Thermodynamic properties of simple alkenes

Employing low temperature thermal measurements, heat capacities (C_s) in the crystal and liquid states, and phase transition data, T_m and ΔH_m, the condensed phase thermodynamic properties, (G_s -H°₀)/T, H_s -H°₀, S_s and C_s, in the temperature range 0–360 K were evaluated for the following eleven alkenes: ethylene, propylene, 1-butene, cis-2-butene, trans-2-butene, 1-pentene, cis-2-pentene, trans-2-pentene, 2-methyl-1-butene, 3-methyl-1-butene and 2-methyl-2-butene. The sources of experimental data, methods of evaluation, and the calculated results are described in detail.     

The reaction of n-butyllithium and potassium t-amyloxide with butenes

1-Butene, cis/trans-2-butene and 2-methylpropene were polymetalated by treatment with the product obtained by combination of n-butyllithium and potassium t-amyloxide. Polymetalation was determined by quenching with deuterium oxide and analysis by gas chromatograph-mass spectrometer combination. The rate of metalation was followed by n-butane evolution. Approximately 20% of cis-2-butene exclusively was realized after H₂O quench of the reaction of 1-butene/n-butyllithium/ potassium t-amyloxide for 1.0 h at room temperature. A small amount (7%) of a cis/trans-2-butene mixture was isomerized to 1-butene and the remaining 2-butene was enriched in the cis-isomer. The assumption that n-butylpotassium was the active metalating species was confirmed by the dependency on lithium/potassium ratio, relative ease of organometallic decomposition at 70°, rapid reaction with monochlorostyrene at room temperature, and the similarity to organosodium and organopotassium isomerization of olefins.     

Oxytelluration of olefins to (β-alkoxy- and β-hydroxy-alkyl)aryltellurium dihalides and their reactions with reducing agents and aqueous NaOH

Treatment of olefinic hydrocarbons with phenyltellurium tribromide or a mixture of diphenylditelluride and bromine in alcohol affords (β-alkoxyalkyl)phenyltellurium dibromides in fair to good yield (alkoxytelluration of olefins). Various aryltellurium trichlorides, diphenylditelluride/CuCl₂, and phenyltellurocyanate/CuCl₂ can be used for the preparation of (β-alkoxyalkyl)aryltellurium dichlorides. Similar reactions in aqueous tetrahydrofuran or aqueous t-butyl alcohol result in the formation of the corresponding β-hydroxy compound (hydroxytelluration of olefins). The reaction is trans stereospecific in the cases of cis-2-butene and cis- and trans-4-octenes and regiospecific in the cases of all terminal olefins examined (1-hexene, 1-octene, 1-decene, styrene, α-methylstyrene, 2-methyl-1-pentene, and isobutylene), tellurium species attacking the terminal carbon solely. The diorganyltellurium dihalide produced is reduced to the corresponding diorganyltelluride by reducing agents such as N₂H₄, Na₂S, Na₂S₂O₃, and NaHSO₄ in aqueous solution. Treatment of the diorganyltellurium dibromide with aqueous NaOH affords either an allylic ether (by telluroxide elimination) or a telluroxide depending on the structure of the telluroxide.     

Isomerization of olefins catalysed by a CoCl2/Ph3P/NaBH4 system

The catalyst generated in situ using CoCl₂/Ph₃P/NaBH₄ in 1/3/1 ratio in THF at −10°C isomerizes 1-decene into predominantly cis-2-decene or trans-2-decene. Allyl benzene and safrole have been converted into the corresponding β-methylstyrenes. The catalyst also isomerizes cis,cis-1,5-cyclooctadiene to cis,cis-1,3-cyclooctadiene.     

