Synthesis and characterization of copolymers of limonene with styrene initiated by azobisisobutyronitrile

The radical copolymerization of limonene with styrene by azobisisobutyronitrile in xylene at 80 ± 0.1 °C for 2 h, under inert atmosphere of N₂, yields alternating copolymers. The kinetic expression is R_p∝[I]^0.5[Sty]^1.0[Lim]^−1.0. The overall activation energy is calculated as 41 kJ/mol. The FTIR and ¹H-NMR spectra of copolymers show bands at 3000 and 1715 cm⁻¹ and peaks at 6.8 δ and 5.3 δ due to phenyl protons of styrene and trisubstituted olefinic protons of limonene, respectively. The values of reactivity ratios r₁(Sty)=0.0625 and r₂(Lim)=0.014, calculated by Kelen-Tüdos method. The Alfrey-Price Q-e parameters for limonene are 0.438 and −0.748, respectively. The penultimate unit effect is favoured in the present system and the value of φ is 38.49.     

J-dependence of the isotope shift in Gd I 4f 7 5d 2 6s(a 11 F)

TheJ-dependence of the isotope shift in the terma ¹¹ F of 4f ⁷ 5d ² 6s between six stable Gd isotopes was found to be represented by these parameter values (in MHz):z _5d (160?158)=19.4(1.8),z _5d (160?157)=37.2(1.0),z _5d (160?156)=42.4(1.7),z _5d (160?155)=49.1(2.0),z _5d (160?154)=59.0(2.0). The normalization with the corresponding changes in the mean-square nuclear charge-radiiδ〈r ²〉 yields values which are almost constant, mean value:z _5d /δ〈r ²〉=134(14) MHZ/fm². This indicates a second order IS interaction of the magnetic and the field shift operator.     

Zero-point average structures of acetyl chloride and acetyl bromide

The zero-point average structures of acetyl chloride and acetyl bromide have been determined by the combined use of their moments of inertia and average distances, obtained by means of microwave spectroscopy and electron diffraction. The r_z parameters determined are as follows: r_z(CO) = 1.185 ± 0.003 Å, r_z(C-Cl) = 1.796 ± 0.002 Å, r_z(C-C) = 1.505 ± 0.003 Å, r_z(C-H) = 1.092 ± 0.005 Å, φ_z(OCCl) = 121.2 ± 0.6°, φ_z(CCCl) = 111.6 ± 0.6°, φ_z(HCH) = 108.8 ± 0.8° and tilt(CH3) = 1.3 ± 1.0°, for chloride; r_z(CO) = 1.181 ± 0.003 Å, r_z(C-Br) = 1.974 ± 0.003 Å, r_z(C-C) = 1.516 ± 0.003 Å, φ_z(OCBr) = 122.3 ± 1.5°, φ_z(CCBr) = 111.0 ± 1.5°, φ_z(HCH) = 109.9 ± 1.1°, tilt(CH₃) = 1.9 ± 1.0°, for bromide. The barriers V₃ to internal rotation have been revised to 1260 and 1256 cal mol⁻¹ for the chloride and bromide, respectively.     

Curcumin,A Novel Natural Photoinitiator for the Copolymerization of Styrene and Methylmethacrylate

Curcumin (Cur), a natural colorant found in the roots of the Turmeric plant, has been reported for the first time as photoinitiator for the copolymerization of styrene (Sty) and methylmethacrylate (MMA). The kinetic data, inhibiting effect of benzoquinone and ESR studies indicate that the polymerization proceeds via a free radical mechanism. The system follows ideal kinetics (R_p α[Cur]^0.5[Sty]^0.97[MMA]¹). The reactivity ratios calculated by using the Finemann–Ross and Kelen‐Tudos models were r₁(MMA)=0.46 and r₂(Sty)=0.52. IR and NMR analysis confirmed the structure of the copolymer. NMR spectrum showing methoxy protons as three distinct groups of resonance between 2.2–3.75 δ and phenyl protons of styrene at 6.8–7.1 δ confirmed the random nature of the copolymer. The mechanism for formation of radicals and random copolymer of styrene and MMA [Sty‐co‐MMA] is also discussed.     

