Series Of Diesters Research Articles

Synthesis, properties and thermokinetics of a kind of diesters as phase change materials

As novel solid–liquid phase change materials (PCMs), a series of diesters were synthesized with high-chain fatty acids and 1,6-hexanediol as raw materials and FeCl3·6H2O as catalyst under vacuum. The purity of the diesters was measured by fourier transform infrared spectrometer (FT-IR), and the thermophysical properties were determined with differential scanning calorimeter (DSC) and thermo-gravimetric analyzer (TGA). The results show that the melting temperatures of the high chain diesters are in the range of 31–63 ℃ and the enthalpies of the phase transition are more than 200 J/g. The diesters exhibit lower phase transition temperature and higher thermal stability than the monoesters with the same carbon chain length. The crystallization kinetics of 1, 6-hexanediol myristate (14-6-14) and cetyl octadecanoate (18-16) characterized by DSC under non-isothermal conditions indicate that the diester has lower crystallization activation energy than the monoester with the same carbon chain length, which implies the diester can crystallize easier than the monoester due to an extra ester group, resulting in a lower phase transition temperature. In addition, due to the contribution of the functional groups such as C=O and CH2, the diesters have the larger enthalpy of vaporization and higher thermostability than the monoester with the same carbon chain length.

Synthesis, Physicochemical Properties, and Thermo-Oxidative Stability of Diesters of 5,7-Dimethyl-1,3-Adamantanediol and 5,7-Dimethyl-1,3-bis(Hydroxymethyl)adamantane

A series of diesters on the basis of 5,7-dimethyl-1,3-adamantanediol and 5,7-dimethyl-1,3- bis(hydroxymethyl)adamantane and C3–C10 aliphatic acids have been synthesized and their physicochemical and thermo-oxidative properties have been studied. The properties of the esters obtained have been compared to those of trimethylolpropane and neopentyl glycol esters.

Citrate- and glycerol triesters as novel dual-functional dispersants and plasticisers for ceramic processing

Short chained triesters of glycerol and citric acid were systematically investigated as novel dual-functional dispersants and plasticisers for use in ceramic processing. Additional systematic studies on a series of diesters having structural similarities with the citrate and glycerol triesters were performed to further assess the significance of specific functional groups for the stabilisation of suspensions.The overall purpose of this work consists in simplifying the formulation for ceramic processing slurries while at the same time limiting the environmental impact and toxicity. The use of multifunctional additives reduces the risk of unwanted interactions between different components. Additionally, the possible use of one additive in more than one role opens the opportunity for an overall reduction in the number and amount of chemicals and therefore reduction of costs and risks.For the citrate ester candidates, different alkoxy groups were tested as well as the acetylation on the hydroxyl group. The glycerol esters differed by the length of the carboxylic chain.Especially triethyl and tributyl citrate are proposed as promising dual-functional additives for ceramic processing. Specifically, for triethyl citrate the dual-function was finally demonstrated by producing a dense piece of 8YSZ through tape casting and subsequent sintering.

Saturated linear diesters from stearic acid as renewable phase change materials

Renewable phase change materials have been gaining traction as a ‘green’ solution to store excess energy and therefore improving energy use efficiency. A series of diesters were synthesized in a solvent-free, melt condensation synthesis from the fatty acid derivative stearoyl chloride, and dialcohols between 2 and 10 carbons in length (18-n-18 diesters where n=2, 4, 6, 8 and 10). Characterization by FTIR, 1H NMR, DSC and TGA reveals significant changes to the thermal performance and stability of these materials in the presence of contaminants. This may explain the poor performance previously reported in literature for this type of material. These diesters have phase change enthalpies between 230 and 247J/g, elucidated for the first time, and all melt above 65°C, with a single, narrow melting and crystallization point, contrary to what was previously reported.

Conformational effects on mesophase stability: numerical comparison of carborane diester homologous series with their bicyclo[2.2.2]octane, cyclohexane and benzene analogues

Three series of diesters of 4‐alkoxyphenols containing 12‐vertex p‐carborane (1A[n], n = 1–22), 10‐vertex p‐carborane (1B[n], n = 1–12) or bicyclo[2.2.2]octane (1C[n], n = 1–12) as the central structural element were prepared and investigated by optical and calorimetric methods. All carborane diesters exhibited exclusively nematic behaviour, whereas the carbocyclic analogues 1C[n] and also cyclohexane (1D[n]) and benzene (1E[n]) derivatives, showed early onset of SmA phase and complete disappearance of nematic behaviour. The isotropic transition temperatures, T MI, for the five series of mesogens were analysed numerically using a three‐parameter exponential function. The resulting limiting values, T MI(∞), provided a quantitative assessment of the central element ability to support the mesogenic state. They demonstrated that, whereas the T MI(∞) values for the carbocycles, C, D, and E, are around 125°C, for carboranes A and B this value is 70±2°C and 49±19°C, respectively. Two types of comparative analysis of trends in T MI relative to those of the terephthalate series 1E[n] demonstrated abnormal behaviour of both carborane series (1A[n] and 1B[n]) and also the cyclohexane series (1D[n]). The former showed progressive destabilisation of the mesophase, whereas the series 1D[n] exhibited increasing mesophase stability relative to 1E[n] with increasing chain length. Both of these effects were explained using conformational analysis of theoretical models and experimental molecular structures for 1A[3], 1B[4] and 1C[4]. The increasing relative destabilisation of the mesophase in the carborane derivatives was rationalised by the high order rotational axes in A and B and D 4d symmetry for B. The trend of the ΔT MI values for series 1D[n] was explained with the existence of the equatorial‐axial conformational equilibrium for the cyclohexane derivatives. The clearing temperatures for the hypothetical pure diequatorial conformers 1D[n]‐ee were estimated.

