1H n.m.r. technique for characterization of polymerized petroleum pitches

A new proton n.m.r. technique has been developed for the chemical characterization of polymerized petroleum pitches with pyridine-insoluble contents as high as 80%. The polymerized pitches were completely solubilized for conventional ¹H n.m.r. evaluation in a mixed solvent system consisting of S₂Cl₂-SO₂Cl₂. Although solubilization occurs via the addition of chlorine to the polynuclear aromatic rings, the n.m.r. spectra can still be quantitatively interpreted. Several applications are discussed.     

13C, 2H, 1H n.m.r. and gpc study of structural evolution of a subbituminous coal during treatment with tetralin at 427 °C

Subbituminous Kaiparowitz coal was treated with 1,1-d₂-tetralin or tetralin in sealed tubes at 427 °C and 500 °C for varying periods of time and rates of temperature rise (15 °C/s, 3 °C/s, and 1 °C/s). The time dependence of yields, average molecular weights, molecular-weight distributions and changes in hydroxyl-group content and elemental composition were determined. Deuterium FT n.m.r. was used to monitor the incorporation of deuterium from 1,1-dideuteriotetralin into aliphatic and aromatic structures in the fractionated products. The exchange of ²H with phenol in the presence of the coal was examined to aid in the interpretation of ²H n.m.r. results. ¹³C and ¹H FT n.m.r. and i.r. spectroscopy were used to monitor the fractionated products over time. The ultimate obtainable yields of THF-soluble product were not significantly altered by the shorter temperature-rise times. The highoxygen-containing subbituminous coal undergoes an extremely rapid loss of about 20% of its oxygen by dehydration, and was found to enhance the rate of reduction of acetophenone and the scrambling of deuterium label in tetralin. The growth of benzylic aliphatic hydrogen at the expense of β (ArCH₂C$\text{H}$₂) hydrogen was rapid in the early stages of reaction. In spite of apparently labile aliphatic structures, the preasphaltenes exhibited products above MW 1200 that were stable for more than 2 h at 500 °C.     

Zum Mechanismus der thermischen Abspaltung von Chlorwasserstoff aus Polyvinylchlorid. 9. mitt.: Zur struktur der verzweigungen in polyvinylchlorid

The reduction of PVC and of copolymers from vinyl chloride and 2-chloropropene with lithium aluminium hydride occurs in a nearly quantitative manner. A selective reduction of the tertiary chlorine atoms in the copolymers, using lithium deuteride, cannot be observed by means of n.m.r. spectroscopy. The amount of CH₃-groupins the reduced samples was determined by i.r. spectroscopic compensation against polymethylene. The number of methyl groups determined in the copolymers agrees well with the copolymer composition found by n.m.r. spectroscopy. The experimental results of the determination of branches and of the thermal degradation indicate no tertiary chlorine atoms in PVC; therefore, one can assume another structure of branches in PVC.     

A novel semi-empirical relationship between aromaticities measured from 1H and 13C n.m.r. spectra

An empirical correlation between ¹H n.m.r. measured aromaticity (H_ar) and ¹³C n.m.r. measured aromaticity (C_ar) has been found. Over 300 samples which are diverse in origins and structural characteristics have been studied. A semi-empirical functional relationship between H_ar and C_ar has been devised. It is suggested that for distillable samples with, nominally, less than 50% boiling above 320 °C, the derived function can be used to rapidly and conveniently approximate C_ar from H_ar. The difference between observed and calculated C_ar values for 303 such samples shows a standard deviation of just 1.8%.     