Structural determination of carvone, a component of spearmint, by means of gas electron diffraction augmented by theoretical calculations

The molecular structure and conformation of carvone, a compound with a minty odor, were investigated by means of gas electron diffraction supported by theoretical calculations. Electron diffraction patterns were recorded by heating the nozzle up to 128 °C to obtain enough scattering intensity. The infrared spectrum was also measured by using an absorption cell with a path length of 10 m. The obtained molecular scattering intensities were analyzed with the aid of theoretical calculations and infrared spectroscopy. It was revealed that the experimental data are well reproduced by assuming that carvone consists of a mixture of three conformers that have the isopropenyl group in the equatorial position and mutually differ in the torsional angle around the single bond connecting the ring and the isopropenyl group. It was also found that the puckering amplitude of the ring of carvone is close to those of menthol and isomenthol, a minty compound and its nonminty isomer. The determined structural parameters (r_g and ∠_α) of the most abundant conformer of carvone are as follows: 〈r(C-C)〉=1.520(3) Å; 〈r(CC)〉=1.360(5) Å; r(CO)=1.225(5) Å; 〈r(C-H)〉=1.104(4)Å; 〈∠CC-C〉=121.1(5)°; 〈∠C-C-C〉=110.4(5)°; ∠C-CO-C=117.1(14)°; 〈∠C-C-H〉=111.1(13)°. Angle brackets denote average values and parenthesized values are the estimated limits of error (3σ) referring to the last significant digit.     

Alternating Copolymers of Limonene with Methyl Methacrylate: Kinetics and Mechanism

The radical copolymerization of limonene (optically active) with methyl methacrylate in xylene at 80±0.1°C for 1 hr, initiated by benzoyl peroxide (BPO) yield alternating copolymer(s), under the inert atmosphere of nitrogen, as evidenced by reactivity ratios r₁ (MMA)=0.07 and r₂ (limonene)=0.012 using the Kelen–Tüdos method. The kinetic expression is Rα[I]^0.5[MMA]^1.0[Lim.]^?1.0. The decrease in the rate of polymerization with increase in concentration of limonene is due to penultimate unit effect. The overall energy of activation is calculated as 49 kJ/mole. FTIR of the copolymer(s) shows the characteristic frequencies at 1732.40 and 2951.40 cm^?1 due to –OCH₃ of MMA and aromatic C–H stretching of limonene, respectively. ¹H NMR spectra shows peak at 3.8–4.1 δ and 5.3–5.6 δ due to –OCH₃ of MMA and trisubstituted olefinic protons [–CH=CH–CH₂–] of limonene, respectively.     

Thermal stability of poly(acryloyl chloride) homopolymer and copolymers of acryloyl chloride with methyl methacrylate

The thermal stabilities of poly(acryloyl chloride) homopolymer and copolymers of acryloyl chloride with methyl methacrylate covering the entire composition range were studied by thermogravimetric analysis. At each extreme of the composition range incorporation of comonomer units results in a copolymer which is less stable than the PMMA homopolymer. The activation energies of the decomposition of the copolymers were calculated using the Arrhenius equation and found to decrease from 32.2 to 12.5 kJ mol^?1 as acryloyl chloride concentration of the copolymer increases, indicating that the copolymers of higher acryloyl chloride concentration should easier decompose than other copolymers. The reactivity ratios of the copolymer were calculated and found to ber ₁(AC)=0.2±0.02 andr ₂(MMA)=0.9±0.1.     

