Olefinic Region Research Articles

The Impact of Different Catalysts on Heterogeneous Hydrogenation of Hydroxyl‐Terminated Polybutadiene

AbstractHydroxyl‐terminated polybutadiene (HTPB) is hydrogenated using catalytic hydrogenation with HTPB as a precursor using various catalysts. The hydrogenation is carried out using iso‐propyl alcohol (IPA) and toluene as an active solvent media. The present paper used (a) charcoal, (b) palladium supported by charcoal (Pd−C), (c) palladium supported by zirconium oxide (Pd‐ZrO2), and (d) copper chromite (CC) as catalysts for hydrogenation of HTPB to study the influence on the degree of hydrogenation with respect to each catalyst. The experimental data shows that hydrogenated HTPB (HHTPB) formation is predominantly controlled by physisorption and chemical reaction with a catalyst. Various techniques like NMR, FTIR and chemical analysis are used to characterize HTPB and HHTPB. Degree of hydrogenation of HTPB is found to be higher with copper chromite when compared to other catalysts in this work. Post‐hydrogenation, no significant change in hydroxyl value and a marginal increase in molecular weight is noticed with all catalysts. HTPB and HHTPB samples are analyzed using FTIR, 1H‐NMR, and 13C‐NMR and TG‐DSC studies, and inferences are derived with respect to the change in the olefinic region, microstructural changes, molecular weight, and thermal decomposition characteristics.

An Exploration of Substituent Effects on the Photophysical Properties of Monobenzopentalenes.

Monobenzopentalenes have received moderate attention compared to dibenzopentalenes, yet their accessibility as stable, non-symmetric structures with diverse substituents could be interesting for materials applications, including molecular photonics. Recently, monobenzopentalene was considered computationally as a potential chromophore for singlet fission (SF) photovoltaics. To advance this compound class towards photonics applications, the excited state energetics must be characterized, computationally and experimentally. In this report we synthesized a series of stable substituted monobenzopentalenes and provided the first experimental exploration of their photophysical properties. Structural and opto-electronic characterization revealed that all derivatives showed 1H NMR shifts in the olefinic region, bond length alternation in the pentalene unit, low-intensity absorptions reflecting the ground-state antiaromatic character and in turn the symmetry forbidden HOMO-to-LUMO transitions of ~2 eV and redox amphotericity. This was also supported by computed aromaticity indices (NICS, ACID, HOMA). Accordingly, substituents did not affect the fulfilment of the energetic criterion of SF, as the computed excited-state energy levels satisfied the required E(S1)/E(T1)>2 relationship. Further spectroscopic measurements revealed a concentration dependent quenching of the excited state and population of the S2 state on the nanosecond timescale, providing initial evidence for unusual photophysics and an alternative entry point for singlet fission with monobenzopentalenes.

Novel insight into structure and content of olefins in thermally cracked heavy oil and its saturates, aromatics, resins and asphaltenes fractions determined by 1H NMR spectroscopy

The factors leading to olefinic hydrogen signal shielding in the 1H NMR spectra of thermally cracked vacuum residue (VR) and its heavy fractions were revealed using a series of model compound systems, and the effect of olefinic hydrogen signal shielding on the determination of olefinic hydrogen content was elucidated. There were two main factors leading to the olefinic hydrogen signal shielding in the 1H NMR spectra of olefins in heavy fractions, i.e. intramolecular and intermolecular. For the olefin itself in heavy fractions, the chemical shift of the olefinic hydrogen closest to the aromatic ring was in the aromatic region rather than the olefinic region due to the π-π conjugation effect between the double bond and the intramolecular aromatic ring. Notably, the response intensity of the olefinic hydrogen signal could be weakened or even disappear due to the suppressive effect of the intermolecular aromatic structures in other polycyclic aromatic hydrocarbons (PAHs), while alkanes and monocyclic aromatics had little effect on the olefinic hydrogen signal response. Although the olefinic hydrogen signal was detected merely at about 5.30 ppm in the 1H NMR spectra of heavy fractions, these olefinic structures may be predominantly of the R─CH═CH2 type rather than the R─CH═CH─R′ type. More importantly, the measured olefinic hydrogen content of thermally cracked VR and its heavy fractions may be considerably lower than the actual content, with the measured content being only about 30–40 % of the actual content. This is mainly due to the weakening and disappearance of the olefinic hydrogen signal, coupled with the fact that the integral area of the possible olefinic hydrogen signal in the aromatic region was overlooked when calculating the total integral area of the olefinic hydrogen signal in the 1H NMR spectrum.

