Subject: PYRROLE Z-MATRIX

From: "E. Lewars" <[email-masked]>
Date: Tue, 7 Mar 1995 16:02:45 -0500

Daniel Glossman asked about a Z-matrix for pyrrole.  Here's one.
The internal coord's of atoms in cyclic systems shouldn't be defined
sequentially, because of the ratcheting effect (Tim Clark, *A Handbook of
Computational Chemistry*).  Labelling distances X2N1..., angles A432..., and
dihedrals D4321.... will make Z-matrices easier to interpret, till the happy
day when they are extinct.
The input param's are from a MM opt with the Sybil forcefield, using Spartan
for visualization.
===========

# am1

PYRROLE, C2V

0 1
N1
X2       N1    X2N1
C3       X2    C3X2      N1    90.
C4       C3    C4C3      X2    A432    N1      0.
C5       X2    C3X2      N1    90.     C3    180.
C6       C5    C4C3      X2    A432    N1      0.
H7       C6    H7C6      C5    A765    X2    180.
H8       C5    H8C5      C6    A856    X2    180.
H9       C3    H8C5      C4    A856    X2    180.
H10      C4    H7C6      C3    A765    X2    180.
H11      X2    H11X2     C3    90.     C4      0.

        X2N1         1.9970
        C3X2         0.7345
        C4C3         1.3351
        H7C6         1.090
        H8C5         1.089                               z
        A432       105.5                               /\
        A765       125.8                 H9            |            H8
        A856       127.5                   \           |          /
        H11X2        3.029                   \         |        /
                                               C3------X2-----C5
                                              /        |        \
                                  H10--- C4 /          |          \C6 ---H7
                                                       |
                                                       |
                            x < ----------------------N1
                                                      /|
                                                     / |
                                                   /   H11
                                                 y