Structure of chlorinated poly(vinyl chloride). I. Determination of the mechanism of chlorination from infrared and NMR spectra

Infrared and NMR spectra of chlorinated poly(vinyl chloride) (CPVC) and of chlorinated α-deuterated poly(vinyl chloride) (α-d-CPVC) have been measured. It was found that the CDCl unit of α-d-PVC does not undergo chlorination. By assuming an analogous mechanism of chlorination in normal PVC, the populations of all the three possible types of two-carbon sequences (? CH₂? CHCl? , ? CHCl? CHCl, ? CHCl? CCl₂) in CPVC could be determined. The mechanism of chlorination of PVC is discussed from the viewpoint of the previous findings on the conformational structure of this polymer. Differences in structure between suspension- and solution-chlorinated PVC have been established.     

Photo-oxidation of the 2,4-dichloropentanes and PVC

The photo-oxidation of PVC and its model compounds, the dl- and meso-2,4-dichloropentanes, were studied by high-resolution NMR spectroscopy. The structure, ? CHCl? CH₂? CO? CH₂? was found to be present in PVC after photo-oxidation. Two peaks, which corresponded to the CHCl and CH₂ groups next to the carbonyl group, were observed in carbon disulfide–acetone-d₅ mixture, at 6.15 and 7.25τ, respectively. From the NMR spectra, the ratio of the CH₂ to CHCl protons in PVC and the model compounds were found to increase linearly with the time of photo-oxidation after induction periods. The initial rates of the model compounds were comparable with that of PVC; i.e., 1.6 × 10^?2 hr^?1, at 30°C. Since similar gaseous products were also detected by mass spectrometry in the initial stage, their photo-oxidation probably assumed the same rate-determining step. According to the results that the dl-2,4-dichloropentane was photo-oxidized 1.5 times faster than the meso-compound, it would be likely that the syndiotactic sequences in PVC might be more easily photo-oxidized than the isotactic sequences.     

NMR studies of chlorinated poly(vinyl chloride) and polybutadiene

Molecular structures of chlorinated poly(vinyl chloride) and polybutadiene have been studied by high resolution NMR. The spectra of the chlorinated polymers give broad signals. New peaks appear in the lower fields of the ? CH₂? and ? CHCl? groups with increasing chlorine content. The chlorination of poly(vinyl chloride) takes place predominantly on ? CH₂? rather than on ? CHCl? , e.g., a 70% chlorinated polymer has about 10 mole-% of ? CCl₂? groups. Polybutadiene reacts first with chlorine by addition to give a head-to-head poly(vinyl chloride), and then the substitution of the hydrogen atom takes place. Chlorinated polybutadiene with 70% Cl has about 18 mole-% of ? CCl₂? . The multiplets characteristic of spin-spin couplings in the spectrum of the original poly(vinyl chloride) are still observed in that of the highly chlorinated product. This fact shows that a considerable number of poly(vinyl chloride) sequences of certain lengths persist in the highly chlorinated polymer.     

Bildung siliciumorganischer Verbindungen. XXXIX. Teilchlorierte Carbosilane

1. Photochlorination in CCl₄ of the Si-chlorinated carbosilanes (Cl₃Si? CH₂)₂SiCl₂ and (Cl₂Si? CH₂)₃ leads to totally chlorinated compounds, e. g. (Cl₃Si? CCl₂)₂SiCl₂. After chlorination has started at one CH₂ group, formation of a CCl₂ group is preferred before another CH₂ group is involved into the reaction. Thus preparation of compounds a, b, c is possible. Cl₃Si? CCl₂? SiCl₂? CH₂? SiCl₃ (a) for (b) and (c) (see “Inhaltsübersicht”). SO₂Cl₂ (benzoyl peroxide) as chlorinating agent reacts more slowly, and opens an access to carbosilanes containing CHCl groups such as (d), Cl₃Si-CHCl? SiCl₂? CH₂? SiCl₃ (e). Reactions of compounds (a) to (d) with LiAlH₄ yields carbosilanes with SiH groups, and partially chlorinated C atoms. 2. By the high reactivity of Si? CCl₂? Si groups an exchange of Cl atoms of CCl groups in perchlorinated carbosilanes is possible for H atoms of Si? H groups in perhydrogenated carbosilanes, thus allowing the preparation of compounds containing CHCl and SiHCl groups, e. g. according to Gl.(1) (Inhaltsübersicht). Further reactions, formulated as the last equations in Inhaltsübersicht, are reported as well as the rearrangement of H₃Si? CHCl? SiH₃.     