Formation of anomalous structures in PVC and their influence on the thermal stability: 2. Branch structures and tertiary chlorine

Branch structures were determined in fractions of a commercial suspension of PVC (S-PVC) and experimental PVC samples obtained at subsaturation conditions (U-PVC). The analyses were performed with ¹³C n.m.r. spectroscopy at 50.31 MHz after reductive dehalogenation with tributyltinhydride. With increasing monomer starvation U-PVC was found to have an increasing amount of butyl and long chain branches (LCB). A polymer prepared at 55°C and 59% of the saturation pressure of vinylchloride had 3.4 butyl branches and 2.0 LCB per 1000 monomer units. In the S-PVC series the total content of these two structures varied between 0.5 and 1.0 per 1000 monomer units. By using tributyltindeuteride as reducing agent the structure of the butyl branches could be determined as ～CHClCH₂CCl(CH₂CHClCH₂CH₂Cl)CH₂CHCl～. A major part of the LCB points also contained tertiary chlorine. The formation of LCB is suggested as occurring after abstraction of hydrogen from the polymer chain by macroradicals and chlorine atoms. The latter will lead to LCB points with tertiary hydrogen and internal double bonds. The rate of dehydrochlorination at 190°C in nitrogen could be related to the amount of tertiary chlorine (correction coefficient=0.97). It was assumed that tertiary chlorine is the most important labile structure in PVC.     

Alkyl aryl ethers in lignite solubilization: 2. Analysis of oil fractions

The FT-i.r. and ¹H n.m.r. spectroscopic analyses of oils or maltenes from a Spanish lignite (Utrillas, Teruel), are reported. These oils were obtained by depolymerization with alkyl aromatic ethers (anisole, 3-methylanisoleand 1,3-dimethoxybenzene) catalyzed by Lewis acids ZnCl₂, AlCl₃, SbCl₃and BF₃ (as boron trifluoride etherate), at atmospheric pressure and temperatures <220 °C. Bands due to aromatic ethers in the i.r. and n.m.r. spectra of the oils obtained by depolymerization indicate solvent incorporation. Oils obtained by direct lignite extraction showed 25% aromatic H and some H_α (≈3%) without OH groups. These appeared in some oils obtained by depolymerization with AlCl₃ and were due to secondary reactions with the aromatic extract. Oils derived from processes with good yields showed increases in aromaticity. The extent of substitution of aromatic rings in oils obtained by depolymerization was less than for oils directly extracted. All the oils studied show a low degree of condensation.     

The characterization of coal tar pitches used in electrode binder manufacture by n.m.r. spectroscopy

Coal tar pitches dissolved in a mixed solvent system comprising S₂Cl₂ and SO₂Cl₂ were analysed by ¹H and ¹³C n.m.r. spectroscopy. The extensive chlorination of the pitch by this solvent unfortunately leads to serious underestimations in aromatic hydrogen concentrations when these solutions are examined by ¹H n.m.r. spectroscopy. However, quantitative data can be obtained using ¹³C n.m.r. spectroscopy where the carbon skeleton is unaffected by the extent of chlorination of the pitch. The ¹H n.m.r. spectra of individual aromatic compounds, similar to those found in coal tars have been recorded. The ¹H n.m.r. spectra confirmed that extensive chlorination of the aromatic nuclei had occurred which results in the non-quantitative estimation of hydrogen concentrations.     

Determination of carbon C,CH, CH2 and CH3 group abundances in liquids derived from petroleum and coal using selected multiplet 13C n.m.r. spectroscopy

Selected, multiplet C n.m.r. spectra are obtained for three test samples deriving from petroleum and coal sources, by combining gated spin echo (GASPE) and conventional spin echo ¹³C n.m.r. procedures. Each selected multiplet spectrum contains resonances due to only one of the following groups: aromatic C or CH or aliphatic C, CH, CH₂orCH₃. In general artifacts contribute only minor intensity to individual spectra, with the separation between aliphatic CH and CH₃ spectra being the most difficult to achieve. Each spectrum can be integrated to yield the relative abundances of CH_n groups (n = 0 to 3). Selected multiplet ¹³C n.m.r. spectra provide a more detailed view of the component hydrocarbon groups in fossil-fuel derived materials than can be deduced from conventional ¹³C n.m.r. spectra.     

Microstructure of solution-chlorinated polyethylene by 13C nuclear magnetic resonance

Solution-chlorinated polyethylene prepared by a modified method has been characterized using ¹³C nuclear magnetic resonance (n.m.r.) and differential thermal analysis (d.t.a.). The results show that the residual paraffin segments, melting point and crystallinity decrease rapidly with increasing chlorine content. The prepared polymer seems to have a homogeneous chlorine distribution.     

