CH3CH2-X-CN: X=S,Se






 


















 










Nitrogen


Nuclear Quadrupole Coupling Constants

in Ethyl Thio- and Seleno-cyanate


 








 








The microwave spectrum of ethyl thiocyanate was observed and assigned by Bjørseth and Marstokk [1], and ethyl selenocyanate by Sakaizuma and Itakura [2].  Rotational constants and dipole moments were determined. 

 









For each title molecule, shown below, calculation of the nitrogen nqcc tensor was made on a molecular structures given by MP2/6-311+G(3df,3pd) optimization with empirically corrected approximate equilibrium single CC and triple CN bond lengths.  These calculated nqcc's are given in Tables 1 and 2.  Structure parameters are given in Z-Matrix format in Table 3, rotational constants and dipole moments in Table 4.


 








Ethyl thiocyanate

Ethyl selenocyanate






















Dihedral CCSC = 61.9o


Dihedral CCSeC = 60.6o












In Tables 1 and 2, subscripts a,b,c refer to the principal axes of the inertia tensor; x,y,z to the principal axes of the nqcc tensor.  ETA = (Xxx - Xyy)/Xzz.  Ø (degrees) is the angle between its subscripted parameters.


RSD is the calibration residual standard deviation of the B3PW91/6-311+G(df,pd) model for calculation of the nitrogen efg's/nqcc's.

 









 








 
 
 






Table 1.  Nitrogen nqcc tensor in Ethyl thiocyanate (MHz).  Calculation was made on  molecular structure given by MP2/6-311+G(3df,3pd) optimization, with approximate re single CC and triple CN bond lengths.
 
 









Calc

Expt

 
 






14N Xaa -
0.661





Xbb -
0.603





Xcc
1.264





Xab
-
3.322





Xac -
0.830





Xbc
0.176





 






RSD
0.030 (1.3 %)




 






Xxx
1.008





Xyy
2.987





Xzz -
3.996





ETA
0.495





Øz,CN
0.40













 









 








 
 






Table 2.  Nitrogen nqcc tensor in Ethyl selenocyanate (MHz).  Calculation was made on  molecular structure given by MP2/6-311+G(3df,3pd) optimization, with approximate re single CC and triple CN bond lengths.
 
 









Calc

Expt

 
 






14N Xaa -
0.459





Xbb -
0.924





Xcc
1.383





Xab
-
3.414





Xac -
0.566





Xbc
0.147





 






RSD
0.030 (1.3 %)




 






Xxx
1.223





Xyy
2.905





Xzz -
4.128





ETA
0.408





Øz,CN
0.31













 








 









Table 3.  CH3CH2-X-CN, X=S,Se:  MP2/6-311+G(3df,3pd) optimized structure parameters (Å and degrees).  Approximate re bond lenths are given in parentheses.










Ethyl thiocyanate
Ethyl selenocyanate

           C
           C,1,B1
           H,1,B2,2,A1
           H,1,B3,2,A2,3,D1,0
           H,1,B4,2,A3,4,D2,0
           H,2,B5,1,A4,5,D3,0
           H,2,B6,1,A5,5,D4,0
           X,2,B7,1,A6,5,D5,0
           C,8,B8,2,A7,1,D6,0
           N,9,B9,2,A8,1,D7,0
















 B1=1.51599151     (1.5141)
 B2=1.08763703
 B3=1.08936661
 B4=1.08841553
 B5=1.08767378
 B6=1.08993972
 B7=1.82024887
 B8=1.68386981
 B9=1.17643598     (1.1609)
 A1=110.87852519
 A2=109.65244951
 A3=110.69143711
 A4=112.13954362
 A5=111.66827931
 A6=113.23780586
 A7=98.09485669
 A8=137.76991586
 D1=120.10162914
 D2=119.32171762
 D3=60.38617404
 D4=-177.89600381
 D5=-62.07899607
 D6=61.92291678
 D7=53.80291966
 B1=1.51563583     (1.5138)
 B2=1.0877583
 B3=1.08996879
 B4=1.08848716
 B5=1.08701077
 B6=1.0899813
 B7=1.96003924
 B8=1.83238579
 B9=1.17617212     (1.1607)
 A1=111.05161745
 A2=109.61248305
 A3=110.82449669
 A4=112.42612556
 A5=112.04826818
 A6=113.11508786
 A7=94.96373213
 A8=135.58561198
 D1=120.04935107
 D2=119.28079231
 D3=59.85828092
 D4=-177.62396892
 D5=-61.65721097
 D6=60.55745631
 D7=52.64307017
























 





Table 4. CH3CH2-X-CN, X=S,Se: Rotational Constants (MHz) and Dipole Moments (D).








____CH3CH2-S-CN____ ____CH3CH2-Se-CN____


Calc
Expt [1]
Calc Expt [2]







A 6259
6283.90(2)
3881
3922.92(18)

B 3154
3083.540(9)
2978
2898.00(8)

C 2281
2245.224(9)
1811
1789.82(2)

a|
4.17
3.80(10)
4.21
4.37(10)

b| 1.08
1.13(5)
1.41
0.80(5)

c| 0.33
0.61(4)
0.30
0.50(5)








 








 








[1] A.Bjørseth and K.M.Marstokk, J.Mol.Struct. 11,15(1972).


[2] T.Sakaizuma and T.Itakura, J.Mol.Spectrosc. 163,1(1994).


 









 








Ethylcyanate
HSCN
ClSCN
BrSCN




Propargylthiocyanate Propargylselenocyanate





 









 








Table of Contents




Molecules/Nitrogen




 








 













CH3CH2XCN.html






Last Modified 17 Feb 2014