Synthesis of HCN Polymer from Thermal Decomposition of Formamide

Prolonged heating of formamide (HCONH₂) at 185°C or 220°C produces a black insoluble product. The FT-IR spectroscopy and the X-ray photoelectron spectroscopy (XPS) suggest that the product has the chemical structure of a polymer of hydrocyanic acid: (HCN)_x. The pyrolysis of (HCN)_x prepared from formamide produces a large amount of gaseous HCN in a wide range of temperatures together with ammonia (NH₃) and isocyanic acid (H─N─C═O).

During the thermal decomposition of formamide to produce (HCN)_x, the volatile products evolved were monitored with gas phase infrared spectroscopy. At 185°C, the gaseous product released were CO₂, CO and NH₃ while at 220°C, also HCN was detected. In both cases, a white sublimate was collected in the upper part of the reaction vessel. It consists of ammonium carbamate and its hydrolysis products ammonium carbonate and hydrogen carbonate. It is therefore possible to synthesize the polymer of hydrocyanic acid (HCN)_x starting from formamide avoiding to handle the dangerous hydrocyanic acid.     

Haloaldehyde polymers. IX. Polybromodichloroacetaldehyde

Bromodichloroacetaldehyde was synthesized by two methods. The first synthesis started from chloral, which was allowed to react with Ph₃P and the resultant compound brominated and hydrolyzed to give bromodichloroacetaldehyde in an overall yield of 60%. Purification by repeated distillation from P₂O₅ gave polymerization grade bromodichloroacetabldehyde. Bromodichloroacetaldehyde could also be synthesized by bromination of dichloroacetaldehyde diethyl acetal. The yields of this synthesis were only 20–30%, and the aldehyde could not be purified readily to give polymerization grade monomer. Bromodichloroacetaldehyde could be homopolymerized at ?30°C with anionic and also some cationic initiators to a polymer which was insoluble and did not melt but degraded to monomer above 200°C. The ceiling temperature of the polymerization was ?15°C in 1M solution. Bromodichloroacetaldehyde could also be copolymerized with isocyanates, primarily aryl isocyanates, and also with chloral.     

Theoretical study and atoms in molecule analysis of hydrogen bonded clusters of ammonia and isocyanic acid

Abstract  

Ab initio and density functional calculations were used to analyze the interaction between a molecule of the isocyanic acid with 1 up to 4 molecules of ammonia at the B3LYP/6-311++G(d,p) and MP2/6-311++G(d,p) computational levels. The cooperative effect is increased with the increasing size of studied clusters. Red shifts of the H–N stretching frequency for complexes involving the isocyanic acid as an H-donor were predicted. Atom in molecules was used to analyze cooperative effects on topological parameters.     

Determination of low degrees of hardness in water using a soap solution according to clark. I

1. The determination of low degrees of hardness in water according to the usual methods does not yield satisfactory results. Therefore an investigation was carried out with a soap solution of sodium, oleate according to clarke, and also nephelometric measurements were made. 2. Measurements were cairied out at degrees of hardness from 0.5 to 39.0 p.p.m. (i.e. 0°.005–3°.09 FH; or 0°.003–2°.18 DH), made out of pure calcium chloride solutions, at different pH values; also with calcium chloride solations, containing NaCI and alcohol. Magnesium, chloride solutions were investigated in the same way. 3. The calcium oleate, that precipitates when the hardness is determined, has a composition of 5 CaOl₂-2NaOl. The magnesium oleate has a corresponding composition. Dependent on the circumstances also 5 CaOl₂-3NaOl and calcium oleates. containing yet more sodium oleate may be formed. This phenomenon occurs especially at very low degrees of hardness. 4. No turbidity of calcium oleate arises when precipitation takes place at degrees of liardness lower tlian 1.2 p.p.m. CaCO₃(0°.07 DH), Magnesium olcate does not precipitate at degrees of hardness lower than 3.2 p.p.m. (0°.18 DH). 5. As a result of the phenomenon referred to in. point 3 the determination according to clarke for degrees of hardness below 5 p.p.m. CaCO₃(0°.3 DH) are only reliable if very important errors (up to 30%) are tolerated. In order to determine these degrees of hardness it is therefore advisable to add so much concentrated CaCl₂ solution as to reach a handy hardness of the water sample.     