Isotope labelling as a probe for free-radical reactions during dibenzyl ether thermolysis

Pyrolysis of dibenzyl ether (DBE) in tetralin-d₁₂ allowed discrimination between possible free radical and concerted reaction mechanisms. Pyrolysis product spectra contained both α-deuteriotoluene and perprotiotoluene, relative fractions of which were determined, by complementary ¹H and ¹³C n.m.r. analyses, to vary with the initial ratio of tetralin-di₁₂ to DBE. Mathematical extrapolation to DBE pyrolysis at infinite dilution indicated that its thermolysis in tetralin-d₁₂ was entirely via free radical mechanisms.     

Nuclear magnetic resonance spectra of two reductively ethylated fuels

A lignite (67.2% C daf) and a coal (89.0% C daf) have been reductively ethylated by Sternberg's procedure⁴ and the spectra, in particular the ¹H and ¹³C n.m.r. spectra, of the products have been obtained. The distribution of hydrogen atoms and, in less detail, of carbon atoms in the reductively ethylated fuels has been determined. It is emphasized that both reductively ethylated fuels contained a variety of structures. The carbon aromaticities of the reductively ethylated lignite and the reductively ethylated coal were 0.41 ± 0.08 and 0.40 ? 0.54 respectively. The aromatic nuclei of the reductively ethylated coal were more highly substituted than those of the reductively ethylated lignite. The ¹H n.m.r. spectra indicate that the reductively ethylated coal and lignite possessed ≈3.5 and ≈2.5 substituents per benzene ring respectively. Resolved absorption in the ¹³C n.m.r. spectra suggests lower figures than these and it was evident that some of the benzene rings in both materials but especially in the reductively ethylated lignite were lightly substituted. The ¹³C n.m.r. spectra show that both materials contained branched and unbranched paraffin chains. Much of the ¹³C n.m.r. spectra however consisted of unresolved absorptions and the ¹³C n.m.r. measurements suggest that the reductively ethylated materials consisted of rigid, relatively immobile molecules of moderate molecular weight. ¹³C n.m.r. absorption by carbon atoms adjacent to aromatic rings was amongst that which was not resolved — though the rings themselves gave resolved absorptions — and this suggests that the aromatic rings were on the periphery of a rigid, perhaps alicyclic, structure.     

Dynamic structure of swollen crosslinked poly(ethylene oxide) gels from n.m.r. line-shape analysis and magic angle rotation n.m.r.

Chemically crosslinked poly(ethylene oxide) gels swollen to equilibrium in CDCl₃ (22.3 w/w% of polymer) and CCl₄ (77.5 w/w% of polymer) were characterized by combination of the results of ¹H n.m.r. spectra measured with magic angle rotation (MAR-n.m.r.) and numerical analysis of static ¹H n.m.r. line shapes. From MAR-n.m.r., activation energies of rapid segmental motions were found to be 1.7 ± 0.3 kcal mol^?1 in CDCl₃ and 9.4 ± 0.6 kcal mol^?1 in CCl₄. Static line-shape analysis yields a parameter which characterizes the deviation of segmental motions from isotropy in space. This parameter was found to be independent of temperature and equal in both systems.     

Analysis of epoxidized natural rubber. A comparative study of d.s.c., n.m.r., elemental analysis and direct titration methods

A comparative analysis of epoxidized natural rubber samples by ¹H and ¹³C n.m.r., titrimetric, elemental and d.s.c. techniques has been made. Whereas the titrimetric method is only applicable at low epoxy contents (< 15 mol%) both n.m.r. methods give reasonable precision over the compositional range of 20–75 mol%. Elemental analysis appears less reliable. D.s.c. analysis through measurement of T_g provides the highest precision of measurement but requires independent calibration by one or more of the primary methods. The epoxy content may also be related to the polymer density.     

