Dilute solutions of nylon 12—II. Relationship between intrinsic viscosity and molecular weight

Samples of poly(12-dodecanelactam) (polylaurolactam, nylon 12) with $\text{M}$_n 1 × 10³?33 × 10³ were prepared. Polymerizations initiated with water or with lauric acid proceeded under conditions for minimum changes in end-group concentration. Values of $\text{M}$_n were calculated from the end-group content and $\text{M}$_n from light scattering in the mixture m-cresol/60 vol% of 2.2,3,3-tetrafluoropropanol. From measurements of intrinsic viscosity in m-cresol, the relationship [n] ? $\text{M}$_n was established in the given range of $\text{M}$_n. The relationship [n] ? $\text{M}$_w for $\text{M}$_w from 3.3 × 10³ to 125 × 10³ has been established.     

Peri-bridged naphthalenes. 4. chalcogen-bridged acenaphthylenes

Three new electron donors, acenaphtho[5,6-$\text{cd}$]-1,2-dithiole ($\text{1}$), acenaphtho[5,6-$\text{cd}$]-1,2-diselenole ($\text{2}$), and acenaphtho[5,6-$\text{cd}$]-1,2-ditellurole ($\text{3}$), can be prepared in 28%, 22%, and 14% yields respectively by reaction of the elemental chalcogens (S, Se, Te) with 5,6-dilithioacenaphthylene ($\text{4}$). Compound $\text{4}$ is generated by treatment of 5,6-dibromoacenaphthylen ($\text{5}$), for which a convenient preparation is described, with $\text{n}$-butyllithium (2 equiv.) in THF at ?78°C.     

A new synthesis of 1,3-dienes from allyl sulfides and allyl sulfones using tri-n-butylstannylmethyl iodide

Allyl 2-pyridyl sulfide $\text{6}$ or allyl phenyl sulfone $\text{7}$ on treatment with n-butyllithium in tetrahyrofuran followed by tri-n-butylstannylmethyl iodide ($\text{4}$) afforded directly the 1,3-diene $\text{8}$ in good yield.     

Contribution à l'étude structurale de la wüstite solide de haute température

The structure of wüstite Fe_1?zO is studied by neutron diffraction on one polycrystalline sample under equilibrium conditions at high temperature. The mean isotrope temperature factor B is expressed as a sum of two parts, B_Th and B_St, which vary linearly with a single parameter, respectively temperature and z. A classification is established for clusters ($\text{m}\text{n}$) settled from m vacancies in octahedral sites and n Fe^III ions in interstitial sites. Sixteen values have been experimentally determined for the vacancies to interstitials ratio $\text{? =}\text{(z + t)}\text{t}\text{=}\text{m}\text{n}$. A constant value of ?, which is lower than 3, is observed. This result characterizes the short-range order. It eliminates several possibilities of clusters like those obeying the relation $\text{? =}\text{(1 + 3n)}\text{n}$. Other clusters, namely ($\text{16}\text{6}$) or ($\text{40}\text{14}$), might agree. The ($\text{8}\text{3}$) and ($\text{9}\text{4}$) clusters obtained from ($\text{4}\text{1}$) clusters joined by an edge would be the more likely. An analysis of diffuse scattering eliminates the hypothesis of large domains with inverse spinel structure. The structural differences between the three varieties W₁, W₂ and W₃ would not be found in a structural change of clusters.     

Intergrowth of hexagonal tungsten bronze and perovskite-like structures: The oxides ACu3M7O21 (A = K,Rb, Cs,TI; M = Nb,Ta)

Seven oxides ACu₃M₇O₂₁ have been isolated with A = K, Rb, Tl, Cs for M = Ta and A = K, Rb, Cs for M = Nb. These phases are orthorhombic: $\text{a ? 28}$ Å, $\text{b ? 7.50}$ Å, and $\text{c ? 7.55}$ Å, probable space group Cmmm. Their structure has been established from an X-ray diffraction study and from high-resolution microscopy observations. The structure consists of an intergrowth of single hexagonal tungsten bronze AM₃O₉ slices and double distorted perovskite Cu₃M₄O₁₂ slabs (M = Nb, Ta) in which copper has a square coordination. The host lattice of these compounds can be considered as the member “n = 1; n′ = 2” of a series of intergrowths corresponding to the formulation |M₃O₉|^H_n|M₂O₆|^P_n′.     

Mössbauer effect study and magnetic properties of a ferromagnetic homologue of bromobis(diethyldithiocarbamato)iron(III)

Mossbauer spectroscopy and magnetic susceptibility properties of a crystal modification of the title complex, denoted Fe(dtc)₂Br, show that the iron atoms in this material become ferromagnetically ordered with T_c = 1.52 × 0.02 K. This result is consistent with a magnetic specific heat anomaly recently observed in similar material by Yoshikawa et al. Mössbauer effect hfs show that the lower Kramers doublet from the orbital singlet, spin quartet ground term is of composition |S = $\text{3}\text{2}$, M_S = ± $\text{1}\text{2}$).     

