Deuterium labelling and thermochemical studies of dissociative ionization of methyl substituted monosilacyclobutanes. Ring expansion in the molecular ion of 1,1,3-trimethyl-1-silacyclobutane

Dissociative ionization of 1,1-dimethyl-1-silacyclobutane, 1,1-bis(trideuteromethyl)-1-silacyclobutane, 1,1,3-trimethyl-1-silacyclobutane, 1,1-bis(trideuteromethyl)-3-methyl-1-silacyclobutane and 1,1,2-trimethyl-1-sila-cyclobutane have been studied. Low energy electron impact fragmentation of 1,1-bis(trideuteromethyl)-3-methyl-1-silacyclobutane results mainly in the loss of ethene with the involvement of the C-methyl group from the rearranged molecular ion. No fragment ions indicating rearrangement of the molecular ion have been detected in mass spectra of 1,1-bis(trideuteromethyl)-1-silacyclobutane. The ionization energies for 1,1,3-trimethyl-1-silacyclobutane, 1,1,2-trimethyl-1-silacyclobutane and 1,1-dimethyl-1-silacyclopentane, and also the appearance energies for the [M ? 28]^+˙ and [M ? 42]^+˙ ions, have been measured by photoioniza-tion mass spectrometry. The heats of formation of these ions and of 1,1,3-trimethyl-1-silacyclobutane and 1,1-dimethyl-1-silacyclopentene molecules have been calculated as have the enthalpies of the transformation processes.     

Cationic 1,2-vinyl addition polymerization of cyclic ketene acetals initiated by conventional acids

Pure 1,2-addition polymers, poly(2-methylene-1,3-dioxolane), 1b , poly(2-methylene-1,3-dioxane), 2b , and poly(2-methylene-5,5-dimethyl-1,3-dioxane), 3b , were prepared using the cationic initiators H₂SO₄, TiCl₄, BF₃, and also Ru(PPh₃)₃Cl₂. Small ester carbonyl bands in the IR spectra of 1b and 2b were observed when the polymerizations were performed at 80°C ( 1b ) and both 67 and 138°C ( 2b ) using Ru(PPh₃)₃Cl₂. The poly(cyclic ketene acetals) were stable if they were not exposed to acid and water. They were quite thermally stable and did not decompose until 290°C ( 1b ), 240°C ( 2b ), and 294°C ( 3b ). Different chemical shifts for axial and equatorial H and CH₃ on the ketal rings were found in the ¹H NMR spectrum of 3b at room temperature. High molecular weight 3b (M̄_n = 8.68 × 10⁴, M̄_w = 1.31 × 10⁵, M̄_z = 1.57 × 10⁵) was obtained upon cationic initiation by H₂SO₄. Poly(2-methylene-1,3-dioxane), 2b , underwent partial hydrolysis when Ru(PPh₃)₃Cl₂ and water were present in the polymer. The hydrolyzed products were 1,3-propanediol and a polymer containing both poly(2-methylene-1,3-dioxane) and polyketene units. The percentages of these two units in the hydrolyzed polymer were about 32% polyketene and 68% poly(2-methylene-1,3-dioxane). No crosslinked or aromatic structures were observed in the hydrolyzed products. The molecular weight of hydrolyzed polymer was M̄_n = 5740, M̄_w = 7260, and M̄_z = 9060. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 3707–3716, 1997     

