HCC-CH2CH2Br



































 









Bromine


Nuclear Quadrupole Coupling Constants


in trans Bromobutyne


 








 

 





Complete nqcc tensors for both 79Br and 81Br in trans bromobutyne were determined by Keske et al. [1].

 








Calculation of the nqcc tensors was made here on molecular structures derived by MP2/aug-cc-pVTZ optimization (ropt), and on this same structure but with corrected CBr, C-C, and triple CC bond lengths (~ re, see here).  These calculated nqcc's are compared with the experimental values in Tables 1 and 2.  Structure parameters are given in Table 3, rotational constants in Table 4.

 








In Tables 1 and 2, 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 for the B1LYP/TZV(3df,3p) model for calculation of the efg's/nqcc's.

 








  








   







Table 1.  79Br nqcc's in trans HCC-CH2CH2Br (MHz).  Calculation was made on (1) the ropt structure, and (2) the ~ re structure.

 









Calc (1)
Calc (2)
Expt. [1]
   







Xaa
471.95
473.08
469.054(22)

Xbb -
 193.36 -
 194.08 -
 190.358(28) *

Xcc - 278.59 - 279.00 - 278.700(28) *

Xab **
242.96
243.77 -
 246.173(65)

 







RMS
2.41 (0.77 %)
3.17 (1.01 %)



RSD
1.58 (0.39 %)
1.58 (0.39 %)



 







Xxx - 278.59  - 279.00 - 278.70

Xyy - 272.64 - 273.66 - 272.12

Xzz
551.24
552.66
550.82

ETA -
 0.0108 -
 0.0097



Øz,a
18.07
18.08
18.373(4)

Øa,CBr







Øz,CBr







 







   








* Calculated here from experimental Xaa = 469.054(22) and (Xbb -  Xcc) = 88.337(52) MHz using Kisiel's QDIAG.f.  See http://info.ifpan.edu.pl/~kisiel/prospe.htm

** Difference in algebraic sign between calc and expt is not significant.

 


















   







Table 2.  81Br nqcc's in trans HCC-CH2CH2Br (MHz).  Calculation was made on (1) the ropt structure, and (2) the ~ re structure.

 









Calc (1)
Calc (2)
Expt. [1]
   







Xaa
394.32
395.26
391.884(73)

Xbb -
 161.56 -
 162.16 -
 159.065(52) *

Xcc - 232.76 - 233.10 - 232.819(52) *

Xab **
202.97
203.64 -
 205.693(96)

 







RMS
2.01 (0.77 %)
2.65 (1.01 %)



RSD
1.38 (0.40 %)
1.38 (0.40 %)



 








 








* Calculated here from experimental Xaa = 391.884(73) and (Xbb -  Xcc) = 71.754(74) MHz using Kisiel's QDIAG.f.  See http://info.ifpan.edu.pl/~kisiel/prospe.htm

** Difference in algebraic sign between calc and expt is not significant.

 












Table 3.  trans HCC-CH2CH2Br.  Molecular structure parameters, ropt = MP2/aug-cc-pVTZ, approximate equilibrium bond lengths (~ re) are given in parentheses (Å and degrees).
 



 Br
 C,1,B1
 C,2,B2,1,A1
 H,2,B3,1,A2,3,D1,0
 H,2,B4,1,A3,3,D2,0
 H,3,B5,2,A4,1,D3,0
 H,3,B6,2,A5,1,D4,0
 C,3,B7,2,A6,1,D5,0
 C,8,B8,3,A7,1,D6,0
 H,9,B9,8,A8,1,D7,0






 B1=1.93086023        (1.9390)
 B2=1.52174203        (1.5152)
 B3=1.08562057
 B4=1.08562057
 B5=1.09061888
 B6=1.09061888
 B7=1.45910656         (1.4535)
 B8=1.21582345         (1.2048)
 B9=1.06209095
 A1=110.24988027
 A2=106.84484469
 A3=106.84484469
 A4=109.56435642
 A5=109.56435642
 A6=109.84155446
 A7=177.56931473
 A8=179.0079643
 D1=-121.29635957
 D2=121.29635957
 D3=-58.75388724
 D4=58.75388724
 D5=180.
 D6=0.
 D7=180.

 




 








 













Table 4.  trans HCC-CH2CH2Br.  Rotational constants (MHz).  79Br species.
 



 
  ropt  ~ re    Expt. [1]






A 26258.  26422. 26200.0737(13)

B   1043.
    1045.
   1032.48560(15)

C   1016.
    1018.
   1005.86478(16)


 








 








[1] J.C.Keske, F.S.Rees, R.D.Suenram, and B.H.Pate, PCCP 5,1599(2003).

 








 








gauche-HCC-CH2CH2Br HCC-CH2Br



 








 








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Molecules/Bromine




 








 













HCCCH2CH2Br_trans.html






Last Modified 26 Dec 2016