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 determined first by Bak et al. [5], later completed and extended by Nygaard et al. [4].  Calculation of the nqcc's was made here on the structure of Nygaard et al.  These are compared with the experimental nqcc's of Bohm et al. [1] in Table 1.  Structure parameters are given in Table 2.
In Table 1, 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 nqcc's.



Table 1. Nitrogen nqcc's in Pyrrole (MHz).  Calculation was made on the rs structure of Nygaard et al. [4].

Expt. [1]

14N Xaa 1.414 1.412(3)
Xbb 1.214 1.292(4)
Xcc - 2.628 - 2.704(4)
RMS 0.063 (3.5 %)
RSD 0.030 (1.3 %)
Table 2. Molecular structure parameters, rs [4] (Å and degrees).
N(1)H 0.996
N(1)C(2) 1.370
C(2)C(3) 1.382
C(3)C(4) 1.417
C(2)H(2) 1.076
C(3)H(3) 1.077
C(5)N(1)C(2) 109.8
N(1)C(2)C(3) 107.7
C(2)C(3)C(4) 107.4
N(1)C(2)H(2) 121.5
C(4)C(3)H(3) 127.1


[1] R.K.Bohm, K.W.Hillig II, and R.Kuczkowski, J.Phys.Chem. 93,3456(1989).
[2] K.Bolton and R.D.Brown, Aust.J.Chem. 27,143(1974).
[3] L.Gaines and G.R.Tomasevich, Symposium on Molecular Structure and Spectroscopy, Ohio,1973.  Cited in Ref.[2].
[4] L.Nygaard, J.T.Nielsen, J.Kirchheiner, G.Maltesen, J.Rastrup-Andersen, and G.O.Sørensen, J.Mol.Struct. 3,491(1969).
[5] B.Bak, D.Christensen, L.Hansen, and J.Rastrup-Andersen, J.Chem. Phys. 24,720(1956).



N-Methyl-Pyrrole Imidazole Pyrazole


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Last Modified 24 May 2003