Kinetic studies on the reaction of formaldehyde with diphenyl sulfide. Formaldehyde resins. 99

Kinetic studies on the acid-catalyzed reaction of formaldehyde with diphenyl sulfide (DPS) were carried out in acetic acid in the presence of sulfuric acid. The rate of the initial stage of the reaction was found to be in agreement with the following equation. The relative rates of diphenyl sulfide and its homologous compounds in the reaction with formaldehyde gave a good correlation with BROWN -OKAMOTO 's σ^⊕ values and a large ρ value. The polar effects of substituents of the substituted diphenyl sulfides on the rates were found to be considerably large. From these results a plausible mechanism of the reaction has been deduced.     

Formaldehyde resins. 93. Reaction rate of polynuclear p-cresol-formaldehyde-condensate with formaldehyde in acidic media

The linear poly nuclear p-cresol-formaldehyde condensates up to octabody^ll were syntHesized, and the rates of their reaction with formaldehyde in ca. 80% dioxane in the presence of perchloric acid were measured. The reaction rates of the one to four nuclear condensates (H? 1? H ～ H? 4? H) were approximately double of those of higher nuclear condensates (H? 5? H ～ H? 8? H). The abrupt decrease of the rate of tetrabody(H? 4? H) to the pentabody (H? 5? H) was explained by two considerations: The first is the rolling up form of the higher molecular condensate where the one end (i.e. the reactive site) is hidden by the molecule itself and the second is the formation of hydrogen bonds between all the hydroxyl groups to decrease the reactivity of the aromatic substitution with a methylol cation.     

Products from the reaction of diphenyl ether with formaldehyde. Resins from formaldehyde. 86

From the reaction products of diphenyl ether with formaldehyde in the presence of acidic catalysts, six compounds were purely isolated: p-methylol and p,p′-dimethylol diphenyl ether, and four compounds of the following structures: Their structures were identified by the IR-absorptions and by the synthesis of their derivatives.     

Studies on formaldehyde resins, 19. General base catalysis in hydroxymethylation of melamine with formaldehyde

Hydroxymethylation of melamine with formaldehyde to form N-(hydroxymethyl)melamine (2,4-diamino-6-hydroxymethylamino-1,3,5-triazine) was investigated kinetically by the use of hydrogen phosphate/phosphate buffers in aqueous media at pH 11 ? 12. This reaction was found to follow a general base catalysis which results from the kinetic investigation, showing that the reaction takes place by a concerted mechanism involving base, melamine, and formaldehyde. This mechanism differs from that of the base catalyzed hydroxymethylation of phenol or benzamide with formaldehyde, because the acidic phenol and benzamide easily form their conjugate bases by addition of the basic catalyst in a preceding equilibrium step.     

Studies on formaldehyde resins, 15. Base-catalyzed hydrolysis of bis(hydroxymethyl)melamine

The hydrolysis of N,N′-bis(hydroxymethyl)melamine [6-amino-2,4-bis(hydroxymethylamino)-1,3,5-triazine] to N-(hydroxymethyl)melamine [2,4-diamino-6-(hydroxymethylamino)-1,3,5-triazine] was studied in dimethyl sulfoxide/water (volume ratio 1:9) using sodium hydroxide as a basic catalyst, in the region [Sodium hydroxide]₀=0 to 2 mol·1^?1. The study of the dependence of logk on the pH revealed that logk is nearly constant in the range of pH≈8–10 and increases with the slope of d(logk)/d(pH)≈1 in the region of pH≈11–13,5, followed by a gradual saturation at a stronger basic region where k is a first order rate constant. A rate equation for the hydrolysis is proposed, and the hydrolysis mechanism was elucidated by comparison of the theoretical curves resulting from this rate equation with the corresponding experimental curves.     

