Über Chalkogenolate. 194 [1]: S-Bis(trimethylsilyl)aminoester von Dithiocarbamidsäuren 3. Kristall- und Molekülstruktur vom Methyl-und i-Propylderivat [1]

Inhaltsübersicht. Die Titelverbindungen R₂N–CS–S–N[Si(CH₃)₃]₂ mit Ii = CH₃ bzw. CH(CH₃)₂ kristallisieren orthorhombisch bzw. monoklin: Gitterkonstanten für R = CH₃ (bei ?165°C) a = 8,397(4) Å, b = 11,917(4) Å, c = 31,966 (11) Å, Pbca (Nr. 61), Z = 8. R = CH(CH₃)₂ (bei ?80°C) a =13,183(3) Å, b = 10,873(11) Å, c = 14,865(2) Å, β = 105,86(2)° P2₁/n (Nr. 14), Z = 4. Die Kristallstrukturen wurden unter Verwendung von 4227 bzw. 3 433 symmetrieunabhängigen Reflexen (gemessen bei ?165 bzw. ?80 °C) bestimmt und bis auf Zuverlässigkeitsfaktoren von R = 0,081 bzw. 0,082 verfeinert (R_w = 0,084 bzw. 0,114). Bei beiden Verbindungen ist der C₂N–CS–S–N-Teil des Moleküls nahezu planar. Zwischen dem Thiocarbonyl-S-Atom und dem N-Atom der silylierten Aminogruppe bestehen Wechselwirkungen. On Chalcogenolates. 194. S-Bis (trimethylsilyl) amino Esters of Dithiocarbamic Acids. 3. Crystal and Molecular Structure of the Methyl and i-Propyl Derivative The title compounds R₂N–CS–S–N[Si(CH₃)₃]₂ with R = CH₃ and CH(CH₃)₂, respectively, crystallize orthorhombic and monoclinic, resp.; cell dimensions and space group see “Inhaltsübersicht”. The structures of both compounds have been determined from single crystal X-ray data measured at ?165°C and ?80°C, resp., and refined to R's of 0.081 and 0.082, resp., (R_w = 0.084 and 0.114, resp.) using 4227 and 3433, resp., independent reflections. In both compounds the C₂N–CS–S–N core of the molecule is nearly plane. Between the thiocarbonyl sulfur atom and the nitrogen atom of the amino group interactions exist. In Fortführung unserer Untersuchungen [1, 2] über N, N-Dialkyldithiocarbamidsäure-S-bis(trimethylsilyl)aminoester R₂N–CS–S–N[Si(CH₃)₃]₂ haben wir die Kristall- und Molekülstrukturen der Verbindungen mit R = CH₃ und CH(CH₃)₂ bestimmt. Dabei sollte untersucht werden, welchen Einfluß sterisch anspruchsvollere Alkylgruppen (R = CH₃ → CH(CH₃)₂) auf die Molekülgeo-metrie haben. Eine strukturchemische Charakterisierung dieser Verbindungs-klasse ist bis jetzt noch nicht erfolgt; vgl. die Literaturzusammenstellung bei [3].     

Investigation by dynamic NMR spectroscopy of the mechanism of rotation about the carbon?double bond in nitroenamines

Rapid Z,E-isomerization of nitroenamines R? NH? CH?C(NO₂)COOCH₃ in solutions was investigated by dynamic NMR spectroscopy. In weakly basic solvents all the studied nitroenamines isomerize by a thermal mechanism. In pyridine the isomerization proceeds by the thermal mechanism in aliphatic enamines with R?? CH₃, ? COCH₃ and H, but involves the formation of an intermediate mesomeric ion with kinetically controlled ionization of the N? H bond in the case of aromatic nitroenamines where R = X—Ph-.     

