79Br-Nuclear quadrupole coupling in the rotational spectrum of HC15N⋯D79Br: determination of the H(D)Br oscillation amplitudes and force constant

The ground-state rotational spectrum of the linear, hydrogen-bonded isotopomer HC¹⁵N⋯D⁷⁹Br has been investigated by pulsednozzle Fourier-transform microwave spectroscopy to give the spectroscopic constants B_o = 1374.4429(3) MHz, d_j = 1.790(9) kHz, χ(⁷⁹Br) = 438.645(9) MHz and M(⁷⁹Br) = 2.4(3) kHz. The HBr subunit oscillation amplitudes /gb_avH = 15.069(8)° and β_AV^D = 12.726 (7)°, determined by combined use of X(⁷⁹Br) for HC¹⁵N⋯H⁷⁹Br and HC¹⁵N⋯D⁷⁹Br, lead to the HBr oscillation force constant k_ββ=6.93(2) × 10⁻²⁰J rad⁻². The variation of k_ββ with k_ββ is considered for the series B⋯HX, where B = CO, PH₃, HCN and X = Cl or Br.     

Hyperfine structure measurements in the B3IIo+u—X 1Σ+g electronic transition of Br2

Hyperfine splittings in some band heads of the B—X system of Br₂ were measured using laser molecular-beam spectroscopy. Quadrupole coupling constants were derived: eqQ(⁷⁹Br) = 810.0(5) MHz for X¹Σ⁺_g, v = 1, and eqQ(⁷⁹Br) = 179.1(16) MHz for B³πino⁺u, v' = 13.     

Millimeter-wave rotational spectrum and molecular constants of diatomic gallium bromide

Gas-phase spectra of four isotopic species of GaBr have been detected in the millimeter wavelength region. The molecules were produced by a flame reaction of gallium and bromine at 1000° C. From the rotational spectra molecular constants have been determined for ⁶⁹Ga⁷⁹Br,⁶⁹Ga⁸¹Br,⁷¹Ga⁷⁹Br,⁷¹Ga⁸¹Br. The equilibrium internuclear distance is r_e = 2.3524907(82).     

Infrared diode laser spectroscopy of the Δυ = 2 band of NaBr using spectrum processing by Fourier transformation

The IR diode laser spectrum of the Δυ = 2 band of NaBr monomer has been observed with a heat-pipe high-temperature cell of a White cell type. Fringes due to optical reflections inside the high-temperature White cell were inherent in highly-sensitive observation of the spectrum. However, they were eliminated, as were high-frequency noises, by Fourier manipulation of the observed diode laser spectrum. The υ = 2-0 up to 6–4 vibration—rotation bands of both Na⁷⁹Br and Na⁸¹Br, 199 lines in total, were assigned in the range between 550 and 600 cm⁻¹. These data, combined with 21 mm wave data from the literature, were analysed with a least squares fit to nine Dunham Y _ij coefficients. Y₁₀ and Y₂₀ for Na⁷⁹Br were determined to be 298.73648(66) and −1.21058(19) cm⁻¹, respectively.     

Rotational spectrum of BiBr

The microwave absorption spectra of Bi⁷⁹Br and Bi⁸¹Br have been measured in the 65–100 GHz region. Frequencies of rotational transitions (υ,J + 1) ← (υ,J) in the 0⁺ electronic ground state with J = 26,27 and 35–39, and in the vibrational state υ = 0–11 can be fitted to the expression: ν = 2[Y₀₁ + Y₁₁(υ + $\text{1}\text{2}$) + Y₂₁(υ + $\text{1}\text{2}$)²] (J + 1) + 4Y₀₂(J + 1)³. The results for the Dunham coefficients are: Y₀₁ = 1295.5609(12) MHz, Y₁₁ = ?3.97809(18) MHz, Y₂₁ = 2.303(18) kHz, Y₀₂ = ?220.26(45) Hz for Bi⁷⁹Br, and: Y₀₁ = 1272.3406(12) MHz, Y₁₁ = ?3.87164(16) MHz, Y₂₁ = 2.225(14) kHz, Y₀₂ = ?212.31(45) Hz for Bi⁸¹Br. From these results we have deduced the value for the equilibrium distance r_e, for the potential constants a₀ and a₁, and for the vibrational constants ω_e and ω_eχ_e. The molecular constants of BiBr are almost the same as of TIBr, the situation found also for BiI and TII.     