Effect of Polycondensation Reaction Conditions on the Properties of Thermotropic Liquid‐Crystalline Copolyester

In this study a range of wholly aromatic copolyesters based on kink m‐acetoxybenzoic acid (m‐ABA) monomer (33 mol%) and equimolar‐linear p‐acetoxybenzoic acid (p‐ABA), hydroquinone diacetate (HQDA) and terephthalic acid (TPA) monomers (67 mol%) have been synthesized by melt polycondensation reaction process at 280°C and 260°C for different time intervals. Characterization of copolyesters were performed by solution viscosity measurement, wide–angle X‐ray diffraction (WAXD), differential scanning calorimetry (DSC), hot‐stage polarized light microscopy, proton‐nuclear magnetic resonance analysis (¹H‐NMR). According to the results obtained, copolyesters showed thermotropic liquid crystalline behavior in an appropriate temperature range. The copolyesters were prepared in high yields. It was observed that the intrinsic viscosities of the copolyesters are increased regularly with increasing polymerization time and temperature. All the copolyesters were soluble in a trifluoroacetic acid/dichloromethane (30:70 v/v) except the copolyesters which were synthesized at 280°C in 5 h. According to the WAXD results; the degree of crystallinity of copolyesters were found to be between 5–15%. DSC and hot stage polarized light microscopy results showed that all the copolyesters are melt processable and a significant molecular interaction exist in a very broad temperature range (160°C and 165°C) in the nematic mesophase. The T_g values are increased with an increasing polycondensation reaction time and temperature and they were observed between 93–126°C. Fibers prepared by a hand‐spinning technique from the polymer melt exhibit well‐developed fibrillar structure parallel to the fiber axis.     

Copolymerization of chloral with trioxane

Copolymers of trichloroacetaldehyde (chloral) and 1,3,5-trioxane have been prepared in solvent-free systems with aluminium bromide as an initiator at 4 and ?15°. CH₂Cl₂ inhibited polymerization. From i.r.-spectra and chlorine determinations, the copolymers were found to have degrees of polymerization of about 40 and to contain 4–17 mole % oxymethylene units. X-ray diffraction studies indicated a completely amorphous material and no melting was observed with differential scanning calorimetry. The latter method indicated a decomposition temperature of 300°, compared with 180 and 220° for polyoxymethylene and polychloral respectively. The copolymers were stable towards chemical treatments deleterious to the corresponding homopolymers viz. 10% aq. KOH at 25° and concentrated H₂SO₄ at 130°. The stability towards alkaline solutions shows that the haloform reaction with polychloral proceeds via depolymerization and not via direct attack on the polymer chain.     

Dyed polyvinyl chloride films for use as high-dose routine dosimeters in radiation processing

Characteristics of the polyvinyl chloride (PVC) films containing 0.11 wt% of malachite green oxalate or 6GX-setoglausine and about 100 μm in thickness were studied for use as routine dosimeters in radiation processing. These films show basically color bleaching under irradiation with ⁶⁰Co γ-rays in a dose range of 5–50 kGy. The sensitivity of the dosimeters and the linearity of dose-response curves are improved by adding 2.5% of chloral hydrate [CCl₃CH(OH)₂] and 0.15% hydroquinone [HOC₆H₄OH]. These additions extend the minimum dose limit to 1 kGy covering dosimetry requirements of the quality assurance in radiation processing of food and healthcare products. The dose responses of both dyed PVC films at irradiation temperatures from 20°C to 35°C are constant relative to those at 25°C, and the temperature coefficients for irradiation temperatures from 35°C to 55°C were estimated to be (0.43±0.01)%/°C. The dosimeter characteristics are stable within 1% at 25°C before and 60 days after the end of irradiation.     

