Thermal isomerization of cis- or trans-2-butene. The unimolecular elimination of hydrogen from cis-2-butene around 500°C

An analytical and kinetic study of the thermal reaction of cis- or trans-2-butene has been performed in a static system over the temperature range of 480–550°C and at a low extent of reaction and initial pressures of 10–100 torr. The rate constant of the unimolecular cis–trans isomerization of cis-2-butene, determined under the conditions (2.3 RT in cal/mole) is in good agreement with previous measurements made at lower pressures. A comparison between the formation rates of hydrogen from the thermal reactions of cis- and trans-2 butene around 500°C leads to the rate constant value (2.3 RT in cal/mole) for the unimolecular 1,4? hydrogen elimination from cis? 2? butene.     

X-ray diffraction studies of diisotactic polymers of cis- and trans-2-butene oxides

Crystalline polymers derived from cis- and trans-2-butene oxides were studied by x-ray diffraction methods. X-ray fiber and powder photographs of poly(trans-2-butene oxide) were indexed by an orthorhombic unit cell with the dimensions a = 13.72 A., b = 4.60 A., and c (chain axis) = 6.90 A.; the space group is P2₁2₁2₁. The crystal structure of this polymer has been determined in projection. The chain has an erythro-diisotactic structure with -dl, dl- carbon sequences. The polymer has a nonplanar zigzag backbone with carbon and oxygen atoms of alternate monomer units lying nearly in a plane. Two chain molecules pass through the unit cell. The unit cell of poly(cis-2-butene oxide) is orthorhombic with lattice constants a = 11.20 A., b = 10.44 A., c (chain axis) = 7.01 A. The polymer has a threo-diisotactic structure with -dd,dd- or -ll,ll- carbon sequences. Four chain molecules pass through the unit cell. The crystal lattice is body-centered but the space group has not yet been established. The polymer has an almost fully extended zigzag chain configuration. Polymers prepared by either metal halide catalysts (FeCl₃, SnCl₄) or organometallic catalysts were essentially identical; the latter catalysts did, however, yield more highly crystalline polymers.     

A kinetic study of the chemistry of the SO2 (3B1) reactions with cis- and trans-2-butene

The chemical reactions of SO₂(³B₁) molecules with cis- and trans-2-butene have been studied in gaseous mixtures at 25°C by excitation of SO₂ within the SO₂(³B₁) → SO₂(+, ¹A₁) ‘forbidden’ band using 3500–4100-Å light. The initial quatum yields of olefin isomerization were determined as a function of the [SO₂]/[2-butene] ratio and added gases, He and O₂. The kinetic treatment of these data suggests that there is formed in the SO₂(³B₁) quenching step with either cis- or trans-2-butene, some common intermediate, probably a triplet addition complex between SO- and olefin. It decomposes very rapidly to form the 2-butene isomers in the ratio [trans-2-butene]/[cis-2-butene] = 1.8. In another series of experiments SO₂ was excited using a 3630 ± 1-Å laser pulse of short duration, and the SO₂(³B₁) quenching rate constants with the 2-butenes were determined from the SO₂(³B₁) lifetime measurements. The rate constants at 21°C are (1.29 ± 0.18) × 10¹¹ and (1.22 ± 0.15) × 10¹¹ l/mole·sec with cis-2-butene and trans-2-butene, respectively, as the quencher molecule. Within the experimental error these quenching constants equal those derived from the quantum yield data. Thus the rate-determining step in the isomerization reaction is suggested to be the quenching reaction, presumably the formation of the triplet SO₂-2-butene addition complex. In a third series of experiments using light scattering measurements, it was found that the aerosol formation probably originates largely from SO₃ and H₂SO₄ mist formed following the reaction SO₂(³B₁) + SO₂ → SO₃ + SO(³Σ^?). Aerosol formation from photochemically excited SO₂-olefin interaction is probably unimportant in these systems and must be unimportant in the atmosphere.     