The molecular Zeeman effect in HCP,HCN, and HCCBr and a comparison with similar molecules

The molecular Zeeman effect has been observed in the J = 0 → 1 ΔM = 0, and ± 1 transitions in H¹²CP, D¹²CP, H¹²C¹⁵N, H¹²C¹²C⁷⁹Br, and H¹²C¹²C⁸¹ Br giving the molecular g-values, magnetic susceptibility anisotropies, and corresponding molecular quadrupole moments. The results are g_⊥(HCP) = ?0.0430 ± 0.0010, g_⊥(DCP) = ?0.0353 ± 0.0010, x_⊥ - x_| = (8.4 ± 0.9) × 10^?6 erg/G² mole and Q_|(HCP) = (4.4 ± 1.2) × 10^?26 esu; g_⊥(HC¹⁵N) = ?0.0904 ± 0.0003, x_⊥ - x_| = (7.2 ± 0.4) × 10^?6 erg/G² mole, and Q_|(HC¹⁵N) = (3.1 ± 0.6) × 10^?26 esu; g_⊥(HCC⁷⁹Br) = ?0.00395 ± 0.00032, g_⊥(HCC⁸¹Br) = ?0.00388 ± 0.00014, x_⊥ - x_| = (9.5 ± 0.9) × 10^?6 erg/G² mole, and Q_| = (8.5 ± 1.1) × 10^?26 esu. The results in HCN agree very well with an earlier prediction of the magnetic properties. The new results presented here are compared to other members in the acetylene and cyanide series of molecules and we conclude that the sign of the g-value in acetylene should be positive.The deuterium nuclear quadrupole coupling constant was also determined in DCP to be x_D = 233 ± 40 kHz.     

Relationship between the 79Br NQR frequencies of crystallographically Inequivalent bromine atoms in CBr4 and their field constants

For the crystallographically Inequivalent positions of the bromine atoms in CBr₄, there exists an equation that relates the frequencies v of ⁷⁹Br NQR to their field constants α = dv/dE _z . This equation can be used to determine the strength of the local electric fields.     

Hyperfine and Stark spectrum of DBr in the millimeter-wave region

The hyperfine and Stark spectrum of the J = 1←0 rotational transition of D⁷⁹Br and D⁸¹Br at 254 CHz has been investigated with a high resolution millimeter-wave beam-spectrometer. The hyperfine coupling constants and the dipole moment of D⁷⁹Br and D⁸¹Br have been determined. A discussion is given on the values of the field gradient and the dipole moment at the equilibrium intermuclear distance of the hydrogen bromide molecule.     

The dissociation energies of gaseous Br2 and I2

New rotational analyses have been made of the B³Π_0⁺u—X¹Σ⁺_g systems of ⁷⁹Br₂, ⁸¹Br₂ and ¹²⁷I₂. The density of vibrational states near the dissociation limit in the upper states follows the LeRoy—Bernstein predictions for n = 5. From short extrapolations, the ground state dissociation energies are found to be: D₀(⁷⁹Br⁸¹Br) = 15895.6 cm^?1, D₀(¹²⁷I₂) = 12440.1 cm^?1.     

Efficient Microscale Preparation of Isotopically Enriched 1‐[79Br]Bromo‐2‐Fluoroethylene, [79Br]BrHC˭CHF

Abstract

An efficient preparation of 1‐[⁷⁹Br]bromo‐2‐fluoroethylene, [⁷⁹Br]BrHC?CHF, was carried out by a three‐step procedure: (a) natural 1‐bromo‐2‐fluoroethylene, BrHC?CHF, was iodinated to 1‐fluoro‐2‐iodoethylene, FHC?CHI; (b) 1‐fluoro‐2‐iodoethylene was ⁷⁹Br₂‐brominated to 1,2‐di[⁷⁹Br]bromo‐1‐fluoro‐2‐iodoethane, [⁷⁹Br]BrFCHCH[⁷⁹Br]BrI; and (c) 1,2‐di[⁷⁹Br]bromo‐1‐fluoro‐2‐iodoethane was dehalogenated to 1‐[⁷⁹Br]bromo‐2‐fluoroethylene, [⁷⁹Br]BrHC?CHF. The yield of isolated product, on a 2‐mmol scale, was 62% with respect to ⁷⁹Br₂.     

