




















H_{2}CCHCCCN

























Nitrogen



Nuclear
Quadrupole Coupling Constants 



in Vinylcyanoacetylene 

































Calculation of the nitrogen
nqcc's in vinylcyanoacetylene 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 ZMatrix
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 yaxis is chosen coincident with the inertia caxis, these
are perpendicular to the plane of the molecule. Ø (degrees)
is the angle between its subscripted parameters. ETA = (X_{xx}
 X_{yy})/X_{zz}. 












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 B3PW91/6311+G(df,pd) model for calculation of
the nqcc's. 































Table 1. Nitrogen
nqcc's in vinylcyanoacetylene (MHz). Calculation was
made on the structure given below in Table 3. 













Calc. 

Expt. [1] 










^{14}N 
X_{aa} 
 
4.152 
 
4.12(2) 



X_{bb} 

2.053 

1.97(3) 



X_{cc} 

2.099 

2.15 



X_{ab}_{} 

0.787 













RMS 

0.06 (2.2 %) 




RSD 

0.030 (1.3 %) 












X_{xx} 

2.152 

2.07 * 



X_{yy} 

2.099 

2.15 



X_{zz} 
 
4.250 
 
4.22 



ETA 
 
0.012 

0.019 



Ø_{z,a} 

7.11 

7.24 



Ø_{a,CN} 

7.11 

7.11 



Ø_{z,CN} 

0.00 

0.13 






















* Calculated here from the diagonal experimental nqcc's and
the calculated offdiagonal nqcc. 































Table 2. Nitrogen
nqcc's in vinylcyanoacetylene (MHz). Calculation was
made on the structure given below in Table 3, but with linear CCCN. 













Calc. 

Expt. [1] 










^{14}N 
X_{aa} 
 
4.166 
 
4.12(2) 



X_{bb} 

2.068 

1.97(3) 



X_{cc} 

2.099 

2.15 



X_{ab} 

1.543 













RMS 

0.07 (2.5 %) 




RSD 

0.030 (1.3 %) 

































Molecular Structure













The molecular structure was optimized
at the MP2/6311G(d,p) level of theory assuming C_{s} 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 r_{opt}, where r_{opt} is obtained
by MP2/631G(d,p) optimization [4]. The CC triple bond was determined
by B3LYP/631+G(df,3pd) optimization and corrected as described in summary/acetylenes. Interatomic angles used
in the calculation are those given by MP2/6311G(d,p) optimization. Structure
parameters thus obtained are shown in Table 3. 












Atomic Numbering 




















H(2) 



H(1) 



C(5) 
= 
C(4) 



H(3) 



C(3)C(2)C(1)N 

















Table 3. Molecular structure
parameters (Å and degrees). 




NC(1) 
1.161 

C(1)C(2) 
1.373 

C(2)C(3) 
1.211 

C(3)C(4) 
1.423 
ZMatrix 
C(4)H(1) 
1.085 

C(4)C(5) 
1.340 

C(5)H(2) 
1.081 

C(5)H(3) 
1.082 

NC(1)C(2) 
180.00 

C(1)C(2)C(3) 
179.20 

C(2)C(3)C(4) 
178.29 

C(3)C(4)C(5) 
122.93 

C(5)C(4)H(1) 
120.45 

C(4)C(5)H(2) 
120.44 

C(4)C(5)H(3) 
121.31 






























Table 4. Rotational Constants
(MHz). 






Calc. r_{opt} 
Expt. [1,2] 





A 
40107 
39922(5) 

B 
1374.7 
1376.63351(9) 

C 
1329.2 
1329.74693(8) 























[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). 













































Table of Contents 





Molecules/Nitrogen 






























H2CCHCCCN.html 






Last
Modified 19 March 2004 









