Hydrolysis Of Acetate Groups Research Articles

Thermally Stable Biodegradable Polyesters with Camphor and Tartaric Acid Coupled Cyclic Diester Monomers for Controlled Hydrolytic Degradations

The development of biodegradable engineering plastics is challenging, because increases in biodegradability mostly degrade other material properties, such as mechanical and thermal properties of polymers. Here, we use bioderivatives of diester monomers, dimethyl (1S,4R)-1,7,7-trimethylspiro[bicyclo[2.2.1]heptane-2,2′-[1,3]dioxolane]-4′,5′-dicarboxylate (camphor dimethyl dl-tartrate, Ct diester), for the synthesis of phthalate-based copolyesters to enhance degradability without a notable loss of thermal stability. Ct diester synthesized by acetalization of tartaric acid and camphor contains a bridged type of rigid bicycling ring with high thermal stability and controlled degradation via hydrolysis of acetal groups within the spiro-ring structure. Various alkyl-length diols of ethylene, butylene, and hexylene are copolymerized with mixtures of dimethyl phthalate (DMT) and Ct diester in a 9:1 molar ratio. The glass transition temperature and degradation temperature of the copolyesters are comparable to those of DMT-based homopolyesters. Due to decreases in crystallinity, copolyesters exhibit slight decreases in melting temperature of 10 to 20 °C, which can be advantageous for reducing processing temperatures. Notably, the copolyesters demonstrate enhanced hydrolytic degradation of 9.3 to 26.2% in pH 2 environment for 18 days, as measured by the degree of molecular weight reductions. These values are between 1.7 and 3.5 times higher than the degradation rates of their control samples of DMT-based homopolyesters under the same degradation conditions.

Rac- and meso-Cyclohexanoids: Their α-, β-glycosidases, antibacterial, antifungal activities, and molecular docking studies.

An efficient and versatile synthesis method has been postulated for hydroxymethylated rac- and meso-cyclohexanoid derivatives. The synthesis of these stereoisomers was achieved easily with traditional methods using hexahydroisobenzofuran 6, prepared from commercially available cis-hydrophthalic anhydride. The study, involving diastereoselective epoxidation and cis-hydroxylation, was conducted to obtain epoxy-, cis-, and trans-diol-furans 7, 8, and 9. After sulfamic acid-catalyzed ring-opening reaction of the epoxide and furan rings, rac- and meso-tetraacetates 14, 15, and 16 were afforded. Hydrolysis of acetate groups with ammonia in absolute methanol yielded the desired tetrols rac-17, meso-18, and meso-19. All structures, after purification by chromatographic methods and elucidation by spectral techniques, were screened against α- and β-glucosidases. Compounds 7, 8, 10, 17, 18, and 19 were also evaluated for their antibacterial and antifungal activity against some selected synthesized compounds with varying degrees of inhibitory effects on the growth of different pathogenic microorganisms by the well-diffusion method. In addition, Saccharomyces cerevisiae α-glucosidase molecular modeling studies were performed for all rac- and meso-compounds 7, 8, 10, 17, 18, and 19.

Synthesis of surfactants by polymerization of glycerol (meth)acrylates with fatty acids derivatives as chain ends

The worldwide production of glycerin exceeds the demand from the chemical industry and new applications have been investigated these last years mainly in the area of additives. Here, water–soluble glycerin-based polyacrylates and polymethacrylates have been prepared by free-radical polymerization of solketal (meth)acrylate using various transfer agents derived from fatty chains. According to specific experimental conditions, linear functional oligomers were obtained. This versatile process allowed designing amphiphilic copolymers after the hydrolysis of acetal groups. These oligomers exhibit critical aggregation concentration values ranging from 5 to 15 × 10−6 mol.L−1 without any strong differences between polyacrylate and polymethacrylate series. In the case of glycerol-based polyacrylate derivatives, the observed monomodal populations can be ascribed to the low polydispersity indexes.