Dynamic Approach for the Estimation of Olefins in Cracked Fuel Range Products of Variable Nature and Composition by 1H NMR Spectroscopy

A dynamic ¹H NMR-based method for the estimation of olefin content in all cracked fuel range products, in general, and in gasoline/naphtha streams, in particular, irrespective of types and composition of olefins and boiling range of samples has been developed. This is in continuation of our earlier works where two methods were described for the determination of hydrocarbon types in straight-run gasoline (no olefins) and cracked full range gasoline/naphtha (with olefins). The average absolute number of unsaturated hydrogen (H) in the olefinic region (4.4–6.5 ppm) was directly estimated with the help of a ¹H NMR spectrum using dynamic variables in terms of differential population of various kinds of olefins. The average alkyl chain length (n) was estimated by various methods including ¹³C NMR and carbon number distribution by a gas chromatography-based detailed hydrocarbon analyzer [DHA, ASTM D6730-01(2016)] and simulated distillation [ASTM D2887-16a] data. The percentage of unsaturated hydrogen (% UH) in an average olefin was then obtained providing a multiplication factor (fₒ) by which the weight percentage of olefin is estimated using a normalized ¹H NMR spectrum. The dynamic estimation of H and n for each sample removes the possibilities of errors in the estimation. The method has efficiently been extended to coker kero and coker diesel range products where there has been no method available for olefin estimation. The method was validated by using DHA following ASTM D6730, by the Reformulyzer-based ASTM D6839 method, and finally by fluorescent indicator adsorption following ASTM D1319. All the methods were compared. Whereas the proposed NMR method is extremely general, free from manual error, the limitations of existing ASTM methods and the old NMR method vis a vis a new NMR method are also discussed.

Enrichment of C20-22 Polyunsaturated Fatty Acids from Refined Liver Oil of Leafscale Gulper Shark, Centrophorus squamosus

ABSTRACTThe C20-22 polyunsaturated fatty acids (C20-22 PUFAs), mainly eicosapentaenoic acid (EPA, 20:5n-3) and docosahexaenoic acid (DHA, 22:6n-3), were concentrated from the refined liver oil of deep sea leafscale gulper shark, Centrophorus squamosus, by sequential processes of winterization, urea complexation, and argentation chromatography. Winterization at 4°C using acetonitrile as solvent showed significant reduction of the total saturated fatty acid content (12%) with a concomitant increase of polyunsaturated fatty acids (36.3%). The urea complexation process significantly enriched the total polyunsaturated fatty acids (49.5%), with a reduction in saturated fatty acids (83.9%). Silica gel based argentation chromatography further concentrated the esters of C20-22 PUFA (>99 percent purity). Nuclear Magnetic Resonance spectroscopy was used as a chemical fingerprinting tool to study the enrichment of C20-22 PUFAs at various stages of the purification process. An increase in the proton signal intensity at the olefinic region (at δ 4–6) and a decrease in the aliphatic signals (at δ 0.5–2) showed that the process successfully enriched the C20-22 PUFAs.Abbreviations: PUFA, polyunsaturated fatty acid; EPA, eicosapentaenoic acid; DHA, docosahexaenoic acid; FAME, fatty acid methyl esters; SFA, saturated fatty acid; MUFA, monounsaturated fatty acid; NMR, nuclear magnetic resonance; GCMS, gas chromatography mass spectrometry; FFA, free fatty acid.

Observation of zirconium allyl species formed during zirconocene-catalyzed propene polymerization and mechanistic insights

Oligomeric Cp2Zr+–allyl species were detected in reaction mixtures of either [Cp2ZrMe][MeB(C6F5)3] or [Cp2ZrMe][B(C6F5)4] with propylene by a combination of 1H NMR spectroscopy and electrospray ionization (tandem) mass spectrometry techniques. Conjointly, the data imply that formation of Cp2Zr+–allyl species occurs via (re)coordination of alkene (propylene and vinylidene end groups of unsaturated polymer chains, respectively) to Cp2Zr+R (R=CH3, H, polymeryl), followed by intramolecular proton transfer from Cγ to R and release of RH. Analysis of the olefinic region of the 1H NMR spectra of the reaction mixture obtained from [Cp2ZrMe][MeB(C6F5)3] and propylene reveals the presence of a triplet resonance at δ∼5.2, which was attributed to the unprecedented 3-propenyl end group. A plausible mechanism for the origin of the 3-propenyl end groups is discussed. Additionally, a mechanism for incorporation of stereodefects into stereoregular polymers is also discussed. The cationic Cp2Zr+–allyl intermediates formed during polymerization may contribute to catalyst deactivation.