Dirac—Fock one-centre calculations. The molecules BH,AlH, GaH,InH and TlH

Relativistic and non-relativistic Hartree—Fock calculations including np_{$\text{1}\text{2}$} and np_{$\text{3}\text{2}$} orbitals in the valence MO are reported for the molecules BH, AlH, GaH, InH and TlH. The relativistic contraction of the bond length reaches 7.0% for TlH. Relativistic effects make the chemical bond stronger for AlH, GaH and InH and weaker for TlH. The calculated force constants and dissociation energies are in reasonable agreement with experiment. A change from npσ towards np_{$\text{1}\text{2}$} bonding takes place along the series. For Tl the MO is only 39% p_{$\text{3}\text{2}$} as compared with the non-relativistic value of 67%. This probably explains the dominant monovalency of thallium.     

Iridoids : Novel total synthesis of (±)- isoiridomyrmecin and of (±)-verbenalol

A novel synthesis of the iridoids (±)-isoiridomyrmecin $\text{1}$ and (±verbenalol $\text{2}$ is described starting from the tricyclo |3.3.0.0^2,8|octan-3-one $\text{3}$ using cis fused bicyclo |3.3.0|octenes as intermediates. The heterocyclic ring of the iridoids was formed in the final stages of the syntheses.     

Study of hyperfine interactions by Mössbauer spectroscopy in mixed crystals

A mixed crystal technique, appropriate for the Mössbauer study of hyperfine interactions in molecules with D > 0, is described. It is based on the magnetic behavior of a |±$\text{1}\text{2}$〉 Kramers doublet. The method has been applied with success to the study of hyperfine structure of Fe(methdtc)₂Br.     

Bis-thallium(I) porphyrin complexes

Treatment of octaethylporphyrin ($\text{1}$) or tetraphenylporphyrin ($\text{2}$) with more than two equiv of thallium(I) ethoxide gives the corresponding stable bis[thallium(I)] porphyrin complexes ($\text{5}$) and ($\text{6}$), respectively; these thallium(I) porphyrins are shown to have very different chemical and spectroscopic properties than do the corresponding thallium(III) porphyrin complexes.     

Über reaktionen mit aluminiumalkylen: XVII. Spektroskopische untersuchungen von komplexen aus butanoliden und äthylaluminium-verbindungen

Three different types of butanolide complexes with Et_nAlCl_3?n in the molar ratios $\text{1}\text{1}$ and $\text{1}\text{2}$ have been investigated by IR with ^1M NMR spectroscopy. The butanolides form $\text{1}\text{1}$ and $\text{1}\text{2}$ complexes with ethylaluminium halides, but with triethylaluminium only $\text{1}\text{1}$ complexes are formed. The complexes are intermediates in the cleavage of butanolides.     

Theory of titration curves: Locations of points of maximum slope on potentiometric heterovalent (“asymmetrical”) precipitation titration curves

By a wholly rigorous general treatment of the potentiometric titration curve representing the titration of B^m+ with A^n- to give the precipitate B_nA_m, where n ≠ m, it is shown on taking into account the effect of dilution that: (1) If $\text{n}\text{m}$ > 1, the inflection point must precede the equivalence point, but there is no inflection point if the initial concentration of the ion titrated is smaller than a certain value, which is determined by the values of m, n, and the solubility product of the precipitate. (2) If $\text{n}\text{m}$ < 1, the inflection point may follow the equivalence point — though not by more than a certain definite amount — or may precede it or coincide with it. In every such case there is a concentration of A^n- that will cause the equivalence point to coincide with an inflection point; this concentration depends on the values of m, n, and the solubility product of the precipitate. (3) Unless the difference between the equivalence and inflection points is negligibly small, the traditional treatment in which dilution is neglected gives seriously erroneous estimates of the location of the inflection point.     

Antiprismatic crystal field and paramagnetic susceptibility of U4+ sulfates

On the basis of the simplified model of the U⁴⁺ ion in a distorted axial crystal field, the temperature dependence of the magnetic susceptibilities of three U⁴⁺ sulfates, U(SO₄)₂ · 4H₂O, U₆O₄(OH)₄(SO₄)₆, and U(OH)₂SO₄, within the temperature range 4.2–300°K has been investigated and interpreted. This model proved to be successful, and the only parameters fitted empirically were the values of the crystal field splitting. The antiprismatic coordination (D_4d) of the uranium ion in these compounds was confirmed and its electronic ground states were determined. The system of two singlets $\text{1}\text{2}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{| 3 > ±}\text{1}\text{2}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{| ? 3 >}$ originating from the doublet 1 ± 3 > is the ground state of the uranium ion in U(SO₄)₂ · 4H₂O. An analogous system of two singlets $\text{1}\text{2}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{| 2 > ±}\text{1}\text{2}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{| ? 2 >}$ is the ground state in U₆O₄(OH)₄(SO₄)₆. For U(OH)₂SO₄, the doublet | ± 2 > is the ground state above 21°K, whereas below this temperature it becomes split into the two singlets $\text{1}\text{2}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{| 2 > ±}\text{1}\text{2}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{| ? 2 >}$, probably because of a crystallographic distortion induced by the cooperative Jahn-Teller effect. Deviations from the D_4d symmetry of the uranium ion coordination occurring in these compounds are discussed.     