Temperature dependence of the rate constants of the reactions of oxygen atoms with trans-2-butene,cis-2-butene, 2-methylpropene, 2-methyl-2-butene,and 2,3-dimethyl-2-butene

The kinetics of the reactions of ground state oxygen atoms with trans-2-butene, cis-2-butene, 2-methylpropene, 2-methyl-2-butene, and 2,3-dimethyl-2-butene was investigated in the temperature range 200 to 370K. In this range, the rate constants are (in units 10^?11 cm³ s^?1): (1.1 ± 0.1) exp[+(180 ± 24)K/T]; (0.98 ± 0.09) exp[+(149 ± 23)K/T]; (1.14 ± 0.13) exp[+(128 ± 33)K/T]; (2.34 ± 0.16) exp[+(250 ± 16)K/T]; and (3.31 ± 0.50) exp[+(257 ± 36)K/T], respectively. The atoms were generated by the H₂ laser photolysis of NO and detected by the time resolved chemiluminescence in the presence of NO. The concentrations of the O(³P) atoms were kept so low that secondary reactions with products are unimportant. © 1995 John Wiley & Sons, Inc.     

Dehydrohalogenations of cis- and trans-1-bromo-2-flourocyclohexanes

Reactions of both diastereomeric vicinal bromofluorocyclohexanes with sodamide, sodium methoxide, potassium tert-butoxide, and triethylamine were studied. cis-1-Bromo-2-fluorocyclohexane eliminated almost exclusively hydrogen bromide giving mainly 1-fluorocyclohexene and a small amount of 3- fluorocyclohexene. trans-1-Bromo-2-fluorocyclohexane eliminated preferentially hydrogen fluoride on treatment with sodamide. Potassium tert- butoxide eliminated hydrogen bromide and yielded 3-fluorocyclohexene and a small amount of 1,3-cyclohexadiene, whereas sodium methoxide converted trans-1-bromo-2-fluorocyclohexane to 3-fluorocyclohexene and 3-methoxycyclohexene. Possible mechanisms and stereochemistry of the preferential elimination of hydrogen fluoride are discussed and new interpretations are offered.     

Boron fluorides of cis- and trans-2-aryl-3-aroylaziridines

The reaction of boron trifluoride etherate with cis- and trans-2-aryl-3-aroylaziridines yields the respective complexes in high yield. According to PMR spectral data the methyl group of boron trifluoride trans-1-methyl-3-aroylaziridines is located in syn-position, and in the cis-aziridine complexes in anti-position, to the carbonyl group.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1047–1049, August, 1987.     

Stereoselectivity observed in cross metathesis of cis- and trans-2-butene with 1-butene over Re2O7/Al2O3 catalyst

Cross metathesis of cis- and trans-2-butene with 1-butene was studied over Re₂O₇/Al₂O₃ catalyst in a recirculation system at 313 K. Formation of ethylene and hexenes was inhibited by 2-butenes; formation of propene and pentene proceeded without induction from trans- and with induction from cis-2-butene and 1-butene. Selective formation of trans-2-pentene was observed from trans-2-butene, but no such selectivity was characteristic for cis-isomers.

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- -2- 1- Re₂O₇/Al₂O₃ 313 . 2-; - -2- 1-. -2 -2-, , - .

     

Self-assisted stereospecific polymerization of unmasked polar 4-methylthio-1-butene