In vivo proton MRS of normal pancreas metabolites during breath-holding and free-breathing

Aim To characterize normal pancreas metabolites using in vivo proton magnetic resonance spectroscopy ( 1 H MRS) at 3T under conditions of breath-holding and free-breathing. Materials and methods The pancreases of 32 healthy volunteers were examined using 1 H MRS during breath-holding and free-breathing acquisitions in a single-voxel point-resolved selective spectroscopy sequence (PRESS) technique using a 3T MRI system. Resonances were compared between paired spectra of the two breathing modes. Furthermore, correlations between lipid (Lip) content and age, body-mass index (BMI), as well as choline (Cho) peak visibility of the normal pancreas were analysed during breath-holding. Results Twenty-nine pairs of spectra were successfully obtained showing three major resonances, Lip, Cho, cholesterol and the unsaturated parts of the olefinic region of fatty acids (Chol+Unsat). Breath-hold spectra were generally better, with higher signal-to-noise ratios (SNR; Z =–2.646, p =0.008) and Cho peak visible status ( Z =–2.449, p =0.014). Correlations were significant between spectra acquired by the two breathing modes, especially for Lip height, Lip area, and the area of other peaks at 1.9–4.1ppm. However, the Lip resonance was significantly different between the spectra of the two breathing modes ( p r =0.491 and 0.521, p =0.007 and 0.004), but not between Lip peak area and BMI. There was no statistical difference in Cho resonances between males and females. The Lip peak height and area were significantly higher in the Cho peak invisible group than in the Cho peak visible group ( t =2.661 and 2.353, p =0.030 and 0.043). Conclusion In vivo 1 H MRS of the normal pancreas at 3T is technically feasible and can characterize several metabolites. 1 H MRS during breath-holding acquisition is superior to that during free-breathing acquisition.

In vivo proton MRS of normal pancreas metabolites during breath-holding and free-breathing

To characterize normal pancreas metabolites using invivo proton magnetic resonance spectroscopy ((1)H MRS) at 3T under conditions of breath-holding and free-breathing. The pancreases of 32 healthy volunteers were examined using (1)H MRS during breath-holding and free-breathing acquisitions in a single-voxel point-resolved selective spectroscopy sequence (PRESS) technique using a 3T MRI system. Resonances were compared between paired spectra of the two breathing modes. Furthermore, correlations between lipid (Lip) content and age, body-mass index (BMI), as well as choline (Cho) peak visibility of the normal pancreas were analysed during breath-holding. Twenty-nine pairs of spectra were successfully obtained showing three major resonances, Lip, Cho, cholesterol and the unsaturated parts of the olefinic region of fatty acids (Chol+Unsat). Breath-hold spectra were generally better, with higher signal-to-noise ratios (SNR; Z=-2.646, p=0.008) and Cho peak visible status (Z=-2.449, p=0.014). Correlations were significant between spectra acquired by the two breathing modes, especially for Lip height, Lip area, and the area of other peaks at 1.9-4.1ppm. However, the Lip resonance was significantly different between the spectra of the two breathing modes (p<0.05). In the breath-holding spectra, there were significant positive correlations between Lip peak height, area, and age (r=0.491 and 0.521, p=0.007 and 0.004), but not between Lip peak area and BMI. There was no statistical difference in Cho resonances between males and females. The Lip peak height and area were significantly higher in the Cho peak invisible group than in the Cho peak visible group (t=2.661 and 2.353, p=0.030 and 0.043). Invivo(1)H MRS of the normal pancreas at 3T is technically feasible and can characterize several metabolites. (1)H MRS during breath-holding acquisition is superior to that during free-breathing acquisition.