Synthese von Plectranthonen,diterpenoiden Phenanthren-1,4-chinonen

Synthesis of Plectranthons, Diterpenoid Phenanthrene-1,4-diones The following phenanthrene-1,4-diones have been synthesized by using the photocyclization of the corresponding highly substituted stilbenes as the key step: 3-hydroxy-5,7,8-trimethyl-2-(prop-2-enyl)phenanthrene-1,4-dione ( 1 ), (RS)-, (R)-, and (S)-2-[3-hydroxy-5,7,8-trimethyl-1,4-dioxophenanthren-2-yl]-1-methylethyl acetate ( 2 , 31 , and 32 , resp.), 3-hydroxy-7,8-dimethyl-2-(prop-2-enyl)phenanthrene-1,4-dione ( 3 ), 3-hydroxy-7,8,10-tri-methyl-2-(prop-2-enyl)phenanthrene-1,4-dione ( 4 ), 5,7,8-trimethyl-2-(prop-2-enyl)phenanthrene-1,4-dione ( 17 ), and 3-hydroxy-2-methylphenanthrene-1,4-dione ( 42 ). The quinones 1 and 3 proved to be identical with the recently isolated plectranthons A and C. Compounds 2 , 31 , and 32 exhibited the same UV/VIS, IR, ¹H-NMR and mass spectra as natural plectranthon B , but had different melting points. This might be due either to crystal modifications or to diastereoisomerism caused by the helical structure of the phenanthrene-1,4-dione skeleton. The spectral data of synthetic 4 were not compatible with those of natural plectranthon D for which structure 4 had been proposed based mainly on ¹H-NMR arguments concerning the chemical shifts of H? C(9) and H? C(10) in 1–3. Extensive ¹H-NMR investigations have now revealed that the currently stated assignments of the H? C(9)/ H? C(10) AB system have to be reversed for highly substituted phenanthrene-1,4-diones: in the model compounds 2-methylphenanthrene-1,4-dione (41) and 2, H? C(10) resonates al lower field as expected (peri-position), whereas in the highly substituted congeners 1 , 2 , 3 , 31 , and 32 , H? C(9) is shifted paramagnetically, a fact which had lead to the erroneous assignment of structure 4 for natural plectranthon D .     

Stereoregularity of poly(2-vinylpyridine) and poly-(4-vinylpyridine)

In order to determine the stereoregularity of poly(4-vinylpyridine), 4-vinylpyridine-β,β-d₂ was synthesized from 4-acetylpyridine. The ¹H-NMR spectra of the deuterated and nondeuterated polymers were measured and analyzed. From the ¹H-NMR spectra of poly(4-vinylpyridine-β,β-d₂), triad tacticity can be obtained, while the ¹H-NMR spectra of nondeuterated poly(4-vinylpyridine) give the fraction of isotactic triad. The ¹³C-NMR spectra of poly(4-vinylpyridine) were also observed, and the spectra of C₄ carbon of polymers were assigned by the pentad tacticities. The fraction of isotactic triad of poly(2-vinylpyridine) and poly(4-vinylpyridine) obtained under various polymerization conditions were determined. The radical polymerization and anionic polymerizations with phenylmagnesium bromide and n-butyllithium as catalysts of 4-vinylpyridine gave atactic polymers.     

MÖSsbauer Spectroscopic Study of Fecl3 Complexes of Poly(N-Methyl-2,5-Pyrrolylene), Poly(2,5-Thienylene), and Poly(3-Methyl-2,5-Thienylene) Prepared by Ni-Catalyzed Polycondensation

Reaction of FeCl₃ with poly(N-methyl-2,5-pyrrolylene) (PNMPy), poly(2,5-thienylene) (PTh), and poly(3-methyl-2,5-thienylene) (P3MeTh) caused reduction of FeCl₃ to afford Fe²⁺ species. Variable temperature Mössbauer spectra of the reaction systems indicated formation of FeCl₂ and FeCl^? ₄. The latter is regarded as a counter-anion for the cation delocalized along the π-conjugated polymer chain.     

Special Reactions of α,β-Unsaturated Ketones III [1]. Formation and Structure Elucidation of Dimers of 2-Aryl-methyleneketones: (5E)-5-Benzylidene-9β-phenyl-trans-4a-1,2,3,4,4a,5,6,7,8,9a-decahydroxanthen-4aα-ol and 3β,5β-Bis-(4-methoxyphenyl)-2α,4β,6α-trimethyl-4α-propionyl-cyclohexanone [2]

Summary.  The reaction of 2-benzylidenecyclohexanone and 1-(4-methoxyphenyl)-2-methyl-1-penten-3-one with guanidine did not yield the expected 4-phenylhexahydro-2-quinazolinamine and 4-(p-methoxyphenyl)-dihydro-2-pyrimidinamine, respectively, but nitrogen-free products which turned out as [3+3]- and [4+2]-cycloadducts of two molecules of the applied vinylogous ketone each. According to elemental analyses, mass spectra, and, in particular, NMR analyses (¹H and ¹³CNMR, HH-COSY, gs-HSQC, gs-HMBC, 1D TOCSY, NOESY, and 1D NOE difference spectra), the prepared dimers were identified as racemic (5E)-5-benzylidene-9β-phenyl-trans-4a-1,2,3,4,4a,5,6,7,8,9a-decahydroxanthen-4aα-ol and 3β,5β-bis-(4-methoxyphenyl)-2α,4β,6α-trimethyl-4α- propionylcyclohexanone, respectively. Structure and stereochemistry of the dimers are elucidated, and mechanisms for their formation are proposed. Received April 11, 2001. Accepted (revised) May 18, 2001     

