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BOND TYPES

Function

These options are used to specify the type of a bond between two atoms.

Remarks

The Current Bond Type is the bond type assigned to newly generated bonds.

It is always highlighted with a box in the bond type area of the BUILD menu.

To change the Current Bond Type simply use the cursor to select the new bond type.

Note that, in MOVE mode, if you select a bond whose type is different from the Current Bond Type then the bond selected is assigned the Current Bond Type.

On entry to the BUILD menu the current bond type is single. This is indicated by the box around SING - see a below.

The various menu options for bond type are:

SING single

DOUB double

TRIP triple

QUAD quadruple

AROM aromatic

POLY polymeric

DELOC delocalised double

PI pi

ANY any

These correspond, in QUEST, to bt = 1, 2, 3, 4, 5, 6, 7, 9, 99.

To change the bond type from the default SING to DOUB

There are two other menu options relating to the construction of bonds:

These are described in the following pages.

V. B. T.

The menu option V. B. T. is used to assign a variable bond type to a bond.

Suppose we wish to search for transition metal carboxylates in which the transition metal is bonded to both oxygen atoms of the carboxylate group.

In the database there may be a mixture of connectivity representations for such structures - see (i) below:

To avoid missing any relevant hits we might proceed as follows:

Build the fragment (ii). Ensure that you are in MOVE mode before you continue.

Other metal complex systems also involve non-standardised connectivity representations in the database and it is advisable to use variable bond types when searching for them. Important examples are:

(v) with
SS = S, O, N;
RR = S, Se, O;
MM = TR, LN, AN
(vi) with
TT = S, O, N;
MM = TR, LN, AN

V. P. A.

The menu option V. P. A. is used to specify a variable point of attachment.

Suppose we wish to search for o-bromochlorobenzenes and m-bromochlorobenzenes - see (i) below.

We might proceed as follows:

Build the fragment (ii).

The above dialogue assumes that when V.P.A. is first selected, the current program state is MOVE. If, on the other hand, the current program state is DRAW then the active atom will be the fixed atom.

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