Pyrrole


















































Nitrogen


Nuclear Quadrupole Coupling Constants


in Pyrrole


 








 








 

 





Nitrogen nqcc's in pyrrole have been reported by a number of investigators [1-4].  A substitution structure  was first determined by Bak et al. [5], later completed and extended by Nygaard et al. [4].  A semi-experimental equilibrium structure reSE was derived by Császár et al.Császár [6].

 








Calculation of the nqcc's was made here on the rs structure of Nygaard et al., on the reSE structure, and on a ropt structure given by B3LYP/cc-pVTZ optimization.  These calculated nqcc's are compared with the experimental nqcc's of Bohn et al. [1] in Table 1, and those of Nygaard et al. in Table 2.   Structure parameters are compared in Table 3.











In Tables 1 and 2, 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.

 








 








 










Table 1. 14N nqcc's in Pyrrole (MHz).  Calculation was made on rs, reSE, and ropt  structures.
 












Calc /rs
Calc /reSE
Calc /ropt
Expt. [1]
 










Xaa
1.414
1.464
1.470
1.412(3)

Xbb
1.214
1.216
1.223
1.292(4)

Xcc - 2.628 -
 2.680
 -
 2.693
 - 2.704(4)












RMS
0.063 (3.5 %)
0.055 (3.0 %)
0.052 (2.9 %)



RSD
0.030 (1.3 %)
0.030 (1.3 %)
0.030 (1.3 %)















 








 








 










Table 2. 14N nqcc's in Pyrrole (MHz).  Calculation was made on rs, reSE, and ropt  structures.
 












Calc /rs
Calc /reSE
Calc /ropt
Expt. [4]
 










Xaa
1.414
1.464
1.470
1.45(2)

Xbb
1.214
1.216
1.223
1.21(2)

Xcc - 2.628 -
 2.680 -
 2.693
 - 2.66(2)












RMS
0.028 (1.6 %)
0.014 (0.8 %)
0.024 (1.3 %)



RSD
0.030 (1.3 %)
0.030 (1.3 %)
0.030 (1.3 %)















 







 
 



Table 3. Molecular structure parameters, rs [4], reSE [6], and ropt (Ĺ and degrees).





 
  rs      reSE   ropt






N(1)H 0.9961.00086(14)
 1.0033

N(1)C(2) 1.3701.36940((17)
 1.3707

C(2)C(3) 1.3821.3723(2)
 1.3734

C(3)C(4) 1.4171.4231(4)
 1.4210

C(2)H(2) 1.0761.07532(13)
 1.0756

C(3)H(3) 1.0771.07527(16)
 1.0765

C(5)N(1)C(2) 109.8109.809(16)
 109.82

N(1)C(2)C(3) 107.7107.762(15)
 107.67

C(2)C(3)C(4) 107.4107.334(12)
 107.42

N(1)C(2)H(2) 121.5120.99(7)
 121.29

C(4)C(3)H(3) 127.1126.73(5)
 126.86



 








 








[1] R.K.Bohn, K.W.Hillig II, and R.Kuczkowski, J.Phys.Chem. 93,3456(1989).

[2] K.Bolton and R.D.Brown, Aust.J.Phys. 27,143(1974).

[3] L.Gaines and G.R.Tomasevich, Symposium on Molecular Structure and Spectroscopy, Ohio,1973. Xaa = 1.4057(11) and Xbb = 1.2945(10) MHz.

[4] L.Nygaard, J.T.Nielsen, J.Kirchheiner, G.Maltesen, J.Rastrup-Andersen, and G.O.Sřrensen, J.Mol.Struct. 3,491(1969).

[5] B.Bak, D.Christensen, L.Hansen, and J.Rastrup-Andersen, J.Chem. Phys. 24,720(1956).

[6] A.G.Császár, J.Demaison, and H.D.Rudolph, J.Phys.Chem. A, 119(9),1731(2015).

 








 








N-Methyl-Pyrrole Imidazole Pyrazole

 








 








Table of Contents




Molecules/Nitrogen




 








 













Pyrrole.html






Last Modified 27 Oct 2014