Protonenresonanzuntersuchungen an Aminoboranen—II: Einflüsse von para-Phenylsubstituenten auf die Rotationsbarriere um die N?B-Bindung

The electronic influence of substituents on the free enthalpy of rotation around the N? B bond in aminoboranes was investigated in two series of compounds: (a) (CH₃)₂N?BCl (phenyl-p-X), containing the para-phenyl substituent at the boron atom, and (b) (p-X-phenyl)CH₃N?B(CH₃)₂, containing the para-phenyl substituent at the nitrogen atom of the N? B linkage (X = ? NR₂, ? OCH₃, ? C(CH₃)₃, ? Si(CH₃)₃, ? H, ? F, ? Cl, ? Br, ? I, ? CF₃ and ? NO₂). By comparing the rotational barriers in corresponding compounds of both series, a reverse effect of the substituents could be observed. Electron-withdrawing substituents in the para position of the phenyl ring increase the ΔG_c^≠ if the phenyl group is attached to the boron atom; on the other hand, a lower ΔG_c^≠ is observed if the phenyl ring is bonded to the nitrogen atom of the N? B system. Substitution of the phenyl ring with electron-donating substituents in the paraposition exerts the opposite effect. Within each series of compounds, the differences of ΔG_c^≠ values [δ(ΔG_c^≠) = ΔG_c^≠ (X) ? ΔG_c^≠ (X = H)] between substituted and unsubstituted compounds can be explained in terms of inductive and mesomeric effects of the ring substituents and can be correlated with the Hammett σ constant of each substituent. A comparison of the slopes of the plotted lines shows that the influence of the ring substituents is more pronounced in compounds with N-phenyl-p-X than in those with B-phenyl-p-X.     

Bond dissociation energies and radical heats of formation in CH3Cl,CH2Cl2, CH3Br,CH2Br2, CH2FCl,and CHFCl2

An analysis of thermochemical and kinetic data on the bromination of the halomethanes CH_4–nX_n (X = F, Cl, Br; n = 1–3), the two chlorofluoromethanes, CH₂FCl and CHFCl₂, and CH₄, shows that the recently reported heats of formation of the radicals CH₂Cl, CHCl₂, CHBr₂, and CFCl₂, and the C? H bond dissociation energies in the matching halomethanes are not compatible with the activation energies for the corresponding reverse reactions. From the observed trends in CH₄ and the other halomethanes, the following revised ΔH°_f,298 (R) values have been derived: ΔH°_f(CH₂Cl) = 29.1 ± 1.0, ΔH°_f(CHCl₂) = 23.5 ± 1.2, ΔH_f(CH₂Br) = 40.4 ± 1.0, ΔH°_f(CHBr₂) = 45.0 ± 2.2, and ΔH°_f(CFCl₂) = ?21.3 ± 2.4 kcal mol^?1. The previously unavailable radical heat of formation, ΔH°_f(CHFCl) = ?14.5 ± 2.4 kcal mol^?1 has also been deduced. These values are used with the heats of formation of the parent compounds from the literature to evaluate C? H and C? X bond dissociation energies in CH₃Cl, CH₂Cl₂, CH₃Br, CH₂Br₂, CH₂FCl, and CHFCl₂.     

Über Chalkogenolate. 81. Untersuchungen über N-Hydroxydithiocarbamidsäure 3. Ester der N-Hydroxydithiocarbimidsäure und -carbamidsäure

On Chalcogenolates. 81. Studies on N-Hydroxy Dithiocarbamic Acid. 3- Esters of N-Hydroxy Dithiocarbimic Acid and Dithiocarbamic Acid The reaction between hydroxylamine, carbon disulfide, and alkyl halide leads to the corresponding ester of N-hydroxy dithiocarbimic acid HO? N?C(SR)₂ with R = CH₃, C₂H₅; R₂ = ? CH₂? CH₂? . The phenyl ester of N-hydroxy dithiocarbamic acid HO? NH? CS(SC₆H₅) has been prepared by reaction of hydroxylammonium chloride with the phenyl ester of chlorodithioformic acid. N-Methyl hydroxylammonium chloride reacts with carbon disulfide and alkyl iodide to form the corresponding ester of the dithiocarbamic acid HO? N(CH₃)? CS(SR) with R = CH₃, C₂H₅. The unstable compounds have been characterized by different methods.     