Synthesis and reactions of 2-naphthyltellurium trichloride

TeCl₄, and naphthalene, when heated to 110° in the absence of a solvent, yielded 2-naphthyltellurium trichloride (2), which on treatment with degassed Raney Ni afforded 2,2'-binaphthyl in excellent yield. Reaction of 2 with propene and cis-2-butene produced the corresponding 1:1-adducts, which however could not be coupled to 2-(2-chloroalkyl)naphthalenes with this reagent.     

Solid state reactions to CdTeMoO6 and its structural characterization

CdTeMoO₆ has been obtained by solid state reactions of CdMoO₄ with orth. TeO₂ at 425°C, with tetr. TeO₂ at 470°C, and with H₆TeO₆ at 490°C. Its crystal structure belongs to the tetragonal system (space group $\text{P4}\text{n}$ or $\text{P4}\text{nmm}$ with unit cell dimensions a = 5.279(2) Å, c = 9.056(2) Å. The specificity of this compound in the allylic oxidation reactions should be strictly related to its structural features, among which the presence of cis MoO₂ groups could be very important.     

Theoretical study of the complex reaction of O(3P) with cis-2-butene

The complex triplet potential energy surface for the reaction of the triplet oxygen atom O(³P) with cis-2-butene is investigated at the CBS-QB3 level of theory. The different possible isomerization and dissociation pathways, including both O-additions and H-abstractions, are thoroughly studied. Our calculations show that as found for the trans-2-butene reaction, in the high-pressure limit, the major product is CH₃CHC(O)H + CH₃ (P1), whereas in the low-pressure limit the most thermodynamically stable product forms CH₃CO + CH₃CH₂ (P4). The experimental negative activation energy reported for the addition step is very well reproduced at the CBS-QB3 level of theory. Various thermodynamic and kinetic values of interest for these reactions are predicted for the first time. A discussion on the negative activation energy for the addition step of the trans- and cis-2-butene reactions with O(³P) focussing on the addition reactant complexes is presented.     

Stabilization and isomerization of radical cations generated by fast electron irradiation of unsaturated organic molecules in a solid argon matrix

Matrix isolation EPR spectroscopy was used to study the fate of “hot” unsaturated radical cations produced by fast electron irradiation in solid argon. It was found that the radical cations of cis-2-butene, trans-2-butene and ethyl vinyl ether resulting from highly exothermic hole transfer (excess energy>6 eV) underwent effective relaxation in an argon matrix. 1-Butene radical cation exhibits isomerization to cis-2-butene radical cation. The role of molecular structure of organic radical cations in excess energy relaxation is discussed.     

Do lipases also catalyse the ring cleavage of inactivated cyclic trans-β-lactams?

Twelve-membered cyclic cis- and trans-β-lactams 1b and 2b and the corresponding cyclic cis- and trans-β-amino acid enantiomers, 1a, 1c and 2a, 2c were prepared through the CAL-B-catalysed enantioselective ring cleavage of racemic cis-13-azabicyclo[10.2.0]tetradecan-14-one, (±)-1, and trans-13-azabicyclo[10.2.0]tetradecan-14-one, (±)-2. High enantioselectivities (E >200) were observed for the ring opening of both the cis- and trans-β-lactams when the Lipolase-catalysed reactions were performed with 0.5 equiv of H₂O in i-Pr₂O at 70 °C. The resolved β-lactams 1b and 2b (yield ⩾47%) and β-amino acids 1a and 2a (yield ⩾32%) could be easily separated.     

Etude structurale de Li2TeO4. Coordination du tellure VI et du lithium par les atomes d'oxygéne

A single crystal of Li₂TeO₄ has been prepared by hydrothermal synthesis and its structure has been determined from three-dimensional X-ray analysis. The crystals are tetragonal, space group P4₁22 with a = b = 6.045(3) Å, c = 8.290(2) Å, and Z = 4. The structure is a distorted inverse spinel with helicoidal chains of Te(VI) octahedra parallel to the [001] axis which can be formulated as [TeO₄]^2n?_n.     

