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EXACT

EXACT is used to specify that an atom must have an exact number of connected atoms, excluding terminal hydrogen atoms.

Examples

Ex. 1 Suppose we wish to search for transition metal complexes having exactly 4 nitrogen atoms connected to the metal.

Suppose we have built the fragment:

• Select EXACT

• Select atom for EXACT specification
  You may re-select an atom to remove the constraint
  (Select another command to end EXACT)

• Select TR atom

The fragment is now:

In this example the starting fragment showed TR with 4 connections ie. mca = 4. Since we wish to set EXACT to 4 we can use EXACT directly.

If we change our mind and wish to remove the EXACT constraint then:

• Select TR atom

The fragment is now:

Ex. 2 Suppose we wish to search for transition metal complexes having exactly 6 atoms connected to the metal and of these 4 must be N.

Suppose we have built the fragment:

• Select MIN-CONNECTIONS

• Type minimum number of NON-H connected atoms.
  (Press <RETURN> to mean "Unspecified")

• Type 6 <R>

  6 appears in the MIN-CONNECTIONS box.

• Move the cursor over the required ATOM and click a BUTTON.
  (Select another command to end MIN-CONNECTIONS)

• Select TR atom

• Select EXACT

• Select atom for EXACT specification
  You may re-select an atom to remove the constraint
  (Select another command to end EXACT)

• Select TR atom

The fragment is now:

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Volume 2 Chapter 2 2D-Constrain Sub-menu GENERATE-HYDS.