Far-infrared laser magnetic resonance spectrum of SeD (X2Π32)

Far-infrared laser magnetic resonance (LMR) spectra of SeD have been detected at 513 μm using a formic acid laser, and assigned to Zeeman components of the J = $\text{3}\text{2}$ → $\text{5}\text{2}$ transition in the six isotopic forms ^{82,80,78,77,76,74}SeD. Analysis yields the following B_o constants (cm^?1): ⁸²SeD 3.96047, ⁸⁰SeD 3.96284, ⁷⁸SeD 3.96532, ⁷⁷SeD 3.96657, ⁷⁶SeD 3.96793 and ⁷⁴SeD 3.97066. These values, combined with B_o for ⁸⁰SeH from 5.6μm LMR, yield r_e = 0.14634 nm for SeD.     

The geometric and electronic structures of I3− and I5− from effective-potential calculations

The (ab initio) effective-potential theory developed by Ewig et al. is applied to the structures of the polyiodide ions, I₃^? and I₅^?. The bare ions I₃^? and I₅^? are found by optimization of the geometry to be symmetric and linear. The counterion environment, however, greatly influences the equilibrium structure. A symmetric, flexible counterion environment produces only a slightly altered symmetric, linear equilibrium structure for the I₃^? anion ; whereas an asymmetric, rigid counterion frame leads to unequal bond lengths and bending of the anion. For the I₅^? anion, the potential energy calculated for bending of the central I—I—I angle, α, is very small so that a slight interaction with the lattice will readily lead to the experimental bent structure with α = 94°. At this value of α, the two outer angles are found to be equal and close to the experimental value. The electronic structures of the I₃^? and I₅^? ions are also discussed.     

The crystal structure of magnesium arsenate,Mg8.5As3O16

Single crystals of magnesium arsenate have been grown from a PbOAs₂O₅ eutectic by flux crystallization of a ceramic preparation having an initial composition of 6MgO·As₂O₅. The crystals are rhombohedral, space group $\text{R}\text{3}\text{m}$, with hexagonal unit cell parameters a = 6.0278(6) and c = 27.600(3) Å. A three-dimensional structural analysis using automatic diffractometer data has been completed and refined by full-matrix least-squares procedures to a residual R = 0.049 (R_w = 0.059) with a data-parameter ratio of 36 in the final anisotropic refinement. The structure analysis indicated that magnesium arsenate has the composition Mg_8.5As₃O₁₆ and is isostructural with the previously reported Co₈As₃O₁₆. The structure is based upon a cubic close-packed oxygen array with charge balance achieved in magnesium arsenate through partial occupancy of a unique magnesium site occurring in an arsenic-substituted MgO-type layer.     

The noncumulative effect of methyl substituents on the rate of addition of benzeneselenenyl chloride to olefins1

The rates and products of addition of benzeneselenenyl chloride to ethylene and its six Me substituted derivatives have been determined in methylene chloride at 25°. Unlike the addition of 4-chlorobenzenesulfenyl chloride to this same series of compounds, the effect of Me groups on the rates of addition is not cumulative. Also the regiochemistry of the product is different. For arenesulfenyl chloride additions, products of anti-Markownikoff orientation are formed preferentially under conditions of kinetic control. Under similar conditions regiospecific formation of the Markownikoff adduct is observed for the addition of benzeneselenenyl chloride to methylpropene and 2-methyl-2-butene. These data indicate a difference in both rate and product determining transition states between additions of arenesulfenyl and selenenyl chlorides to alkenes.     

Ionic conductivity in Na+, K+, and Ag+ β″-alumina

This paper presents measurements of the ionic conductivity in single crystals of β″-alumina (0.84 M₂O · 0.67 MgO · 5.2 Al₂O₃, M = Na, K, Ag). Single crystals of sodium β″-alumina were grown from a melt of Na₂O, MgO, and Al₂O₃ at 1660 to 1730°C. Selected crystals were converted to the other isomorphs by ion exchange. The conductivity of sodium β″-alumina varies from 0.18 to 0.01 (ohm · cm)^?1 at 25°C depending upon crystal growth conditions. Potassium β″-alumina has the unusually high room temperature conductivity of 0.13 (ohm · cm)^?1. Silver β″-alumina has a slightly lower conductivity, 4 × 10^?3 (ohm · cm)^?1 at 25°C. The activation energies of sodium and potassium β″-alumina decrease with increasing temperature, while that of silver β″-alumina is constant from ?80 to 450°C.     

