Molecular Arrangement and Intermolecular Hydrogen Bonding in Crystals of Methyl 6-<i>O</i>-Acyl-d-glycopyranosides

The crystal structures and thermal properties of methyl 6-O-n-decanoyl-α-d-glucopyranoside (1), methyl 6-O-n-dodecanoyl-α-d-glucopyranoside (2), methyl 6-O-n-dodecanoyl-β-d-glucopyranoside (3), and methyl 6-O-n-dodecanoyl-α-d-galactopyranoside (4) were studied by X-ray and thermal analysis. Anhydrous crystals obtained from methanol solution by slow evaporation are monoclinic and in space group P21 with Z = 2. Cell dimensions:  1, a = 4.967(1) Å, b = 7.513(1) Å, c = 25.917(2) Å, β = 92.92(1)°; 2, a = 4.968(1) Å, b = 7.503(1) Å, c = 28.443(2) Å, β = 92.68(1)°; 3, a = 7.722(1) Å, b = 7.346(1) Å, c = 18.626(2) Å, β = 91.51(1)°; 4, a = 5.760(1) Å, b = 7.986(1) Å, c = 23.339(1) Å, β = 90.21(1)°. The sugar moieties of 1 and 2 are disordered. The pyranose rings of β-d-glucopyranoside and α-d-galactopyranoside in 3 and 4, respectively, are in 4C1 chair conformation, and the alkyl chains in 1−4 are all-trans. Molecules are arranged in a bilayer structure with interdigitated alkyl chains. The hydrogen bonds between sugar moieties in 3 and 4, which are found only between adjacent layers, form infinite and finite chains in respective crystals. The melting point of compounds which have the same alkyl chain length are 70.1, 93.5, and 137.8 °C for 2, 3, and 4, respectively. Epimers of these molecules exhibit packing arrangements which explain the wide variety in their melting temperatures

Isolation and Quantification of Polyamide Cyclic Oligomers in Kitchen Utensils and Their Migration into Various Food Simulants

<div><p>Small amounts of cyclic monomers and oligomers are present in polyamide (PA)-based kitchen utensils. In this study, we isolated eight PA-based cyclic monomers and oligomers from kitchen utensils made from PA6 (a polymer of ε-caprolactam) and PA66 (a polymer of 1,6-diaminohexane and adipic acid). Their structures were identified using high-resolution mass spectrometry and ¹H- and ¹³C-nuclear magnetic resonance spectroscopy, and their residual levels in PA-based kitchen utensils and degree of migration into food simulants were quantified by high-performance liquid chromatography/mass spectrometry using purchased PA6 monomer and isolated PA66 monomers, and isolated PA6 and PA66 oligomers as calibration standards. Their total residual levels among 23 PA-based kitchen utensils made from PA6, PA66, and copolymers of PA6 and PA66 (PA6/66) ranged from 7.8 to 20 mg/g. Using water, 20% ethanol, and olive oil as food simulants, the total migration levels of the PA monomers and oligomers ranged from 0.66 to 100 μg/cm² under most examined conditions. However, the total migration levels of the PA66 monomer and oligomers from PA66 and PA6/66 kitchen utensils into 20% ethanol at 95°C were very high (1,700 and 2,200 μg/cm², respectively) due to swelling by high-temperature ethanol.</p></div

Migration levels of PA cyclic monomers and oligomers from ladles 1 (PA6), 8 (PA66), and 5 (PA6/66) into three simulants at 95°C.

Migration levels of PA cyclic monomers and oligomers from ladles 1 (PA6), 8 (PA66), and 5 (PA6/66) into three simulants at 95°C.</p

Retention times and MS (SIR mode) conditions for quantification.

<p>Retention times and MS (SIR mode) conditions for quantification.</p

Hydrolysis of CPL to 6-aminohexanoic acid.

<p>(A) Before and (B) after hydrolysis.</p

Recovery rates of PA cyclic monomers and oligomers from olive oil.

<p>Recovery rates of PA cyclic monomers and oligomers from olive oil.</p

Migration levels of PA cyclic monomers and oligomers from the sesame grinder (PA6) and cake server (PA6/66) into three simulants at 60°C.

<p>Migration levels of PA cyclic monomers and oligomers from the sesame grinder (PA6) and cake server (PA6/66) into three simulants at 60°C.</p

Migration levels of PA cyclic monomers and oligomers from turners 1 and 2 (PA66), and 10 (PA6/66) into olive oil at 121°C.

<p>Migration levels of PA cyclic monomers and oligomers from turners 1 and 2 (PA66), and 10 (PA6/66) into olive oil at 121°C.</p

High-resolution mass data of PA6 cyclic oligomers and PA66 cyclic monomer and oligomers.

<p>High-resolution mass data of PA6 cyclic oligomers and PA66 cyclic monomer and oligomers.</p

Condensation reactions of PA6 and PA66.

<p>Condensation reactions of PA6 and PA66.</p