Quantum chemical model of dehydration of 2-butanol catalyzed by zeolite X

The CNDO/2 method was used for quantum chemical calculations of the 2-butanol interaction with zeolite X modelled by the cluster Si₃AlO₁₂H₉. Two-site adsorption on a pair consisting of an acidic and a basic catalytic site promotes dehydration of the alcohol. The activation energy of trans-2-butene formation was estimated to be much higher than those of cis-2-butene and 1-butene formation, in agreement with experimental findings.     

Quantitative estimation of trans-1,4 and cis-1,4 isomers in polychloroprene by high-resolution NMR

In the ¹H-NMR spectrum of polychloroprene dissolved in C₆D₆, the ?CH proton signal was separated into two triplet peaks. These triplet signals were assigned to the ?CH proton in the trans-1,4 and cis-1,4 isomers by measurement of ¹H-NMR spectra of 3-chloro-1-butene and a mixture of trans- and cis-2-chloro-2-butene as model compounds for the 1,2, trans-1,4 and cis-1,4 isomers. In ¹H-NMR spectra (220 Mcps) of polychloroprene dissolved in C₆D₆, two triplet signals were separated completely from which the relative concentrations of trans-1,4 and cis-1,4 isomers could be obtained quantitatively.     

Stability of the first-generation Grubbs metathesis catalyst in a continuous flow reactor

Ethylene pretreatment of the (PCy₃)₂Cl₂RuCHPh catalyst (1) prior to cross-metathesis of ethylene and cis-2-butene to form propylene in the continuous flow reactor produced a direct effect on catalyst deactivation. Similar cis-2-butene pretreatment of the same catalyst exhibited far less change in the catalyst activity. These results support the assumption that the ruthenium methylidene intermediate generated from ethylene and 1 is unstable and promotes catalyst loss while ruthenium alkylidenes, e.g. derived from 2-butene, exhibit significantly enhanced stability and sustained catalyst integrity. Continuous removal of products in the continuous flow reactor was important for separating the catalyst decay and the catalyst deactivation caused by a terminal olefin, in this case propylene.The amount of produced propylene during the 1 lifespan was determined in a series of tests using identical catalyst concentrations ([Ru] = 60 ppm) in pentadecane while varying the olefin pretreatment times from 0 to 420 min. The catalyst turnover numbers in the cross-metathesis experiments proved inversely proportional to the duration of ethylene treatment prior to the reaction. The activity of 1 pre-exposed to ethylene closely matched with the activity of the catalyst that decayed in the reaction mixture containing ethylene and cis-2-butene for the same period of time. A significant contribution of the Ru-methylidene decay to the activity losses in metathesis reactions was demonstrated directly in the cross-metathesis reaction environment. The catalyst proved to be less sensitive to cis-2-butene pretreatment and showed turnover numbers for subsequent cross-metathesis essentially similar to the reference cross-metathesis test.     

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.     

Crystal structure of a new gallium tellurite: Ga2Te4O11

Ga₂Te₄O₁₁ crystallises with triclinic symmetry (space group P1) and unit cell parameters: a = 5.125(1) Å, b = 6.559(1) Å, c = 8.173(2) Å, α = 75.06(2), β = 89.25(2), γ = 69.62(2), Z = 1. Its crystal structure has been refined by a full matrix least-squares process to R₁ = 0.023 and wR₂ = 0.060 values, on the basis of 2931 independent single crystal X-ray reflections. It can be described as a three-dimensional polyhedral network of independent Te₂O₆ groups of TeO₃ trigonal pyramids and TeO₄ disphenoids sharing corners, and infinite (Te₂O₅)_∞ quasi-linear chains of the same corner-sharing TeO₃ and TeO₄ units, linked one to the other via common corner or common edge by GaO₄ and GaO₅ polyhedra. The stereochemical activity of the lone pair of each Te atom has been analysed and a comparison is made with all the known other M₂Te₄O₁₁ crystal structures.     