Carbon-13 NMR spectra of some polychloro hydrocarbons and related compounds

Data derived from the carbon-13 NMR spectra of 37 organic polychloro compounds allow one to identify readily the ? CHCl₂, ? CCl₂? and ? CH₂Cl groups, the ¹³C signals of which are registered in the shift ranges of 67 to 78 (80), 85 to 96 and 38 to 55 (59) ppm (from TMS), respectively, and have the distinctive one bond spin-spin coupling constants ¹J(C? H) 170 to 184 Hz (for the ? CHCl₂ groups) and 147 to 158 Hz (for the ? CH₂Cl groups). The ? CCl₂CH₂CH₂Cl fragment features characteristic diamagnetic shieldings of the ? CCl₂? and ? CH₂Cl that may be related to increased electron density on both of these groups.     

Changes of vibrational lifetimes with minor structural modification of small polyatomic molecules

Substantial changes of population lifetimes of CH-stretching modes are observed when two atoms are exchanged in CH₂CCl₂ to form trans CHClCHCl and when three deuterons are substituted in C₆H₆ to form 1,3,5.-C₆H₃D₃. The measured lifetimes are in good agreement with estimates based on Fermi resonance-mixing which is inferred from infrared and Raman spectra.     

The structure of chlorinated poly(vinyl chloride). VI. Comparison of the chlorination of poly(vinyl chloride) and β,β-d2-poly(vinyl chloride) with 1H-NMR and 13C-NMR spectroscopy

Samples of chlorinated poly(vinyl chloride) (CPVC) and chlorinated β,β-dideuterated poly(vinyl chloride) (β,β-d₂-CPVC) were prepared under identical reaction conditions. The microstructure of CPVC and β,β-d₂-(CPVC) was characterized by a combination of ¹H-NMR, ¹³C-NMR spectroscopy, and analytically determined chlorine content. A difference was observed in the reaction rates of chlorination of PVC and β,β-d₂-PVC, and, in their thermal chlorination in solution, also in the structure of the chlorinated products. It was proved that in the chlorination of β,β-d₂-PVC a new chlorine atom can also enter the original? CHCl? group. The results are discussed from the standpoint of the chlorination mechanism.     

Bildung siliciumorganischer Verbindungen. 70 [1]. Reaktionen Si-fluorierter 1,3,5-Trisilapentane mit CH3MgCl und LiCH3

Formation of Organosilicon Compounds. 70. Reactions of Si-fluorinated 1,3,5-Trisilapentanes with CH₃MgCl and LiCH₃ F₃Si? CCl₂? SiF₂? CH₂? SiF₃ 3 reacts with meMgCl. (me = Ch₃ starting with a Si-methylation and not with a C-metallation as in the corresponding Si- and C-chlorinated compounds, e. g. (Cl₃Si? CCl₂)₂SiCl₂ [2]. A CCl-hydrogenation is observed too, which in the case of F₃Si? CCl₂? SiF₂? CHCl? SiF₃ 4 gives meS₃Si? CCl₂? Sime₂? CH₂? Sime₃. (F₃Si? CCl₂)_{2 5} reacts with meMgCl to form preferentially 1,2-Disilapropanes by cleaving a Si? Cbond. The isolation of F₃Si? CCl₂H and meF₂Si? CCl₂? SiF₂me allows to locate the bond where 5 is cleaved at the beginning of the reaction. With meLi 5 reacts to form mainly me₃Si? C?C? Sime₃, showing that in the reaction of meLi, being a stronger reagent than meMgCl, and 5 a C-metallation occurs, following the same mechanism as in the reaction with (Cl₃Si? CCl₂)₂)SiCl₂ [2]. The reaction conditions for the synthesis of Si-fluroinated and C-chlorinated 1,3,5-Trisilapentanes in a 0.1 mol scale are reported. N.m.r. data of all investigated compounds are tabulated.     