Microstructure of polyisoprene produced by cationic polymerization: NMR spectroscopic study

High-resolution 1H and 13C NMR spectroscopy, including two-dimensional heteronuclear experiments, has been used to study the microstructure of polyisoprene produced by cationic polymerization. It is shown that macromolecules resulting from both regular and inverse additions are predominantly composed of trans-1,4-units, while 1,2- and 3,4-units are present in small amounts. NMR spectra demonstrate the absence of cis-1,4-units in the polymer, whereas broad signals (pedestals) are related to the presence of saturated structures. It is proposed to determine the content of trans-1,4-, 1,2-, and 3,4-units in cationic polyisoprene via the combined measurements of intensities of signals in the olefinic regions of 1H and 13C NMR spectra.

NMR Assignment of Carbonyl and Olefinic Regions of Amescla Resin

The structural assignment of amescla resin was carried out using a methodology already established in a previous work published by Tavares and Silva. From the methodology, three structural fragments were determined, allowing us to conclude that this natural resin was polymerized from the double bond localized in the middle of the aliphatic chain.

H NMR Analysis of Chain Unsaturations in Ethene/1-Octene Copolymers Prepared with Metallocene Catalysts at High Temperature

In this paper, we report the full resonance assignments in the olefinic region of the 600 MHz 1H NMR spectra of a typical ethene/1-octene copolymer (4.0 mol % of octene units) produced with a metallocene catalyst at high temperature, and of an ethene homopolymer prepared under similar conditions for comparison. The assignments were based on a thorough analysis of 1D (1H, 1H{1H}, 13C) spectra and of 2D 1H−1H (COSY, TOCSY) and 1H−13C (HSQC, DEPT-HSQC) maps. Thirteen different olefinic structures were identified, and their formation explained in terms of plausible mechanistic paths associated with the high polymerization temperature. The fraction of internal chain unsaturations traceable to allylic activation turned out to be comparable to that of terminal ones in both samples. Despite its complexity, the said spectral region is now amenable to deconvolution and full simulation in terms of known and recognizable patterns, and usable for fast (possibly on-line) measurements of chain unsaturation degree, as we...

Decreases in free cholesterol and fatty acid unsaturation in renal cell carcinoma demonstrated by breath-hold magnetic resonance spectroscopy

Increased utilization of cross-sectional imaging has resulted in increased detection of incidental renal tumors. The noninvasive characterization of renal tissue has important implications for the diagnosis of renal malignancies and treatment monitoring. Recently, multiple breath-hold averaged proton magnetic resonance spectroscopy ((1)H-MRS) performed at high field has enabled the use of this noninvasive metabolic profiling technique for the investigation of the abdomen. Multiple breath-hold averaged (1)H-MRS at high field (3T) was obtained in the kidneys of 10 healthy volunteers and in renal cell carcinoma tumors of 14 patients. The spectra of normal kidneys showed four main groups of resonances: 1) at 5.4-5.6 ppm, attributed to C6 of cholesterol and the unsaturated parts of the olefinic region of fatty acids; 2) at 4.7 ppm, attributed to the residual water signal; 3) at 3.2 ppm, attributed to trimethylamine moiety of choline metabolites; and 4) at 1.3 and 0.9 ppm, attributed to the methylenes and terminal methyls of lipids. The ratio of the signal at 5.4 ppm to that of 1.3 ppm was 19-fold lower in renal cell carcinomas than in healthy kidneys, tied P = 0.0003 Mann-Whitney U-test, suggesting a decrease in both free cholesterol and the degree of unsaturation of fatty acids in the malignant tissue. This metabolic shift is in agreement with previous ex vivo studies of human renal cell carcinoma. The ability to detect renal metabolic shifts noninvasively may improve the specificity of preoperative renal tissue characterization and may provide a new modality for treatment monitoring.