Multiscale Porosity from Thermoreversible Poly(vinylidene fluoride) Gels in Diethyl Azelate

AbstractPoly(vinylidene fluoride) (PVF2) produces thermoreversible gels in a series of diesters. The polymer‐solvent complexation occurred for intermittent number of carbon atoms n ⩾ 2 and the enthalpy of complexation increased with increasing n. The gels were dried by replacing the diesters with low boiling solvent like cyclohexane (bp. 80 °C) and methylcyclohexane (bp. 99 °C). The porosity of the dried gels was measured using Poremaster‐60. For PVF2‐DEAZ gel meso and macro porosity have been observed. The former pore dimensions have been attributed for polymer‐solvent complexation while the macroporosity has been attributed for caging of solvent between the PVF2 fibrils The porosity measured from nitrogen adsorption isotherms using BJH method indicate presence of minimum pore diameter of 3.8 nm for the 10% dried gel of PVF2.

Synthesis and Characterization of Bent-rod Liquid Crystals

Two series of diesters with bend-rod shapes were synthesized and their thermal properties characterized by POM and DSC. The central group conformational mobility and polarity as well as the length of the mesogenic groups were varied in order to correlate these parameters with mesophase stability. Results indicate that series II diesters are enantiotropic and that their mesophase sensitivity to central group structural changes is limited.

NMR Study of Intramolecular Interactions between Aromatic Groups: Van der Waals, Charge-Transfer, or Quadrupolar Interactions? J. Am. Chem. Soc. 1998, 120, 9632−9645NMR Study of Intramolecular Interactions between Aromatic Groups: Van der Waals, Charge-Transfer, or Quadrupolar Interactions?

Proton nuclear magnetic resonance spectroscopy has been used to investigate intramolecular interactions between different aromatic groups in a series of diesters. The materials investigated comprise two aromatic groups linked by a 2-methyl-1,3-propanedioxy spacer. This spacer permits U-shaped conformations which place the two terminal aromatic groups close together, parallel in a face-to-face arrangement. For the symmetrical diesters, 1,3-bis(9-anthracenecarbonyloxy)-2-methylpropane (A2) and 1,3-bis[(3,5-dinitrobenzoyl)oxy]-2-methylpropane (N2), neither the chemical shifts of the aromatic group protons nor the vicinal coupling constants measured in the spacer provide any evidence for a high fraction of U-shaped conformers. In both cases, the conformational distribution of the spacer is similar to that found for 1,3-diacetoxy-2-methylpropane (M2), indicating that the planar aromatic groups in A2 and N2 experience no significant mutual attractive interactions. In contrast, substantial upfield shifts are obs...

Preparation of Benzyl γ-Benxoyloxybutyrates

Abstract As part of our investigation of intramolecular phenolic coupling reactions we required a series of diesters of the general structure, 5 1. Since esters of γ-hydroxybutyric acid have been prepared by acid2 or base3 catalyzed alcoholysis of γ-butyrolactone, it appeared that the desired esters might be prepared by alcoholysis of the lactone with a benzyloxide followed by trapping the new alkoxide, 1, with an acyl chloride. However, treatment of γ-butyrolactone with sodium benzyloxide under conditions analogous to those used in the preparation of ethyl γ-hydroxybutyrate3 failed to yield any of the corresponding benzyl ester. We were also unable to trap alkoxide 1 by acylation with acetyl chloride or benzoyl chloride.

ChemInform Abstract: DIESTER DERIVATIVES AS APOMORPHINE PRODRUGS

A series of diesters of apomorphine was synthesized to serve as prodrugs. They were converted in vivo to free apomorphine, which could be detected in the brain. Stereotyped gnawing behavior and unilateral rotation similar to that produced by apomorphine were induced by all of the diesters but the time course of action of the latter was prolonged. The duration of action generally increased with the size of the ester substituent and appeared to correlate inversely with the rate of hydrolysis of the esters by liver extracts. It is concluded that the diesters serve as prodrugs of apomorphine and their prolonged duration is partly explained by a decreasing rate of hydrolysis attributable to increased steric hindrance at the acyl carbon atoms.

Evaluation of Some of the Factors Involved in the Selective Hydrolysis of Aromatic Ester Protecting Groups by α-Chymotrypsin

Studies have been carried out which delineate some of the factors involved in the exploitation of α-chymotrypsin as a catalyst for the specific hydrolysis of selected aromatic ester protecting groups under mild conditions with a specificity not achievable by non-enzymic reagents. The reactions can be carried out under heterogeneous conditions and examination of a series of diesters has shown dihydrocinnamyl to be the most satisfactory of the hydroxyl protecting groups evaluated so far. The degree of specificity achievable is demonstrated by the fact that α-chymotrypsin-catalyzed hydrolysis of 2-acetoxyethyl dihydrocinnamate at pH 7.8 stops when the latter function has been cleaved. In addition, some guidelines have been developed regarding the application of literature specificity data for predicting the course and rate of preparative scale reactions.