Thermal decyanation,a new organic reaction. II

When heated in solution at about 160°C, pyridine quaternary salts of bromomalonamides lose 1 mole of cyanic or isocyanic acid almost quantitatively in a manner quite analogous to the decarboxylation of an acid. By DTA and DSC, the crystalline salts are stable up to their melting points (>220°C) at which temperatures concurrent fusion and decyanation processes occur (endotherm); these are immediately followed by an exotherm related to the trimerization of cyanic acid. TGA measurements on the solid salts do not clearly define the loss of 1 mole of cyanic acid because in the solid state, thermal decyanation is accompanied to some extent by other pyrolytic reactions. Preparative methods for quaternizing poly(4-vinylpyridine) with bromomalonamide are described and two polymeric quaternary salts (33 and 100% substituted) were prepared and analyzed. These polyelectrolytes are water soluble and upon the addition of base the yellow polymeric nitrogen ylids are generated. Infrared spectra on the polymeric quaternary salts and visible spectra on the polymeric ylids are included. The ylid chromophore has an ε = 1800 at λ_max = 415 nm. The dilute solution viscosity behavior of these polymers in H₂O and in 0.05N KBr is typical of polyelectrolytes. Both polymers in dilute solution show a maximum in η_sp versus pH plots. In water, the viscosity of these polymers decreases with time, and it is proven that this results from a conformational change which accompanies amide hydrolysis rather than polymer backbone degradation. Glass transitions are not detectable by DTA but both polymers show well-defined trimerization exotherms for cyanic acid starting at 170–175°C. Thus, decyanation of the solid polymeric quaternary salts is more analogous to decyanation of the crystalline quaternarys in solution than as solids. TGA measurements on the polymers show weight losses which are of the correct order of magnitude and in the correct temperature range for monodecyanation. Some data are presented which suggest that perhaps a second mole of cyanic acid is lost at about 250°C. Quaternization of poly(4-vinylpyridine) with bromomalonamide reduces its gross decomposition temperature from 385°C to about 285–317°C. It is demonstrated how thermal decyanation can be used for the in situ generation of cyanic acid for the modification of organic compounds. The preparation of a partial urethane of poly(vinyl alcohol) using this method is described. We have also shown that aliphatic quaternary salts can be prepared and that they too undergo the decyanation reaction.     

Phase diagram for the ternary system LiClCaCl2CaCrO4

The phase diagram for the system LiClCaCl₂CaCrO₄ has been studied using differential thermal analysis. LiClCaCl₂CaCrO₄ has been shown by X-ray diffraction to be a stable, diagonal section of the Li, Ca//Cl, CrO₄ reciprocal ternary system. The three binary systems are: LiClCaCl₂ which exhibits a double salt (LiCaCl₃), which decomposes without melting at 439°C and a eutectic at 36.3 mole % CaCl₂ (m.p. 487°C); CaCl₂CaCrO₄ which shows a eutectic at 23.4 mole % CaCrO₄ (m.p. 660°C); and LiClCaCrO₄ with a eutectic at 14.3 mole % CaCrO₄ (m.p. 538°C).In the ternary system, a eutectic exists at 63.2 mole % LiCl32.9% CaCl₂3.9% CaCrO₄ (m.p. 479°C). In addition, a four-phase equilibrium, involving all solid phases, exists at nearly all compositions at 435°C.Isotherms are shown for the liquidus surface (primary crystallization) and for the secondary crystallization surface. Isothermal and vertical sections through the ternary phase diagram are shown.     

Dynamics of CO formation in the photodissociation of HNCO and CH2CO at 193nm

The photodissociation of isocyanic acid (HNCO) and ketene (CH₂CO) at 193 nm was investigated using an ArF laser to dissociate the carbonyl compound and a CO laser to probe the resulting vibrationally excited CO. The dissociation of HNCO at 193 nm produces CO with an average vibrational energy of 4.6 ± 0.3 kcal/mol. The dissociation Gf CH₂CO at 193 nm produces CO with an average vibrational energy of 6.4 ± 0.8 kcal/mol. The observed CO vibrational energy distributions were found to be in close agreement with those predicted statistically assuming NH(a ¹Δ) + CO and CH₂(¹A₁) + CO were the photodissociation products.     

Thermal degradation of bromine-containing polymers: Part 6—An equimolar copolymer of 2-bromoethyl methacrylate and acrylonitrile

The thermal degradation of an equimolar copolymer of 2-bromoethyl methacrylate and acrylonitrile occurs in two well defined steps. Below 310°C, ethylene, carbon dioxide, vinyl bromide, acetaldehyde and 1,2-dibromoethane are the principal products and certain well defined chemical changes in the residual polymer are revealed by infra-red spectroscopy. In the second stage, which occurs in the range 250–500°C, propane, isobutene, carbon dioxide, hydrogen cyanide and isocyanic acid are the principal volatile products, as well as a substantial yellow coloured chain fragment fraction.All of these—and certain additional trace products—have been accounted for mechanistically.     