Etude spectroscopique de derives mercuriques d'amides-thiols: I. Spectres de vibration et structure des thiol-2 N-méthylacétamide,thiol-3 N-méthylpropanamide et N-(thiol-2 éthyle) acétamide

Raman and infrared spectra of CH₃NHCOCH₂SH, CH₃NHCO(CH₂)₂SH and CH₃CONH(CH₂)₂SH have been recorded between 3800 and 200 cm^?1. Some structural information is obtained from their analysis: for pure liquids or solids, molecules form linear chains with NH ? OC hydrogen bonds, the SH group being probably bound to the oxygen of an adjacent molecule. For CCl₄ solutions, an intramolecular hydrogen bond NH ? S is observed for the first compound only, corresponding to the formation of a five-membered ring.     

Carbon-13 NMR spectra of some polychlorinated telomerisation products

The study of 28 specially selected compounds containing chlorine shows that ¹³C NMR signals of the CCl₃, CCl₃CH₂ and CH₂Cl groups are registered in the ranges of 93 to 105, 49 to 71 and 38 to 59 ppm (from TMS), respectively and are readily identified in ¹³C NMR spectra of polychloro compounds. The weak electron withdrawing ability of the CCl₃CHCl and CH₂Cl groups, as well as the extremely strong influence of CCl₃ and CH₂Cl groups on the methylene group between them in 1,1,1,3-tetrachloropropane, is noted.     

Über Trichlorphosphazo-Verbindungen aus Nitrilen. III. Die Reaktion zwischen Acrylnitril und PCl3

On Trichlorophosphazo Compounds from Nitriles. III. The Reaction between Acrylonitrile and PCl₃. The reaction of PCl₃ with acrylonitrile at higher temperatures gives CH₂Cl? CCl₂? CCl₂? N? PCl₃ ( II ). On pyrolysis of (II), CH₂Cl? CCl₂? CN (IV) is form- ed. Treatment of (II) with SO, results in CHzCL? CCl₂? CCl?N-P(0)Cl₂ ( III ). At lower temperatures and/or in the presence of PCl₃, acrylonitrile reacts with PCl₃ to give the cis/ trans isomers VIa and VIb .     

Synthesis of block cotelomers involving a perfluorinated chain and a hydrophilic chain. Part I. Use of fluorinated telogens with trichloromethyl end groups

The synthesis of compounds involving a perfluorinated chain and a trichloromethyl group at the end of the chain is carried out by esterifying an alcohol with trichloracetic acid or by adding CCl₄ to a perfluorinated alcohol acrylate. Cl₃C? CO₂? (CH₂)₂? C₆F₁₃ and Cl₃C? CH₂? CHCl? CO₂? (CH₂)₂? C₆F₁₃ are obtained, respectively. These telogens are both used to initiate a polyacrylamide chain, thus allowing the synthesis of new highly hydrosoluble surfactants. The transfer constant of ferric chloride to the polyacrylamide chain can be calculated by studying the kinetics of the telomerization reaction. We found C = 16 at 125°C. Telomers can be prepared in which the polymer chain contains between 10 to 1000 acrylamide units; the degree of polymerization can be precisely predicted according to the amounts of products allowed to react.     

Vibrational analysis of molten poly(ethylene glycol)

The infrared absorption of poly(ethylene glycol) was measured in the molten state. Characteristic bands of the molten state were identified. Normal vibrations and frequency distributions were treated for various conformation models with CH₂CH₂O repeat units. The infrared absorption peaks of the molten state closely correspond to the frequency distribution peaks of the TGT conformation with gauche O? CH₂? CH₂? O groups, although infrared bands due to trans O? CH₂? CH₂? O groups are also observed. Vibrational assignments of the infrared bands and Raman lines were made on the basis of potential energy distributions.     

