HCCCHCHCN


 







 

Nitrogen


Nuclear Quadrupole Coupling Constants


in t-Cyanovinylacetylene


 







 
 
Calculation of the nitrogen nqcc's in t-cyanovinylacetylene was made on a molecular structure derived ab initio as discussed below.  These are compared with the experimental nqcc's of Thornwirth et al. [1] in Tables 1 and 2.  Structure parameters are given in Table 3, rotational constants in Table 4.  A link is provided below to the Gaussian input file in Z-Matrix format.
 
In Tables 1 and 2, subscripts a,b,c refer to the principal axes of the inertia tensor, subscripts x,y,z to the principal axes of the nqcc tensor.  The nqcc y-axis is chosen coincident with the inertia c-axis, these are perpendicular to the plane of the molecule.  Ø (degrees) is the angle between its subscripted parameters. ETA = (Xxx - Xyy)/Xzz.
 
RMS is the root mean square difference between calculated and experimental nqcc's (percentage of average experimental nqcc).  RSD is the residual stand deviation of calibration of the B3PW91/6-311+G(df,pd) model for calculation of the nqcc's.
 
 
   







Table 1. Nitrogen nqcc's in t-Cyanovinylacetylene (MHz).  Calculation was made on the structure given below in Table 3.
   










Calc.
Expt. [1]
   






14N Xaa - 3.924 - 3.90(2)
Xbb 1.851 1.82(3)
Xcc 2.074 2.08
|Xab| 1.536
 
RMS 0.023 (0.89 %)
RSD 0.030 (1.3 %)
 
Xxx 2.234 2.21 *
Xyy 2.074 2.08
Xzz - 4.308 - 4.29
ETA - 0.037 - 0.030
Øz,a 14.00 14.12
Øa,CN 13.48 13.48
Øz,CN   0.52   0.64
 
   
* Calculated here from the diagonal experimental nqcc's and the calculated off-diagonal nqcc.
 
 
   







Table 2. Nitrogen nqcc's in t-Cyanovinylacetylene (MHz).  Calculation was made on the structure given below in Table 3, but with linear HCCC and CCN.
   










Calc.
Expt. [1]
   






14N Xaa - 3.919 - 3.90(2)
Xbb 1.846 1.82(3)
Xcc 2.073 2.08
|Xab| 1.543
 
RMS 0.019 (0.74 %)
RSD 0.030 (1.3 %)
 
Xxx 2.234 2.21 *
Xyy 2.073 2.08
Xzz - 4.306 - 4.29
ETA - 0.037 - 0.030
Øz,a 14.08 14.17
Øa,CN 13.90 13.90
Øz,CN   0.18   0.27
 
 
* Calculated here from the diagonal experimental nqcc's and the calculated off-diagonal nqcc.
 
 
Molecular Structure
 
The molecular structure was optimized at the MP2/6-311G(d,p) level of theory assuming Cs symmetry.  The optimized CC single and CC double bond lengths were then corrected using the equation obtained from linear regression analysis of the data given in Table IX of Ref.[3].  The CH bond lengths were corrected using r = 1.001 ropt, where ropt is obtained by MP2/6-31G(d,p) optimization [4].  The CC triple bond was determined by B3LYP/6-31+G(df,3pd) optimization and corrected as described in summary/acetylenes.  Interatomic angles used in the calculation are those given by MP2/6-311G(d,p) optimization.  Structure parameters thus obtained are shown in Table 3.
 
Atomic Numbering
 
HC(5)C(4) H
C(3) = C(2)
H C(1)N
 
 
Table 3.  Molecular structure parameters (Å and degrees).
 
C(1)N 1.158
C(2)C(1) 1.427
C(3)C(2) 1.347
C(2)H 1.083
C(3)H 1.085
C(3)C(4) 1.421
C(4)C(5) 1.206
C(5)H 1.062
C(2)C(1)N 179.23
C(3)C(2)C(1) 121.71
C(3)C(2)H 120.82
C(2)C(3)H 119.55
C(2)C(3)C(4) 122.57
C(3)C(4)C(5) 178.59
C(4)C(5)H 179.58

 
Gaussian Input:  Z-Matrix
 
 
Table 4.  Rotational Constants (MHz).
 
Calc. ropt    Expt. [1,2]
A 46352 46199(18)
B   1473.5   1472.1538(2)
C   1428.1   1426.2484(2)
 
 
[1] S.Thorwirth, M.C.McCarthy, J.B.Dudek, and P.Thaddeus, J.Mol. Spectrosc. 225,93(2004).
[2] J.August, H.W.Kroto, D.McNaughton, K.Phillips, and D.R.M.Walton, J.Mol.Spectrosc. 130,424(1988).
[3] J.Demaison, J.Cosléou, R.Bocquet, and A.G.Lesarri, J.Mol.Spectrosc. 167,400(1994).
[4] J.Demaison and G.Wlodarczak, Structural Chem. 5,57(1994).

 








 







H2C=CHCN c-Crotononitrile Vinylcyanoacetylene
HCCCN t-Crotononitrile Methacrylonitrile
 

 








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Molecules/Nitrogen
 

 













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Last Modified 25 June 2004