O=C(NH2)2












 








Nitrogen

Nuclear Quadrupole Coupling Constants


in Urea


 








 








 








Calculation of the nitrogen nqcc's in urea was made on the rs/ro structure of Godfrey et al. [1].  These are compared in Tables 1 and 2 respectively with the experimental nqcc's of Kretschmer et al. [2] and Kassi et al. [3].  Structure parameters are given in Table 3,  and atomic coordinates in Table 4.

 








In Tables 1 and 2, 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 B3PW91/6-311+G(df,pd) model for calculation of the nitrogen nqcc's.

 








Subscripts a,b,c refer to the principal axes of the inertia tensor; x,y,z to the principal axes of the nqcc tensor.  Ø (degrees) is the angle between its subscripted parameters.  ETA = (Xxx - Xyy)/Xzz.

 








 








   






Table 1. Nitrogen nqcc's in O=C(14NH2)2 (MHz).  Calculation was made on the rs/ro structure [1].
   









Calc.
Expt. [2]
   






14N Xaa
2.246
2.2005(26)


Xbb
1.990
1.8884(29)


Xcc - 4.236 - 4.0889


Xab - 0.068 *




Xac
0.548 *




Xbc - 1.191 *



 







RMS
0.107 (3.9 %)




RSD
0.030 (1.3 %)



 







Xxx
2.078




Xyy
2.420




Xzz - 4.498




ETA
0.076




Øz,a
94.47




Øz,b
79.68




Øz,c
11.27



 







 








* The algebraic signs of the off-diagonal components depend upon the orientation of the molecule with respect to a,b,c axes.  Here, the algebraic signs correspond to the atomic a,b,c coordinates given in Table 4.

 








 








   






Table 2. Nitrogen nqcc's in O=C(14NH2)(15NH2) (MHz).  Calculation was made on the rs/ro structure [1].
   









Calc.
Expt. [3]
   






14N Xaa
2.218
2.131(11)


Xbb
2.018
1.964(64)


Xcc - 4.237 - 4.095


Xab - 0.104 *




Xac
0.360 *




Xbc - 1.260 *



 







RMS
0.101 (3.7 %)




RSD
0.030 (1.3 %)



 







 








* The algebraic signs of the off-diagonal components depend upon the orientation of the molecule with respect to a,b,c axes.  Here, the algebraic signs correspond to the atomic a,b,c coordinates given in Table 4.

 








 

Table 3.  Molecular structure parameters, rs/ro [1] (Å and degrees).
 

Point Group: C2

O(1)C(2) 1.2211
C(2)N(3) 1.3779
N(3)H(5) 0.9978
N(3)H(6) 1.0212
O(1)C(2)N(3) 122.64
C(2)N(3)H(5) 119.21
C(2)N(3)H(6) 112.78
H(5)N(3)H(6) 118.61



Dihedral angles?  See Z-Matrix.



 








 
















Table 4.  Urea.  Atomic coordinates, normal species; rs/ro [1].
(More figures are shown than are significant.)
 









  a (Å)
  b (Å)
  c (Å)









O
0.0
1.304933
0.0

C
0.0
0.083833
0.0

N
1.159672 - 0.659450 - 0.036028

N - 1.159672 - 0.659450
0.036028

H
1.148165 - 1.597599
0.306529

H
1.006593 - 0.093978
0.114483

H - 1.148165 - 1.597599 - 0.306529

H - 1.006593 - 0.093978 - 0.114483


 








 








[1] P.D.Godfrey, R.D.Brown, and A.N.Hunter, J.Mol.Struct. 413-414,405(1997).

[2] U.Kretschmer, D.Consalvo, A.Knaack, W.Schaade, W.Stahl, and H.Dreizler, Mol.Phys. 87,1159(1996).

[3] S.Kassi, D.Petitprez, and G.Wlodarczak, J.Mol.Spectrosc. 228,293(2004).

 








W.Kasten and H.Dreizler, Z.Naturforsch. 41a,1173(1986):  Xaa = 2.165(27), Xbb = 1.888(33), and Xcc = -4.053(50) MHz.

R.D.Brown, P.D.Godfrey, and J.Storey, J.Mol.Spectrosc. 58,445(1975):  Xaa = 2.16, Xbb = 1.88, and Xcc = -4.04 MHz.

 








 








NH2CHO NH2SH NF3 (NH2)2

NH3 NF2H NFH2


 








 








Table of Contents




Molecules/Nitrogen




 








 













OCNH22.html






Last Modified 17 Nov 2005