Über Chalkogenolate. 113 Umsetzung von Chloramin mit Kohlenstoffdisulfid und mit Methylestern von Dithiocarbamidsäuren

On Chalcogenolates. 113. Reactions of Chloramine with Carbon Disulfide and with Methylesters of Dithiocarbamic Acids The reactions of chloramine with CS₂ and with H₂N? CS? SCH₃, CH₃? NH? CS? SCH₃, and (CH₃)₂N? CS? SCH₃ have been studied. The reaction with the methylester of dithiocarbamic acid gives the known dimethyl perthiocyanate and the reaction with the methylester of N-methyldithiocarbamic acid leads to CH₃S? CS? N(CH₃)? C(?NCH₃)? SCH₃. The latter compound has been characterized by means of electron absorption spectra, infrared spectra, nuclear magnetic resonance spectra (¹H and ¹³C), and mass spectra.     

Recherches sur la formation et la transformation des esters LXXII. Aryl(ou aralcoyl ou alcoyl)amino-2-tétrahydro-m-thiazines ou aryl(ou aralcoyl ou alcoyl)amino-2-dihydro-Δ2-m-thiazines et dérivés

3-Aminopropanol reacts with aryl(or aralkyl or alkyl)isothiocyanates R? N?C?S to yield the corresponding thio-ureas R? NH? CS? NH? (CH₂)₃OH which, refluxed with hydrochloric acid, are cyclized by elimination of water. The cyclization products are identical with the hydrothiazines resulting by elimination of sulfate or phosphate from the sulfuric or phosphoric monoesters of these thio-ureas. The resulting hydrothiazines are either 2-(R-imino)-tetrahydro-m-thiazines (I) or 2-(R-amino)-dihydro-Δ²-m-thiazines (II). Their structure has been established by comparison of their spectra with those of model compounds in one of which the C?N double bond is certainly endocyclic (2-methyl-dihydro-Δ²-m-thiazine), the other presenting an exocyclic C?N double bond (3-methyl-2-phenylimino-tetrahydro-m-thiazine). When R is an aryl group, the C?N double bond is exocyclic (structure I with >C?N? Ar), and one may presume that this structure is stabilized by resonance. When R is an aralkyl or an alkyl group, the C?N double bond is endocyclic (structure II). The nmr spectra were taken with three types of solvent: CDCl₃ or CCl₄; (CD₃)₂SO; CF₃COOH. In CF₃COOH solution the benzylic protons of the hydrothiazine with R = pF? C₆H₄CH₂? couple with NH (J=5,5cps) which confirms the endocyclic position of the C?N double bond in this case.     

New insight into the substituent effects on the hydrolytic deamination of saturated and unsaturated cytosine