Hydrogen bonding between solvation shells around gd3+ from cooperative vibronic spectra

Cooperative vibronic spectra involving Gd³⁺ electronic transitions and the vibrational transitions of nearby water molecules are used to determine the stretching spectrum for isotopically dilute OH in a solution of GdCl₃ in D₂O. The OH stretching spectrum of water molecules in the first hydration sphere is shifted to lower energy than that of the bulk liquid.     

Quasiclassical trajectory study of colinear Cl− + HBr → HCl + Br−

Energy distributions in the products of the ion-molecule reaction Cl^? + HBr → HC1 + Br^? have been studied using quasiclassical trajectories on a semi-empirical collinear potential energy surface. Vibrational energy is favored in the products. While some trajectories are long-lived, the kinematic factor of the light central atom prevents effective energy redistribution.     

Molecular structure and properties of CH3BeF and CH3MgF

The molecules methylberyllium fluoride and methylmagnesium fluoride have been studied using a priori electronic structure theory. Self-consistent-field wavefunctions have been computed over a double zeta basis set of contracted gaussian functions. The geometrical structure of each molecule has been predicted assuming the three heavy atoms are collinear. For CH₃ BeF, the predicted C-Be and Be-F distances are 1.70 and 1.40 Å. For CH₃MgF, the analogous bond distances are 2.08 Å and 1.78 Å. A number of molecular properties have been predicted including dipole moments, which are 1.75 and 2.38 debye for CH₃BeF and CH₃MgF.     

The molecular structure of selenonyl fluoride,SeO2F2, and sulfuryl fluoride,SO2F2, as determined by gas-phase electron diffraction

The molecular structure of selenonyl fluoride (SeO₂F₂) and sulfuryl fluoride (SO₂F₂) has been studied by gas-phase electron diffraction. The geometries of both molecules are consistent with predictions of VSEPR (valence-shell electron-pair repulsion) theory. The results for the more important distance (r_a), bond angle, and r.m.s. amplitude (l) parameters with estimated uncertainties estimated at 2σ are for SeO₂F₂r(Se = 0) = 1.575 Å (0.002), r(Se-F) = 1.685 Å (0.002), ∠OSeO = 126.2° (0.5), ∠FSeF = 94.1° (0.5), l(Se = 0) = 0.0440 Å (0.0046), l(Se-F) = 0.0472 Å (0.0042), and for SO₂F₂r(S = 0) = 1.397 Å (0.002), r(S-F) = 1.530 Å (0.002), ∠OSO = 122.6° (1.2), ∠FSF = 96.7° (1.1), l(S = 0) = 0.0331 Å (0.0015), l(S-F) = 0.0393 Å (0.0018).     

Structure-reactivity relationship in the solvolysis of 5,10-secosteroidal 5-p-nitrobenzoates1

The solvolysis of (Z)- and (E)-3β-acyloxy-5,10-seco-1(10)-cholesten-5β-ol p-nitrobenzoates 4 and 5 has been investigated and compared with the solvolytic reactivity of the epimeric (Z)- and (E)-5α-p-nitrobenzoates 1 and 2, as well as of the reference compound, i.e. the 1,10-saturated 5α-p-nitrobenzoate. Kinetic data and product analysis revealed that the relative spatial orientation of the 1(10)-olefinic double bond and the chiral center at C(5) in the 10-membered ring, which these secosteroidal 5-p-nitrobenzoates can adopt in the transition state, is the main factor which determines their solvolytic behaviour, so that the esters 1,2 and 5 solvolyse with transannular double bond participation, while such an interaction is not present in the case of the (Z)-5β-ester 4.     

Production of the n2 herman infrared system by the energy pooling reaction of N2(Δ3Σ+u) metastable nitrogen molecules

Molecular N₂ emission, observed from an Ar(³Po, 2) and Xe(³P₂) + N₂ flowing afterglow apparatus, indicates that the energy pooling reaction by 2N₂(A ³Σ⁺_u) generates the emission from the Herman infrared system, which is an unassigned nitrogen band system. A lower limit to the formation rate constant for the upper state of the Herman infrared system was found to be 2.5 × 10^-11 cm³ molecule^?1 s^?1. The information presented here may help in the identification of the upper and lower states of the emission system. The 2N₂(A) energy pooling reaction also forms N₂(B³ Π_g, v? 8) but a rate constant cannot be assigned from the present data.     