PONA analyses of cracked gasoline by 1H NMR spectroscopy. Part II

A direct and fast method based on 1H NMR spectroscopy for the determination of paraffins (P), olefins (O), naphthenes (N) and aromatics (A), i.e. PONA content of FCC and coker (visbreaker) gasoline containing olefinic hydrocarbons has been developed. This is in continuation of our earlier work where a direct method was developed for the determination of naphthenes and aromatics content in straight run gasoline (no olefins). The total naphthenes have been estimated by applying the overlapping factor ( F) due to the overlapping of signals of olefinic hydrocarbons with those of saturated cyclic hydrocarbons in the region of 1.4–2.0 ppm in the 1H NMR spectrum. The application of F eliminates contribution of substituted olefinic protons in the naphthenic region and allow measurement of integral area exclusively due to naphthenic protons. The estimation of absolute number of olefinic hydrogens ( H) or carbons (Co) in the olefinic region (4.5–6.6 ppm) together with the estimation of average alkyl chain length ( n) of gasoline samples have facilitated the determination of total olefin content in the sample. The overlapping factor is different for FCC and coker gasoline due to the presence of different types of olefinic structures and their relative distribution. The utilisation of these parameters ( F, n, H and Co), and average group molecular weight concept have helped the derivation of equation enabling the direct estimation of PONA content of a sample. The developed 1H NMR method is direct, fast, and reliable method and offers an alternative to long and tedious GC and MS methods.

A novel analytical method to detect adulteration of virgin olive oil by other oils

AbstractThe present study focuses on the olefinic region of the 13C nuclear magnetic resonance (13C NMR) spectrum of virgin olive oil which shows 12 peaks resonating between 127.5 and 130 ppm. These peaks are assigned to the most abundant unsaturated fatty acid moieties of the olive oil, oleic and linoleic acids, which are present in α and β positions of the glycerol backbone. With the use of an internal reference pyrazine, the 12 peaks were integrated and their areas were expressed in mmol/g of virgin olive oil. The intensities of the 12 observed peaks were affected when an authentic virgin olive oil was mixed with a seed oil. This observation was used to develop a semiquantitative method to detect adulteration of virgin olive oil by other oils based on 13C NMR spectroscopy.

Determination of 2-Acyl Positional Fatty Acid Distribution in Vegetable Oils by High Resolution 13C Nuclear Magnetic Resonance Spectroscopy

2-Acyl positional fatty acid distribution of edible vegetable oils was determined by high resolution 13C nuclear magnetic resonance spectroscopy. Quantitative analysis of each 2-acylpositional fatty acids were carried out by dividing each peak area by that of total carbonyl or olefinic carbon on 13C-NMR. Individual chemical shifts were observed for the fatty acids with resolution enhancement. The carbonyl region could be used to identify oils containing only saturates, oleyl and linoleyl group at 2-acyl position. The olefinic region was useful for determining the number of acyl groups that gave rise to superimposed carbonyl peaks, as in the case of linoleyl and linolenyl. 13C-NMR conditions which affect time saving and quantitative analsis was examined. As a result, total time required to obtain the data from olefinic region is reduced to about 3h per each sample. The 13C-NMR method was assessed for capacity in making quantitative determinating using the Lipase-GC method. Regression of data obtained by the two methods showed satisfactory correlation. The olefinic and carbonyl spectral regions when used together provide information essential for determining full acyl positional distribution.

Characterization of mechanically sheared ethylene-propylene copolymers by high resolution NMR

We report high-resolution solution-state NMR experiments on chain ends generated in ethylene–propylene copolymers by mechanical shearing in an extruder. The use of the higher resolution of the 13C-NMR spectrum, in a two-dimensional 1H-13C chemical shift correlation experiment, has allowed the complete resolution and assignment of the olefinic chain-end region of the 1H-NMR spectrum. Simultaneously, the assignments of the 13C olefinic resonances, previously identified [A. C. Kolbert, J. G. Didier, and L. Xu, Macromolecules, 29, 8591 (1996)] are confirmed. An iterative method for calculating the average molecular weight, based on quantitative measurements of the olefinic 1H-NMR peak intensities is introduced and these results are compared with measurements from 13C-NMR and size exclusion chromatography and correlated to reduced viscosities. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 1955–1961, 1997

Identification of conjugated diolefins in fossil fuel liquids by 1H n.m.r. two-dimensional correlated spectroscopy

Conjugated diolefins in fossil fuel liquids were identified by a two-dimensional (2D) 1H n.m.r. chemical shift correlated spectroscopy (COSY) experiment. The trans-terminal, trans-internal and ( cis, trans)-internal conjugated diolefin isomers were clearly identified in the olefinic region of the 2D COSY spectrum by comparison with the 2D COSY spectra of model compounds. At 11.7 T, the cross peaks due to conjugated diolefins are well resolved from the cross peaks of non-conjugated olefins and styrene-like compounds. The resonance peaks corresponding to conjugated diolefins in the one-dimensional (1D) 1H n.m.r. spectrum were assigned based on the positions of cross peaks in the 2D COSY spectrum. Quantitation of conjugated diolefins from the 1D 1H n.m.r. spectra showed that conjugated diolefins were easily detected in the 2D COSY spectra when present at about 0.01 mmol of diene per gram of sample. For lower levels (0.001 mmol of diene per gram of sample) verification of the presence of diolefins was done by a 1D 1H n.m.r. homodecoupling experiment.

