Synthesis and thermal behavior of linear neryl diesters in inert and oxidative atmosphere

The studies on the synthesis and thermal properties of linear neryl diesters were presented. The linear neryl diesters can be successfully obtained during butylstannoic catalyzed esterification process. The final conversion of nerol and carboxylic groups was higher than 95 % using a stoichiometric molar ratio of reagents in mild conditions. The high yield products were prepared after longer time than previously studied geranyl diesters. It was directly connected with the steric hindrance and lower susceptibility of nerol to esterification process than geraniol. The TG/FTIR/QMS studies proved that the thermal properties and decomposition mechanism of neryl diesters differ considerably in inert and oxidative atmosphere. The diesters were thermally stable up to 200 °C in inert atmosphere. Their decomposition was run as a one-step process. The analyses of the volatile products emitted during their pyrolysis indicated on the ester and O-neryl bonds cleavage. It resulted in the formation of monoterpene hydrocarbons, cyclic acid anhydrides, ketones, or aldehydes. However, the studied compounds were less thermally stable in air than in helium. Their decomposition happened in two steps. The first step ranges from 185–228 °C to almost 326–380 °C with mass loss above 88 %. The formation of acyclic or alicylic monoterpene hydrocarbons, cyclic acid anhydrides, ketones, alkenes, alkanes, carbon dioxide, and water was expected. It indicated on the asymmetrical distrupt of the bonds, partial oxygenation, and decarboxylation of emitted gaseous fragments. The second step of decomposition was observed in temperatures ranges from 380 to above 560 °C. In this step carbon dioxide and water were mainly emitted. It was the result of the oxidation of the residue formed during the fist step.