Wannier states of molecular impurity in a liquid rare gas

We have measured the vacuum ultraviolet absorption spectra of CH₃I in solid and in liquid krypton in the spectral region 2000–1450 Å. In both phases we have observed two Wannier series n(²E_{$\text{3}\text{2}$}) and n(²E_{$\text{1}\text{2}$}) up to n = 3. Information has been obtained concerning the features of the conduction band in a liquid rare gas.     

Nephelauxetic effect in some lanthanide(III) complexes with 2-pyridineamidoxime

Diffuse reflectance spectra of tris-(2-pyridineamidoximato) lanthanide(III) chlorides, [Ln(PAO)₃] Cl₃, Ln = Pr, Nd, Sm, Eu, Dy and Ho, in the visible region have been recorded for the first time. Shifts (100–150 cm^?1) of their f ? f transitions have been observed towards lower wave numbers in relation to the lanthanide aquoions. These data have been used for evaluation of the nephelauxetic ratio β′ and the covalency parameters b^{$\text{1}\text{2}$}. Sublevels with J = 0 and J = $\text{1}\text{2}$ as well as hypersensitive bands, obeying the selection rules|ΔJ|?2,|ΔL|?2, have been considered. The results have been discussed in terms of weak covalent bonding between the lanthanide ion and the nitrogen atoms of the ligands.     

KxP2W2O16: A bronze with a tunnel structure built up from PO4 tetrahedra and WO6 octahedra

The structure of a $\text{K}{}_{\mathrm{x}}\text{P}{}_2\text{W}{}_4\text{O}{}_{16}\text{(x ? 0.4)}$ crystal was established by X-ray analysis. The solution in the cell of symmetry $\text{P2}{}_1\text{m}$, with a = 6.6702(5), b = 5.3228(8), c = 8.9091(8) Å, β = 100.546(7)°, Z = 1, has led to R = 0.033 and R_w = 0.036 for 2155 reflections with $\text{σ(I)}\text{I}\text{≤ 0.333}$. This structure can be described as two octahedra-wide ReO₃-type slabs connected through “planes” of PO₄ tetrahedra. A new structural family K_xP₂W_2nO_6n+4 can be foreseen which is closely related to the orthorhombic P₄W₈O₃₂ and the monoclinic Rb_xP₈W_8nO_24n+16 series.     

Isomerization reactions of lithium N-butyl-4-pentenylamide

Lithium N-butyl-4-pentenylamide ($\text{1}$) in tetrahydrofuran at 22 °C rearranged smoothly to give a mixture (after protonation) of 1-butyl-2-methylpyrrolidine, formed by an unusual cyclization process, and $\text{cis}$- and $\text{trans}$-N-butyl-3-pentenylamine; in the presence of 2.0 molar equiv of hexamethylphosphoramide, the total rate of isomerization was accelerated by a factor of 2.5.     

Critical mathematical considerations involving the Abel integral equation for converting side-on experimental data in plasma spectroscopy—I: A study of basic analytical solutions

The particular form of the Abel integral equation used in plasma spectroscopy is investigated from the point of view of the computational error introduced in radial emission coefficient determinations from side-on experimental intensities. Since this emission coefficient is the basis of measurements of fundamental physical properties of the plasma, its values are to be obtained with minimal error.In this first part of this work, the mathematical properties of basic analytical solutions are investigated. Polynomial solutions resulting from positive powers of the variable in intensity profiles are described with reduced coordinates in terms of “rough parabolas” I(x) = 1 ?xⁿ (n = 2p, x = $\text{x}\text{?}$_exptl/$\text{x}\text{?}$_{max exptl}, I(x)=$\text{I}\text{?}$ ($\text{x}\text{?}$)_exptl/$\text{I}\text{?}$_{max exptl}) up to the 26th degree. For negative powers a new and original method is developed; it leads to ABEL inversion of intensity profites of the Lorcntzian kind. These profiles may be of interest when center-to-edgc intensity decay ends with a positive curvature.In following papers, all these results will then be applied to numerical approximation of theoretical standards and side-on experimental data in the spectroscopy of an inductivcly coupled plasma (ICP).     

Phase equilibria for the separation of aromatic and nonaromatic compounds using mixed solvents. Part I. The system n-heptane—toluene—N-methylpyrrolidone/monoethyleneglycol

The solvent combination of N-methylpyrrolidone (NMP) and monoethyleneglycol (MEG) is used in industry for the separation of aromatics and nonaromatics (Arosolvan process).In this paper experimental results obtained for the system n-heptane—toluene—N-methylpyrrolidone/monoethyleneglycol are presented. Liquid—liquid equilibrium compositions were obtained at three different temperatures (50°C, 60°C, 70°C). For each temperature, three different solvent compositions corresponding to weight ratios of NMP/MEG equal to $\text{50}\text{50}$, $\text{62}\text{38}$ and $\text{70}\text{30}$ were considered. The different sets of experimental results obtained are correlated using the NRTL equations.Equilibrium compositions obtained using an industrial solvent mixture (NMP/MEG-$\text{58}\text{42}$) are compared with data based on the use of purified solvents.