Synthesis of novel water‐soluble fluorescent coumarins bearing sulphonic and hydroxyl groups

Two dihydroxynaphtaldehydes (2,5‐dihydroxynaphtaldehyde and 2,7‐dihydroxynaphtaldehyde) and 2,4‐dyhydroxybenzaldehyde were sulphonated. These intermediates were used in subsequent reactions with 2‐cyanomethylbenzothiazole, 2‐cyanomethylbenzoimidazole and 1‐methyl‐2‐cyanomethylbenzoimidazole to synthesise sulphonated coumarin derivatives. The absorption and steady‐state fluorescence characteristics of the prepared coumarins were studied in ethanol and in water.     

Acid decomposition of highly substituted cellulose xanthate

The acid decomposition of cellulose xanthate was studied spectrophotometrically with a stopped-flow technique. The reactivity of the xanthate groups was found to decrease with an increase in the viscose γ number. This was explained by the occurrence of stabilizing interactions exerted between closely spaced xanthate groups. With uniformly substituted xanthates this effect began to be noticeable at γ numbers above 50. At higher γ numbers partial decomposition by acid resulted in an uneven distribution of xanthate groups along the chain molecules. Another feature of cellulose xanthate is that the degree of dissociation at constant acid concentration decreases with an increase in the γ number. This can be ascribed to variations in the dielectric constant inside the macromolecules.     

Selective alkylation of acidic hydroxyl groups in coal

The organic molecules which make up coal are held together not only by covalent bonds, but also by a substantial network of hydrogen bonds as well as certain other weak intermolecular associations, which together are called the secondary structure. It is believed that acidic hydroxyl groups are responsible for most of the secondary structure. These attractive forces have been diminished traditionally by solvent swelling the coal, then permanently removed by selective silylation or acetylation of the polar functionalities. A new selective alkylation procedure has been developed which converts polar hydroxyls into relatively non-polar ethers and esters, and has been successfully tested on a bituminous and sub-bituminous coal. This selective O-alkylation proceeds rapidly under very mild conditions and renders the coal essentially free from its secondary structure.     

Accelerated biodegradation of poly(vinyl alcohol) by a glycosidation of the hydroxyl groups

Biodegradability of N-acetyl-d-glucosamine (GlcNAc)-substituted poly(vinyl alcohol) (PVA) (1) in a soil suspension (pH 6.5) was investigated at 25°C for 40 days. Biochemical oxygen demand (BOD) of 1 with degree of substitution of 0.2-0.3 (DP=430-480) was higher than that of PVA under the degradation condition. Size exclusion chromatography (SEC), ¹H NMR, and FT-IR measurements of the recovered sample indicated that biodegradation of PVA main chain was accelerated by partial glycosidation of hydroxyl groups in PVA.     

Simplified hydrolysis of cellulose and substituted cellulose: Observations on trifluoroacetic acid hydrolyses

Hydrolyses of selected soluble polysaccharides (e.g., polyoses) and disordered and crystalline celluloses, each bearing 2-diethylaminoethyl (DEAE) substituents at low degree of substitution (DS < 0.05) were explored in 100% and 2N trifluoroacetic acid (TFA). Analyses were evaluated relative to hydrolysis with 72% sulfuric acid. DEAE–polyoses hydrolyzed readily in 100% and 2 N TFA during extended reaction periods with complete liberation of DEAE–glucoses. Hydrolyses of cellulose and DEAE–celluloses in 100% TFA were critically dependent upon cautious incremental dilution of the TFA during stepwise reaction to avoid precipitation of incompletely hydrolyzed products. DEAE–celluloses were partially solubilized and hydrolyzed in heterogeneous reaction in 2N TFA at 121°C. Complete liberation of DEAE-glucoses in the solubilized components was achieved after supplementary hydrolysis at 121°C. In all hydrolyses, including those with 72% sulfuric acid, extended hydrolyses were essential for complete liberation of the 2-O- and 6-O-DEAE–glucoses. Under optimum conditions, results of hydrolyses in 100% TFA were comparable to those in 72% sulfuric acid. Ease of release of DEAE-glucopyranoses in hydrolyses of DEAE-cellulose in 2N TFA was in the same order (3-O- > 6-O-> 2-O-) as in homogeneous hydrolyses in sulfuric acid and in 100% TFA. Differences in release of isomeric DEAE–glucoses were greater in the heterogenous system. Degradation of glucose and DEAE–glucopyranoses occurred in extended periods of reaction in all acidic media. Rates of degradation of glucose and DEAE–glucopyranoses in dilute acid at 100°C were similar for glucose and 6-O-DEAE–glucose. The rates were about half as fast for 3-O-DEAE–glucose and an order of magnitude lower for 2-O-DEAE–glucose.     

Relative esterifiability of the primary and secondary hydroxyl groups of glycerol

Summary A method has been devised for determining the relative esterifiability of the primary and secondary hydroxyl groups of glycerol. Contrary to the theory previously advanced by Feuge and Bailey, the primary and secondary hydroxyls are not equally esterifiable. The equilibrium constant favoring esterification of primary hydroxyl over secondary isca. 2.3 at reaction temperature (200°C.) and between 6 and 10 at room temperature. Since the equilibrium constant is substantially different at room temperature from that at reaction temperature, monoglycerides as customarily prepared are not at equilibrium at room temperature and undergo intramolecular migration of acyl groups frombeta toalpha hydroxyl positions. The rate of migration depends on the physical form of the ester and is accelerated by basic catalysts. In the vicinity of room temperature intermolecular rearrangement occurs only over very prolonged periods. The method of calculating relative esterifiability of primary and secondary hydroxyls should be applicable to other polyols. Presented at the 50th annual meeting, American Oil Chemists’ Society, New Orleans, La., April 20–22, 1959.     

