Computational Chemistry

Table 3.3

Error in MMFF molecular mechanics and MP2(fc)/6–31G* bond lengths and angles (From Fig.

3.13

). Errors are given as MMFF/MP2. In some

cases (e.g. MeOH) errors for two bonds are given, on one line and on the line below. A minus sign means that the calculated value is less than the experimen

tal.

The numbers of positive, negative, and zero deviations from experiment are summarized at the bottom of each column. The averages at the bottom of eachcolumn are arithmetic means of the absolute values of the errorsC–H

Bond length errors,

r-r

exp

̊(A

)

Bond angle errors,

a-

aexp

O–H, N–H, S–H

C–C

C–O, N, F, Cl, S

Angles

MeOH

H

O 2

Me

CO 2

MeOH

H

O (HOH) 2

$

0.001/

$

0.004

0.011/0.011

$

0.002/0.006

$

0.005/0.007

$

0.5/

$

0.6

$

0.001/0.003

HCHO

H

O 2

2

CH

CH 3

3

HCHO

H

O 2

2

(HOO)

$

0.014/

$

0.012

0.011/0.011

$

0.019/

$

0.005

0.017/0.013

$

3.2/

$

1.4

MeF

MeOH

CH

CH 2

2

MeF

MeOH (HCO)

$

0.008/

$

0.008

0.009/0.007

$

0.013/

$

0.017/

$

0.002

$

0.008/0.009

1.8/

$

0.9

(COH)$

0.9/

$

0.6

HCN

HOF

HCCH

HCN

HCHO (HCH)

0.000/0.004

0.006/0.013

$

0.003/0.015

0.007/0.024

$

1.0/

$

0.9

MeNH

2

MeNH

2

CH

CH 3

CH 2

3

MeNH

2

MeF (HCH)

$

0.005/0.001

0.009/0.008

$

0.007/0.000

$

0.019/

$

0.006

$

0.4/

$

0.8

$

0.005/

$

0.007

CH

CH 3

3

HOCl

CH

CHCH 2

3

Me

CO 2

HOF (HOF)

$

0.002/

$

0.003

$

0.003/0.004

$

0.008/

$

0.002

0.008/0.006

13.6/0.4

0.021/0.020

CH

CH 2

2

H

S 2

HCCCH

3

MeCl

MeNH

2

(HCN)

0.000/0.000

0.005/0.004

0.004/0.004

$

0.014/

$

0.002

$

3.3/1.5

$

0.005/0.014

CHCH

MeSH

MeSH

Me

CO (CCC) 2

0.005/0.005

0.005/0.005

$

0.015/

$

0.003

$

0.5/

$

0.8

MeCl

Me

SO 2

CH

CH 3

(HCH) 3

$

0.004/

$

0.007

0.010/0.010

0.6/

$

0.1

MeSH

CH

CH 2

(HCH) 2

0.002/0.000

0.1/

$

1.2

0.002/

$

0.001

(continued

)

3.4 Geometries Calculated by MM 69