Ab initio calculations were carried out to understand the effect of electron donating groups (EDG) and electron withdrawing groups (EWG) at the C5 position of cytosine (Cyt) and saturated cytosine (H₂Cyt) of the deamination reaction. Geometries of the reactants, transition states, intermediates, and products were fully optimized at the B3LYP/6-31G(d,p) level in the gas phase as this level of theory has been found to agree very well with G3 theories. Activation energies, enthalpies, and Gibbs energies of activation along with the thermodynamic properties (ΔE, ΔH, and ΔG) of each reaction were calculated. A plot of the Gibbs energies of activation (ΔG^‡) for C5 substituted Cyt and H₂Cyt against the Hammett σ-constants reveal a good linear relationship. In general, both EDG and EWG substituents at the C5 position in Cyt results in higher ΔG^‡ and lower σ values compared to those of H₂Cyt deamination reactions. C5 alkyl substituents ( H,  CH₃,  CH₂CH₃,  CH₂CH₂CH₃) increase ΔG^‡ values for Cyt, while the same substituents decrease ΔG^‡ values for H₂Cyt which is likely due to steric effects. However, the Hammett σ-constants were found to decrease at the C5 position of cytosine (Cyt) and saturated cytosine (H2Cyt) on the deamination reaction. Both ΔG^‡ and σ values decrease for the substituents Cl and Br in the Cyt reaction, while ΔG^‡ values increase and σ decrease in the H₂Cyt reaction. This may be due to high polarizability of bromine which results in a greater stabilization of the transition state in the case of bromine compared to chlorine. Regardless of the substituent at C5, the positive charge on C4 is greater in the TS compared to the reactant complex for both the Cyt and H₂Cyt. Moreover, as the charges on C4 in the TS increase compared to reactant, ΔG^‡ also increase for the C5 alkyl substituents ( H,  CH₃,  CH₂CH₃,  CH₂CH₂CH₃) in Cyt, while ΔG^‡ decrease in H₂Cyt. In addition, analysis of the frontier MO energies for the transition state structures shows that there is a correlation between the energy of the HOMO–LUMO gap and activation energies.     

Sels de Pyrylium. XVIII. Etude par RMN du Carbone-13 de Sels d'Aminopyrylium et des Barrières de Rotation dans quelques Cations N,N-Diméthylaminopyrylium

The C-2—N bond of 2-N,N-dimethylaminopyrylium cations has a partial π character due to the conjugation of the nitrogen lone-pair with the ring. The values of ΔG^≠, ΔH^≠, ΔS^≠ parameters related to the corresponding hindered rotation have been determined by ¹³C NMR total bandshape analysis. This conjugation decreases the electrophilic character of carbon C-4 so that the displacement of the alkoxy group is no longer possible. Such a hindered rotation also exists in 4-N,N-dimethylaminopyrylium cations and the corresponding ΔG^≠ parameters have been evaluated. Comparison of these two cationic species shows that hindered rotation around the C—N bond is larger in position 4 than in position 2. Furthermore, the barrier to internal rotation around the C-2? N bond decreases with increasing electron donating power of the substituent at position 4. ΔG^≠ values decreases from 19.1 kcal mol^?1 (79.9 kJ mol^?1) to 12.6 kcal mol^?1 (52.7 kJ mol^?1) according to the following sequence for the R-4 substituents: -C₆H₅, -CH₃, -OCH₃, -N(CH₃)₂.     

13C relaxation times,T1, in six-coordinate cobalt(III) complexes: Study of the axial Co?N (heterocyclic) bond

Carbon-13 relaxation times, T₁, have been measured for ten cobalt(III)–cyclohexanedione dioxime complexes: CH₃CH₂? Co(Niox)₂-p-R-pyridine [R?H, N(CH₃)₂, CH₃, C₂H₅, C(CH₃)₃, Cl, Br, CN and COCH₃] and CH₃CH₂? Co(Niox)₂-3-N-methylimidazole. The values obtained have been rationalized by making assumptions on the length of the metal—hetrocyclic nitrogen bond. The internal rotation around the axial Co? N (heterocyclic) bond is faster for the 3-N-methylimidazole ligand than for the pyridine ligands. Correlations of the T₁ values with the σ-donor and π-acceptor character of the pyridine ligands were attempted. The interpretation of the results suggests the existence of π-back-bonding from the metal to the N-1 pyridine nitrogen atom, in agreement with the results of other workers. This conclusion, however, was not supported by the use of the para-C chemical shift as a criterion for back-bonding in pyridine–transition metal complexes.     

Die Addition von Säuren an Alkinderivate mit Push-pull-Gruppen,

The addition of proton acids as HF, HCl, HBr, HOAc and phenol to alkyne-derivatives of the type (CH₃)₂N? C?C? CO? R( 1 ) yielding the adducts 2 to 6 is investigated. The stereochemical course of the reaction is mainly influenced by the structure of the alkyne 1 . Kinetic investigations show that the rate of the third-order-reaction increases from 1 a (R?H) to 1 b (R ? CH₃) and 1 c (R ? OCH₃) and decreases drastically in polar solvents. According to these results a reaction mechanism is outlined and discussed.     