Studies on formaldehyde resins, 18. Kinetics of acid-catalyzed hydrolysis of bis(hydroxymethyl)melamine

Kinetics and mechanism of the acid-catalyzed hydrolysis of N,N′-bis(hydroxymethyl)melamine [6-amino-2,4-bis(hydroxymethylamino)-1,3,5-triazine] (M2F) were studied in the pH region of 0,5 ? 7,6 at 30°C, where 30 vol.-% DMSO aqueous solution was used as a solvent. The main results are as follows. The hydrolysis of M2F was of ca. 1,5th order in [M2F]₀ at constant pH of 2,7 ? 7,6, and was of ca. 1st order in the strongly acidic region of pH 0,5 ? 1,0. Moreover, the hydrolysis rate of M2F attained a maximum at pH 4,0 corresponding to [HCl]₀/[M2F]₀ = 0,5 and a minimum at pH 1,9. On the basis of these results and kinetic investigations, the main reaction of the hydrolysis of M2F is plausible to be a reaction of the conjugate acid of M2F with a M2F molecule in the acidic range of pH > 2,7.     

Studies on formaldehyde resins, 25. Kinetic study on the hydroxymethylation of melamine by means of HPLC

The kinetics of hydroxymethylation of melamine (2,4,6-triamino-1,3,5-triazine) with formaldehyde to form N-(hydroxymethyl)melamine (2,4-diamino-6-hydroxymethylamino-1,3,5-triazine) was investigated in aqueous hydrogen phosphate/phosphate buffer solutions in the range of pH 10,51 to 12,20 at 20°C, determining unreacted melamine by means of HPLC. As a result, this reaction is subject to a general base catalysis, and the second order rate constant k is expressed by k = k′ + k_A ? [A^?] + k[A^?]²/[HA] (or k [A^?][OH^?]), where HA and A^? denote acid and basic constituents of the buffer, and k′ is the rate constant in unbuffered media. This rate equation is compared with those reported previously.     

Reaction of fungal products with amebocyte lysates of the Japanese horseshoe crab, Tachypleus tridentatus.

A commercially available endotoxin assay (CS-TAL) employing a chromogenic peptide and an amebocyte lysate from the Japanese horseshoe crab, Tachypleus tridentatus, gave a positive result with aqueous extracts of all 15 strains of Candida albicans and 1 strain each of Candida tropicalis, Cryptococcus neoformans, and a Mucor species that we tested. Purified glucans prepared from the Candida strains gave the same results. Reconstruction experiments showed that the positive results were not due to contaminating endotoxin. By contrast, assays employing amebocyte lysates of the American horseshoe crab, Limulus polyphemus, were inconsistent. Japanese workers have presented evidence that glucans activate the Tachypleus amebocyte lysate system by acting on an enzyme different from that on which endotoxin acts. Using a Tachypleus lysate preparation (Endospecy; Seikagaku Kogyo, Tokyo, Japan) from which this enzyme was excluded, we demonstrated a 5- to 10-fold drop in reactivity to the aqueous Candida extracts and glucans, whereas reactivity to endotoxin was unchanged. Normal human plasma was shown to decrease the effect of fungal extracts on CS-TAL. This inhibition was completely removed by heating the plasma. Our results suggest that Tachypleus systems may be of use clinically in distinguishing bacterial from fungal infections.     

Reaction of Bacillus subtilis products with amebocyte lysates of the Japanese horseshoe crab, Tachypleus tridentatus.

