Pyrrolidine

PDF  equatorial

C4H8NH

PDF  axial

 








 








 









Nitrogen and Deuterium


Nuclear Quadrupole Coupling Constants

in Pyrrolidine (eq and ax)

 








 








 

 





Calculation of the nitrogen and deuterium nqcc's in equatorial and axial pyrrolidine (aka tetrahydropyrrole) was made here on the ro molecular structures of Velino et al. [1], and on molecular structures given by MP2/6-311+G(2d,2p) optimization, ropt.  These are compared with the experimental nqcc's [2,3] in Tables 1 - 3.  Structure parameters are given in Table 4, ropt rotational constants in Table 5.

 








In Tables 1 - 3, subscripts a,b,c refer to the principal axes of the inertia tensor; x,y,z to the principal axes of the nqcc tensor.  The nqcc y-axis is chosen coincident with the inertia b-axis, these are perpendicular to the molecular symmetry plane.  Ø (degrees) is the angle between its subscripted parameters.  ETA = (Xxx - Xyy)/Xzz.

RMS is the root mean square difference between calculated and experimental 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 nitrogen efg's/nqcc's, and of the  B3LYP/6-31G(df,3p) model for calculation of deuterium efg's/nqcc's.

 








 








   







Table 1. 14N nqcc's in equatorial Pyrrolidine (MHz).  Calculation was made on the ro and ropt molecular structures.
   









Calc. / ro 
Calc. / ropt 
Expt. [2]
   







Xaa
2.160
2.127
2.12(5)

Xbb
2.832
2.826
2.84 *

Xcc - 4.992 - 4.953 - 4.96 *

|Xac|
0.629
0.673



 







RMS
0.03 (0.90 %) 0.01 (0.31 %)  

RSD
0.030 (1.3 %) 0.030 (1.3 %)


 







Xxx
2.215
2.191



Xyy
2.832
2.826



Xzz - 5.047 - 5.016



ETA
0.122
0.127



Øz,a
  95.0
  95.4



Øa,NH
  16.6
  16.6



Øz,NH
111.6
112.0



 








 








* Calculated here from Xaa and Xbb - Xcc = 7.80(8) MHz [1].

 








 








   







Table 2. 14N nqcc's in axial Pyrrolidine (MHz).  Calculation was made on the ro and ropt molecular structures.
   









Calc. / ro 
Calc. / ropt 
Expt. [3]
   







Xaa - 3.502 - 3.607 - 3.3904(14)

Xbb
2.825
2.746
2.7642(14)

Xcc
0.677
0.861
0.6262(20)

|Xac|
2.886
2.724



 







RMS
0.079 (3.5 %)
0.184 (8.2 %)



RSD
0.030 (1.3 %) 0.030 (1.3 %)


 







Xxx
2.151
2.149



Xyy
2.825
2.746



Xzz - 4.976 - 4.896



ETA
0.136
0.122



Øz,a
  27.0
  25.3



Øa,NH
  84.9
  86.6



Øz,NH
111.9
111.9



 








 








 








   







Table 3. 14N and 2H nqcc's in axial Pyrrolidine-ND (MHz and kHz respectively).  Calculation was made on the ro and ropt molecular structures.
   









Calc. / ro 
Calc. / ropt 
Expt. [3]
   







Xaa(14N) - 3.334 - 3.449 - 3.253(9)

Xbb
2.825
2.746
2.760(9)

Xcc
0.589
0.703
0.493(17)

|Xac|
3.001
2.845



 







RMS
0.061 (3.0 %)
0.166 (8.3 %)



RSD
0.030 (1.3 %) 0.030 (1.3 %)


 







Xaa(2H) -
 141.2
 -
 136.6
 -
 117(8)

Xbb -
 108.0
 -
 102.4
- 94(11)

Xcc
249.3
239.0
211(15)

|Xac|
  52.9
  36.7












RMS
27. (19. %)
20. (14. %)



RSD
  1.1 (0.86 %)
  1.1 (0.86 %)



 








 







 
 


Table 4. Heavy atom and NH molecular structure parameters, ro and MP2/6-311+G(2d,2p) ropt (Å and degrees).
Complete molecular structures for the equatorial conformer are given here, and for the axial conformer, here.
 




ro [1] ropt
 


Equatorial NH 1.017 1.0111

C(1)N 1.464 1.4662
C(1)C(2) 1.547 1.5345
C(2)C(3) 1.558 1.5513
C(4) - - - C(1) 2.314 2.3045
C(2)C(3)C(4) 104.1 104.21
C(4)NC(1) 104.4 103.60

C(4)NC(1)-NH 126.9 126.94

C(2)C(1)C(4)N 133.0 132.74
 


 


Axial NH 1.006 1.0136

C(1)N 1.477 1.4698
C(1)C(2) 1.547 1.5445
C(2)C(3) 1.555 1.5494
C(4) - - - C(1) 2.309 2.3007
C(2)C(3)C(4) 104.1 104.08
C(4)NC(1) 102.9 103.01
C(4)NC(1)-NH 122.2 120.40

C(2)C(1)C(4)N 142.4 142.54



 








 














Table 5.  Pyrrolidine Rotational Constants (MHz).  MP2/6-311+G(2d,2p)  ropt structures.
 





  eq ropt eq Expt. [1] ax ropt  ax Expt. [3]







A 6918.6 6864.678(5)
 6885.9
 6834.5324(79)

B 6843.4 6791.950(5)
 6717.9
 6677.8513(79)

C 3939.5 3902.3(20)
 3916.2
 3888.0602(81)


 








 








[1] B.Velino, A.Millemaggi, A.Dell' Erba, and W.Caminati, J.Mol.Struct. 599,89(2001).

[2] W.Caminati, A.Dell' Erba, G.Maccaferri, and P.G.Favero, J.Mol.Spectrosc. 191,45(1998).

[3] H.Ehrlichmann, J.-U.Grabow, and H.Dreizler, Z.Naturforsch. 44a,837(1989).











W.Caminati, H.Oberhammer, G.Pfafferatt, R.R.Filguerira, and C.H.Gomez, J.Mol.Spectrosc. 106,217(1984).

 








 








 N-Methyl-PyrroleMorpholine Piperidine
 Pyrrole

 








 








Table of Contents




Molecules/Nitrogen




 








 













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Last Modified 15 Dec 2015