(CH3)2-CH-CH2Br





 





 





 





 





Bromine


Nuclear Quadrupole Coupling Constants


in gauche Isobutyl Bromide


 








 








 








Calculation of the iodine nqcc tensor in gauche isobutyl bromide was made on a molecular structure obtained by MP2/6-311+G(2d,p) optimization, and on this same structure but with empirically corrected C-C, CH (approximate re), and CBr (see 2-bromoethanol).  These calculated nqcc's are compared with the experimental values of Niide and Ohkoshi [1] 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, subscripts x,y,z to the principal axes of the nqcc tensor.  Øz,CBr (degrees) is the angle the z-principal axis makes with the CBr bond axis.  ETA = (Xxx - Xyy)/Xzz.

RMS is the root mean square difference between calculated and experimental diagonal nqcc's (percent of the average of the magnitudes of the experimental nqcc's).  RSD is the residual standard deviation of calibration of the B1LYP/TZV(3df,3p) model for calculation of the nqcc's.


 








 








   








Table 1.  79Br nqcc's in g-(CH3)2-CH-CH2Br (MHz).

 







Calculation was made on the following structures:

ropt (1) = MP2/6-311+G(2d,p) optimization, and

ropt (2) = MP2/6-311+G(2d,p) optimization with empirically corrected C-C, CH, and CBr bond lengths.
   










Calc. (1)

Calc. (2)
Expt. [1]
   








Xaa
399.13
396.42
380.0(22)

Xbb -
165.90 -
164.52 -
144.8(41)

Xcc -
233.22 -
231.90 -
235.2(46)

|Xab|
270.49 *

270.03 *

282.5(17)

|Xac|
158.97
158.64



|Xbc|
  69.06

  69.21




 







RMS
16.5 (6.5 %)
14.9 (5.9 %)



RSD
1.58 (0.39 %)
1.58 (0.39 %)



 







Xxx -
268.19 -
266.96



Xyy -
278.06 -
276.91



Xzz
546.25
543.87



ETA
0.0181
0.0183



Øz,CBr
0.55

0.56




 








 








* The algebraic sign of the product XabXacXbc is positive.

 








 









   








Table 2.  81Br nqcc's in g-(CH3)2-CH-CH2Br (MHz).

 







Calculation was made on the following structures:

ropt (1) = MP2/6-311+G(2d,p) optimization, and

ropt (2) = MP2/6-311+G(2d,p) optimization with empirically corrected C-C, CH, and CBr bond lengths.
   










Calc. (1)

Calc. (2)
Expt. [1]
   








Xaa
333.52
331.26
302.5(20)

Xbb -
138.60 -
137.45 -
110.4(33)

Xcc -
194.92 -
193.81 -
192.1(38)

|Xab|
226.01 *

225.62 *

236.4(20)

|Xac|
132.69
132.41



|Xbc|
  57.64

  57.77




 







RMS
24.2 (12.0 %)
22.8 (11.3 %)



RSD
1.38 (0.40 %)
1.38 (0.40 %)



 








 









* The algebraic sign of the product XabXacXbc is positive.

 









 


Table 3.  g-(CH3)2-CH-CH2Br.  Heavy atom structure parameters (Å and degrees).  Complete structures are given here in Z-matrix format.
 


ropt(1) = MP2/6-311+G(2d,p) optimization.
ropt(2) = MP2/6-311+G(2d,p) optimization with empirically corrected C-C, CH, and CBr bond lengths.
 



ropt(1) ropt(2)



C(3)Br 1.9560 1.9455
C(2)C(3) 1.5178 1.5161
C(2)C(4) 1.5302 1.5247
C(2)C(5) 1.5247 1.5197
C(2)C(3)Br 113.22 113.22
C(3)C(2)C(4) 108.02
108.02
Click on image to enlarge. C(3)C(2)C(5) 112.17
112.17


 























Table 3.  g-(CH3)2-CH-CH279Br.  Rotational Constants (MHz).
 





ropt(1) ropt(2) Expt. [1]
 




A 7543.3 7583.5 7483.20(28)

B 1409.8 1420.1 1411.1193(57)

C 1250.6 1259.6 1250.5110(56)



  








 








[1] Y.Niide and I.Ohkoshi, J.Mol.Spectrosc. 142,227(1990).

 








 








Isobutyl Chloride Isobutyl Iodide



 








 








Table of Contents




Molecules/Bromine




 








 













gCH32CHCH2Br.html






Last Modified 5 May 2013