2-Br-C4H3S




 





 
 
 

Bromine and Sulfur

Nuclear Quadrupole Coupling Constants


in 2-Bromothiophene


 







 
Calculation of the bromine nqcc's in 2-bromothiophene was made on molecular structures obtained by B3PW91/6-31G(2d,2pd) and B3P86/6-31G(3d,3p) optimization.  These are compared with the experimental nqcc's [1] in Table 1.  33S nqcc's calculated on the B3PW91/6-31G(2d,2pd) ropt structure are given in Table 2.  Structure parameters are given in Table 3, atomic coordinates in Table 4, and rotational constants in Table 5.
 
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 (percent of the average of the magnitudes of the experimental nqcc's).  RSD is the residual standard deviation of calibration of the model for calculation of the nqcc's.
 
 
   






Table 1.  79Br nqcc's in 2-Bromothiophene-32S (MHz).
 
Calculation was made on
the [a] B3PW91/6-31G(2d,2pd) ropt structure, and
the [b] B3P86/6-31G(3d,3p) ropt structure.
   







Calc. [a]
Calc. [b]
Expt. [1]
   





Xaa 589.34 586.81 592.7(15)
Xbb - 294.93 293.69 - 295.3(6)
Xcc - 294.41 293.12 - 297.4(16)
|Xab|   85.20   84.45   80(9)
 
RMS 2.6 (0.66 %) 4.3 (1.1 %)
RSD 1.58 (0.39 %) 1.58 (0.39 %)
 
Xxx - 303.06 - 301.72 - 302.4(27)
Xyy - 294.41 - 293.12 - 297.4(16)
Xzz 597.48 594.84 599.8(22)
ETA - 0.0145 - 0.0145 - 0.008(5)
Øz,a 5.45 5.43 5.11(56)
Øa,CBr 6.40 6.35
Øz,CBr 0.95 0.92
 
 
 
   






Table 2.  33S nqcc's in 3-Bromothiophene-79Br (MHz).  Calculation was made on the B3PW91/6-31G(2d,2pd) ropt structure.
Calc. [a] B3LYP/6-311G(3df,3p) Model.
Calc. [b] B3LYP/TZV+(3df,3p) Model.
   







Calc. [a]
Calc. [b]
Expt.
   





Xaa - 28.12 - 28.21
Xbb   3.95   4.07
Xcc 24.17 24.14
|Xab|   7.74   7.77
 
RSD 0.39 (1.7 %) 0.35 (1.5 %)
 
Xxx   5.72   5.84
Xyy 24.17 24.14
Xzz - 29.89 - 29.98
ETA 0.617 0.610
Øx,a 77.13 77.15
Øa,bi 81.44 81.44
Øx,bi*   4.32   4.29
 
 
* The x-axis makes an angle of 4.32o / 4.29o with the external bisector ( 'bi' ) of the CSC angle and tilts toward C(2).
 
 
Table 3.  2-Bromothiophene and Thiophene.  Structure parameters (Å and degrees).
 
B3P86 B3PW91 B3PW91
X = Br X = Br X = H
S(1)C(2) 1.7155 1.7262 1.7197
C(2)C(3) 1.3648 1.3648 1.3660
C(3)C(4) 1.4201 1.4227 1.4229
C(4)C(5) 1.3657 1.3652 1.3660
C(5)S(1) 1.7133 1.7221 1.7197
C(2)X(2) 1.8553 1.8590 1.0787
C(3)H(3) 1.0812 1.0804 1.0816
C(4)H(4) 1.0825 1.0814 1.0816
C(5)H(5) 1.0800 1.0789 1.0787
C(5)S(1)C(2)   91.36   92.26   91.95
S(1)C(2)C(3) 112.43 112.18 111.42
C(2)C(3)C(4) 111.62 111.89 112.60
C(3)C(4)C(5) 112.83 113.00 112.60
C(4)C(5)S(1) 111.76 111.66 111.42
S(1)C(2)X(2) 120.32 120.42 119.93
S(1)C(5)H(5) 119.81 119.64 119.93
C(3)C(4)H(4) 123.89 123.58 124.04
C(4)C(3)H(3) 125.01 124.86 124.04
 
 
Table 4.  2-Bromothiophene, normal species.  Atomic coordinates.  B3PW91/6-31G(2d,2pd) ropt structure.
  a (Å)   b (Å)
S(1) 1.3017 - 1.1555
C(2) 0.2670 0.2263
C(3) 0.9697 1.3963
C(4) 2.3745 1.1714
C(5) 2.7025 - 0.1538
Br(2) - 1.5804 0.0190
H(3) 0.5000 2.3693
H(4) 3.1075 1.9664
H(5) 3.6814 - 0.6062

Table 5.  2-Bromothiophene, normal species.  Rotational Constants (MHz).
   
[a] B3PW91/6-31G(2d,2pd) opt structure.
[b] B3P86/6-31G(3d,3p) opt structure.
 
Calc [a] Calc [b]    Expt. [1]
A 5410.9 5437.9 5403.432(111)
B 1142.4 1150.1 1139.0689(10)
C   943.2   949.3   940.5142(18)


  







 
[1] P.J.Mjöberg, W.M.Ralowski, and S.O.Ljunggren, Z.Naturforsch. 30a,541 (1975).
 

 







Thiophene 2-Bromofurane 2-Chlorothiophene
Thiazole 3-Bromofurane 3-Chlorothiophene
3-Bromothiophene
 

 








Table of Contents



Molecules/Bromine
Molecules/Sulfur
 

 













2BrThioph.html






Last Modified 23 May 2006