First heterobimetallic MnII/MII(M = Cu,Ni) complexes with open-chain aliphatic schiff-base ligands obtained by direct template synthesis

Four new heterobimetallic complexes [CuL¹][MnCl₄] (1), [CuL²][MnCl₄] (2), [NiL¹][MnCl₄] (3), [NiL²][MnCl₄] (4) (L¹?=?4,6,6-trimethyl-1,9-diamino-3,7-di-aza-nona-3-ene; L²?=?1,15-dihydroxy-7,9,9-trimethyl-3,6,10,13-tetra-aza-pentadeca-6-ene) have been prepared from elemental metals, ethylenediamine dihydrochloride or its N-(2-hydroxyethyl) derivative and acetone by the template condensation reaction. All complexes have been characterized by elemental analysis, IR and UV-Visible spectroscopy. The structures of 2 and 3 have been determined by X-ray crystallography (2: Orthorhombic, Pna2 _1, a?=?20.136(4), b?=?11.185(2), c?=?10.251(2)Å, Z?=?4; 3: Orthorhombic, Pca2 _1, a?=?14.335(2), b?=?11.405(2), c?=?11.154(2)Å, Z?=?4 ). Both crystals consist of alternating complex cations [ML]²⁺ and anions [MnCl₄]^2? linked together by N–H···Cl–Mn and O–H···Cl–Mn hydrogen bonds forming 2D corrugated sheets in (2) and 1D helical chains in (3). Complex 2 represents the first single crystal structure elucidation of the complex containing L².     

Determination of the erythro and threo configuration of the two diastereoisomeric 2-amino-3-mercaptobutyric acids by NMR spectroscopy of derived thiazolidines

A study of the ¹H and ¹³C NMR spectra of the N-formyl-2,2,5-trimethyl-4-carboxythiazolidines and the N-formyl-4-carboxy-5-methylthiazolidines derived from the two diastereoisomeric 2-amino-3-mercapto-DL-butyric acids, permits unambiguous assignment of the erythro and threo configuration of these amino acids. The spectra of the N-formylthiazolidines, recorded in DMSO-d₆ solution, reveal the presence of two conformational isomers with a low rate of interconversion. The geometry around the carbon–nitrogen bond and correlated conformations of the 5-membered ring in both forms are discussed.     

Effects of substituted side‐chain position on donor–acceptor conjugated copolymers

The optical properties and electrical properties of a series of low‐band‐gap conjugated copolymers, in which alkyl side chains were substituted at various positions, were investigated using donor–acceptor conjugated copolymers consisting of a cyclopentadithiophene derivative and dithienyl‐benzothiadiazole. With substituted side chains, the intrinsic properties of the copolymers were significantly altered by perturbations of the intramolecular charge transfer. The absorption of poly[2, 6‐(4,4‐bis(2‐octyl)‐4H‐cyclopenta‐[2,1‐b:3,4‐b′]dithiophene)‐alt‐4, 7‐bis(4‐octyl‐thiophene‐2‐yl)benzo‐2,1,3‐thiadiazole] [ PCPDT‐ttOTBTOT ( P2 )], which assumed a tail–tail configuration, tended to blue shift relative to the absorption of poly[2,6‐(4,4‐bis(2‐octyl)‐4H‐cyclopenta‐[2,1‐b:3,4‐b′]dithiophene)‐alt‐4,7‐bis (thiophene‐2‐yl)benzo‐2,1,3‐thiadiazole] [ PCPDT‐TBTT ( P1 )]. The absorption of poly[2,6‐(4,4‐bis(2‐octyl)‐4H‐cyclopenta‐[2,1‐b:3, 4‐b′]dithiophene)‐alt‐4,7‐bis(3‐octyl‐thiophene‐2‐yl)benzo‐2,1,3‐thiadiazole] [ PCPDT‐hhOTBTOT ( P3 )], which assumed a head–head configuration, was blue shifted relative to that of P2 . The electrical transport properties of field‐effect transistors were sensitive to the side chain position. The field‐effect mobility in P2 (μ₂ = 1.8 × 10^?3 cm²/V s) was slightly lower than that in P1 (μ₁ = 4.9 × 10^?3 cm²/V s). However, the mobility of P3 was very low (μ₃ = 3.8 × 10^?6 cm²/V s). Photoexcitation spectroscopy showed that the charge generation efficiency (shown in transient absorption spectra) and polaron pair mobility in P1 and P2 were higher than in P3 , yielding P1 and P2 device performances that were better than the performance of devices based on P3 . © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Dynamic 1H NMR spectroscopy of η2-ethylene transition metal complexes