Autoclaved aqueous extracts of Candida albicans cells (and the glucans isolated from them) give a positive reaction with a chromogenic substrate combined with amebocyte lysates of the Japanese horseshoe crab, Tachypleus tridentatus (CS-TAL). The extracts and glucans activate the lysate enzyme compound G, which in turn activates clotting enzyme. Activated clotting enzyme causes a positive CS-TAL reaction. C. albicans extracts and glucans react positively with a commercially available, unaltered CS-TAL preparation (Toxicolor), but they give a negative reaction with a CS-TAL from which compound G has been excluded (Endospecy). An autoclaved, sterile preparation of Sabouraud glucose broth used as a control in one experiment gave (like Candida extracts) a positive reaction with Toxicolor and a negative reaction with Endospecy. We found that the peptone powder used to make the Sabouraud glucose broth was contaminated with a strain of Bacillus subtilis. Autoclaved aqueous extracts of culture-grown B. subtilis cells were positive with Toxicolor and negative with Endospecy. This was also the case with two other strains of B. subtilis. Polysaccharides obtained from these extracts gave the same result. Endotoxin activates clotting enzyme through activation of the lysate enzyme compound C, which is present in both Toxicolor and Endospecy. Endotoxin, therefore, reacts with both CS-TAL preparations. Simultaneous assay with Toxicolor and Endospecy distinguishes endotoxin from fungal products, but since products of fungi and B. subtilis both give a positive Toxicolor and a negative Endospecy test, a simultaneous assay cannot differentiate them. However, this does not decrease the clinical value of the simultaneous Toxicolor-Endospecy assay for distinguishing fungal infection from endotoxemia because B. subtilis so rarely causes disease that it can be excluded from clinical consideration.     

Polymer resins with amino acid containing pendants for sorption of bilirubin. I. Comparison of Merrifield and polyamide resins

Merrifield resins with various amino acid containing pendants and a water swellable polyamide resin with the peptide alanine-alanine-alanine-arginine as the pendant group have been prepared by solid phase peptide synthesis. Merrifield resins with either arginine or lysine pendants are capable of sorbing bilirubin from aqueous solution (pH = 7.8) but those with other amino acid pendants gave no indication of sorption. The polyamide-arginine resin showed, on a functional group basis, a higher capacity for bilirubin than does cholestyramine. It is proposed that the formation of salt linkages causes a strong interaction of bilirubin with arginine and lysine.     

Immunologic studies of subjects with asthma exposed to formaldehyde and urea-formaldehyde foam insulation (UFFI) off products

There has been concern in recent years as to the health hazards of exposure to potentially carcinogenic or immunotoxic substances in the environment. This study was done to determine the effects of exposure to urea-formaldehyde foam insulation (UFFI) off products on various hematologic and immunologic parameters in subjects with asthma: complete blood count and differential, erythrocyte sedimentation rate, lymphocyte subpopulations (E-rosetting, T3, T4, T8, B73.1, and Fc receptor positive lymphocytes and large granular lymphocytes), lymphocyte response to phytohemagglutinin and formalin-treated red blood cells (Form-RBC), serum antibody against the Thomsen-Friedenreich RBC antigen and against Form-RBC, and natural killer (NK), interferon (IFN)-boosted NK (IFN-NK), and antibody-dependent cell-mediated cytotoxicity. Four control subjects with asthma from conventionally insulated homes (control group) and 23 subjects with asthma from UFFI-insulated homes (home group) were exposed to placebo, formaldehyde, dust, and UFFI off gas at levels ordinarily found in UFFI-containing homes for four separate periods in an environmental chamber. Immunologic testing was carried out before the exposure series and 1 day after completion 7 days later as part of an investigation of respiratory and possible allergic effects of such exposure. Data from the UFFI-insulated home group were not significantly different from data of the normal conventionally insulated home control group for any of the variables studied, either before or after UFFI exposure. Paired t tests comparing data from each of the two groups before and after UFFI exposure demonstrated minimal but statistically significant increases in percent eosinophils and T8 positive cells in the UFFI-insulated home group only. Although NK, relative NK, and IFN-NK were normal in all groups, IFN-NK assays by use of a low concentration of alpha-interferon demonstrated a statistically significant decrease in NK response to IFN in both the control and UFFI-insulated home groups after UFFI exposure. These differences were not observed at optimum levels of IFN stimulation. These data indicate that long-term exposure to UFFI off products in the home apparently had no effect on the immunologic parameters studied. Short-term exposure resulted in minor immunologic changes in this subject population.     