Molecular structure and microwave spectra of isotopic chloro-, bromo-, and iodocyanoacetylene

The microwave spectra of the halogeno-cyanoacetylenes, X-CC-CN (X = ¹²⁷I, ⁸¹Br, ⁷⁹Br, ³⁷Cl, ³⁵Cl), have been investigated. The molecules were found to be linear. The vibration-rotation constants of the three bending vibrations and the lower stretching vibration were determined. Lines belonging to the monosubstituted ¹³C and ¹⁵N species in their natural abundances were measured and the rotational constants obtained. The bond distances based on the substitution coordinates were: for I-CC-CN r(I-C) = 1.984₆ Å, r(CC) = 1.207_o Å, r(C-C) = 1.370₂ Å, r(CN) = l.l60₄ Å; for Br-CC-CN, r(Br-C) = 1.785₈ Å, r(CC) = 1.204₁ Å, r(C-C) = 1.369₉ Å, r(CN) = 1.159₃ Å; and for C1-CC-CN, r(Cl-C) = 1.624₅ Å, r(CC) = 1.209_o Å, r(C-C) = 1.369_o Å, r(CN) = 1.160₂ Å.     

Schwingungsspektren und Kraftkonstanten symmetrischer Kreisel. XXI [1]. Das Schwingungs-Rotationsspektrum von CF379Br und CF381Br im Bereich von v2

Vibrational Spectra and Force Constants of Symmetric Tops. XXI. Rovibrational Spectrum of CF₃⁷⁹Br and CF₃⁸¹Br in the v₂ Region The rovibrational spectrum of CF₃⁷⁹Br and of natural CF₃Br has been recorded in the region of the fundamental v₂ near 750 cm^?1 in the i.r. with a resolution of 0.04 cm^?1. From the analysis of the spectra the values of v₀, the anharmonicity constants x₂₃, x₂₅ and x₂₆ as well as B″ and B′ from the J structure have been obtained both for CF₃⁷⁹Br and CF₃⁸¹Br. v₂ displays Fermi resonance with 2v₃ which is located near 700 cm^?1.     

Thermodynamic functions of gaseous beryllium,titanium and germanium organometallic molecules

The thermal functions S⁰_T, -(G⁰_T-H⁰_O)/T and (H⁰_T-H⁰_O) have been calculated from structural and spectroscopic data for the gaseous organometallics C₅H₅BeX (X = Cl, Br and BH₄), C₅H₅MX₃ (M = Ti and Ge; X = Cl, Br and I) and CH₃TiX₃ (X = Cl, Br and I). The rotational barriers of the C₅H₅ and CH₃ groups have been evaluated and discussed.     

Br + Br2 atom exchange: an isotopically selective,laser-initiated,chemical study

The ratio of the Br + Br₂ halogen atom exchange rate, k₂, to the Br + HI reaction rate k₁, has been determined experimentally by using an isotopically selective, laser-initiated chemical reaction. At 294 K, k₂/k₁ = 4, and thus, k₂ = 4 × 10^?11 cm³ molecule^?1 s^?1.     

Photofragmentation of CH3Br in the A band

CH₃Br is photodissociated in the first continuum. Dissociation takes place into ground state CH₃ and Br [ = Br(²P_{$\text{3}\text{2}$}] or Br* [ = Br(*P_{$\text{1}\text{2}$})]. Time of flight and angular distributions of the CH₃ fragments are measured. The Br*/Br ratios upon excitation at 222 and 193 nm are found to be 1.00 and 0.20 respectively. The anisotropy parameters at these wavelengths are β = 0.28±0.04 and β = ?0.23±0.02, respectively. The total absorption cross section is decomposed into partial absorption cross sections of the ¹Q, ³Q₀ and ³Q₁ states. It appears that excitation at 222 nm takes place to the ³Q₀ and ³Q ₁ states whereas at 193 nm the ¹Q and ³Q₀ states are excited. Contrary to CH₃I, the adiabatic curve crossing between the ³Q₀ and the ¹Q states in Ch₃Br is not important. The dissociation energy of the CBr bond is determined to be D₀(CH₃Br) = 2.87±0.02 eV.     