1λ6,2,4-Thiadiazetidine und 1,2λ6,3-Oxathiazetidine

1λ⁶,2,4-Thiadiazetidines and 1,2λ⁶,3-Oxathiazetidines From the reaction of the sulfur triimides (RN?)₃S ( 2a R?(CH₃)₃C, 2b R?(CH₃)₃Si) with pentafluoroazapropene ( 11 ) the appropriate 1λ⁶,2,4 thiadiazetidines ( 13a, 13b ) are formed, while from ClSO₂N?CCl₂ ( 14 ) and 2a (CH₃)₃C? N?C?N? SO₂Cl ( 17 ) is isolated. 2b and hexafluoroacetone ( 18 ) give the rather unstable 1,2λ⁶,3-oxathiazetidine ( 20 ).     

Ab initio studies of structural features not easily amenable to experiment. 25. Conformational analysis of methyl propanoate and comparison with the methyl ester of glycine

The molecular geometries of three conformations of methyl propanoate (MEP) (C? C? C?O torsions of 0°, 120°, and 180°) and the potential-energy surfaces of MEP (C? C? C?O torsions) and of the methyl ester of glycine (MEG) (N? C? C?O torsions) have been determined by ab initio gradient calculations at the 4-21G level. MEP has conformational energy minima at 0° and 120° of the C? C? C?O torsion, while the 60–90° range and 180° are energy maxima. For MEG there are two minima (at 0° and 180°) and one barrier to N? C? C?O rotation in the 60–90° range. The N? C? C?O barrier height is about twice as high (4 kcal/mol) as the C? C? C?O barrier. The 180° N? C? C?O minimum is characteristically wide and flat allowing for considerable flexibility of the N? C? C?O torsion in the 150–210° range. This flexibility could be of potential importance for polypeptide systems, since the N? C? C?O angles of helical forms are usually found in this region. The molecular structures of the methyl ester group CH₃OC(?O)CHRR′ in several systems are compared and found to be rather constant when R ? H and R′ ? H, CH₃, CH₃CH₂; or when R ? NH₂ and R′ ? H, CH₃, or CH(CH₃)₂.     

3‐Rhoda‐1,2‐diazacyclopentanes: A Series of Novel Metallacycle Complexes Derived From CN Functionalization of Ethylene

Rh‐containing metallacycles, [(TPA)Rh^III(κ²‐(C,N)‐CH₂CH₂(NR)₂‐]Cl; TPA=N,N,N,N‐tris(2‐pyridylmethyl)amine have been accessed through treatment of the Rh^I ethylene complex, [(TPA)Rh(η²‐CH₂CH₂)]Cl ([ 1 ]Cl) with substituted diazenes. We show this methodology to be tolerant of electron‐deficient azo compounds including azo diesters (RCO₂N?NCO₂R; R=Et [ 3 ]Cl, R=iPr [ 4 ]Cl, R=tBu [ 5 ]Cl, and R=Bn [ 6 ]Cl) and a cyclic azo diamide: 4‐phenyl‐1,2,4‐triazole‐3,5‐dione (PTAD), [ 7 ]Cl. The latter complex features two ortho‐fused ring systems and constitutes the first 3‐rhoda‐1,2‐diazabicyclo[3.3.0]octane. Preliminary evidence suggests that these complexes result from N–N coordination followed by insertion of ethylene into a [Rh]?N bond. In terms of reactivity, [ 3 ]Cl and [ 4 ]Cl successfully undergo ring‐opening using p‐toluenesulfonic acid, affording the Rh chlorides, [(TPA)Rh^III(Cl)(κ¹‐(C)‐CH₂CH₂(NCO₂R)(NHCO₂R)]OTs; [ 13 ]OTs and [ 14 ]OTs. Deprotection of [ 5 ]Cl using trifluoroacetic acid was also found to give an ethyl substituted, end‐on coordinated diazene [(TPA)Rh^III(κ²‐(C,N)‐CH₂CH₂(NH)₂‐]⁺ [ 16 ]Cl, a hitherto unreported motif. Treatment of [ 16 ]Cl with acetyl chloride resulted in the bisacetylated adduct [(TPA)Rh^III(κ²‐(C,N)‐CH₂CH₂(NAc)₂‐]⁺, [ 17 ]Cl. Treatment of [ 1 ]Cl with AcN?NAc did not give the Rh?N insertion product, but instead the N,O‐chelated complex [(TPA)Rh^I ( κ²‐(O,N)‐CH₃(CO)(NH)(N?C(CH₃)(OCH?CH₂))]Cl [ 23 ]Cl, presumably through insertion of ethylene into a [Rh]?O bond.     