The point of zero charge of manganese dioxides

Chemically prepared δ-MnO₂ (sample A) was characterised by chemical and size analyses and by t.g.a. and d.t.a. Sample B was the well-characterised International Common Sample ICS 5, which is a chemical λ-MnO₂. Potentiometric acid/base titration of sample A gave a point of zero charge, p.z.c., at pH 3.3±0.5, which is close to the isoelectric point obtained from sedimentation-coagulation results. Fast acid/base titration of sample B gave a p.z.c. at pH 5.9±0.3, which is close to the isoelectric point estimated from electrophoretic measurements. Temperature in the range 298–346 K (25°–73°C) had a minor effect on the titration results.     

The synthesis of perfluoro(alkyletherphenyl) phosphines

The first perfluorophenyl substituted phosphine, C₆F₅)₃P was prepared by Wall et al. [1]. Since then numerous pentafluorophenylphosphorous compounds [2] have been prepared and their properties studied. Substituted perfluorophenylphosphines (R_fC₆F₄)₃P however not been extensively studied. Those that have been reported are all solids: (C₆F₅)₃P, m.p. 116° [1]; (p-CF₃C₆F₄)₃P, m.p. 103-105° [3]; (p-C₈F₁₇C₆F₄)₃P m.p. 117° [3]; and (p-C₆F₅OC₆F₄)₃P, m.p. 135-137° [4].     

The determination of traces of osmium in ruthenium sponge by neutron activation analysis

Tracer techniques confirmed that a quantitative separation of osmium and ruthenium is possible by distillation from a hydrogen peroxide-sulphuric acid solution. Osmium distils quantitatively as OsO₄ at a temperature of 105 ± 5° in about 30 min. The ruthenium contamination is approximately 0.01 %.In the present work a neutron activation analysis is described for the determination of traces of osmium in ruthenium sponge. When quantities of osmium below 30 p.p.m. are determined, the ruthenium contamination of the distillate must be taken into account, when the measurement is made with a 3” x 3” NaI(Tl) crystal. This can easily be achieved by measurement in two energy regions with a γ-spectrometer or with a multichannel pulse-height analyzer. With a NaI(T1) wafer as detector, the correction for ruthenium can be omitted for osmium concentrations above 10 p.p.m.With the addition method of analysis, 10–2000 p.p.m. in 10-mg samples of ruthenium sponge can be determined by neutron activation analysis. Chemical separation is necessary but no carriers are required. The lowest limit of determination is about 3 p.p.m. for a 3” x 3” crystal; for the wafer, about 1 p.p.m. can be determined.     

Chemistry of silicon-nitrogen compounds. 165. On the crystalline products from the reaction of silicon tetrachloride with nitrogen in a glow discharge. Single crystal X-ray structure determination of N(SiCl3)3 and Cl3SiN(SiCl2)2NSiCl3

Of the two crystalline products obtained by reacting a silicon tetrachloride/nitrogen mixture in a glow discharge tube, the more volatile (m. p. 78°C) has been confirmed to be tris(trichlorosilyl)amine NSi₃Cl₉ whereas the less volatile component (m. p. 66°C) has been identified as N,N′-bis(trichlorosilyl)-Si,Si′-tetrachloro-cyclodisildiazane N₂Si₄Cl₁₀. These conclusions are supported by mass and vibrational spectroscopy and single crystal X-ray structures. NSi₃Cl₉ possesses a nearly planar NSi₃ skeleton with average N? Si distances of 1.734(2) Å. The N₂Si₄ fragment of N₂Si₄Cl₁₀ is roughly planar with endocyclic N? Si? N and Si? N? Si angles of 89.2(1) and 90.8(1)°, respectively, and mean N? Si distances of 1.731(3) (endocyclic) and 1.687(3) Å (exocyclic).     

