Table I. Force Constants and Reference Values in the QMFF for Amides A. Bond length
E =
2
K
b
b - b
2
+
3
K
b
b - b
3
+
4
K
b
b - b
4
b
2
K
b
3
K
b
4
K
b
bond Å
kcal mol
-1
Å
-2
kcal mol
-1
Å
-3
kcal mol
-1
Å
-4
C-O 1.1920
-2568.6 3155.8 C-N
1.3983 443.4
1415.3 C-H
1.0934 -780.5
896.3 C-N
1.4416 -676.4
650.0 H-N
1.0015 -1300.8 1908.3
C-C 1.5103
-522.3 490.0
H-C 1.0845
-851.3 1040.0
C-C 1.5297
-586.1 758.0
B. Bond angle
E =
2
K
-
2
+
3
K
-
3
+
4
K
-
4
2
K
3
K
4
K
angle degrees
kcal mol
-1
rad
-2
kcal mol
-1
rad
-3
kcal mol
-1
rad
-4
N-C-O 124.5
115.2 -41.0
-13.3 H-C-O
117.8 54.7
-26.8 0.0
H-C-N 110.4
62.1 -22.0
0.0 C-N-C
111.0 38.0
-8.0 -8.1
C-N-H 117.0
44.6 -9.7
0.0 C-N-H
113.9 54.7
-23.9 0.0
C-C-N 114.3
50.8 -12.6
-11.1
H-C-N 108.9
68.3 3.5
0.0 C-C-O
123.1 66.1
-20.5 0.2
C-C-N 116.9
46.9 -13.1
-10.4 H-N-H
112.9 46.7
-11.3 0.0
C-C-C 108.5
61.9 -11.3
-13.1 C-C-H
107.7 48.3
-34.3 0.0
C-N-C 111.6
47.2 -10.2
-10.1 C-C-N
100.6 62.0
-6.3 -12.7
N-C-N 122.5
123.9 -43.7
-28.9 C-N-C
122.0 90.8
-31.3 -21.1
H-C-H 107.7
51.5 -8.9
-10.8 H-C-C
110.8 52.7
-10.9 -11.3
C. Torsion angle
E =
1
K
1 - cos +
2
K
1 - cos2
+
3
K
1 - cos3
1
K
2
K
3
K
torsion kcal mol
-1
kcal mol
-1
kcal mol
-1
O-C-N-C 0.830
3.723 -0.050
O-C-N-H -1.882
3.043 -0.373
H-C-N-C 0.334
2.584 -0.401
H-C-N-H -0.008
2.619 -0.090
C-C-N-C 0.020
-0.019 0.013
H-C-N-C 0.031
-0.037 -0.058
C-C-N-H -0.069
-0.011 -0.002
H-C-N-H -0.021
-0.113 -0.175
C-C-C-N 0.108
0.080 -0.287
H-C-C-N -0.025
0.031 -0.207
C-C-N-H -0.915
2.385 -0.238
C-C-C-O 0.063
0.042 0.080
H-C-C-O -0.258
0.002 0.053
C-C-C-N -0.053
0.056 -0.076
H-C-C-N 0.241
-0.013 -0.098
C-C-C-C 0.108
0.080 -0.287
C-C-C-H -0.025
0.031 -0.207
C-C-N-C -0.002
-0.010 0.001
H-C-N-C 0.058
0.051 -0.236
C-C-C-C 0.108
0.080 -0.287
C-C-C-N 0.108
0.080 -0.287
C-C-N-C -0.098
0.109 -0.088
C-C-N-H 0.078
0.108 0.104
N-C-C-O 0.128
0.174 0.129
N-C-C-N -0.127
0.180 -0.126
C-C-N-C -0.753
2.739 0.090
C-C-N-C -0.005
0.007 0.006
N-C-N-H -0.818
0.516 -1.233
O-C-N-C -0.452
1.390 -0.834
H-C-N-C 0.212
1.246 0.047
H-C-C-H -1.152
0.012 -0.179
D. Out-of-plane E =
2
K
2 2
K
out-of-plane kcal mol
-1
rad
-2
H-C-N-O 42.126
C-N-C-H 1.250
C-C-N-O 44.242
C-N-H-H 0.000
C-N-C-C 4.247
N-C-N-O 49.203
C-N-C-H 0.000
E. Van der Waals interaction
E = [2rr
9
- 3rr
6
] where r = [r
i
6
+ r
j
6
2]
16
and =
i
j 12
2 r
i
r
j
3
r
i
6
+ r
j
6
r
i
i
atom Å
kcal mol
-1
H 1.098
0.013 O
3.535 0.267
C 3.308
0.120 N
4.070 0.106
H 2.995
0.020 C
4.010 0.054
F. Bond increment
E = 332.0 q
i
q
j
r
ij
; where q
i
=
k
ik
. Each
ik
donates positive charge to the first atom listed and corresponding negative charge to the second atom.
ik
bond electrons
C–O 0.396
C–N 0.211
H–N 0.440
C–N 0.000
H–C 0.046
C–C 0.000
H–C 0.053
C–C 0.000
G. Bondbond