Über Chalkogenolate. 181 [1]. Thiocarbamoyl-methylsulfane

On Chalcogenolates. 181. Thiocarbamoyl Methyl Sulfanes The thiocarbamoyl methyl sulfanes H₂N? CS? S_x? CH₃? NH? CS? S_x? CH₃, and (CH₃)₂N? CS? S_x? CH₃ with x = 1 and 2 have been prepared by known procedures (for x = 1) and by reaction of the corresponding dithiocarbamate with the S-methylester of methanethiosulfonic acid CH₃? SO₂? SCH₃ (for x = 2). The compounds have been studied by means of diverse spectroscopic methods.     

Trivalent-pentavalente Phosphorverbindungen/Phosphazene. IV. Darstellung und Eigenschaften neuer N-silylierter Diphosphazene

Trivalent-Pentavalent Phosphorus Compounds/Phosphazenes. IV. Preparation and Properties of New N-silylated Diphosphazenes Phosphazeno-phosphanes, R₃P = N? P(OR′) ₂ (R = CH₃, N(CH₃)₂; R′ = CH₂? CF₃) react with trimethylazido silane to give N-silylated diphosphazenes, R₃P = N? P(OR′)₂ = N? Si(CH₃)₃ compounds decompose by atmospherical air to phosphazeno-phosphonamidic acid esters, R₃ P?N? P(O)(O? CH₂? CF₃)(NH₂). Thermolysis of diphosphazene R₃P = N? P(OR′) ₂ = N? Si(CH₃)₃ (R = CH₃, R′ = CH₂? CF₃) produces phosphazenyl-phosphazenes [N?P(N?P(CH₃)₃)OR′] _n. The compounds are characterized by elementary analysis, IR-, ¹H_-, ²⁹Si-, ³¹P-n.m.r., and mass spectroscopy.     

Kristall- und Molekülstruktur von Tetra-n-butylammonium-N-methyl-N-thioformyldithiocarbamat

Crystal and Molecular Structure of Tetra-n-butylammonium N-Methyl-N-Thioformyl Dithiocarbamate [N(n-C₄H₉)₄][S₂C? N(CH₃)? CS? H] crystallizes in the triclinic space group P1 (Z = 2) with cell dimensions (?45°C) a = 9.185(2) Å, b = 10.263(3) Å, c = 13.301(3) Å, α = 101.73(2)°, ß = 99.59(2)°, γ 100.57(2)°. The crystal structure was solved by means of direct methods and refined to a conventional reliability index R = 0.066 (R_ω = 0.070). 5945 independent intensities being measured.     