Phase diagrams for the binary systems CaCl2-KCl and CaCl2-CaCrO4

Phase diagrams have been determined using differential thermal analysis for the binary systems CaCl₂-KCl and CaCl₂-CaCrO₄. CaCl₂-KCl phase diagrams have been previously reported but results were not consistent. No prior studies have been reported for the CaCl₂-CaCrO₄ system. In the CaCl₂-KCl binary system two eutectics have been located at 24.0 mole % KCl (m.p. 615°C) and 74.3 mole % KCl (m.p. 594°C). A double salt of composition CaKCl3 melting congruently at 741°C has been found. The CaCl₂-CaCrO₄ system is a simple eutectic system with the eutectic occurring at 23.4 mole % CaCrO₄ and melting at 660°C.     

Spectrophotometric determination of vanadium (V) with 2-naphthohydroxamic acid

2-Naphthohydroxamic acid in methanol gives an intense and stable red-orange color with vanadium (V), sensitive to 0.009 μg V/cm², for log I₀/I = 0.001 abs. unit at wavelength 450 mμ. The value for σ is ±0.006 a.u., equivalent to ±0.08 p.p.m. V. The colored complex obeys Beer's law over the range 1–10 p.p.m. vanadium. The absorbance (in 1-cm cell) at 10 p.p.m. was so great that no data were obtained at higher concentrations. Under the conditions of the reaction, the combining ratio of vanadium and 2-naphthohydroxamic acid appears to be 1 to 2. Optimum conditions for the use of 2-naphthohydroxamic acid as a spectrophotometric reagent for vanadium-(V) were established; the procedure was applied to the determination of vanadium in steels and non-ferrous alloys with good precision and accuracy.     

Neutron activation analysis of high-purity selenium : Determination of phosphorus,sulfur and chlorine

Chlorine was determined in selenium by irradiation of 2-g samples for 37 min at a flux of 8·10¹⁰ n/cm²/sec. Chlorine was volatilised from hot concentrated nitric acid and precipitated as silver chloride. The isotope ³⁸Cl (T_{$\text{1}\text{2}$}=37.3 min) was counted by γ-spectrometry. Sulfur and phosphorus were determined by irradiating 50-mg samples with and without cadmium shielding for 4 days at a thermal flux of 6·10¹² n/cm²/sec and a fast flux of 4·10¹¹ n/cm²/sec. The matrix activities were separated by distillation from sulfuric acid-hydrobromic acid at 200–220°. The isotope ³²P (T_{$\text{1}\text{2}$}=14.3 d) was then precipitated, together with phosphate carrier, as ammonium phosphomolybdate, and counted with a G.M. tube. Amounts of 0.4–1 p.p.m. chlorine, 65–520 p.p.b. phosphorus and 1.5–4.6 p.p.m. sulfur were found in high-purity selenium samples.     

Synthesis and polymerization of racemic and optically active β-substituted β-propiolactones. II: β-monosubstituted and β-disubstituted monomers and polymers with different optical purities

β-(trichloromethyl)-β-propiolactone (CCl₃-PL), β-(trifluoromethyl,methyl)-β-propiolactone (CF₃, Me-PL) and β-(trifluoromethyl,ethyl)-β-propiolactone (CF₃,Et-PL) have been obtained by the reaction of ketene with chloral, 1,1,1-trifluoroacetone and 1,1,1-trifluorobutanone, respectively. Chiral catalysis lead to optically active monomers. The enantiomeric excess of the lactones has been measured by ¹H-NMR spectroscopy, in the presence of 2,2,2-trifluoro-1-(9-anthryl)ethanol or an europium chiral shift reagent. Polymerizations have been carried out in bulk or in toluene, at 60°C or 80°C, using mainly organometallic initiators. The Polymers become insoluble and crystalline at enantiomeric excesses over 80% for CCl₃-PL and 70% for CF₃,Me-PL. Melting temperatures were recorded from 238 to 268°C for poly(CCl₃-PL) and from 78 to 100°C for poly(CF₃,Me-PL), depending upon the molecular weight and the enantiomeric excess. The ¹³C-NMR specroscopy of poly(CCL₃-PL) indicates that the polymerization of the corresponding lactone leads to polymers of increasing degrees of isotacticity with the enantiomeric excess of the monomer.