C2H2N2S





 






 






 







Nitrogen


Nuclear Quadrupole Coupling Constants


in 1,2,5-Thiadiazole


 








 








 

 





The microwave spectra of 1,2,5-Thiadiazole was first investigated by Dobyns and Pierce in 1963 [1], who determined a substitution molecular structure.  The nitrogen hyperfine structure was only partially resolved (see Table 1).

 








The complete substitution structure was reported in 1978 by Stiefvater [2].  Calculation of the nqcc's was made here on this structure.  These are compared with the experimental data [1] 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 root mean square difference between calculated and 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.  N(2,5) nqcc's in 1,2,5-Thiadiazole (MHz).  Calculation was made on the rs structure of Stiefvater [2].
   









Calc.
Expt. [1]
   






14N Xaa
0.995
0.90(1)


Xbb - 3.058 -
 3.13(6)


Xcc
2.063
2.22(6)


Xab ± 2.244



 







RMS
0.114 (5.5 %)




RSD
0.030 (1.3 %)



 







Xxx
1.992




Xyy
2.063



  Xzz - 4.055



  ETA
0.003




Øz,a
66.0




Øa,bi
77.0




Øz,bi *
11.0



 







 








* The z-axis makes an angle of 11.0o with the external bisector ('bi') of the SNC angle and tilts toward S(1).

 







 
 

Table 2.  1,2,5-Thiadiazole.  Molecular structure parameters, rs [2] (Å and degrees).
 


SN 1.6296

NC 1.3270

CC 1.4167

CH 1.0805

NSN   99.44

SNC 106.51

NCC 113.77

CCH 126.27



 








 








[1] O.L.Stiefvater, Z.Naturforsch. 33a,1518(1978).

[2] O.L.Stiefvater, Z.Naturforsch. 33a,1511(1978).











Sr.V.Dobyns and L.Pierce, J.Am.Chem.Soc. 85,3553(1963): |Xaa| < 1 MHz, Xcc - Xbb = 5.2(3) MHz.

 








 








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

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

 








 








Table of Contents




Molecules/Nitrogen




 








 













125TDZ.html






Last Modified 24 May 2003