Sex pheromone candidates with a conjugated triene system: Synthesis and chemical characterization

Sex pheromone candidates with a conjugated triene system, 8,10,12-, 9,11,13- and 11,13,15-hexadecatrienyl acetates (double bond positional isomers of theGlyphodes pyloalis pheromone, 10,12,14-triene) were synthesized by introducing anE configuration stereospecifically to two of three double bonds and rather nonspecifically to another double bond, so as to obtain two geometrical isomers;E,E,E andE,E,Z orE,Z,E isomers. The two geometrical isomers of each triene acetate were separated on a reverse-phase HPLC column and characterized by(1)H NMR analysis. The(13)C NMR signals in the olefinic region of each isomer were assigned by two-dimensional NMR techniques and also by an empirical rule based on the changes of the chemical shifts by converting the configuration. Based on the assignments, substituent parameters for calculating the chemical shifts of 1,6-dialkyl conjugated trienes were generated. Electron impact mass spectrometry showed characteristic fragment ions that enabled the double bond positional isomers to be distinguished from each other.

Algal carotenoids 47–NMR study of all‐trans‐peridinin, including complete 1H and 13C NMR assignments

AbstractThe allenic C37 skeletal carotenoid all‐trans‐(3S, 5R, 6R, 3′S, 5′R, 6′S)‐peridinin, isolated from Amphidinium carterae by an improved isolation procedure, was subjected to a detailed 1H and 13C NMR spectroscopic analysis. Complete assignments of the 500.13 MHz 1H and 125.76 MHz 13C spectra, including determination of coupling constants and relative stereochemistry, were obtained by ID and 2D techniques. These included 1H1H chemical shift correlated spectroscopy (2D COSY), phase‐sensitive double‐quantum COSY, difference 1D NOE experiments, 1D and 2D total correlation spectroscopy (HOHAHA, TOCSY) and 1D and 2D rotating frame nuclear Overhauser spectroscopy (ROESY, CAMELSPIN). The 13C NMR assignments were obtained through editing sequences (DEPT) and heterocorrelated 2D experiments. In particular, the 1H detected multiple bond 1H13C correlated 2D experiment proved valuable for assignments of all 13 quatenary carbons together with 13 methine carbons in peridinin [C37H47O6(COCH3)]. Detailed analysis of the proton coupling constants supported the conformations and relative stereochemistry of the two end‐groups. Spectral simulation of protons in the conjugated chain was necessary in order to ascertain more accurate chemical shifts for some protons in the strongly overlapping olefinic region. Variation in the trans double bond 3J(H, H) coupling was noted along the conjugated chain.

13C NMR analysis of α‐olefins copolymers with 1,3‐butadiene obtained with zirconocenes/methylalumoxane catalysts

AbstractEthylene copolymers with propene and/or 1,3‐butadiene were obtained using bis(η5‐cyclopentadienyl)zirconium dichloride (1) or ethylenebis[1‐3a, 7a‐η‐(4,5,6,7‐tetrahydro)‐1‐indenyl]zirconium dichloride (2) and methylalumoxane as catalytic systems. A detailed 13C NMR analysis of the copolymers was performed. The resonances in the olefinic region of the terpolymers were assigned to ethylene/butadiene/ethylene and propene/butadiene/ethylene sequences while the butadiene/propene sequence was ruled out. Analogously, no polymers were obtained from the polymerization of propene in the presence of 1,3‐butadiene. It is thus shown that the conjugated diene is an inhibitor for the polymerization of α‐olefins. The presence of trans‐1,2‐cyclopentane rings was detected both in the ethylene/butadiene copolymers and in the ethylene/propene/butadiene terpolymers. A different behaviour of the two catalysts was observed.