3-Br-C4H3S




 





 

Bromine and Sulfur

Nuclear Quadrupole Coupling Constants


in 3-Bromothiophene


 







 
Calculation of the bromine nqcc's in 3-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 Tables 1 and 2.  Calculated 33S nqcc's are given in Table 3.  Structure parameters are given in Table 4, atomic coordinates in Table 5, and rotational constants in Table 6.
 
In Tables 1 - 3, 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 average absolute experimental nqcc).  RSD is the residual standard deviation of calibration of the model for calculation of the nqcc's.
 
 
   






Table 1.  79Br nqcc's in 3-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 573.18 571.85 571.60(1)
Xbb - 293.74 - 293.39 - 292.98
Xcc - 279.44 - 278.46 - 278.62(2)
|Xab|   54.12   53.54   54.1(6)
 
RMS 1.12 (0.29 %) 0.29 (0.07 %)
RSD 1.58 (0.39 %) 1.58 (0.39 %)
 
Xxx - 297.11 - 296.69 - 296.36(10)
Xyy - 279.44 - 278.46 - 278.62(2)
Xzz 576.55 575.15 574.97(9)
ETA - 0.0306 - 0.0317
Øz,a 3.56 3.53 3.57(4)
Øa,CBr 3.84 3.84
Øz,CBr 0.28 0.31
 
 
 
Because B3PW91/6-31G(2d,2pd) optimization gives structures on which good agreement is obtained between calculated and experimental 33S nqcc's in thiophene and thiazole, and because  B3P86/6-31G(3d,3p) works for bromine in bromine substituted benzene, furane, and pyridine; calculation was made on a structure consisting of the B3PW91/6-31G(2d,2pd) ring with the B3P86/6-31G(3d,3p) CBr bond length.  The results are given below in Table 2 for both 79Br and 81Br, and in Table 3 for 33S.
 
 
   






Table 2.  Bromine nqcc's in 3-Bromothiophene-32S (MHz).  Calculation was made on the B3PW91/6-31G(2d,2pd) ring structure with the B3P86/6-31G(3d,3p) optimized CBr bond length.
   









Calc.
Expt. [1]
   





79Br Xaa 571.21 571.60(1)
Xbb - 293.02 - 292.98
Xcc - 278.20 - 278.62(2)
|Xab|   54.04   54.1(6)
 
RMS 0.33 (0.09 %)
RSD 1.58 (0.39 %)
 
Xxx - 296.38 - 296.36(10)
Xyy - 278.20 - 278.62(2)
Xzz 574.58 574.97(9)
ETA - 0.0316
Øz,a 3.56 3.57(4)
Øa,CBr 3.85
Øz,CBr 0.28
   
81Br Xaa 477.26 477.57(1)
Xbb - 244.84 - 244.81
Xcc - 232.42 - 232.76
|Xab|   44.89
 
RMS 0.26 (0.08 %)
RSD 1.38 (0.40 %)
 
   
 
   






Table 3.  33S nqcc's in 3-Bromothiophene-79Br (MHz).  Calculation was made on the B3PW91/6-31G(2d,2pd) ring structure with the B3P86/6-31G(3d,3p) optimized CBr bond length.
Calc. [a] B3LYP/6-311G(3df,3p) Model.
Calc. [b] B3LYP/TZV+(3df,3p) Model.
   







Calc. [a]
Calc. [b]
Expt.
   





Xaa - 2.60 - 2.58
Xbb - 19.48 - 19.54
Xcc 22.08 22.12
|Xab| 15.01 15.09
 
RSD 0.39 (1.7 %) 0.35 (1.5 %)
 
Xxx   6.18   6.25
Xyy 22.08 22.12
Xzz - 28.26 28.37
ETA 0.563 0.560
Øx,a 30.32 30.34
Øa,bi 29.25 29.25
Øx,bi*   1.08   1.07
 
 
* The x-axis makes an angle of 1.08o / 1.07o with the external bisector ( 'bi' ) of the CSC angle and tilts toward C(2).
 
 
Table 4.  3-Bromothiophene and Thiophene.  Structure parameters (Å and degrees).
 
B3P86 B3PW91 B3PW91
X = Br X = Br X = H
S(1)C(2) 1.7093 1.7190 1.7197
C(2)C(3) 1.3649 1.3645 1.3660
C(3)C(4) 1.4190 1.4219 1.4229
C(4)C(5) 1.3644 1.3640 1.3660
C(5)S(1) 1.7108 1.7205 1.7197
C(2)H(2) 1.0782 1.0773 1.0787
C(3)X(3) 1.8662 1.8707 1.0816
C(4)H(4) 1.0810 1.0799 1.0816
C(5)H(5) 1.0798 1.0784 1.0787
C(5)S(1)C(2)   92.34   92.16   91.95
S(1)C(2)C(3) 110.67 110.51 111.42
C(2)C(3)C(4) 113.60 113.91 112.60
C(3)C(4)C(5) 111.59 111.62 112.60
C(4)C(5)S(1) 111.80 111.79 111.42
S(1)C(2)H(2) 120.89 121.02 119.93
S(1)C(5)H(5) 120.04 119.93 119.93
C(3)C(4)H(4) 124.13 123.75 124.04
C(4)C(3)X(3) 122.84 122.76 124.04
 
 
Table 5.  3-Bromothiophene, normal species.  Atomic coordinates.  B3PW91/6-31G(2d,2pd) ring structure with the B3P86/6-31G(3d,3p) optimized CBr bond length.
  a (Å)   b (Å)
S(1) 2.6055 - 0.5185
C(2) 0.9587 - 1.0117
C(3) 0.1341 0.0754
C(4) 0.8215 1.3201
C(5) 2.1745 1.1471
H(2) 0.6918 - 2.0554
Br(3) - 1.7279 - 0.0499
H(4) 0.3254 2.2793
H(5) 2.9445 1.9021

Table 6.  3-Bromothiophene, normal species.  Rotational Constants (MHz).
   
[a] B3PW91/6-31G(2d,2pd) opt structure.
[b] B3P86/6-31G(3d,3p) opt structure.
[c] B3PW91/6-31G(2d,2pd) ring structure with the B3P86/6-31G(3d,3p) optimized CBr bond length.
 
Calc [a] Calc [b] Calc [c]    Expt. [1]
A 7119.2 7164.8 7119.5 7102.6529(42)
B   937.1   940.5   939.2   933.1055(5)
C   828.1   831.4   829.8   824.6167(5)


  







 
[1] D.Hübner, E.Fliege, and D.H.Sutter, Z.Naturforsch. 38a,1238(1983).
 
Y.Sasada, M.Saitoh, and S.Tobita, J.Mol.Spectrosc. 92,363(1982).  In the normal species, Xaa, Xbb, Xcc, and |Xab| respectively for 79Br are 568.0(11), -284.4(23), -283.6(25), and 47(29) MHz; and for 81Br, 485.4(11), -243.4(24), -242.0(26), and 33(28) MHz.
 

 







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

 








Table of Contents



Molecules/Bromine
Molecules/Sulfur
 

 













3BrThioph.html






Last Modified 7 Oct 2004