Volume 2 Chapter 2 2D-Constrain Sub-menu NO-CYCLIC-ROUTES

Function

NO-CYCLIC-ROUTES is used to constrain the fragment such that:

either one or more specified atoms can not be connected by cyclic bonds to any atoms outside the fragment

or none of the atoms of the fragment can be connected by cyclic bonds to any atoms outside the fragment.

Examples

Ex. 1 Suppose we have built the fragment (i) - see below - and suppose we wish to constrain the fragment to have no cyclic route at atom a.

Select NO-CYCLIC-ROUTES

If NO-CYCLIC-ROUTES applies to the WHOLE fragment, select another
command. If it   applies to individual atoms, select each of these atoms.
(Select another command to complete NO-CYCLIC-ROUTES)

Select atom a
The fragment is now as in (ii).
The loop with an x through it is the symbol for no-cyclic-route at this atom.

Select an atom for NO-CYCLIC-ROUTES (Re-select an atom to change
your mind.)
(Select another command to complete NO-CYCLIC-ROUTES)

Select DEFINE-STRUCTURE

A search conducted with fragment (ii) would register hits for (iii) - (vi) but not for (vii).

Ex. 2 Suppose we have built the fragment (i) and suppose we wish to constrain the fragment to have no cyclic routes at any of the atoms of the fragment.

Select NO-CYCLIC-ROUTES

If NO-CYCLIC-ROUTES applies to the WHOLE fragment, select another command.
If it applies to individual atoms, select each of these atoms.
(Select another command to complete NO-CYCLIC-ROUTES)

in this case we wish NO-CYCLIC-ROUTES to apply to the WHOLE fragment.

Select DEFINE-STRUCTURE

A search conducted with this fragment would register hits for (iii) - (v)

but not for (vi) , (vii).

Ex. 3 This simply illustrates how to change a NO-CYCLIC-ROUTES specification.

Suppose we have constructed the fragment:

(a) If we now wish to remove the constraint on the N atom, with the NO-CYCLIC-ROUTES command active:

Select N atom
The fragment is now

(b) At this stage there is still a red box around the NO-CYCLIC-ROUTES command. This would then have the effect of applying NO-CYCLIC-ROUTES to the complete fragment.
If we wish to remove the constraint completely:
Select NO-CYCLIC-ROUTES
The red box around this command vanishes.

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Volume 2 Chapter 2 2D-Constrain Sub-menu NO-LINKS .