Konformationsanalyse freier und komplexierter Kronenether in Lösung

Conformational Analysis of Free and Complexed Crown Ethers in Solution The conformational analysis of the crown ether family by means of n.m.r. spectroscopy is reviewed here. Conclusions about preferred conformations are drawn from dipolar (NOE) and scalar couplings (ⁿJ_H,H),¹³C chemical shifts and their temperature dependences as well. Information about the flexibility are available from dynamic n.m.r. spectroscopy and the spin-lattice relaxation times T₁ Also conformational variations as result of the complexation of cations or other guest molecules, flexibility variations and the stoichiometry of the complexes obtained can be readily studied by the same n.m.r.-parameters. Special remarks are referenced to the respective possibilities of CP-MAS-¹³C- n.m.r. spectroscopy in the solid state as well as other alternative methods of conformational analysis in solution as are dipole moment measurements and the RAMAN vibrational spectroscopy. The conformational peculiarities of the crown ether family are summarized.     

Application of lanthanide n.m.r. shift reagents for functional group studies of shale bitumen asphaltenes

Ytterbium (fod)₃ was used as a shift reagent in conjunction with solution ¹H n.m.r. studies of asphaltene isolated from Devonian shale bitumen. Upon addition of the reagent, bands attributed to protons on alkyl groups alpha to oxygen atoms were shifted and separated from that attributed to protons alpha to two aromatic systems. Similar experiments with Green River bitumen asphaltene did not show any observable shift. The presence and absence of the ether formations in shale asphaltenes can be substantiated by ¹³C n.m.r.     

Electrochemical treatment of ammonia in wastewater by RuO<Subscript>2</Subscript>–IrO<Subscript>2</Subscript>–TiO<Subscript>2</Subscript>/Ti electrodes

This study investigated the removal of ammonia in wastewater by an electrochemical method using titanium electrodes coated with ruthenium and iridium (RuO₂–IrO₂–TiO₂/Ti) with low chlorine evolution over-voltage. The effects of operating parameters, including chloride ion concentration, current density and initial pH, were also investigated. The results were evaluated primarily by considering the efficiency of the elimination of NH₄⁺-N. The removal of ammonia by electrochemical oxidation mainly resulted from the indirect oxidation effect of chlorine/hypochlorite produced during electrolysis. The direct anodic oxidation efficiency of ammonia was less than 5%, and the current efficiency was less than 10%. The ammonia removal followed pseudo-first-order kinetics. The electrochemical process can be applied successfully as a final polishing step, or as an alternative method to biological nitrification. The process seems to be most beneficial for small coastal cities     

Zur Chlorierung von N-Aryl-2,4-dimethyl-buta-1,3-dien-1,4-sultamen

About Chlorination of N-Aryl-2,4-dimethyl-buta-1,3-dien-1,4-sultames The sultames of structure 1 are easily chlorinated by sulfurylchloride, chlorine or tertbutylhypochlorite. The structure of the mono-( 2a-c,3a, d ), di-( 4a-d ), tri- ( 5c, d ) and pentachlorosultames ( 6a, b ) is determined by ¹³C-n.m.r. spectroscopy. Contrary to the bromination the chlorination (by SO₂Cl₂) starts with the substitution of the sultamring (formation of mono- and di-chlorosultames) followed of the substitution of the (C-4)-CH₃- group (formation of trichlorosultames). By 1,4-addition of an other molecule of chlorine to 5 the pentachlorosultames 6a, b are obtained. Already by recrystalisation of 6a, b in an alcohol the chlorine in 4-position is exchanged by the corresponding alkoxy group (CH₃O, C₂H₅O, n-C₃H₇O) and the compounds 7-9 are formed.     

Monomer sequence determinations of aryl ether sulphone copolymers as determined by 13C n.m.r.

The monomer sequence distributions of three types of aryl ether sulphone copolymers have been determined by ¹³C n.m.r. spectroscopy. Two amorphous aryl ether sulphone copolymers were shown to have transetherified (or ether interchanged) during polymerisation to become random copolymers. The residues in these copolymers were (i)—OøOøSO₂øS—and (ii)—OøSO₂øøSO₂ø—-where ø denotes 1,4-phenylene. Copolymers of 50:50 aryl ether sulphone and aryl ether ketone made from different combinations of monomers were found to have different solubilities in dimethyl sulphoxide, and from ¹³C n.m.r. data this was shown to correlate with the amount of transetherification which had taken place during the polymerisations. The ¹³C n.m.r. chemical shifts for some of the carbon nuclei in these polymers were sensititive to functional groups situated even as far away as three or four aromatic nuclei along the polymer chain.     