Bildung siliciumorganischer Verbindungen. XXXVIII. Umsetzung perchlorierter Carbosilane mit LiAlH4

By LiAlH₄ (Cl₃Si)₂CH₂, (Cl₂Si? CH₂)₂SiCl₂ are reduced to (H₃Si)₂CH₂ (a), (H₃Si? CH₂)₂SiH₂ (b) and (H₂Si? CH₂)₃(c). However with the compounds (Cl₃Si)₂CCl₂, (Cl₃Si? CCl₂0₂SiCl₂ and (Cl₂Si? CCl₂)₃ cleavages of the Si? C-bond and reduction of the CCl-groups occur apart from the normal reduction of the Si-Cl-groups to (H₃Si)₂CCl₂ (d), (H₃SiCCl₂)₂SiH₂ (e) and (H₂Si? CCl₂)₃. Excess LiAlH₄ favours this cleavage, the exact amount of a quarter of a mole LiAlH₄ per SiCl-group allows the formation of (d), (e), (f). The cleavage of (e) is in accordance with: (1), (2),(3). Therefore SiH₃₄ and (H₃Si)₂CCl₂ are the main-reaction-products and CH₃SiH₃ is formed acc. to equ. (3). Because of the cleavage of (H₂Si? CCl₂)₃ with LiAlH₄ H₃Si? CCl₂? SiH₂? CH₃and H₃Si? CH₂? SiH₂? CH₂? SiH₂? CH₃ are preferentially formed after the hydrolysis. The CH₂-containing compounds (a), (b), (c) cannot be cleaved in an analogous reaction.     

The structure,magnetic and spectral properties of 4-acetylpyridine N-oxide complexes of copper(II) propionates

The synthesis and characterization of CuX₂L; (X = CH₃CH₂COO^?, ClCH₂CH₂COO^?, CH₃CHClCOO^? or CH₃CCl₂COO^?; and L = 4-acetylpyridine N-oxide) is reported. The characterization of these compounds was based on electronic, infrared and EPR spectra, as well as magnetic measurements over the temperature range. Several correlations between the spectral and magnetic data as well as pK_a values of the respective acids were found and discussed. On the basis of spectral and magnetic data the structures of the compounds are discussed.     

Synthesis of block cotelomers involving a perfluorinated chain and a hydrophilic chain. III. Synthesis and use of fluorinated telogens with a trichloromethyl end group

The addition by redox catalysis (CuCl or FeCl₃ with benzoin) of CCl₄ and CCl₃? CF₂? CCl₃ on pentafluorostyrene and on fluorinated allyl ether, C₆F₁₃? C₂H₄? O? CH₂? CH?CH₂ was performed. The monoaddition compounds were mainly obtained with satisfactory yields and characterized by NMR (¹³C, ¹H, and ¹⁹F). These compounds were then used as telogens in telomerization by redox catalysis of acrylamide, methyl methacrylate, and acrylic acid and in radical-initiated telomerization of N-vinyl-pyrrolidone. The chain lengths of the hydrocarbonated sequences were determined from fluorine elemental analysis. A critical investigation of correlations between DP _n and concentrations of products involved was made.     

A comparison of light scattering and far infrared absorption spectra of simple liquids

Light scattering and far infrared absorption spectra of CCl₄, C₂Cl₄, C₆H₁₂, CHCl₃, and CH₂Cl₂ in the liquid phase have been obtained in the range of 2 – 200 and 20 – 200 cm^?1 respectively. The energy absorption spectra obtained by the two techniques and the corresponding relaxation times were compared for each liquid. We observe systematic differences between the energy absorption profiles obtained from the light scattering spectra and the far infrared absorption spectras. We also find generally shorter relaxation times from the infrared absorption spectra. Despite the similarity of the physical processes leading to light scattering and to far infrared absorption some significant differences are observed (ref. 1,2).     