Heteronuclear diatomic transition-metal cluster ions in the gas phase: Reactivity and thermochemistry of AgFe+

The gas-phase chemistry of AgFe⁺ was studied by using Fourier transform ion cyclotron resonance mass spectrometry. AgFe⁺ is unreactive with alkanes but reacts with cyclic and linear (C4–C8) alkenes. The primary reactions are dominated by dehydrogenation and condensation. In addition, cluster splitting is observed in the reaction of AgFe⁺ with benzene. Secondary reactions generally involve cluster splitting with the loss of Ag, although AgFeC₅H ₆ ⁺ is observed to dehydrogenate cyclopentene to yield AgFeC₁₀H ₁₂ ⁺ . Ion-molecule reactions, collision-induced dissociation, and photodissociation experiments were used to determine the bond energiesD°(Fe⁺–Ag)=53±7 kcal/mol andD°(Ag⁺–Fe)=46±7 kcal/mol. These values in turn were used to calculateH _f (AgFe⁺)=296±7 kcal/mol andIP(AgFe)=6.5±0.3 eV. Related chemical and physical properties of CuFe⁺ are presented for comparison.     

The preparation of CdO nanowires from solid-state transformation of a layered metal-organic framework

A new coordination polymer formulated as [C₈H₁₀CdO₇]_n·4H₂O has been prepared via a hydrothermal procedure by using 1,4-benzenedicarboxylic (p-BDC) and Cd^II salt as starting materials. The structure was determined by single-crystal X-ray diffraction and the result shows that the complex crystallizes in orthorhombic system, space group Pcca, with M_r=402.62, a=7.293(2) Å, b=9.980(3) Å, c=19.889(6) Å, V=1447.6(8) Å³, Z=4, D_c=1.847 g/cm³, F(000)=808, μ(MoKα)=1.559 mm⁻¹, R=0.0478, wR=0.1150, GOF=1.199. It displays a neutral layered framework along ab plane constructed by hydrogen-bonding interaction through infinite zigzag chains. Its thermal decomposition and solid-state transformation course between 30 and 550 °C was recorded by TG curve and XRD pattern, respectively. Interestingly, it is found that at higher temperature the crystal material was converted to uniform CdO nanowires, suggesting an effective and reasonable complex-precursor procedure for preparing one-dimensional crystalline nanomaterials.     

Molecular structure of propargylgermane (2-propynylgermane) determined by gas-phase electron diffraction and quantum chemical calculations

The molecular structure of propargylgermane, HCCCH₂GeH₃, has been determined by gas-phase electron diffraction. The electron-diffraction investigation has been supported by density functional theory and ab initio calculations. The r_a value of the bond lengths (pm) are: r(C–Ge)=197.2(1); r(C–C)=143.9(2); r(CC)=123.1(1); r(H–C_acetylene)=108.5(3); r(C–H)=111.6(3) and r(Ge–H_average)=153.7(2). The Ge–C–C angle is 111.7(1)° and the C–CC angle is 178.3(4)°. The uncertainties are one standard deviation from the least-squares refinement.     

Homopolymer and copolymers of 4-nitro-3-methylphenyl methacrylate with glycidyl methacrylate: Synthesis, characterization, monomer reactivity ratios and thermal properties

The novel methacrylic monomer, 4-nitro-3-methylphenyl methacrylate (NMPM) was synthesized by reacting 4-nitro-3-methylphenol dissolved in ethyl methyl ketone (EMK) with methacryloyl chloride in the presence of triethylamine as a catalyst. The homopolymer and copolymers of NMPM with glycidyl methacrylate having different compositions were synthesized by free radical polymerization in EMK solution at 70 ± 1 °C using benzoyl peroxide as free radical initiator. The homopolymer and the copolymers were characterized by FT-IR, ¹H NMR and ¹³C NMR spectroscopic techniques. The solubility tests were tested in various polar and non-polar solvents. The molecular weight and polydispersity indices of the copolymers were determined using gel permeation chromatography. The glass transition temperature of the copolymers increases with increase in NMPM content. The thermogravimetric analysis of the polymers performed in air showed that the thermal stability of the copolymer increases with NMPM content. The copolymer composition was determined using ¹H NMR spectra. The monomer reactivity ratios were determined by the application of conventional linearization methods such Fineman-Ross (r₁ = 1.862, r₂ = 0.881), Kelen-Tudos (r₁ = 1.712, r₂ = 0.893) and extended Kelen-Tudos methods (r₁ = 1.889, r₂ = 0.884).     