Quantitative Bestimmung geringer Phosphatmengen in Trinatrium-Phosphonoformiat mittels 31P-NMR-Spektroskopie

Determination of Small Quantities of Residue Phosphate in Tris-Sodium Phosphane Formiate by Means of ³¹P NMR Spectroscopy The concentration of residue phosphate in tris-sodium-phosphon-formiate (TPF·6H₂O) water solutions has been determined via comparing integration of the ³¹P n.m.r. signal of the residue phosphate and one of the ³¹C NMR satellites of the TPF·6H₂O ³¹P n.m.r. signal. The ³¹P n.m.r. spectra have been obtained in inverse gated detection mode; statistical methods of validation prove the certainty of the phosphate concentrations obtained to be excellent and strongly recommend the quantitative method employed for the detection of concentrations down to 0,1%.     

Essais d'insertion dans le graphite d'halogenures de titane(IV): Structure et proprietes du compose lamellaire graphite-tetrafluorure de titane

Syntheses of lamellar compounds were attempted by heating mixtures of graphite and halides of titanium(lV), TiCl₄ and TiF₄ in chlorine atmosphere confined in sealed tubes.The whole liquid range of TiCl₄ was explored without observing any reaction. Thus Croft's result [4] about the non-intercalation of this compound was confirmed.In case of TiF₄, a synthesis was obtained at 300°C. Differential thermal analysis (DTA, see Fig. 1) and X-ray powder diffraction show clearly that TiF₄ is intercalated into the lattice of graphite.DTA: Fig. 1(c, d and e) are the curves for the intercalated compound: 1(c and d) are obtained under dry argon, 1(e) under air. No indications of physical transformation of pure TiF₄ (Fig. 1a) are observed.An X-ray pattern of a product obtained at 25 atm of chlorine is given in Table 1: the strong band for pure graphite is split in two lines around 3 and 3.7 Å. Elemental analysis gives a certain range of non stoichiometry from C₁₉ to C₂₄,TiF₄ for the product made under chlorine at a pressure larger than 5 atm. In all cases, no chlorine has been found in the compound.Assuming a 3rd stage layer structure and atomic configuration of TiF₄ as shown in Fig. 2. the relative intensities of X-rays diffraction lines were calculated for C₁₅ to C₂₇TiF₄. The results are shown in Fig. 3 for the 00l diffraction lines: 001 reflexion has a minimum for C₂₁ TiF₄ and as we have never seen this reflexion, we assume that this is the ideal stoichiometry. Table 2 compares the observed and calculated intensities for C₂₁TiF₄. Agreement is quite good.Synthesis carried out under pressure of chlorine lower than 5 atm gave disordered products. Table 3 compares the obtained X-ray pattern for a product made at 1 atm of chlorine and the pattern calculated on the following assumptions: 4th stage, stoichiometry of C₂₈TiF₄. The pattern of TiOF₂ is also present in the table. Agreement is not very good, and moreover the pattern of products depends on the pressure of chlorine as shown on Fig. 4 for the 004 and 005 reflexions. We have had then to introduce a “pseudo-stage” n + x (formula (2) in appendix).On Fig. 5 the inverse of this pseudo-stage is plotted vs the Cl₂ pressure. A stable domain of 3rd stage is observed between 5 and 19 atm. Below 5 atm higher stages and disordered products are obtained.Figures 6 and 7 relate to a thermal stability study of the C₂₁ TiF₄ product. Figure 6 is a thermolysis curve made under dry argon (a) and under vacuum (10 ²torr) (b). Figure 7 is a thermolysis curve made in a diffraction high temperature chamber under vacuum (10^?5 torr): $\text{1}\text{(n + x)}$ is plotted vs temperature. In all cases the product gives higher stages and disordered products.