Dissociation Constants (pKa) of Eight Amines: Measurements,
Computational Chemistry Calculations, and ANN
Abstract
This work focused on determining the dissociation constants (pKa) for
eight amines, namely, 3-(Diethylamino) propylamine, 1,3-Diaminopentane,
3-Butoxypropylamine, 2-(Methylamino) ethanol, Bis(2-methoxyethyl) Amine,
α-Methylbenzylamine, 2-Aminoheptane, and 3-Amino-1-phenylbutane at
temperatures ranging from 293.15 K to 323.15 K. The protonated order of
two polyamines, 3-(Diethylamino) propylamine and 1, 3-Diaminopentane,
were determined using computational chemistry methods. The dissociation
constants at the standard temperature of 298.15 K were estimated using
group functional models (paper-pencil) and computational methods using
software such as COSMO-RS and Gaussian. In addition, the pKas at various
temperatures were calculated using computational methods for two
different thermodynamic cycle. A simple artificial neural network (ANN)
method was also employed to reduce the calculation time as well as
improve the accuracy. Instead of using the experimental property data,
these could be generated using Aspen Plus or CosmothermX. The simulated
model provided a very good fit to the pKa values.