C2H2N2S












































Nitrogen


Nuclear Quadrupole Coupling Constants


in 1,3,4-Thiadiazole


 








 








 

 





Calculation of the nitrogen nqcc's in 1,3,4-Thiadiazole was made on the substitution molecular structure of Stiefvater [1].  These are compared with the experimental nqcc's [2] in Table 1.  Structure parameters are given in Table 2.

 








In Table 1, subscripts a,b,c refer to the principal axes of the inertia tensor; 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 molecular plane.  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 (percent of the average magnitude of the experimental nqcc's).  RSD is the calibration residual standard deviation of the B3PW91/6-311+G(df,pd) model for calculation of nitrogen efg's/nqcc's.

 








 








   






Table 1.  Nitrogen nqcc's in 1,3,4-Thiadiazole (MHz).  Calculation was made on the rs structure of Stiefvater [1].
   









Calc.
Expt. [2]
   






14N Xaa - 3.618 - 3.72(2)


Xbb
1.596
1.61(5)


Xcc
2.022
2.11(5)


Xab ± 2.737



 







RMS
0.078 (3.1 %)




RSD
0.030 (1.3 %)



 







Xxx
2.769




Xyy
2.022



  Xzz - 4.791



  ETA - 0.156




Øz,a
23.19




Øa,bi
33.92




Øz,bi *
10.72



 







 








* The z-axis makes an angle of 10.72o with the external bisector ('bi') of the CNN angle and tilts toward the adjacent N.

 







 
 

Table 2.  1,3,4-Thiadiazole.  Molecular structure parameters, rs [1] (Å and degrees).
 


SC 1.7200(3)

CN 1.3031(5)

NN 1.3711(5)

CH 1.0771(4)

CSC   86.38(2)

SCN 114.64(3)

CNN 112.17(1)

SCH 122.49(2)



 








 








[1] O.L.Stiefvater, Z.Naturforsch. 44a,29(1989).

[2] See ... L.Nygaard, E.Asmussen, F.H.Høg, R.C.Maheshwari, C.H.Nielsen, I.B.Petersen, J.Rastrup-Andersen, and G.O.Sørensen, J.Mol.Struct. 8,225(1971).

 








B.Bak, L.Nygaard, E.J.Pedersen, and J.Rastrup-Andersen, J.Mol.Spectrosc. 19,283(1966); rs structure.

 








 








Thiazole 1,3,4-Oxadiazole 1,2,5-Oxadiazole

1,2,3-Thiadiazole 1,2,4-Thiadiazole 1,2,5-Thiadiazole

 








 








Table of Contents




Molecules/Nitrogen




 








 













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Last Modified 23 June 2004