CH3CH2NH2












 








Nitrogen


Nuclear Quadrupole Coupling Constants


in Ethylamine


 








 








 








Calculation of the nitrogen nqcc tensors in ethylamine - anti and gauche - was made on structures obtained by MP2/aug-cc-pVTZ optimization.  These are compared with the experimental nqcc's in Tables 1 and 2. Molecular structure parameters are given in Table 3.

 









anti

gauche



 










Egauche < Eanti



by 0.70 kJ/mole



at MP2/aug-cc-pVTZ



level of theory














 








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 anti CH3CH2NH2 (MHz).  Calculation was made on MP2/aug-cc-pVTZ optimized structure.
   










Calc.
Expt. [1]
   







14N Xaa - 1.835 - 1.65122(301)


Xbb - 0.198 - 0.1473(34)


Xcc
2.033
1.7985 *


|Xab|
3.655



 







RMS
0.174 (14.5 %)





RSD
0.030 (1.3 %)



 







Xxx
2.729




Xyy
2.033




Xzz - 4.762




ETA - 0.146




Øz,CN
109.5



 







 








* Calculated here from zero trace condition.

 








 








   







Table 2. Nitrogen nqcc's in gauche CH3CH2NH2 (MHz).  Calculation was made on MP2/aug-cc-pVTZ optimized structure.
   










Calc.
Expt. [2]
   







14N Xaa
2.441
2.268(43)


Xbb
0.443
0.426 *


Xcc - 2.884 - 2.694 *


Xab
0.523




Xac
0.272




Xbc - 2.884



 







RMS
0.149 (8.3 %)





RSD
0.030 (1.3 %)



 







Xxx
2.686




Xyy
2.015




Xzz - 4.701




ETA - 0.143




Øz,CN
107.9



 







 








* Calculated here from experimental Xaa and Xbb - Xcc = 3.120(35) MHz.

 








 
Table 2.  CH3CH2NH2 Molecular structure parameters, MP2/aug-cc-pVTZ opt (Å and degrees).


anti-CH3CH2NH2
 C
 C,1,B1
 H,1,B2,2,A1
 H,1,B3,2,A2,3,D1,0
 H,1,B4,2,A3,3,D2,0
 H,2,B5,1,A4,3,D3,0
 H,2,B6,1,A5,3,D4,0
 N,2,B7,1,A6,3,D5,0
 H,8,B8,2,A7,1,D6,0
 H,8,B9,2,A8,1,D7,0
      Variables:
 B1=1.52440502
 B2=1.090604
 B3=1.09088024
 B4=1.090604
 B5=1.09064722
 B6=1.09064722
 B7=1.46300806
 B8=1.01368062
 B9=1.01368062
 A1=110.62561772
 A2=111.2343473
 A3=110.62561772
 A4=109.75928437
 A5=109.75928437
 A6=115.35466609
 A7=109.98343609
 A8=109.98343609
 D1=120.18546965
 D2=-119.62906069
 D3=-178.52865947
 D4=-61.84227984
 D5=59.81453035
 D6=58.30027837
 D7=-58.30027837

 
gauche-CH3CH2NH2  
 C
 C,1,B1
 H,1,B2,2,A1
 H,1,B3,2,A2,3,D1,0
 H,1,B4,2,A3,3,D2,0
 H,2,B5,1,A4,3,D3,0
 H,2,B6,1,A5,3,D4,0
 N,2,B7,1,A6,3,D5,0
 H,8,B8,2,A7,1,D6,0
 H,8,B9,2,A8,1,D7,0
      Variables:
 B1=1.51776452
 B2=1.08855338
 B3=1.08936107
 B4=1.09113633
 B5=1.09614461
 B6=1.09047827
 B7=1.46518624
 B8=1.01289974
 B9=1.01379884
 A1=110.21387581
 A2=111.03443024
 A3=110.54315651
 A4=109.44060465
 A5=109.64582009
 A6=109.67921442
 A7=110.69064814
 A8=109.84021891
 D1=120.86636322
 D2=-119.43986026
 D3=-177.23320045
 D4=-60.04799746
 D5=57.83449188
 D6=-179.7417793
 D7=63.01642908
 



 








 








[1] A.J.Apponi, M.Sun, D.T.Halfen, L.M.Ziurys, and H.S.P.Müller, Astrophys. J. 673,1240(2008).

[2] E.Fischer and I.Botskor, J.Mol.Spectrosc. 104,226(1984).

 








E.Fischer and I.Botskor, J.Mol.Spectrosc. 91,116(1982):  In trans (anti) conformer, X+ = 1.62 ± 0.035 and X- = 1.89 ± 0.08 MHz.


 









 








CH3NH2








 








 








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Molecules/Nitrogen




 








 













CH3CH2NH2.html






Last Modified 3 Oct 2005