Contributions can be associated with individual groups:

Group	Contribution
-CO-CH3	60.45
-CO-O-	64.14
-O-	22.74
-O-CH2-O-	65.41

Contributions can be associated with pairs of groups, typically to model the interaction between groups:

Group 1	Group 2	Interaction
=C<	-F	-0.3824
=C<	-H	-0.1005
=C<	-O-	0.2051
=C<	-OH	3.4369

A single estimation technique can also use contributions for several parameters. For example, several estimation techniques estimate the coefficients of a temperature dependent polynomial from group contributions.

Group	Coefficient A	Coefficient B	Coefficient C	Coefficient D
-Cl	33.3	-0.0963	0.000187	-9.96E-08
-Br	28.6	-0.0649	0.000136	-7.45E-08
-I	32.1	-0.0641	0.000126	-6.87E-08

The Group Contributions Dialog is used to edit and store all of these types of group contributions

The Group Contributions dialog provides capabilities for editing, sorting and verifying group contribution values.

1	Display Table: the dialog's Group Contributions table displays the groups, keys and contributions.
2	Edit: activates the Group Contribution dialog enabling you to add and edit a contribution's groups, key and value. See below for documentation on the Group Contribution Dialog for details.
3	Commands: displays the table control's commands menu. Clicking the right mouse button on the table control will also activate the commands menu. See below for documentation on the Commands Menu for details.
4	Set Source: activates the Assign References and Comments dialog enabling you to assign a reference an comments to all selected datum rows. See documentation on the Assign References and Comments Dialog for additional details.)
5	Sort: activates the Sort Attribute Dialog enablign you to sort by group, key, value or reference.
6	Add Rows: adds additional rows to the table.
7	Verify: the dialog's commands enable you to add and paste group contributions. Pressing the Verify button activates the Verified Group Structures dialog which checks that each named group is present in the current knowledge base and has an entered molecular structure.
8	Find: activates the Find Contribution's Group dialog which enables you search for an entered group by name.

Cranium and Synapse allow you to enter any name for a contribution's group - the validity of the group's name is not checked upon editing or pasting. We thus recommend you use the Group Contributions Dialog's Verify button to check the validity of groups after you have entered all contributions.

Pressing the dialog's Commands button or clicking the right mouse button on the dialog's table control displays the table's commands menu.

The menu displays standard table commands. See documentation on Table Menu Commands for an explanation of each command.

Selecting a table row and pressing the Edit button or double-clicking on a table row activates the Group Contribution Dialog. This dialog enables you to enter one or two groups, a keyword, a contribution value, a reference and comments.

1	Group 1: the first group of the contribution. This is a required value.
2	List (Group 1): activates the group selection dialog listing all the groups present in the current knowledge base. Selecting a group from the selection dialog will insert its name into the Group 1 edit control.
3	Group 2: the second group of the contribution. Not all group contributions use two groups. Thus, this is not a required value.
4	List (Group 2): activates the group selection dialog listing all the groups present in the current knowledge base. Selecting a group from the selection dialog will insert its name into the Group 2 edit control.
5	Key: used to designate different types of group contributions. Keys are often used to designate corrections.
6	List (Key): activates the key selection dialog listing all the keys used by the current estimation technique. Selecting a key from the selection dialog will insert its value into the Key edit control.
7	Contrib: the contribution's value and uncertainty. The contribution's value is a required value. The contribution's uncertainty is optional.
8	Reference: the name of the reference from which this contribution was obtained. See documentation on the Choose Reference Dialog for details.
9	List (Reference): activates the Choose Reference dialog that lists all the references present in the current document. Selecting a reference from the dialog will insert its identifier into the Reference edit control.
10	Comments: any information providing additional details about the entered contribution. Very often, a group contribution must be modified from its original form before entry. The Comments control is often used to document such a modification.
11	Date: inserts the current date and time into the Comments control.
12	Phrase: inserts the default phrase into the Comments control.
13	Set: activates the Set Phrase dialog that enables you to change the default comment phrase. (See the documentation on the Set Phrase dialog for details.)
14	Show Ref: shows the document associated with the reference cited in the Reference control.

Very often all contributions are obtained from the estimation techniques original source. So, entering a reference for each contribution may seem redundant. However, it is not uncommon to add new group contributions, group contributions that you derive, to an estimation technique. Entering a reference for each contribution makes it easy to identify which contribution was from the original source and which were added later.

Topic	Description
Estimating Chemical Properties	a short video demonstrating how to estimate the physical properties of pure chemical using either Synapse or Cranium.
Estimating Mixture Properties	a short video demonstrating how to estimate the physical properties of mixtures using either Synapse or Cranium.
Getting Started using Cranium	provides a quick tour of Cranium's capabilities including physical property estimation and a discussion of structure editing.
Getting Started using Synapse	provides a quick tour of Synapse's capabilities including examples of chemical product design.