Synthesis of 1,1′-di-t-butylstannocene and its reaction with trifluoroborane. The crystal and molecular structure of η5-(CH3)3CC5H4Sn+BF4−

The reaction of Li(CH₃)₃CC₅H₄ with SnCl₂ in THF affords 1,1′-di-t-butylstannocene in 78% yield as an air-sensitive oil. ¹H and ¹³C NMR spectra are consistent with a pentahapto-structure. Mössbauer parameters of the stannocene and its trimethylsilyl counterpart match closely those of known stannocenes and neither compound appears to undergo oligomerization. The reaction of 1,1′-di-t-butylstannocene with BF₃ in CH₂Cl₂ affords η⁵-(CH₃)₃CC₅H₄Sn⁺ BF₄^? and other uncharacterized product(s) thought to involve tetracoordinate tin. The structure of η⁵-(CH₃)₃CC₅H₄Sn⁺ BF₄^? was determined by single crystal X-ray diffraction (orthorhombic,Pbcn, (T 25°C), a 18.423(3), b 11.723(1), c 11.044(2) Å, Z Å, m.p. 95–96°C, colorless, Mo-K_α, R = 0.043).     

Predissociation of the 3pπ D 1Πu+ state in H2, HD,and D2

Predissociation linewidths and lineshapes are reported for selected vibrational levels of the 3_pπ D ¹Π⁺_u state of H₂, HD, and D₂. We also discuss the effect of a perturbation by the 4_pδ B″B? ¹|gs_u⁺ state on the predissociation rate of the D state.     

A crossed molecular beam study of the chemiluminescent reaction Xe(3P2,0) + BrCN → Xe(1S0) + Br + CN(B2Σ+)

The chemiluminescent interaction of Xe(³P_2,0) and BrCN has been studied under crosscd-beam conditions at collision energies ranging up to 70 kj mol^?1. The CN(B → X) fluorescence spectrum, the excitation function for its production and the fluorescence polarisation - or rather its absence - have been determined. The results can be explained by a two-stage harpooning mechanism involving an inert-gas cyanide (Xe⁺CN^?)¹ intermediate but not by a “sensitisation” mechanism proceeding through electronic energy transfer.     

Crystal structure of dimeric p-phenoxyphenyltellurium(IV) trichloride

p-PhOC₆H₄TeCl₃ crystallises with a dimeric molecular unit. The two approximately square pyramidal coordination polyhedra are linked trans to each other through two bridging chlorine atoms. The dimeric units are further connected through Te…Cl secondary interactions producing a distorted octahedral geometry about each tellurium atom. The crystals are triclinic, space group P$\text{1}$, with unit cell dimensions a 8.521(2), b 10.917(2), c 14.813(2) Å, α 81.84(1), β 83.38(1), γ 88.41(1)°, V 1353.4(4) ų and Z = 2(dimers) from 3887 observed reflections [I > 3σ(I)], R = 0.0359.     

Molecular structure of F2POPF2: an electron diffraction study

The most important geometric parameters and associated uncertainties (2σ) determined for F₂POPF₂ are the distances (r_g) P-O = 1.631 ± 0.010 Å, P-F = 1.568 ± 0.004 Å, and angles POP = 135.2 ± 1.8°, OPF = 97.6 ± 1.2°, and FPF = 99.2 ± 2.4°. Amplitudes of vibration were also found. The large POP angle and relatively short P-O bond length are consistent with a significant degree of pπ-dπ bonding. Our structure interpretation differs from an earlier one reported by Arnold and Rankin in the relative P-O and P-F bond lengths and in the conclusion that the molecule exists in a distribution of not very rigid, probably staggered, conformers instead of one fairly rigid structure.     

Rate coefficient for the reaction OH + HO2 = H2O + O2 at 1 atmosphere pressure and 308 K

The rate coefficient for the reaction OH + HO₂ =H₂O + O₂ has been determined from measurements of the steady-state absorption of HO₂ at 210 nm, in low-frequency square-wave modulated photolysis of O₃ + H₂O mixtures. The value obtained was (9.9 ± 2.5) × 10^?11 cm³ molecule^?1 s^?1 at 308 K and 1 atm pressure.     

Microwave spectrum and substitutional structure of CH2DF

Forty-two transitions of the microwave spectrum of CH₂DF have been observed in the region between 75 and 450 GHz. The measurement of both a-type and b-type transitions makes possible the analysis of the spectrum and the accurate calculation of the rotational constants (in MHz): = 119 675.0535 ± 0.074, = 24 043.4415 ± 0.072, ? = 22959.3732 °0.072, °j = 0.049371 ±0.00011, °_jk = 0.34268 ±0.0006, 2_k = 3,3774 ± 0.0035, δ _j = 0.002329 ± 0.000045, δ_k = 0.0687 ± 0.036. These constants, in combination with the results of earlier work on the symmetric speci r_s structure calculation based entirely on high-accuracy microwave data. The structural parameters are r_CH = 1.100 Å, r_CF = 1.383 Å, and ∠HCH = 110° 37'.