Phase equilibria in the pseudo-binary system SrO-Fe2O3

The phase relations in the pseudo-binary system SrO-Fe₂O₃ have been investigated in air up to 1150°C by means of powder X-ray diffraction and thermal analysis. Sr₃Fe₂O_7−δ, SrFeO_3−δ and SrFe₁₂O₁₉ are stable phases in the entire investigated temperature region, whereas Sr₂FeO_4−δ and Sr₄Fe₃O_10−δ decompose above 930±10°C and 850±25°C, respectively. Sr₄Fe₆O_13±δ is entropy-stabilized relative to SrFeO_3−δ and SrFe₁₂O₁₉ above 775±25°C. Extended solid-solution Sr_1±xFeO_3−δ was demonstrated. On the Fe-deficient side, the extent of solid solubility appeared to decrease gradually with temperature, whereas an abrupt decrease due to formation of Sr₄Fe₆O_13±δ was observed above 775°C on the Sr-deficient side.     

Two new octahedral/pyramidal frameworks containing both cation channels and lone-pair channels: syntheses and structures of Ba2MnMn2(SeO3)6 and PbFe2(SeO3)4

The hydrothermal syntheses, single crystal structures, and some properties of Ba₂Mn^IIMn₂^III(SeO₃)₆ and PbFe₂(SeO₃)₄ are reported. These related phases contain three-dimensional frameworks of vertex (FeO₆) and vertex/edge linked (MnO₆) octahedra and SeO₃ pyramids. In each case, the MO₆/SeO₃ framework encloses two types of 8 ring channels, one of which encapsulates the extra-framework cations and one of which provides space for the Se^IV lone pairs. Crystal data: Ba₂Mn₃(SeO₃)₆, M_r=1201.22, monoclinic, P2₁/c (No. 14), a=5.4717 (3) Å, b=9.0636 (4) Å, c=17.6586 (9) Å, β=94.519 (1)°, V=873.03 (8) Å³, Z=2, R(F)=0.031, wR(F²)=0.070; PbFe₂(SeO₃)₄, M_r=826.73, triclinic, (No. 2), a=5.2318 (5) Å, b=6.7925 (6) Å, c=7.6445 (7) Å, α=94.300 (2)°, β=90.613 (2)°, γ=95.224 (2)°, V=269.73 (4) Å³, Z=1, R(F)=0.051, wR(F²)=0.131.     

The molecular structure of gaseous tetrachloro-p-benzoquinone and tetrachloro-o-benzoquinone by electron diffraction

The structures of tetrachloro-p-benzoquinone and tetrachloro-o-benzoquinone (p- and o-chloranil) have been investigated by gas electron diffraction. The ring distances are slightly larger and the carbonyl bonds slightly smaller than in the corresponding unsubstituted quinones. The molecules are planar to within experimental error, but small deviations from planarity such as those found for the para compound in the crystal are completely compatible with the data. Values for the geometrical parameters (r_a distances and bond angles) and for some of the more important amplitudes (l) with parenthesized uncertainties of 2σ including estimated systematic error and correlation effects are as follows. Tetrachloro-p-benzoquinone: D_2h symmetry (assumed); r(CO) = 1.216 Å(4), r(CC) = 1.353 Å(6), r(C-C) = 1.492 Å(3), r(C-Cl) = 1.701 Å(3), ∠C-C-C = 117.1° (7), ∠CC-C1 = 122.7° (2), l(CO)= 0.037 Å(5), l(CC) = l(C-C) - 0.008 Å(assumed) = 0.049 Å(7), and l(C-Cl) = 0.054 Å(3). Tetrachloro-o-benzoquinone: C_2v symmetry (assumed); r(CO) = 1.205 Å(5), r(CC) = 1.354 Å(9), r(C_cl-C_cl) = 1.478 Å(28), r(Co-C_cl) = 1.483 Å(24), r(C_o-C_o) = 1.526 Å(2), r(C-Cl)= 1.705 Å(3), <C_o-CO = 121.0° (22), ∠C-C-C = 117.2° (9), ∠C_co, ClC-Cl = 118.9° (22), ∠C_ccl, ClC-Cl = 122.2°(12), l(CO) = 0.039 Å(5), and l(C_cl-C_cl) = l(C_o-C_cl) = l( Co-Co) = l(CC) + 0.060 Å(equalities assumed) = 0.055 Å(9). Vibrational'shortenings (shrinkages) of a few of the long non-bond distances have also been measured.     

