(CH3)2-CH-CH2I





 





 





 





 





Iodine


Nuclear Quadrupole Coupling Constants


in gauche Isobutyl Iodide


 








 








 








Calculation of the iodine nqcc tensor in gauche isobutyl iodide 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 and CH bond lengths (approximate re).  These calculated nqcc's are compared with the experimental values of Niide and Ohkoshi [1] in Table 1.  Structure parameters are given in Table 2, rotational constants in Table 3.

 








In Table 1, 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.  z,CI (degrees) is the angle the z-principal axis makes with the CI 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/6-311G(df,p) model for calculation of the nqcc's, which may be taken as an estimate of the uncertainty in the calculated nqcc's.

 








 








   








Table 1.  127I nqcc's in g-(CH3)2-CH-CH2I (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 and CH bond lengths.
   










Calc. (1)

Calc. (2)
Expt. [1]
   








Xaa - 1382.3 - 1381.6 - 1371.1(38)

Xbb
  601.7
  601.6
  590.8(42)

Xcc
  780.6
  780.0
  780.3(56)

|Xab|
  840.5  *
  839.8  *
  841.7(19)

|Xac|
  495.0
  494.8



|Xbc|
  198.3
  198.1



 







RMS
  9.0 (0.99 %)   8.7 (0.95 %)


RSD
15.2 (1.23 %) 15.2 (1.23 %)



 







Xxx
  882.1
  881.6



Xyy
  918.5
  917.9



Xzz - 1800.6 - 1799.5



ETA
0.0202
0.0202



z,CI
0.67
0.68



 








 








* The algebraic sign of the product XabXacXbc is negative.

 








 


Table 2.  g-(CH3)2-CH-CH2I.  Heavy atom structure parameters ( 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 MP2/6-311+G(d,p) corrected C-C bond lengths, and MP2/6-31G(d,p) corrected CH bond lengths (approximate re).
 



ropt(1) ropt(2)



C(3)I 2.1455 2.1455
C(2)C(3) 1.5198 1.5176
C(2)C(4) 1.5245 1.5195
C(2)C(5) 1.5304 1.5256
C(2)C(3)I 114.22 114.22
C(3)C(2)C(4) 112.32 112.32
Click on image to enlarge. C(3)C(2)C(5) 108.01 108.01


 























Table 3.  g-(CH3)2-CH-CH2I.  Rotational Constants (MHz).
 





ropt(1) ropt(2) Expt. [1]
 




A 7522.2 7561.6 7433.57(67)

B 1093.4 1095.5 1088.9006(35)

C   995.6   997.9   991.2657(35)



  








 








[1] Y.Niide and I.Ohkoshi, J.Mol.Spectrosc. 143,284(1990).

 








 








CH3CH2I CH3I CH3-CHI-CH3 g-CH2I-CH2F

 








 








Table of Contents




Molecules/Iodine




 








 













gCH32CHCH2I.html






Last Modified 11 Dec 2008