ACD/pK_a DB

List of Features

ACD/pK_a DB is an easy-to-use program that enables you to:

• Calculate the apparent dissociation constants (approximate and exact) for organic and some inorganic chemical compounds (based on the choice of the dominant ionic form in the system at the equilibrium state) under standard conditions (25°C and zero ionic strength).
• Calculate microscopic constants of dissociation of specific ionic forms that could be present in an equilibrium system.
• Calculate single pK_a values for all possible dissociation centers when the rest of the molecule is considered neutral.
• Import and remember up to 999 structures with their calculated pK_a values, and display all of them in the History window.
• Refer to databases containing experimental pKa values for thousands of structures with literature references provided.
• Create your own databases.
• Train the system with experimental data of high degree of confidence in order to calculate more accurate pK_a values for novel chemical classes. We offer two tools for algorithm training—System Training, where you can use your pK_a user database, and/or ACD/pK_a Accuracy Extender.
• Search both the internal database containing nearly 16,000 chemical structures with references to more than 31,000 experimental pK_a values and your own databases. Searching can be done by structure, substructure, molecular weight, molecular formula, pK_a value, etc.
• For small libraries and other data sets with fewer than 999 structures, you can import and process SDfiles using the standalone desktop ACD/pK_a DB package.
• For customers who have several ACD/PhysChem modules, it is possible to calculate all properties for that compound at once, view them all on one screen (the History Window), and export them to an SDfile.

This product includes: ACD/pK_a predictor, an ACD/PhysChem databasing module with two databases of experimental pK_a values, ACD/ChemSketch, and ACD/pK_a Accuracy Extender module.

Distinguish between the two types of pK_a: see Microscopic vs. Macroscopic pK_a.

Limitations of ACD/pK_a DB

ACD/pK_a DB has the following limitations:

1. It cannot calculate pK_a values for structures that:
   • Contain more than 255 atoms (note that the program refuses to predict pK_a for some cyclic compounds having less than 255 atoms due to the fact that the program uses a cycle-breaking algorithm that increases the 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 structure fragments.
      
2. ACD/pK_a does not take into account the specific features of different stereomers (R-, S-isomerism), conformers, and isotopes.