The low-temperature ¹H NMR spectra of bis(ethylene)trimethylphosphinenickel (1), η⁵-cyclopentadienyl(ethylene)methylnickel (2a), bis(ethylene)-η⁵-cyclopentadienylcobalt (2b), [bis(1-ethyl-2,4,6-triphenylphosphorinyl)nickel]P,P′-nickel(ethylene) (3) and η⁵-cyclopentadienyl(ethylene)hydrido(triphenylphosphine)ruthenium (4) exhibit {AA′B′B} (1) {ABB′A} (2a and 2b), {ABA′B′} (3) or {ABCD} (4) spin patterns, respectively, for the complexed ethylene. A full line shape analysis including all the proton couplings was performed for the ethylene rotation in 1, 2a and 2b. In addition to olefin rotation, a reversible intramolecular β-H-elimination was confirmed for 4 by magnetization transfer experiments.     

A reinvestigation of the stevens rearrangement of 1-benzyl-1,3,4-trimethyl-1,2,5,6-tetrahydropyridinium salts

Authentic samples of 1,3,3-trimethyl-2-(3,4,5-trimethoxyphenyl)-4-methylenepiperidine (Ia) and 2-(p-chlorophenyl)-1,3,3-trimethyl-4-methylenepiperidine (Ib) are prepared by Mannich condensation between 4-methyl-1-methylamino-3-pentanone hydrochloride (VI) and an aromatic aldehyde, followed by a Wittig reaction on the resulting 4-piperidone. Comparing the physical and spectroscopic properties of Ia and Ib with those of the methylene derivatives IIa and IIb obtained as by-products in the Stevens rearrangement of 1-benzyl-1,3,4-trimethyl-1,2,5,6-tetrahydropyridinium salts IIIa and IIIb, respectively, it is shown that the assignment previously made for IIa and IIb is incorrect. Spectroscopic analysis (ir, ¹H nmr, ¹³C nmr, ms) of these compounds and of its hydrogenation products VIII allows the structural and stereochemical assignment of 11a as cis-3-isopropenyl-1,3-dimethyl-2-(3,4,5-trimethoxyphenyl)pyrrolidine and of IIb as cis-2-(p-chlorophenyl)-3-isopropenyl-1,3-dimethylpyrrolidine. The formation of these rearrangement products is mechanistically interpreted as a Stevens [3,2] type process.     

Kinetics studies of 5-methyl-2-hexanol, 2,2-dimethyl-3-hexanol,and 2,4,4-trimethyl-1-pentanol with chlorine atoms: Photooxidation mechanism of 2,4,4-trimethyl-1-pentanol

The rate constants for the reaction between chlorine atoms and either 5-methyl-2-hexanol, 2,2-dimethyl-3-hexanol, or 2,4,4-trimethyl-1-pentanol at 298 K were determined using the relative method with 2-butanol and 1-pentanol as reference compounds. The values obtained for 5-methyl-2-hexanol, 2,2-dimethyl-3-hexanol, and 2,4,4-trimethyl-1-pentanol (k × 10¹⁰ cm³ molec⁻¹ s⁻¹) were, respectively, (2.64 ± 0.5), (2.72 ± 0.5), and (2.50 ± 0.4), in agreement with the values of the rate constants reported in bibliography for similar alcohols and the values estimated by structure activity relationship methods. The photooxidation products of 2,4,4-trimethyl-1-pentanol initiated by chlorine atoms were identified (formaldehyde, 2-propanone, 2,2-dimethyl propanal, 4,4,-dimethyl-2-pentanone, and 3,3-dimethylbutanal), and the reaction mechanism was determined.     

