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Chemical and Physical Properties
Published in Leon Golberg, Hazard Assessment of Ethylene Oxide, 2017
The base strength or nucleophilicity of the amine is generally parallel to the equilibrium as determined in the dissociation of the hydrochloride (or other acid salt) of the amine. Aliphatic amines are stronger bases than aromatic amines, and accordingly react more rapidly with EO; these factors do not affect the reversibility of the reactions — they are all essentially irreversible in the usual chemical sense. In biological systems, it can be predicted on the basis of chemical reactivity that aliphatic amine groups (e.g., histidine, glutamine, the NH2-group of a terminal amino acid, or lysine residues of macromolecules) can, under proper conditions, react with EO irreversibly to form N- hydroxyethyl derivatives. Caution must be exercised in drawing conclusions regarding the quantitative aspects of such parallel systems: amine groups in macromolecules are often “masked” because of configurational or “neighboring group” effects in the system. Steric hindrance is a particular form of such modifying effect on relative rates of chemical reactivity by neighboring or adjacent groups, the extent of such blocking being principally dependent on the steric bulk of the chemical group. A substantial degree of alkylation of valine-NH2 in mouse hemoglobin after exposure to EO has been reported.21a
Synthesis and properties of photochromic polymer contain spiro-oxazine induced by ultraviolet light
Published in Soft Materials, 2023
Cheng-Dong Su, Yi-Yuan Shi, Jun Gao
To check the polymerization efficiency of SO and MMA, a standard curve was established to intuitively express the changes in polymerization efficiency with a different mass of added SO. Firstly, ultraviolet–visible spectroscopy of SO ethanol standard solutions of different concentrations (5 × 10−5 mol/L, 4 × 10−5 mol/L, 3 × 10−5 mol/L, 2 × 10−5 mol/L, 1 × 10−5 mol/L, 5 × 10−6 mol/L as 1 ~ 6) was performed. Secondly, the standard curve was established with the absorbance of SO ethanol standard solutions at the wavelength of 270 nm as shown in Fig. 4a. Regression of the solution concentration and absorbance was performed with fitting equation y = 0.181x – 0.0014 as shown in Fig. 4b. Thirdly, after the photopolymerization of SO (M1) and MMA, the unpolymerized monomers were thoroughly eluted with anhydrous ethanol. All eluent was collected and diluted to 600 mL before ultraviolet spectroscopy. The mass (M2) of unpolymerized monomers was calculated with the absorbance at 270 nm according to the standard equation. Then, the polymerization efficiency of SO was calculated through (M1 – M2)/M1. According to Table 1, the polymerization efficiency peaked at 92.65% when the proportion of SO was 0.4 wt%, which was much higher than the 78% that we reported before.[28] This may be attributed to the weaker steric hindrance of the active group methyl acrylate at the N position so that the polymerization efficiency is higher.
Polymer-sustained-alignment liquid crystal cell produced from the monomer containing benzophenone-moiety and its image-sticking property
Published in Liquid Crystals, 2021
Masanobu Mizusaki, Satoshi Enomoto, Yuki Hara
The VrDC values after 10 hours and ∆tilt are plotted as a function of the weight ratio of 4,4ʹ-DMABenz in the mixed monomers of 4,4ʹ-DMABiph and 4,4ʹ-DMABenz in Figure 9. The VrDC value was remarkably decreased when only 9% of 4,4ʹ-DMABenz was included in the mixed monomers of 4,4ʹ-DMABiph and 4,4ʹ-DMABenz, whereas the ∆tilt was proportionally increased with increasing the weight ratio of 4,4ʹ-DMABenz. It is known that the ∆tilt becomes small with the LC cell having the polymer layer produced from the monomer having the biphenyl and polymerisable groups [7,17,22]. We estimate that a molecular flexibility of 4,4ʹ-DMABenz is higher than that of 4,4ʹ-DMABiph because a carbonyl group between the phenylene groups of 4,4ʹ-DMABenz would rotate freely. In contrast, a rigidity of 4,4ʹ-DMABiph would be relatively high owing to a steric hindrance of the biphenyl group. Thus, one can presume that the effect for obtaining the small ∆tilt is lowered with the addition of 4,4ʹ-DMABenz because the relative ratio of the biphenyl unit in the polymer layer is decreased due to addition of 4,4ʹ-DMABenz. The result of the ∆tilt shown in Figure 9 indicates that the composition ratio of the monomer unit in the polymer layer affects the ∆tilt.
Reactivity of titanium imidazolin-2-iminato complexes with 2,6-diisopropylaniline and 2-{(2,6-diisopropylphenyl)-iminomethyl}pyrrole
Published in Journal of Coordination Chemistry, 2018
Kishor Naktode, Suman Das, Hari Pada Nayek, Tarun K. Panda
The titanium ion adopts a distorted trigonal bipyramidal geometry (τ5 = 0.74) through the coordination of three nitrogen atoms (N1) of the imidazolin-2-iminato ligand, N6 of dimethyl amide group, and imine nitrogen (N5) of iminopyrrolyl group, which occupy the equatorial position, whereas two nitrogen atoms (N4) of the pyrrolide group and N7 of second dimethylamido group are located in apical positions of the distorted trigonal bipyramidal structure. In the case of 5a, the average deviation of the titanium ion from the mean plane made by N1, N5, and N6 is 0.268 Å. The imidazole ring of the ligand is placed almost perpendicular to the axis of the equatorial plane and the tert-butyl group results in steric hindrance, causing a deviation in the bond angles of equatorial atoms. The bond angles N1−Ti1−N5, N1−Ti1−N6 and N5−Ti1−N6 deviated from the standard 120° to 126.86(9)°, 121.23(10)°, and 109.37(9)°. Also, the κ2 coordination mode of the chelating iminopyrrolyl ligand makes a bite angle of 73.01(8)° (N4−Ti1−N5). The bond angle of N4−Ti1−N7 is 165.92(10)°. The bond length of Ti1−N5 is 2.235(2) Å, indicating the dative coordination of the imine nitrogen to the titanium metal ion. The length of the Ti1−N1 bond is 1.826(2) Å, which is comparable to that of the parent complex 2a (1.8243(16) Å) [60]. The Ti1−N6 and Ti1−N7 bond lengths are 1.960(2) and 1.938(2) Å, respectively.