ACD/pKa Batch      Click image to magnify

ACD/pKa Batch allows rapid and automatic calculation of acid-base ionization constants (pK_a values) for large sets of compounds at once.

With ACD/pK_a Batch you can:

• Calculate apparent or single pK_a values
• Specify the pH range of interest
• Calculate the most basic and most acidic pK_a values
• Define amides or sulfonic/sulfuric groups as non-ionizable to speed up the calculation
• Label the ionized groups and corresponding pK_a values (OH, NH group, etc.)
• Limit your calculation time per structure to ensure high throughput

For each compound, ACD/pK_a Batch calculates the apparent pK_a values (those that are measured in aqueous solution at 25°C and at zero ionic strength) and/or single pK_a values (those that are measured for all possible dissociation centers when the rest of the molecule is considered neutral) at the specified pH range.
Note: the number of ionization centers in a molecule should not exceed 20.

How ACD/pK_a Batch works:

I. Input file such as:

1. ACD/ChemFolder database (.CFD)
2. SMILES text file (.TXT)
3. MDL SDfile (.SDF)*
4. ISIS database (.DB)**

*Note: For more detail about this common text data exchange format, please refer to "MDL File Formats" at the MDL Inc. web site.
**Note: ISIS/Base 2.2 must be installed on the same PC. 

II. Set options:

1. Calculate apparent pK_a values.
2. Calculate single pK_a values.
3. Choose to calculate pK_a values at a specified pH range.
4. Calculate the most basic and most acidic pK_a values.
5. Treat certain groups as nonionazible.
6. Label pK_a values by functional groups.
7. Set a time limit for one structure calculation.

III. Choose to report results to .DB, .SDF, .RDF, .CFD, or .TXT files.

Limitations on Structure for pKa Predictions

• Structures must contain less than 255 atoms (some cyclic compounds having less than 255 atoms may not be accepted due to the use of a cycle-breaking algorithm that increases the apparent number of atoms)
• Contain more than 20 ionization centers
• Contain no ionization centers
• Contain atoms other than C, H, O, S, P, N, F, Cl, Br, I, Se, Si, Ge, Pb, Sn, As, and B
• Contain atoms of non-typical valence
• Contain two or more fragments
• Contain d-block or f-block metal atoms
• Contain textual abbreviations that cannot be transformed to structures fragments

ACD/pK_a does not take into account the specific features of different stereomers (R-, S- isomerism), conformers, and isotopes.

ACD/pKa Batch can be used independently, or as part of ACD/PhysChem Batch which includes modules for batch prediction of other physicochemical parameters such as logP, logD, aqueous solubility, and more.

This package is available for Microsoft Windows, SUN, and Linux platforms, and can be run from a Windows command line.