Studies on the stereochemistry of 1,2,6-trimethyl-4-piperidone

In the effort to create new derivatives of analgesically active spiropiperidines intermediate 1,2,6-trimethyl-4-piperidone was synthesized. The substitution of the skeleton gives rise to configurational as well as conformational isomerism. Despite the symmetry of 1,2,6-trimethyl-4-piperidone two different sets of signals were present in the ¹H and ¹³C NMR spectra. They were supposed to arise from a cis/trans mixture of 1,2,6-trimethyl-4-piperidone. In contrast to this explanation only two signals of the methyl groups and hydrogens at carbon atoms 2 and 6 were observed in the ¹H and ¹³C NMR spectra, normally expecting one for the cis- and two for the trans-isomer. To solve this discrepancy, the kind of isomeric mixture of 1,2,6-trimethyl-4-piperidone leading to the ¹H and ¹³C NMR spectra was examined. Energy differences between chair conformations of both the cis- and the trans-isomer of 1,2,6-trimethyl-4-piperidone and the potential energy surface of the equilibration process of the trans-isomer of 1,2,6-trimethyl-4-piperidone between its chair conformers were determined by quantum chemical calculations. The barrier height of the equilibration process was measured by high and low temperature NMR measurements to confirm the theoretical outcome. The results of all investigations agree nicely and proved a cis-/trans-mixture of 1,2,6-trimethyl-4-piperidone being present at room temperature.     

Plectranthone A,B, C und D. Diterpenoide Phenanthren-1,4-dione aus Blattdrüsen einer Plectranthuus sp. (Labiatae)

Plectranthons A, B, C, and D. Diterpenoid Phenanthrene-1,4-diones from Leaf-glands a Plectranthus sp. (Labiatae) The following structures of four new 1,4-phenanthraquionones, isolated in minute amounts from the coloured leaf-glands of a Plectranthus sp. obtained from the borders of Lake Kiwu₂, Rwanda, are proposed: plectranthon A ( 1 ; 3-hydroxy-5, 7,8-trimethyl-2-(2-propenyl)phenanthrene-1, 4-dione), plectranthon B ( 2 ; 2-(2ξ-acetoxypropyl)-3-hydroxy-5,7,8-trimethylphenanthrene-1,4-dione), plextranthon C ( 3 ; 3-hydroxy- 7,8-diemethyl-2-(2-propenyl)phenanthrene-1,4-dione), and plectranthon D ( 4 ; 3-hydroxy-7,8,10-trimethyl-2-(2-propenyl)phenanthrene-1,4-dione). 2-(2ξ-Hydroxypropyl)-3,6-dihydroxy-5,7,8-trimethylphenanthrene-1,4-dione ( 11 ), a compound very similar to 1–4 , was prepared by a Wagner-Meerwein, rearrangement of coleon E (⁵). Biogenetically, the plectranthons are derived from abietanoic precursors. The compounds 1, 2 and 4 are the first natural C₂₀-phenanthrenes of diterpenoid origin.     

Control of chain ends of polyesters in polycondensation of AA and BB monomers by use of solid‐phase reagent

For selective synthesis of linear polyester having a functional group at one end, polycondensation between 1,4‐butanediol ( 1a ) and sebacoyl chloride ( 2a ) and between 1,12‐dodecanediol ( 1b ) and isophthaloyl chloride ( 2b ) was conducted in the presence of oxime resin or oxime silica gel, followed by cleavage of the formed polyester from the solid‐phase support with aniline. Matrix‐assisted laser desorption ionization time‐of‐flight mass spectra and ¹H NMR spectra of the cleaved polyester showed that the products contained not only polyester with anilide at one end ( poly 1 ), but also polyester with anilides at both ends ( poly 2 ). The product ratio of poly 1 to poly 2 ( poly 1 / poly 2 ) was dependent on monomers, monomer concentration, feed ratio of monomer to oxime moiety in the support, oxime content in the support, reaction solvent, and the nature of the support. Polyester with a high poly 1 / poly 2 ratio of 81/21 and moderate molecular weight (M_n = 1430 g/mol) was obtained by polycondensation of 1b and 2b in the presence of oxime silica gel in dichloromethane. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1379–1386     

α‐Propargyl amino acid‐derived optically active novel substituted polyacetylenes: Synthesis,secondary structures,and responsiveness to ions

