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

Abstract

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.

Thermal properties of neryl long-chain esters obtained under microwave irradiation

“…Also, in this decomposition stage, the evaporation of water vapor (3,600-3,740 cm -1 ) [26-30, 35, 36] and emission of carbon dioxide (670 cm -1 and 2,330-2,365 cm -1 ) [26-30, 34, 37] are indicated. At T max2 , besides the products observed at T max1 , the evaporation of an acid anhydride (signals at 900, 1,050, 1,811 and 1,870 cm -1 responsible for m C-O and C=O groups) is clearly indicated for neryl esters obtained using shorter acid chain length (succinic anhydride and glutaric anhydride) [26][27][28][29][30]. For neryl esters based on adipic acid and sebacic acid, the evaporation of an acid anhydride…”

“…The 7 and 11 membered anhydrides due to their low stability, decomposes in air losing CO 2 . In this reaction, as a main decomposition compounds, cyclic ketones are formed [26][27][28][29][30]. The formation of those compounds during decomposition of neryl esters based on adipic and sebacic acids was confirmed by the presence of absorption signals at 1,768-1,790 cm -1 (m C=O) and at 1,008-1,178 cm -1 (m C-O) on FTIR spectra [31].…”

“…Traditionally, chemically those esters are prepared in catalyzed esterification process of monoterpene alcohols with acid anhydrides or acid chlorides using large excess of terpene alcohol and often toxic solvents [13,25]. Recently, we have proposed the method of the preparation of geranyl, neryl and citronellyl diesters [26][27][28] and long-chain esters of geraniol [29,30] using butylstannoic acid as a catalyst under conventional conditions. The use of such catalyst allowed reducing the formation of by-products, using of stoichiometric amount of reagents and significantly increasing the yields of pure product which consequently reduced the production cost of flavor esters for cosmetic, laundry and perfume applications.…”

TG/DSC/FTIR/QMS studies on the oxidative decomposition of terpene acrylate homopolymers

“…2 and 3, one can see that under oxidative decomposition process, firstly and mainly the emission of acyclic or cyclic terpene hydrocarbons is observed [29][30][31][32][33][34][35]. It is Absorbance/a.u.…”

“…Wavenumber/cm -1 Absorbance/a.u. confirmed by the presence of the characteristic bands for -CH 3 and -CH 2 -at 1378-1446 cm -1 (the deformation vibrations) and at 2870-2974 cm -1 (the stretching vibrations) and the presence of absorption bands for carboncarbon double bonds at 895-985 cm -1 (the out-of-plane deformation vibrations of =C-H groups), at 1590-1640 cm -1 (the stretching vibrations of C=C), and the bands centered at 3090 cm -1 (the stretching vibrations of =C-H) [29][30][31][32][33][34][35]. In addition, the creation of other terpene derivatives containing oxygen functional groups at the first decomposition stage was expected due to the presence of the bands at 1700-1790 cm -1 (the stretching vibrations of carbonyl groups), the bands from 1050 up to 1210 cm -1 (the stretching vibrations of C-O), the band at 2720 cm -1 (the stretching vibrations of C-H in aldehyde groups) and the bands above 3500 cm -1 (the stretching vibrations of -OH) on the FTIR spectra.…”