Thermal decomposition of di-t-butyl peroxide in the presence of (CH3)2CCH2: Reactions of CH3, (CH3)2ĊCH2CH3, and (CH3)2ĊCH2C(CH3)2CH2CH3 radicals

A study of the reaction initiated by the thermal decomposition of di-t-butyl peroxide (DTBP) in the presence of (CH₃)₂C?CH₂ (B) at 391–444 K has yielded kinetic data on a number of reactions involving CH₃ (M·), (CH₃)₂CCH₂CH₃ (MB·) and (CH₃)₂?CH₂C(CH₃)₂CH₂CH₃ (MBB·) radicals. The cross-combination ratio for M· and MB· radicals, rate constants for the addition to B of M· and MB· radicals relative to those for their recombination reactions, and rate constants for the decomposition of DTBP, have been determined. The values are, respectively, where θ = RT ln 10 and the units are dm^3/2 mol^?1/2 s^?1/2 for k₂/k and k₉/k, s^?1 for k₀, and kJ mol^?1 for E. Various disproportionation-combination ratios involving M·, MB·, and MBB· radicals have been evaluated. The values obtained are: Δ₁(M·, MB·) = 0.79 ± 0.35, Δ₁(MB·, MB·) = 3.0 ± 1.0, Δ₁(MBB·, MB·) = 0.7 ± 0.4, Δ₁(M·, MBB·) = 4.1 ± 1.0, Δ₁(MB·, MBB·) = 6.2 ± 1.4, and Δ₁(MBB·, MBB·) = 3.9 ± 2.3, where Δ₁ refers to H-abstraction from the CH₃ group adjacent to the center of the second radical, yielding a 1-olefin. © 1994 John Wiley & Sons, Inc.     

Recherches sur la formation et la transformation des esters LXVII. Note sur la scission des acides ω-(N-phénylthiocarbamylamino)-alcoyl-sulfuriques à divers pH

In aqueous solutions at 100°C varying from HCl 2N to NaOH 2N , N-phenylthiocarbamoyl derivatives of aminoalkylsulfuric monoesters C₆H₅NH? CS? R? OSO₃H are split in the following ways:

• (a) With R = ? CH₂? CH(CH₃)? or ? (CH₂)₃? the scission of the monoester group is very rapid in the hole pH-range studied, especially in alkaline medium; the resulting cyclic products, 5-methyl-2-phenylamino-thiazoline and 2-phenylimino-tetrahydrothiazine respectively, formed by nucleophilic attack of an unshared pair of the S atom on the C bearing the monoester group, have been isolated and identified.
• (b) With R = ? (CH₂)₄? , the rate of the scission in alkaline or neutral medium is very much higher than that of an alkylsulfuric monoester; in these media a cyclic product is also formed (this time by nucleophilic attack of the unshared pair of the thiocarbamoylated N atom on the C bearing the monoester function) which has been isolated after alcaline scission, and identified as N-phenylcarbomoyl-pyrrolidine. In acid medium, no special influence of the phenylthiocarbamoyl group is observed.
• (c) With R = ? (CH₂)₅? or ? (CH₂)₆? , the rate of the scission in alkaline medium is 30 to 1000 times lower than in the previous cases; no pure organic scission products have been isolated. In acid or neutral medium, these two esters behave like usual alkylsulfuric acids.

     

Synthesis of polyphosphazenes bearing alkoxyethoxy and trifluoroethoxy groups

The synthesis of various phosphoranimines including (CH₃OCH₂CH₂O) (CF₃CH₂O)₂P?N? Si(CH₃)₃, (CH₃OCH₂CH₂OCH₂CH₂O) (CF₃CH₂O)₂P?N? Si (CH₃)₃, (CH₃OCH₂CH₂O)₂(CF₃CH₂O) P?N? Si(CH₃)₃, and (CH₃OCH₂CH₂OCH₂CH₂O)(CF₃CH₂O) P?N? Si(CH₃)₃ via the Staudinger reaction of (CH₃)₃SiN₃ with the suitably substituted phosphite is reported. These monomers were polymerized using tetra-n-butylammonium fluoride and N-methylimidazole in various solvents at several temperatures. In situ ³¹P-NMR kinetic studies and M_n versus time studies were also performed for the monomers to understand the propagation mechanism. © 1994 John Wiley & Sons, Inc.