Even the best charge models are useless if protonation states are wrong. QUACPAC attempts to offer everything necessary to do charges correctly. It includes pKa and tautomer enumeration in order to get correct protonation states, partial charges using multiple models that cover a range of speed and accuracy, and electrostatic potential map construction and storage.

This update contains amount other things

• Significant improvements have been made to the reasonable tautomer algorithm that affect its aliphatic and non-aromatic resonance portions.
• Inclusion of AM1BCC ELF10, a new method for applying partial charges to a molecule
• TIP3P water charges are now assigned when using Amber charge sets on molecules containing waters.

Support for Mac OS X 10.10 and 10.11 has been added.
Mac OS X 10.7 and 10.8 are no longer supported.

Full release notes are here