Sorption of water by modified polyamide films containing substituted amino groups

Conclusions -- The sorption-diffusion properties of aminated copolymers of polycaproamide have been studied. An effect of the structure of the aminating reagent on the sorptive power of the polymers has been shown.-- Experimental proofs have been obtained for an invariance of the diffusion coefficient of water in graft copolymers of polycaproamide which have been aminated with dimethylamine and polyethylenepolyamine.Translated from Khimicheskie Volokna, No. 2, pp. 35–36, March–April, 1993.     

Relative reactivities of amylose hydroxyl groups in the reaction with diketene

¹³C nuclear magnetic resonance (n.m.r.) spectra at 75.4 MHz of partially modified amylose with β-keto ester groups (degree of substitution (DS) ranging from 0.52 to 2.42) were studied in order to evaluate the selectivity of the reaction of amylose with diketene in the homogeneous phase. Analysis of the spectra of ring carbons in the anhydroglucose units shows that the reactivity of individual hydroxyl groups decreases in the order C-6>C-3>C-2 for DS values up to ∼1.8. For higher DS values a negative deviation is observed for the hydroxyl group at C-6 and a positive deviation for the hydroxyl groups at C-2 and C-3. The DS values determined by ¹³C n.m.r. spectra are in good agreement with those found by chemical analysis.     

Infrared absorption characteristics of hydroxyl groups in coal tars

Tar evolution was observed over a temperature range of 150–600 °C for four coals: Pittsburgh bituminous, Illinois No. 6, Rawhide subbituminous, and Texas lignite. Isolation of the evolved tars in a nitrogen matrix at 15 °K produced better resolved infrared spectra than those in a coal matrix, thus enhancing structural characterization of the tar molecules. Two distinct hydroxyl functional groups in the tar molecules free of hydrogen bonding were identified for the first time without interference from H₂O absorptions. These absorptions at 3626.5 and 3580.9 cm⁻¹ have been assigned to phenolic hydroxyls. It is suggested that carboxylic and aliphatic hydroxyl groups do not survive the vaporization process. Tars from Illinois No. 6 were found to contain the largest amount of phenolic hydroxyl ; Pittsburgh No. 8 tar contains approximately half of that for Illinois No. 6 while Rawhide and Texas lignite contain much less phenolic than either of the other coals.     

Copolymerization of styrene with vinyl monomers substituted by nitrile and sulfonyl groups

Two trisubstituted vinyl monomers, 2-phenylsulfonyl (crotonitrile) and 2-phenylsulfonyl (cinnamonitrile) were synthesized and characterized by proton NMR, IR, ¹³C-NMR, and mass spectroscopy. Both monomers were copolymerized with styrene by free-radical initiation. The copolymerization parameters of both systems were determined, and the mutual reactivity of the monomers of the two systems is discussed. The new copolymers were characterized by proton NMR and IR spectroscopy, melting range, T_g, and intrinsic viscosity. The influence of the chemical structures of the two comonomers on these two latter properties of the copolymers is discussed.     

Dielectric relaxation studies of heterogeneously substituted cellulose acetate and its plasticization by dibutyl phthalate

Dielectric relaxation measurements are reported on plasticized commercial and heterogeneously substituted cellulose acetate. Differences in the observed behaviour are attributed to the retention of a degree of crystallinity and microscopic structure in the original substituted cellulose samples. A comparison of dynamic mechanical and dielectric relaxation data further emphasizes the influence of the nature of the original morphology on the micro dynamics.     

Gelation behaviors of cellulose solution dissolved in aqueous NaOH/thiourea at low temperature

Cellulose was dissolved rapidly in 9.5 wt% NaOH/4.5 wt% thiourea aqueous solution pre-cooled to −5 °C, as a result of the formation of an inclusion complex (IC) associated with cellulose, NaOH and thiourea, which could bring cellulose to the aqueous system. To clarify the rheological behaviors of the system dissolved at low temperature, this cellulose solution was investigated by dynamic viscoelastic measurement. The shear storage modulus (G′) and loss modulus (G″) as a function of the angular frequency (ω), concentration (c), temperature (T) and weight-average molecular weight (M_w) were analyzed and discussed. The results revealed that gels could form in the cellulose solution at either high temperature or low temperature, or for longer time. Interestingly, 4 wt% cellulose solution having cellulose M_w of 12.0 × 10⁴ remained at liquid state for longer time (12 days) at the temperature ranging from 0 to 5 °C. The gels already formed at elevated temperature were irreversible, i.e., after cooling to lower temperature including the temperature of cellulose dissolution (−5 °C), they could not be dissolved to become liquid. The Arrhenius analysis of the temperature dependence of viscosity in the cellulose solution indicated that a high apparent activation energy (E_a) occurred at 0 to −5 °C, suggesting the relatively stable IC structure. However, the viscosity of the cellulose solution increased slowly with an increase in the temperature at 0-40 °C, leading to the negative E_a values. The results suggested that the cellulose solution in NaOH/thiourea system is complex to differ from normal polymer systems.     

双取代基纤维素醚水凝胶的流变性质

以有机锆化合物交联双取代基纤维素醚（DSCE）产生水凝胶,采用动态小振幅振动实验方法测定凝胶流体的C’、C”、η*等粘弹参数,以及应力松弛、剪切触变行为,考察温度、盐对凝胶性能的影响,并对形成交联作用的微观机理与影响因素进行了初步的探讨。