C3N2H3Br


















 





 





Bromine and Nitrogen

Nuclear Quadrupole Coupling Constants


in 4-Bromopyrazole


 








 








Bromine and nitrogen nuclear quadrupole coiupling constants in 4-bromopyrazole were determined by Cooper et al. [1].

 








Calculation of the Br and 14N nqcc's was made here on molecular structures given by B3LYP/cc-pVTZ and B3PW91/6-31G(2d,2pd) optimization.  Bromine nqcc's are compared with the experimental values in Table 1, nitrogen nqcc's in Tables 2 and 3.  Structure parameters are given in Table 4, rotational constants in Table 5.











In Tables 1 - 3, 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.  RMS is the root mean square difference between calculated and experimental diagonal nqcc's (percentage of the average of the magnitudes of the experimental nqcc's).  RSD is the calibration residual standard deviation of the B1LYP/TZV(3df,3p) model for calculation of bromine efg's/nqcc's; and in Tables 2 and 3, of the B3PW91/6-311+G(df,pd) model for nitrogen.





















   








Table 1.  Bromine nqcc's in 4-Bromopyrazole (MHz).  Calculation was made on (1) B3LYP/cc-pVTZ and (2) B3PW91/6-31G(2d,2pd) optimized molecular structures.
   











Calc (1)
Calc (2)
Expt [1]
   








79Br Xaa
602.25
590.46
590.178(13)


Xbb - cc
 + 2.34
 + 0.27
  - 1.977(10)


Xbb -
 299.95
 -
 295.09
 -
 296.077 *


Xcc -
 302.30
 -
 295.36
 -
 294.101 *


|Xab|
    6.12
    5.34














RMS
8.72 (2.2 %)
0.94 (0.24 %)




RSD
1.58 (0.39 %)
1.58 (0.39 %)



 









Xxx -
 300.00
 -
 295.12




Xyy -
 302.30
 -
 295.36




Xzz
602.29
590.49




ETA
0.0038
0.0004




Øz,a
0.39
0.35




Øa,CBr
0.29
0.28




Øz,CBr
0.10
0.07













81Br Xaa
503.16
493.31
493.009(10)


Xbb - cc
 + 1.96
 + 0.23
 - 1.666(10)


Xbb -
 250.60
 -
 246.54
 -
 247.338 *


Xcc -
 252.56
 -
 246.77
 -
 245.671 *


|Xab|
    5.11
    4.45
    7.3(21)












RMS
7.33 (2.2 %)
0.80 (0.24 %)




RSD
1.38 (0.40 %)
1.38 (0.40 %)














 








* Calculated here from experimental Xaa and Xbb - cc

 








 








   








Table 2.  Nitrogen nqcc's in 4-79Br-Pyrazole (MHz).  Calculation was made on (1) B3LYP/cc-pVTZ and (2) B3PW91/6-31G(2d,2pd) optimized molecular structures.  N(1) is pyrrolic, N(2) pyridinic.
   











Calc (1)
Calc (2)
Expt [1]
   








14N(1) Xaa
0.846
0.830
0.786(17)


Xbb - cc
5.310
5.034
5.377(10)


Xbb
2.232
2.200
2.295 *


Xcc -
 3.078
 -
 3.030
 -
 3.082 *


|Xab|
0.196
0.193














RMS
0.051 (2.5 %)
0.067 (3.3 %)




RSD
0.030 (1.3 %)
0.030 (1.3 %)













14N(2) Xaa -
 3.623
 -
 3.609
 -
 3.707(15)


Xbb - cc
2.030
1.980
2.058(10)


Xbb
2.826
2.799
2.882 *


Xcc
0.796
0.810
0.825 *


|Xab|
2.395
2.380




 








RMS
0.061 (2.5 %)
0.075 (3.0 %)




RSD
0.030 (1.3 %)
0.030 (1.3 %)



 









 








* Calculated here from experimental Xaa and Xbb - cc

 








 








   








Table 3.  Nitrogen nqcc's in 4-81Br-Pyrazole (MHz).  Calculation was made on (1) B3LYP/cc-pVTZ and (2) B3PW91/6-31G(2d,2pd) optimized molecular structures.  N(1) is pyrrolic, N(2) pyridinic.
   











Calc (1)
Calc (2)
Expt.
   








14N(1) Xaa
0.846
0.830
0.847(18)


Xbb - cc
5.310
5.230
5.3736(96)


Xbb
2.232
2.200
2.263 *


Xcc -
 3.078
 -
 3.030
 -
 3.110 *


|Xab|
0.196
0.193




 








RMS
0.026 (1.3 %)
0.060 (2.9 %)




RSD
0.030 (1.3 %)
0.030 (1.3 %)




 







14N(2) Xaa -
 3.623
 -
 3.609
 -
 3.651(14)


Xbb - cc
2.030
1.988
2.0764(96)


Xbb
2.826
2.799
2.864 *


Xcc
0.796
0.810
0.787 *


|Xab|
2.395
2.380




 








RMS
0.028 (1.1 %)
0.047 (1.9 %)




RSD
0.030 (1.3 %)
0.030 (1.3 %)



   








 








* Calculated here from experimental Xaa and Xbb - cc

 








 


Table 4.  4-Bromopyrazole: Optimized structure parameters ropt(1) = B3LYP/cc-pVTZ, ropt(2) = B3PW91/6-31G(2d,2pd) (Å and degrees).
 



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





     ropt(1)      ropt(2)
 



 B1=1.3437089
 B2=1.32639916
 B3=1.40773212
 B4=1.35307924
 B5=1.00463059
 B6=1.07640066
 B7=1.07494082
 B8=1.88381066
 A1=104.75860872
 A2=110.88516509
 A3=113.33277244
 A4=119.06462344
 A5=120.6910809
 A6=123.0155239
 A7=127.58361294
 D1=0.
 D2=0.
 D3=180.
 D4=180.
 D5=180.
 D6=180.
  B1=1.33896722
 B2=1.32775194
 B3=1.40803411
 B4=1.35064715
 B5=1.00465796
 B6=1.07827788
 B7=1.07690251
 B8=1.85670796
 A1=104.56109668
 A2=111.04529142
 A3=113.69641406
 A4=118.9201164
 A5=120.63029961
 A6=123.00496837
 A7=127.76262668
 D1=0.
 D2=0.
 D3=180.
 D4=180.
 D5=180.
 D6=180.


 








 








 



Table 5.  4-Bromopyrazole, 79Br species: Rotational Constants (MHz), ropt(1) and ropt(2) (see Table 4).
 





 ropt(1) ropt(2)    Expt [1]






A
  9555.
  9578.
 9481.0546(10)

B
  1258.
  1277.
 1268.29655(20)

C
  1112.
  1126.
 1118.43383(18)


 








 








[1]  G.A.Cooper, C.Medcraft, J.D..Littlefair, T.J.Penfold, and N.Walker, J.Chem.Phys. 147,214303(2017).

 








G.A.Cooper, C.Medcraft, A.Legon, N.Walker, Abstract FB04, 72nd ISMS, Champaign-Urbana, Illinois, 2017.

 








 








Bromobenzene
 3-Bromofurane
2-Bromothiophene
 Pyrazole

4-Iodopyrazole
















 








Table of Contents




Molecules/Bromine





Molecules/Nitrogen




 








 













4Brpyrazole.html






Last Modified 3 Dec 2017