Effects of ring strain on gas-phase rate constants. I. Ozone reactions with cycloalkenes

Rate constants for the gas-phase reactions of O₃ with a series of cycloalkenes and with cis-2-butene have been determined at 297 ± 1 K. The rate constants obtained were (in units of 10^?16 cm³/molecule·s): cis-2-butene, 1.38 ± 0.16; cyclopentene, 2.75 ± 0.33; cyclohexene, 1.04 ± 0.14; cycloheptene, 3.19 ± 0.36; 1,3-cyclohexadiene, 19.7 ± 2.8; 1,4-cyclohexadiene, 0.639 ± 0.074; bicyclo[2.2.1]-2-heptene, 21.4 ± 3.5; bicyclo[2.2.1]-2,5-heptadiene, 46.8 ± 12.9; and bicyclo[2.2.2]-2-octene, 0.728 ± 0.090. These data for cis-2-butene, cyclopentene, and cyclohexene are compared with previous literature data, and the effects of ring strain on the rate constants are discussed.     

Etude structurale d'un nouveau tellurate alcalin: Na2TeO4. Evolution de la coordination du tellure(VI) et du cation quand on passe du cation lithium au sodium

Single crystal Na₂TeO₄ has been prepared by hydrothermal synthesis and its structure determined from three dimensional X-ray analysis. The crystal is monoclinic, space group $\text{P}\text{P2}{}_1\text{c}$ with a = 10.632(5)Å, b = 5.161(2)Å; c = 13.837(11)Å, and β = 103.27(4)°. The crystal structure is built up of chains of Te(VI)O₆ octahedra parallel to the [010] axis which can be formulated as [TeO₄]_n^2n?. All sodium cations are in very distorted octahedral coordination.     

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.     

Rate constants for the reactions of OH radicals with alkyl substituted olefins

Relative rate constants for the reactions of hydroxyl radicals with a series of alkyl substituted olefins were measured by competitive reactions between pairs of olefins at 298 ± 2 K and 1 atmospheric pressure. Hydroxyl radicals were produced by the photolysis of H₂O₂ with 254-nm irradiation. The obtained rate constants were (× 10^?11 cm³ molecule^?1 s^?1): 2.53 ± 0.06, propylene; 5.49 ± 0.17, cis-2-butene; 5.47 ± 0.1, isobutene; 6.46 ± 0.13, 2-methyl-1-butene; 6.37 ± 0.16, cis-2-pentene; 6.23 ± 0.1, 2-methyl-1-pentene; 8.76 ± 0.14, 2-methyl-2-pentene; 6.24 ± 0.08, trans-4-methyl-2-pentene; 10.3 ± 0.1, 2,3-dimethyl-2-butene; 9.94 ± 0.1, 2,3-dimethyl-2-pentene; 5.59 ± 0.07, trans-4,4-dimethyl-2-pentene. A trend in alkyl substituent effect on the rate constant was found, which is useful to predict k_OH on the basis of the number of alkyl substituents on the double bond.     

Crystal structure of the new compound Co6(TeO3)2(TeO6)Cl2

The new compound Co₆(TeO₃)₂(TeO₆)Cl₂ has been isolated during an investigation of the system CoO:CoCl₂:TeO₂. The new compound is deep purple in color and crystallizes in the tetragonal system, space group P4₂/mbc, a=8.3871(7) Å, c=18.5634(19) Å, Z=4. The Co(II) ions have octahedral [Co1O₆] and tetrahedral [Co2O₃Cl] coordinations. Tellurium is present both as Te(IV) with a tetrahedral [Te1O₃E] coordination, where E is the 5s² lone-pair and as Te(VI) with an octahedral [Te2O₆] coordination. The structure is made up of intersecting layers of tetrahedra forming channels comprising octahedra chains that run along the c-axis. The new compound is the first cobalt tellurium oxochloride described.