Novel optically active substituted acetylenes HC? CCH₂CR¹(CO₂CH₃)NHR² [(S)‐/(R)‐ 1 : R¹ = H, R² = Boc, (S)‐ 2 : R¹ = CH₃, R² = Boc, (S)‐ 3 : R¹ = H, R² = Fmoc, (S)‐ 4 : R¹ = CH₃, R² = Fmoc (Boc = tert‐butoxycarbonyl, Fmoc = 9‐fluorenylmethoxycarbonyl)] were synthesized from α‐propargylglycine and α‐propargylalanine, and polymerized with a rhodium catalyst to provide the polymers with number‐average molecular weights of 2400–38,900 in good yields. Polarimetric, circular dichroism (CD), and UV–vis spectroscopic analyses indicated that poly[(S)‐ 1 ], poly[(R)‐ 1 ], and poly[(S)‐ 4 ] formed predominantly one‐handed helical structures both in polar and nonpolar solvents. Poly[(S)‐ 1a ] carrying unprotected carboxy groups was obtained by alkaline hydrolysis of poly[(S)‐ 1 ], and poly[(S)‐ 4b ] carrying unprotected amino groups was obtained by removal of Fmoc groups of poly[(S)‐ 4 ] using piperidine. Poly[(S)‐ 1a ] and poly[(S)‐ 4b ] also exhibited clear CD signals, which were different from those of the precursors, poly[(S)‐ 1 ] and poly[(S)‐ 4 ]. The solution‐state IR measurement revealed the presence of intramolecular hydrogen bonding between the carbamate groups of poly[(S)‐ 1 ] and poly[(S)‐ 1a ]. The plus CD signal of poly[(S)‐ 1a ] turned into minus one on addition of alkali hydroxides and tetrabutylammonium fluoride, accompanying the red‐shift of λ_max. The degree of λ_max shift became large as the size of cation of the additive. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Über die Reaktionen von monosubstituierten Guanidinen mit α,β-ungesättigten Ketonen

Action of methyl-, benzyl- and phenylguanidine on mesityloxide yields the 2-R ³-imino-4,4,6-trimethyl-1,2,3,4-tetrahydropyrimidines resp. 2-R³-aminopyrimidines8 b, c ande, cyclohexylidenacetone reacts with benzylguanidine to give the 2-benzylimino-4-methyl-1,3-diazaspiro[5.5]undeca-4-en resp. the benzylaminodiazaspiroundecadien (8 d). The isomeric 1- and 3-R³-pyrimidinimines (resp.-amines)9 b-e and10 b-e are not formed in the reaction. The structures were proved by spectroscopical and chemical methods.

Herrn Prof. Dr.G. Zigeuner zum 60. Geburtstag gewidmet.     

Combining Steric and Electrostatic Stabilization Using Hydrophilic MacroRAFT Agents in an Ab Initio Emulsion Polymerization of Styrene

Hydrophilic (co)polymers carrying a thiocarbonyl thio end group such as poly(dimethylaminoethyl methacrylate), poly(ethylene oxide), and poly(ethylene oxide)‐block‐poly(dimethylaminoethyl methacrylate) have been evaluated as precursors of stabilizers in batch ab initio emulsion polymerization of styrene under acidic conditions to form electrosterically stabilized polystyrene latex particles. As a mixture of P(DMAEMA/H⁺Cl⁻)‐RAFT and PEO‐RAFT failed to give satisfactory results, PEO‐RAFT was used as a control agent for the RAFT polymerization of DMAEMA, and the resulting block copolymer was successfully used in ab initio styrene emulsion polymerization.

     

Solvent-induced allylic rearrangements in poly(trichlorobutadiene) chains

It was established by Fourier-transform IR and¹H NMR spectroscopy that a portion of the units of poly(1,1,2- and 1,2,3-trichlorobuta-1,3-diene) chains rearrange with migration of the allylic chlorine (1–4%) and allylic hydrogen (3–10%) under the influence of chloroform. Rearrangement with the migration of hydrogen under the influence of CDCl₃, CCl₄, and THF was also observed. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 763–768, April, 1997.     

Stereoregularity of poly(2-vinylpyridine) determined by 1H-NMR and 13C-NMR spectroscopy

In order to determine the stereoregularity of poly(2-vinylpyridine), 2-vinylpyridine-β,β-d₂ was synthesized. The ¹H-NMR spectra of the deuterated polymer in D₂SO₄ and o-dichlorobenzene solutions showed three peaks, which were assigned to triad tacticities. Since the absorptions of heterotactic and syndiotactic triads of methine protons overlap those of methylene protons in nondeuterated polymers, only isotactic triad intensities can be obtained from the ¹H-NMR spectra of nondeuterated poly(2-vinylpyridine). The ¹³C-NMR spectra of poly(2-vinylpyridine) were obtained in methanol and sulfuric acid solutions. In methanol solution the absorption was split into three groups, which cannot be explained by triads, and in sulfuric acid solution several peaks were observed. These splittings may be due to pentad tacticity. The results show that poly(2-vinylpyridine) obtained by radical polymerization is an atactic polymer.