Quantum molecular modeling of oxazolidines as detergent-dispersant additives for gasoline: A valuable technological adviser

Patented detergent-dispersant (DD) additives based on oxazolidines [1] were quantum-mechanics modeled in order to get molecular-level insights into their functionality for removing and preventing formation of gum deposits in gasoline internal-combustion engines. The DDs are derived from polyalkenyl N-hydroxyalkyl succinimides whose polarities were modulated through a radical (R) substituent which can be either a phenol derivative (phenyl, 2-hydroxy-), pentyl or atomic hydrogen attached to the oxazolidine ring. We propose a mechanism for the performance of DDs consisting in the attraction of gum molecules by the DDs’ polar heads and their subsequent transference onto the DDs’ hydrophobic alkyl tails. Density-Functional-Theory (DFT) calculations of electrostatic properties and interaction energies support the above molecular mechanism, and furthermore make the prediction that the best performance is reached when R = atomic hydrogen, as it was found through experimental tests [1]. DFT also allowed to realize that gum agglomerates within gasoline because the attractive interaction among gum monomers is stronger than among gum and gasoline molecules due to the gum's high polarity induced by the carbonyl and alkene functional groups. Likewise, these functional groups are responsible for gum to adhere firmly to oxidized metallic surfaces in contact with gasoline because they complete the octahedral coordination of the exposed superficial iron atoms, reaching at this manner the same strongest spin polarization that iron atoms have at the bulk crystalline oxidized metal. However, the oxazolidine-based DDs remove deposited gum since they adhere stronger to these surfaces than gum does because their polar heads have more bonding sites than gum, the DD having the radical hydrogen being easiest to be desorbed after gum removal avoiding so be burned by sticking to the metallic surface during gasoline combustion.