Starve fed emulsion copolymerization of vinyl acetate and 1‐hexene at ambient pressure

A novel emulsion copolymer of vinyl acetate (VAc) and 1‐hexene was synthesized at ambient pressure. The feeding technique, initiation system and reaction time of the copolymerization were optimized based on molecular characteristics such as the weight contribution of 1‐hexene in the copolymer chains and glass transition temperature (Tg) as well as on bulk properties like minimum film‐formation temperature (MFFT) and solid content. According to nuclear magnetic resonance spectroscopy and differential scanning calorimetry results, the combination of starve feeding and redox initiation, within a reaction time of 4 h, effectively led to the copolymerization at ambient pressure between highly reactive polar VAc monomers and non‐polar 1‐hexene monomers of low reactivity. The copolymer showed a lower Tg and MFFT, and a reasonable solid content compared to the poly(vinyl acetate) (PVAc) homopolymer. The consumption rate, hydrolysis of acetate groups and chain transfer reactions during the polymerization were followed using infrared spectroscopy. Based on the results, the undesirable reactions between the VAc blocks were hindered by the neighbouring 1‐hexene molecules. Tensile testing revealed an improvement in the toughness and elongation at break of VAc–1‐hexene films compared to PVAc films. © 2014 Society of Chemical Industry

Synthesis of polyrotaxanes from acetyl-β-cyclodextrin

Polyrotaxanes are intermediary products in the synthesis of topological gels. They are created by inclusion complex formation of hydrophobic linear macromolecules with cyclodextrins or their derivatives. Then, pairs of cyclodextrin molecules with covalently linkage were practically forming the nodes of the semi-flexible polymer network. Such gels are called topological gels and they can absorb huge quantities of water due to the net flexibility allowing the poly(ethylene oxide) chains to slide through the cyclodextrin cavities, without being pulled out altogether. For polyrotaxane formation poly(ethylene oxide) was used like linear macromolecules. There are hydroxyl groups at poly(ethylene oxide) chains, whereby the linking of the voluminous molecules should be made. To avoid the reaction of cyclodextrin OH groups with stoppers, they should be protected by, e.g., acetylation. In this work, the acetylation of the OH groups of β-cyclodextrin was performed by acetic acid anhydride with iodine as the catalyst. The acetylation reaction was assessed by the FTIR and HPLC method. By the HPLC analysis was found that the acetylation was completed in 20 minutes. Inserting of poly(ethylene oxide) with 4000 g/mol molecule mass into acetyl-β-cyclodextrin with 2:1 poly(ethylene oxide) monomer unit to acetyl-β-cyclodextrin ratio was also monitored by FTIR, and it was found that the process was completed in 12 h at the temperature of 10°C. If the process is performed at temperatures above 10°C, or for periods longer than 12 hours, the process of uncontrolled hydrolysis of acetate groups was initiated.

ChemInform Abstract: Regioselective Deacylation of Polyacetoxy Aryl-Methyl Ketones by Lipases in Organic Solvents.

Abstract Lipases from porcine pancreas and Candida cylindraea, suspended in organic solvents have been used to study regioselective deacylation of polyacetoxy acetophenones. It has been observed that the hydrolysis of acetate groups at positions other than ortho predominates.

Regioselective deacylation of polyacetoxy aryl-methyl ketones by lipases in organic solvents

Lipases from porcine pancreas and Candida cylindraea, suspended in organic solvents have been used to study regioselective deacylation of polyacetoxy acetophenones. It has been observed that the hydrolysis of acetate groups at positions other than ortho predominates.

A method for the modification of ethylene: Vinyl acetate copolymer surfaces by chemically coupling bovine serum albumin and collagen

A method for coupling proteins on to the surfaces of copolymers of ethylene: vinyl acetate (Elvax) is presented. Both collagen and bovine serum albumin were successfully coupled. The amount of protein coupled depended on (i) the type of protein used and (ii) the acetate content of the copolymer, as well as some critical reaction conditions. This method incorporates three main steps: (i) hydrolysis of acetate groups, (ii) incorporation of a bifunctional isocyanate, and (iii) conversion to a reactive amino derivative and subsegent protein coupling. This appears to be less complicated than other reported methods and may improve or expand the range of applications for which Elvax may be useful as a biomaterial.

Neighbouring group effects. Part 2. Effect of epoxide on the hydrolysis of adjacent acetate groups

The presence of an epoxide at the 4,5-position of a steroid accelerates the hydrolysis of an acetate group at the 3β- or 6β-positions. This effect is also observed for a 1α-acetoxy-2β,3β-epoxide. A suitable fixed dipole–dipole orientation between the ester group and the adjacent polar group may be an important factor in the rate acceleration, since this neighbouring effect does not occur when a non-rigid side chain is present. Fluorine or bromine substitution at the 5α-position also enhances the rate of hydrolysis of a 6β-acetoxy-group.