Stereospecific polymerization of polar olefins has always been an attractive but challenging project because the Lewis basic polar groups of monomers are usually poisonous to the Lewis acidic metal centers of the catalysts. In this contribution,thiophene-fused cyclopentadienyl scandium complexes 1-3 were successfully synthesized. Combined with alkylaluminium and organoborate, these complexes showed extremely low activity and no selectivity for 1-hexene polymerization. Surprisingly,highly stereo-selective coordination polymerization of unprotected polar 4-methylthio-1-butene has been achieved in high activity for the first time under the same polymerization conditions. High-molecular-weight(M_n=110×10~3) and perfectly syndiotactic(rrrr99%) poly(4-methylthio-1-butene)(P(MTB)) was afforded. Thus the methylthio-group-assisted mechanism that the unmasked methylthio group promoted the polymerization through σ-π chelation to the active scandium center together with the vinyl group was proposed. Moreover, the methylsulfonyl functionalized syndiotactic poly(1-butene) was also easily prepared by the oxidation of P(MTB). These results provided a new route for the synthesis of functionalized stereo-regular polyolefins.     

Conformational equilibrium of cis- and trans-3-chloromethylcyclohexanes

Conclusions It has thus been shown both by calculations of the van der Waals interactions and from the molar extinction coefficients of the valence vibration bands of the equatorial C–Cl bonds that cis-3-CMCH consists of the conformer having the CH₃ group and the chlorine atom oriented equatorially, in agreement with the usual assumptions as to the conformations of cis-1,3-disubstituted cyclohexanes.For trans-3-CMCH the calculated E(_e–) values (+150 and +650 cal/mole) are somewhat lower than the experimental value (+870 cal/mole), but all the same there is quite reasonable agreement between them within the limits of the usual errors. In this case the equatorial is preferentially occupied by the CH₃ group, the chlorine atom being axially oriented.Institute for Petrochemical Processes, Academy of Sciences of the Azerbaidjanian SSR, Sumgaitskii Branch. Translated from Zhurnal Strukturnoi Khimii. Vol. 15, No. 1, pp. 148–151. January–February, 1974.     

Stereochemistry of cis- and trans-1-hydroxy-1-phenylquinolizidines

cis and trans-1-Hydroxy-1-phenylquinolizidines were prepared from 1-ketoquinolizidine and isolated by column chromatography. Infrared and nuclear magnetic spectral data were utilized for the elucidation of the structures.     

The SO2(3B1) photosensitized isomerization of cis- and trans-1,2-difluoroethylene

Quantum yield measurements for the SO₂(³B₁) photosensitized isomerization of cis-1,2-difluoroethylene have been made at 3712 Å and 22°C. The [SO₂]/[cis-C₂F₂H₂] ratio was varied from 47.4 to 455 and the quantum yield measurements over this variation of concentration ratios were consistent with a mechanism in which SO₂(³B₁) molecules and the cis isomer form a collision intermediate which decomposes with a probability of 0.42 ± 0.17 and 0.58 ± 0.17 of producing trans- and cis-1,2-difluoroethylene, respectively. When SO₂ was subjected to prolonged irradiations in the presence of initially either pure cis- or pure trans-1,2-difluoroethylene, a photostationary composition, [cis]/[trans] = 1.0 ± 0.2, was obtained. The rate constant at 22°C for removal of SO₂(³B₁) molecules by cis-1,2-difluoroethylene was estimated to be (1.72 ± 0.72) × 10¹⁰ 1./mole · sec.     

Solid-state structures of cis- and trans-1-cyclohexyl-2-phenyl-3-(p-toluyl)aziridines

