TG/DSC/FTIR characterization of linear geranyl diesters

Abstract

The synthesis, thermal behavior, and characterization of the decomposition products of linear geranyl diesters: digeranyl succinate, digeranyl glutarate, digeranyl adipinate, and digeranyl sebacinate were presented. The linear geranyl diesters were prepared in direct esterification process of a molar stoichiometric ratio of geraniol and suitable acidic reagent in solvent-free medium at 130°C using butylstannoic acid as a catalyst. Their structure was confirmed based on FTIR, 1 H-and 13 C-NMR spectra. It was proved that the use of tin catalyst allowed decreasing the reaction time and increasing the final conversion of substrates when compared to non-catalyzed process. It considerably simplifies the processing by reduction of the preparation cost and thus this new method of synthesis of aroma diesters may be attractive for practical applications. The thermal behavior of prepared compounds was studied by TG/DSC/FTIR coupled method. TG analysis showed that diesters are thermally stable up to temperatures above 200°C. The DTG curves confirmed that these decomposition run as a single-stage process. The T max1 were in the range of 294.5-313.8°C depending on the aliphatic chain length (-CH 2 -) n in the structure of aroma diesters, which was in accordance with DSC data. The analysis of the gases evolved during heating of diesters in inert atmosphere indicated on the asymmetrical disrupt of their bonds. The cleavage of ester bond and O-geranyl bond was expected. It resulted in production of the mixture of derivatives of geraniol (acyclic and alicyclic monoterpene hydrocarbons) like myrcene, ocimene, or limonene as main decomposition products. In addition, the formation of anhydride, lactone, or ketone functionalities among the degradation products clearly confirmed the proposed degradation path of studied diesters.

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.…”