Kinetics and mechanism for the oxidation of 1,1,1-trichloroethane

The reaction mechanisms for oxidation of CH₃CCl₂ and CCl₃CH₂ radicals, formed in the atmospheric degradation of CH₃CCl₃ have been elucidated. The primary oxidation products from these radicals are CH₃CClO and CCl₃CHO, respectively. Absolute rate constants for the reaction of hydroxyl radicals with CH₃CCl₃ have been measured in 1 atm of Argon at 359, 376, and 402 K using pulse radiolysis combined with UV kinetic spectroscopy giving ??(OH + CH₃CCl₃) = (5.4 ± 3) 10^?12 exp(?3570 ± 890/RT) cm³ molecule^?1 s^?1. A value of this rate constant of 1.3 × 10^?14 cm³ molecule^?1 s^?1 at 298 K was calculated using this Arrhenius expression. A relative rate technique was utilized to provide rate data for the OH + CH₃ CCl₃ reaction as well as the reaction of OH with the primary oxidation products. Values of the relative rate constants at 298 K are: ??(OH + CH₃CCl₃) = (1.09 ± 0.35) × 10^?14, ??(OH + CH₃CClO) = (0.91 ± 0.32) × 10^?14, ??(OH + CCl₃CHO) = (178 ± 31) × 10^?14, ??(OH + CCl₂O) < 0.1 × 10^?14; all in units of cm³ molecule^?1 s^?1. The effect of chlorine substitution on the reactivity of organic compounds towards OH radicals is discussed.     

Ring-opening polymerization of ethylene organophosphorothioates: Stereoregular polymerization involving asymmetry at phosphorus

Stereoregular polymerization involving asymmetry at phosphorus has been obtained from ethylene methyl or phenyl phosphorothioate with R₂Mg? NH₃ catalysts, or, in some cases, with R₂Mg alone. The methyl ester gave two types of polymer: an amorphous rubber and a low-melting (75°C) crystalline polymer. The phenyl ester gave mainly a low-melting (68°C) crystalline polymer of 2.2 inherent viscosity. Proton and ³¹P NMR and infrared spectra of these polymers are in accord with the expected chain unit, ? CH₂CH₂? O? P(S)(OR)? O? . The polymerization mechanism probably involves an anionic ring-opening step with P? O cleavage. Ring opening with C? O cleavage appears to be largely excluded. This conclusion is based on the expectation that anionic ring opening with C? O cleavage should lead to a rearranged chain unit, ? CH₂CH₂? O? P(O)? (OR)? S? , because of the high nucleophilicity of sulfur as compared with oxygen. Proton and ³¹P NMR spectra give no evidence for the rearranged unit within the limit of detection (ca. 3%). However, on aging, the methyl ester polymer changes drastically to form up to 40% CH₂SP groups. Presumably, the polymer undergoes the well-known thiono-thiolo rearrangement characteristic of simple phosphorothioate esters to form ? CH₂CH₂? O? P(O)(SCH₃)? O? chain units. The phenyl ester polymer is stable under the same aging conditions.     

Degradation of PVCs obtained by controlled chemical dehydrochlorination

Thermal and thermo-oxidative degradation of poly(vinyl chloride)s (PVCs) containing increased concentrations of allylic chlorines, PVC(A)s, prepared by controlled chemical dehydrochlorination with potassium-t-butoxide (t-BuOK) have been studied. The introduction of small amounts of internal allylic chlorines into PVC significantly decreases the thermal and thermo-oxidative stability of the resin. A linear relationship exists between the initial rates (V_HCl)₀ of thermal and thermooxidative dehydrochlorination of solid PVC(A)s and the concentration S of internal allylic chlorines. Both the slope and the intercept of the thermo-oxidative (V_HCl)₀ vs. S plot are higher in oxygen than those obtained in nitrogen at the same temperature; this finding is attributed to fast oxidation of polyenes, and to peroxy radicals formed during polyene oxidation, which initiate subsequent HCl loss by attacking normal repeat units in PVC. The extent of HCl loss as a function of time during thermal degradation of PVC(A)s in intert solvent shows a rapid initial phase followed by a slower stationary phase. The first phase is due to dehydrochlorination involving the labile chlorines, while the stationary phase indicates random initiation of HCl loss at normal? CH₂? CHCl? repeat units. Initial rates of HCl loss increase with S, while the rates of HCl loss during the stationary phase are independent of S. The rate constant of initiation of HCl loss at internal allylic chlorines is almost four orders of magnitude higher than that of random initiation; however, the former is still orders of magnitude lower than that of chain propagation. Quantitative analysis of UV-visible spectra of PVC(A)s degraded in solution suggests geometric polyene distribution. The average length of polyenes decreases as the extent of HCl loss increases and reaches a constant value of ca. 3 at ca. 1% HCl loss for all the investigated PVC(A) samples.