Solid-state structures have been determined for cis- and trans-1-cyclohexyl-2-phenyl-3-(p-toluyl)aziridines using single-crystal X-ray diffraction techniques. The cis isomer crystallizes in the centrosymmetric monoclinic space group P2₁/c (No. 14), with a = 18.669(3)Å, b = 5.709(1)Å, c = 17.412(2)Å, β = 96.29(1)° and Z = 4; the trans isomer crystallizes in the noncentrosymmetric orthorhombic space group Pna2₁ (No. 33), with a = 17.089(2)Å, b = 18.729(3)Å, c = 5.749(1)Å and Z = 4. Full-matrix least-squares refinement of the structural parameters led to the following final agreement factors: R₁ (unweighted, based on F) = 0.040 and R₂ (weighted, based on F) = 0.054 for the 2592 independent reflections of the cis isomer having 2θ_MoK¯α <55° and I>3σ₁, and R₁ = 0.033 and R₂ = 0.031 for the 1504 independent reflections of the trans isomer having 2θ_MoK¯α <55° and I>3σ₁. The statistically significant differences that exist between the two isomers for two bond lengths and ten bond angles (p < 0.05) appear to be the direct result of the p-toluyl group orientation with respect to the cyclohexyl and phenyl substituents. In the cis isomer it is anti with respect to the N-cyclohexyl group and cis with respect to the phenyl group, whereas in the trans isomer it is syn with respect to the N-cyclohexyl and trans with respect to the phenyl group. Three-ring to carbonyl hyperconjugation is correlated with stereoelectronic interactions in the trans isomer. Bonding, determined by X-ray and nmr studies, is discussed for the three-membered aziridine ring proper; while bonding, determined by X-ray studies, is discussed for substituents of the aziridine ring. These aziridinyl ketone compounds are of importance as potential mammalian DNA alkylating anti-tumor agents in solid-state solid-state systems. To date only a trans isomer has demonstrated this biological activity in tumor-bearing rats.     

The SO2(3B1) photosensitized isomerization of cis- and trans-1,2-dichloroethylene

The photolysis of SO₂ at 3712 Å in the presence of the 1,2-dichloroethylenes has been investigated at 22deg;C. The data are consistent with the SO₂(³B₁) photosensitized isomerization of the 1,2-dichloroethylene isomer. A kinetic treatment of the initial quantum yield data was consistent with the formation of a polarized charge-transfer intermediate whenever SO₂(³B₁) molecules and one of the 1,2-dichloroethylene isomers collide which ultimately decays unimolecularly to the cis-isomer with a probability of 0.70 ± 0.26 and to the trans-isomer with a 0.37 ± 0.16 probability. Quenching rate constants for removal of SO₂(³B₁) molecules by cis- and trans-1,2-dichloroethylene have been estimated from quantum yield data and from laser excited phosphorescence lifetimes using an excitation wavelength of 3130 Å. Estimates of the quenching rate constant (units of 1./mole ± sec) are for the cis-isomer, (1.63 ± 0.71) × 10¹⁰, quantum yield data, and (2.44 ± 0.11) × 10¹⁰, lifetime data; and for the trans-isomer,(2.59 ± 0.09)×10¹⁰, lifetime data, and (2.35 ±0.89) × 10¹⁰, quantum yield data. An experimentally determined photostationary composition,[cis-C₂Cl₂H₂]/[trans-C₂Cl₂H₂] = 1.8 - 0.1, was in good agreement with a value of 2.00 - 1.15 which was predicted from rate constants derived in this study.     

Diene condensation of cis- and trans-2-cyclododecenone

Conclusions In the diene condensation of the cis- and trans-2-cyclododecenones with butadiene only the transisomer reacts, with the formation of trans-bicyclo [10. 4. 0]-14(15)-hexadecen-2-one, which when treated with t-C₄H₃OK is isomerized completely to cis-bicyclo[10. 4. 0]-14(15)-hexadecen-2-one.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 2157–2159, September, 1973.     

Stereoselective Methods for the Synthesis of 4-Benzoyl-1-benzoylamino-3-(2-chlorophenyl)-2-cyano-1-methylthio-1-butene and Its Structure

Selective methods were developed for the synthesis of 4-benzoyl-1-benzoylamino-3-(2-chlorophenyl)-2-cyano-1-methylthio-1-butene on the basis of the reaction of N-methylmorpholinium and piperidinium 5-benzoyl-4-(2-chlorophenyl)-3-cyano-6-hydroxy-6-phenyl-1,4,5,6-tetrahydropyridine-2-thiolates with methyl iodide. The structure of the product was established by X-ray crystallographic analysis.