYSICS LETTERS
1.8939
_c0.0001
H2 2.2046 * 0.0001 .0.6X? _L0.0003 .I13 ‘_ L;34s3.~.o.oooi -0606 i 0.0001
0. 0.
+_0. L 0. * 0.
+ 0. + 0.
A least squares fitting of all experimental rotational constants has been carried out and the structural parameters obtained are shown in the SecGnd column of table 4. By comparing the rS and ‘0 parameters it can be seen that the values obtained by the two methods are coincident within the quoted standard deviations.
5. Conclusions The structural parameters found for the carbon atom ring are in good agreement with the previous ones determined by Scharpen and Laurie. By considering the complete structurai set of CP now obtained, some useful comments can be made by comparison with open-chain structures having similar groups and with the other five-membered ring molecules (table 5). It appears that the methylene group structure is quite similar in propane [ll] , cis-1-butene [ 121 and cyclopentadiene. The two bond lengths for the C=C-Cgroup in cyclopentadiene are very similar to those found in propene 1131 and cis-l-butene. The C2-CJ length irxreases from cyclopentadiene to furar? [I 41 , thiophen [ 15 ] and pyrrole [ 16],, whereas the C3-C4 length decreases in the same order. Tnesc facts support the coxiclusion that the latter compounds are essentially perturbed cis-dienes [5].
Volume 37, number Table 5 Structural
parameters
2
CWMICAL
PHYSICS LETTERS
1.5 Jam&
of related molecules”) Propane 1111
Propene [131
Cis-1 -butene 1121
Cyclepcntadiene
I!uran I141
Thiophnne [ISI
I.501 1.335
1.096
l.OSOb)
1.093
1.099
r(CZ-H2)
1.090
1.cL9:
1.051
1.078
1.078
1.076
r(C3-H3) LCZ-Cl -cs
1.081
1.093 114.5
1.082 102.8
1.077 106.5e)
1.081
1.077 109.8”)
rCCl-HI)
112.4 124.3
UZl-C2-C3
126.1
fC2-C3-C4 LH-Cl-H ~C3-c2-H2 ~C2-c3-H3
106.1
1.362c) 1.361
1.714c’ 1.370
1.465
1.431
1.423
1.37oc) 1.382
1.501 1.336
ric3-C4)
1.505 1.342
Pyrrole 1161
I.526
r(c1 -C2) rtC2-C3)
1976
1.417 0.996d)
109.3
110.6
III.5
107.7
109.3
106.0
112.5
107.4
107.7b) 119.0
105.7 119.0
106.3 !27.1
133.4
128.7
130.8
121.5
119.8
126.0
126.0
123.2
125.5
109.0
105.1
LC’Z-Cl-H
‘) Distances are in A and &es in degrees. b) Assumed. ‘) Heteroatom-C2 distance. d) N-H distance. e) C2-X-C5 angle, X = heteroatom.
References
[I] V. Shomaker and L. Pauling, J. Am. Chem. Sot. 61 (1939) 1769. [2] P.S. O’Sullivan and H.F. xameka, Chem. Phys. Letters 4 (1969) 123. [31 R-C’. Benson and W.H. Flygare, J. Am. Chem. Sot. 92 (1970) 7223. 141 L.H. Scharpen and V.W. Laurie, _I. Chem. Phys. 43 (1965) 2765. I51 F. biomicchioli and G. Del Rc. J. Chem. Sot. B (1S69) 674. 161 C.A. Vera&i, \I. Guidi, hl. Longeri ahd A.h!. Serm, Chem. Phys. Letters 24 (1974) 99. 171 E.R. Coher. and B.N. Taylor, J. Phys. Chem. Ref. Data 2 (1973) 663.
[8l E. Gnllinelln and P. Mirone, Atti Sot. Nat. Mat. Jlodcna 100 (1969) 215;J. Labelled Compounds7 (1971) 183. PI H. hleistcr, Angew. Chem. 69 (19.57) 553. 1101V.A. hlironov, E.V. Sobolev and AX. Elizarova, Doklady Akad. Nnuk SSSR 143 (1962) 1112. [I11 D.R. Lide Jr., J. Chem. Phys. 33 (1968) 1514. (121 S. Kondo, E. Hirofa and Y. hiorino, J. Mol. Spectry. 28 (1968) 471. [I31 D-R. Lide Jr. and D. Christensen, J. Chem. .Phys. 35 (1961) 1374. 1141 B. Bak, D. Christensen, W.B. Dixon, L. Hansen-Nygzard, J. Rastrup-Andersen and %I. Schottlander, J. Mol. Spectry. 9 (1962) 124. [I51 B. Bak, D. Christensen, L. Hansen-Nygaard and J. RnstrupAndersen, J. hIo1. Spectry. 7 (1961) 58. iI61 L. Nygaard, J.T. Nielsen, J. Kirchheiner, G. hlaltesen, J. Rastrup-Ande:sen and G.O. Sorensen, J. Mol. Struct. 3 (1969) 491.
269