Molecular structures of isobutene and 2,3-dimethyl-2-butene as studied by gas electron diffraction

The structures of isobutene and 2,3-dimethyl-2-butene have been studied by gas electron diffraction. For isobutene the rotational constants obtained by Laurie by microwave spectroscopy have also been taken into account. Leastsquares analyses have given the following r_g bond distances and valence angles (r_av for isobutene and r_α for dimethylbutene): for isobutene, r(CC) = 1.342±0.003 Å, r(C-C)= 1.508±0.002Å, r(C-H, methyl) = 1.119±0.007 Å, r(C-H, methylene) = 1.095±0.020 Å, ∠(C-CC) = 122.2±0.2°, ∠(H-C-H) = 107.9±0.8°, and ∠(C-C-H) 121.3±1.5°; for dimethylbutene, r(CC)= 1.353 ±0.004 Å, r(C-C) = 1.511±0.002 Å, r(C-H) = 1.118± 0.004 Å, ∠(C-CC)= 123.9±0.5°, and ∠(H-C-H)= 107.0±1.0°, where the uncertainties represent estimated limits of experimental error. The bond distances and valence angles in these molecules and in related molecules are compared with one another. The CC and C-C bond distances increase almost regularly with the number of methyl groups, and the C-C bonds in isobutene and dimethylbutene are shorter than those in acetaldehyde and acetone by about 0.01 Å. Systematic variations in the C-CC angles suggest the steric influence of methyl groups.     

Molecular structure of ethynylbenzene from electron diffraction and ab initio molecular orbital calculations

The molecular structure and benzene ring distortions of ethynylbenzene have been investigated by gas-phase electron diffraction and ab initio MO calculations at the HF/6-31G^* and 6-3G^** levels. Least-squares refinement of a model withC _2v, symmetry, with constraints from the MO calculations, yielded the following important bond distances and angles:r _g(C _i -C _o )=1.407±0.003 Å,r _g(C _o -C _m )=1.397±0.003 Å,r _g(C _m -C _p )=1.400±0.003 Å,r _g(Cr _i -CCH)=1.436 ±0.004 Å,r _g(C=C)=1.205±0.005 Å, C _o -C _i -C _o =119.8±0.4°. The deformation of the benzene ring of ethynylbenzene given by the MO calculations, including o-C_i-C_o=119.4°, is insensitive to the basis set used and agrees with that obtained by low-temperature X-ray crystallography for the phenylethynyl fragment, C₆H₅-CC-, in two different crystal environments. The partial substitution structure of ethynylbenzene from microwave spectroscopy is shown to be inaccurate in the ipso region of the benzene ring.     

Reactivity ratios in conventional and nickel-mediated radical copolymerization of methyl methacrylate and functionalized methacrylate monomers

Copolymerization of an excess of methyl methacrylate (MMA) relative to 2-hydroxyethyl methacrylate (HEMA) was carried out in toluene at 80 °C according to both conventional and controlled Ni-mediated radical polymerizations. Reactivity ratios were derived from the copolymerization kinetics using the Jaacks method for MMA and integrated conversion equation for HEMA (r_MMA = 0.62 ± 0.04; r_HEMA = 2.03 ± 0.74). Poly(ethylene glycol) α-methyl ether, ω-methacrylate (PEGMA, M_n = 475 g mol⁻¹) was substituted for HEMA in the copolymerization experiments and reactivity ratios were also determined (r_MMA = 0.75 ± 0.07; r_PEGMA ∼ 1.33). Both the functionalized comonomers were consumed more rapidly than MMA indicating the preferred formation of heterogeneous bottle-brush copolymer structures with bristles constituted by the hydrophilic (macro)monomers. Reactivity ratios for nickel-mediated living radical polymerization were comparable with those obtained by conventional free radical copolymerization. Interactions between functional monomers and the catalyst (NiBr₂(PPh₃)₂) were observed by ¹H NMR spectroscopy.     

