Esters, Organic

Riemenschneider, Wilhelm

doi:10.1002/14356007.a09_565

Cited by 14 publications

(16 citation statements)

References 36 publications

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“…93 However, the electrostatic repulsive forces associated with the charged deprotonated carboxyls is also effectively screened at high salt concentrations (e.g., in PBS), yet this has been shown not to cause significant short term loss of stability. This suggests there are other factors involved, one of which could be an increase in hydrogen bonding between protonated carboxyl termini at pH values near or below their pK a ; carboxyls are known to self-associate when fully protonated 94 . Another possibility is that highly acidic solutions reduce the chemical stability of the Au-S bond that anchors the dendrons to the Au surface; loss of chemical stability would lead subsequently to a loss of colloidal stability as the protective layer is degraded.…”

Section: Resultsmentioning

confidence: 99%

Newkome-Type Dendron-Stabilized Gold Nanoparticles: Synthesis, Reactivity, and Stability

et al. 2011

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We report the synthesis and evaluation of four Newkome-type dendrons, G1-COOH, G2-COOH, SH-G1-COOH, and TA-G1-COOH, and their respective gold-dendron conjugates, where GX represents the generation number. G1- and G2-COOH are 2-directional symmetric dendrons that have cystamine cores containing a disulfide group. SH-G1-COOH was prepared by treatment of G1-COOH with dithioerythritol to yield a free thiol group to replace the disulfide linkage. TA-G1-COOH has a thioctic acid moiety, which is a 5-member ring containing a disulfide group that cleaves to produce two anchoring thiols to bond with the gold surface. All dendrons have peripheral carboxylate groups to afford hydrophilicity and functionality. Gold nanoparticle conjugates were prepared by reaction of each dendron solution with a suspension of gold colloid (nominally 10 nm diameter) and purified by stirred cell ultrafiltration. Chemical structures were confirmed by 1H and 13C nuclear magnetic resonance spectroscopy and matrix assisted laser desorption/ionization time-of-flight mass spectrometry. Particle size and surface plasmon resonance of the conjugates were characterized by dynamic light scattering (DLS) and UV-Vis spectroscopy, respectively. X-ray photoelectron spectroscopy (XPS) was utilized to confirm covalent bonding between the thiols on the dendron and the gold surface. XPS also revealed changes in the S/Au intensity ratio as a function of the dendron chemical structure, suggesting steric effects play a role in the reaction and/or conformation of dendrons on the gold surface. The colloidal and chemical stability of the conjugates as a function of temperature, pH, and suspending medium, and with respect to chemical resistance toward KCN, was investigated using DLS and UV-Vis absorption.

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Section: Resultsmentioning

confidence: 99%

Newkome-Type Dendron-Stabilized Gold Nanoparticles: Synthesis, Reactivity, and Stability

et al. 2011

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“…Therefore, MMM with higher selectivity was selected, since its permeation flux was not very low for studying PV‐esterification that has industrial importance. Esters are widely used as solvents, extractants, and diluents 38. Esterification reactions are equilibrium‐limited, but different possibilities exist to achieve higher conversions of the required product.…”

Section: Resultsmentioning

confidence: 99%

Pervaporation‐aided dehydration and esterification of acetic acid with ethanol using 4A zeolite‐filled cross‐linked sodium alginate‐mixed matrix membranes

Bhat

Aminabhavi

2009

J of Applied Polymer Sci

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Filled mixed matrix membranes (MMM) of sodium alginate (NaAlg) were prepared by solution casting method and were filled with 4A zeolite particles in varying compositions from 0 to 10 wt % with respect to weight of NaAlg polymer. Membranes were cross-linked with glutaraldehyde and tested for pervaporation (PV) dehydration of acetic acid and ethanol in the temperature range from 30 to 70 C. Flux and selectivity data increased simultaneously for both feed mixtures at higher loadings of 4A zeolite, due to its high hydrophilic nature as well as molecular sieving effect in addition to its favorable interaction with hydrophilic NaAlg. At increasing temperature, flux increased, but selectivity decreased. Arrhenius activation parameters for permeation process were dependent upon the extent of filler content. Pervaporation-aided catalytic esterification of acetic acid with ethanol was attempted at 70 C, resulting in considerable increase of ethyl acetate conversion at reduced reaction time due to continuous removal of water by the membrane.

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“…Viscosity generally increases as the molecular mass (chain length) increases. 9 The physical and chemical properties of the benzoates are shown in Table 2. At room temperature and pressure, methyl benzoate, ethyl benzoate, butyl benzoate, and isobutyl benzoate are fragrant, colorless oils, and are insoluble in water.…”

Section: Chemistrymentioning

confidence: 99%

“…In general, the alkyl benzoates can be produced industrially via esterification of benzoic acid. 9 The manufacture of butyl benzoate, for example, is traditionally accomplished via an acid-catalyzed (eg, sulfuric acid) reactive distillation process between benzoic acid and butyl alcohol (Figure 3). 12…”

Section: Chemistrymentioning

confidence: 99%

Safety Assessment of Alkyl Benzoates as Used in Cosmetics

et al. 2012

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The functions of alkyl benzoates in cosmetics include fragrance ingredients, skin-conditioning agents--emollient, skin-conditioning agents--miscellaneous, preservatives, solvents, and plasticizers. The Cosmetic Ingredient Review Expert Panel reviewed the relevant animal and human data and noted gaps in the available safety data for some of the alkyl benzoates. Similar structure activity relationships, biologic functions, and cosmetic product usage allowed the available data of many of the alkyl benzoates to be extended to the entire group. Carcinogenicity data were not available, but available data indicated that these alkyl benzoate cosmetic ingredients are not genotoxic. Also benzoic acid and tested component alcohols were not reproductive or developmental toxicants, are not genotoxic in almost all assays, and are not carcinogenic. These ingredients were determined to be safe in the present practices of use and concentration.

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Esters, Organic

Cited by 14 publications

References 36 publications

Newkome-Type Dendron-Stabilized Gold Nanoparticles: Synthesis, Reactivity, and Stability

Newkome-Type Dendron-Stabilized Gold Nanoparticles: Synthesis, Reactivity, and Stability

Pervaporation‐aided dehydration and esterification of acetic acid with ethanol using 4A zeolite‐filled cross‐linked sodium alginate‐mixed matrix membranes

Safety Assessment of Alkyl Benzoates as Used in Cosmetics

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