Allergy in chronic haemodialysis. 1. Double-blind intravenous challenge with formaldehyde

Patients undergoing chronic haemodialysis are often exposed to formaldehyde, formaldehyde (F) has been reported to cause IgE-mediated anaphylactic shock. Many other patients reported pruritus or anaphylaxis-like symptoms when dialysed with F-sterilized dialysers. Ten patients presenting such symptoms were compared with five control subjects. Intravenous double-blind challenges were performed on six consecutive occasions, with capillary flow dialysers sterilized with or without F. Dialysis was performed by an investigator who was not aware of the sterilization procedure. Among the ten F-sensitive patients, five had symptoms with F-sterilized dialysers and no symptoms with new dialysers, sterilized by ethylene oxide and free of F. Symptoms included pruritus and hypotension. These five patients were subsequently dialysed with new dialysers, not sterilized with F, and symptoms subsided. The five other patients had inconclusive challenges. The five control subjects had no symptoms during challenges. Skin-prick tests with F showed that only one of the five patients who had symptoms with F-dialysers had a strongly positive prick test. RAST to F was titrated with HSA-discs but it was negative in all patients and control subjects. Formaldehyde was shown to cause symptoms in some patients under chronic haemodialysis but an IgE-mediated mechanism was not demonstrated.     

Impregnation of soft biological specimens with thermosetting resins and elastomers.

A new method for impregnation of biological specimens with thermosetting resins and elastomers is described. The method has the advantage that the original relief of the surface is retained. The impregnation is carried out by utilizing the difference between the high vapor tension of the intermedium (e.g., methylene chloride) and the low vapor tension of the solution to be polymerized. After impregnation, the specimen is subject to polymerization conditions without surrounding embedding material. The optical and mechanical properties can be selected by proper choice from various kinds of resins and different procedures, for example, by complete or incomplete impregnation. Acrylic resins, polyester resins, epoxy resins, polyurethanes and silicone rubber have been found suitable for the method. Excellent results have been obtained using transparent silicone rubber since after treatment the specimens are still flexible and resilient, and have retained their natural appearance.     

Reaction of oral mucosa depends on surface physicochemical characteristics of acrylic resins of plate dentures

The reactions of oral mucosa (denture bed) contacting with removable plate dentures made of acrylic resins were studied. The reaction depended on physicochemical characteristics of denture surface. Glow discharge treatment of denture improved their hygienic characteristics and biocompatibility. Microscopic study of oral mucosa scrapings from patients with modified dentures showed normalization of cytogram and increased keratinization index. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 129, No. 1, pp. 109–112, January, 2000     

Effect of filler content on the profile of released biodegradation products in micro-filled bis-GMA/TEGDMA dental composite resins.

This study assesses the effect of the filler content, in a micro-filled composite (0.04 microm), on the liberation of biodegradation products derived from two model composite systems. The materials were based on bis-phenyl glycidyl dimethacrylate (bis-GMA) and triethylenene glycol dimethacrylate (TEGDMA) monomers. The composites were produced using silica filler concentrations of 20 and 40%) by weight. Samples were incubated with either cholesterol esterase (CE) or phosphate buffer solutions (PBS) for 8, 16 and 32 days. Products were isolated by high-performance liquid chromatography (HPLC) and identified by mass spectrometry. The identified products included TEGDMA, 2,2-bis[4(2,3-hydroxypropoxy)-phenyl]propane (bis-HPPP) and triethylene glycol methacrylate (TEGMA). Bis-HPPP was only produced in the presence of enzyme. The amount of isolated TEGMA, in both composite systems, was shown to be significantly higher for materials incubated with enzyme than their buffer counterparts (P < 0.05). Between 0 and 8 days incubation with enzyme, significantly higher amounts of Bis-HPPP and TEGMA were generated with the lower filler model material (composite-20) than the higher filled composite (composite-40), while the opposite effect was observed between 8 and 16 days. The data indicate that biodegradation product release profiles are dependent on the filler/resin ratios, and suggests that this parameter should be considered when assessing product release for biocompatibility issues pertaining to dental composite systems.