Synthesis of Re(I) complexes bearing tridentate 2,6-bis(7-azaindolyl)phenyl ligand with green emission properties

The Re(I) complexes bearing 2,6-bis(7^′-azaindolyl)phenyl ligand as a tridentate ligand were synthesized by treatment with Re₂(CO)₁₀. The structures of the complexes were confirmed by X-ray crystallography. Both 7-azaindolyl ligands of Re(I) complexes are present in butterfly forms. The Re-C_ipso bonds showed a partial double bond character by π back-donation between the phenyl moiety and Re atom. In THF solution at room temperature, these complexes exhibited green emission (λ_em=510 nm), which is considered to be attributable to MLCT (dz²(Re) →π^* (7^′-azaindolyl group)) transition containing π→π^* (7^′-azaindolyl group) transition.     

Radical copolymerization of vinylidene fluoride with perfluoroalkylvinyl ethers

The radical copolymerization of perfluoromethylvinyl ether (PMVE) and perfluoropropylvinyl ether (PPVE) with vinylidene fluoride (VDF), initiated by tertiobutyl peroxypivalate (TBPPI) and ditertiobutyl peroxide (DTBP), respectively, are presented. The kinetics of copolymerization were investigated for each monomer from series of at least eight reactions for which the initial [VDF]₀/[fluorinated vinyl ether]₀ molar ratios ranged between 20/80 and 80/20. The copolymer compositions of these random-type copolymers were calculated by means of ¹⁹F NMR spectroscopy and allowed one to quantify the respective amounts of each monomeric unit in the copolymer. According to the Tidwell and Mortimer method, the reactivity ratios (r_i) of both comonomers for each type of copolymerization were obtained : r_VDF = 3.40 ± 0.40 and r_PMVE = 0 at 74 °C; and r_VDF = 1.15 ± 0.36 and r_PPVE = 0 at 120 °C. Moreover, the glass transition temperatures (T_g’s) of poly(VDF-co-PMVE) and poly(VDF-co-PPVE) copolymers containing different amounts of VDF and PMVE or PPVE, were determined and the theoretical glass transition temperatures of poly(PMVE) and poly(PPVE) homopolymer were deduced.     

6-Nitro-[1,10]phenanthroline-1-ium nitrate: crystal structure, ab initio calculations and protonation character

The title compound, 6-nitro-[1,10]phenanthroline-1-ium nitrate, has been synthesized and characterized by elemental analysis, electron absorption spectroscopy, IR, ¹H and ¹³C NMR spectroscopy. The X-ray crystal structure study showed that the compound crystallizes in the monoclinic system, space group Cc, with M_r=288.22 (C₁₂H₈N₄O₅), a=13.861(3), b=10.142(2), c=8.7320(17) Å, β=103.70(3)°, V=1192.6(4) Å³, Z=4, D_c=1.605 g/cm³, F(000)=592, μ(Mo Kα)=0.129 mm⁻¹, R=0.0439, wR=0.1125, GOF=1.110. In the crystal lattice, the molecules create a network structure through hydrogen bonds. Ab initio calculations of the structures, charges distribution, natural bond orbitals, topological analysis and thermodynamic functions of 5-nitro-[1,10]phenanthroline and its protonated cation were performed at HF/6-311G** and B3LYP/6-311G** levels of theory. The calculation results are in a good agreement with the X-ray data and show that the protonated structure is stable. The calculation of second order optical nonlinearity was carried out and a higher molecular hyperpolarizability of 24.66×10⁻³⁰ esu was predicted.