Study of the spectrum of CH379Br between 1520 and 1700 cm−1: The ν3 + ν6 and the ν5 rovibrational bands

The ν₃ + ν₆ band of CH₃ ⁷⁹Br has been directly analyzed for the first time, and an r.m.s. standard deviation of 0.0035 cm⁻¹ was obtained over 394 lines of K″ΔK = 2 up to 12, through a least-squares calculation using an unperturbed model. Nevertheless discrepancies occur on sub-bands with K″ ⩾ 9, which remain not yet understood. In particular it seems difficult to explain them by a Fermi resonance with the ν₅ band, since it has been possible to fit properly around 580 lines of this band, belonging to sub-bands K″ΔK = 7 up to 16, taking only into account the Coriolis resonance with the ν₂ band and the l(2,2) resonance of ν₅.     

Diode laser i.r. spectrum and rovibrational analysis of CF3Br in the ν2 + ν3 region

The gas phase i.r. spectrum of CF₃Br, with natural isotopic abundance, has been investigated in the ν₂+ ν₃ region near 1120 cm⁻¹ using a tunable diode laser spectrometer. The measurements have been carried out at low temperature (⋍ 200 K) to minimize the effects due to the “hot” band absorptions. The K structure of many P(J) and R(J) manifolds has been resolved and analyzed: the maximum J value reached for individual lines was 62 and 70 for CF₃⁷⁹Br and CF₃⁸¹Br, respectively. The identified transitions have been used in a least-squares fit to the energy expression up to the quartic terms and molecular parameters for the ν₂ + ν₃ combination have been obtained. Residual weak features due to “hot” bands of ν₃ and ν₆ have been assigned; the J structure has been analyzed by means of a polynomial procedure and spectroscopic constants for both the isotopomers have been derived.     

Changes in <Superscript>79</Superscript>Br NQR spectra of EBr<Subscript>4</Subscript> (E = C,Si, Ge,Sn) impurity molecules in the TiBr<Subscript>4</Subscript> crystal lattice upon a phase transition of the matrix crystal

Changes found in ⁷⁹Br NQR spectra of EBr₄ (E=C, Si, Ge, Sn) impurity molecules upon the phase transition of the TiBr₄ matrix crystal are analyzed. The influence of the long-range order in the environment is evaluated.     

Synthesis and reactivity of ω-haloalkyltin compounds

ω-Haloalkyltin trihalides, X(CH₂)_nSnX₃ (n ≧ 3; X = halogen) can readily be prepared in high yields by the direct reaction of stannous halides with α,ω-dihaloalkanes, catalysed by trialkylantimony compounds. The compounds are versatile starting materials for the synthesis of a variety of ω-functionallysubstituted organotin compounds R_3-mX_mSn(CH₂)_n Y (R = alkyl, phenyl; m = 0-3; X = Cl, Br, O; Y = Br, NMe₂, NEt₂, COOH, CHOHR, R₃Sn). ¹H-NMR spectral data for a series of such compounds are presented. The trends observed in the chemical shifts and the ¹¹⁹Sn—methyl proton coupling constants of Me_3-m Br_mSn(CH₂)_nBr (m = 0-3; n = 3-5) are discussed in terms of inductive effects. Intramolecular coordination between the ω-bromine atom and tin could not be demonstrated.     

Polymerization by alkaline earth metal compounds—II Polymerization of 2- and 4-vinylpyridine,styrene and butadiene by triphenylmethyl derivatives of calcium,strontium and barium

Investigations are reported on polymerizations of 2- and 4- vinylpyridine, styrene and butadiene by a series of related alkaline earth metal initiators, Ph₃CMX(THF)_n (M = Ca, Ba, X = Cl, n = 2; M = Ca, X = Br, n = 4; M = Sr, X = Cl, n = 4; M = Sr, X = Br, n = 5) in tetrahydrofuran (THF) or 1,2-dimethoxyethane (DME) at various temperatures and in the absence of solvent. The polymers have been examined by GPC and aspects of their microstructures determined by ¹³C and/or ¹H NMR spectroscopy and, for polybutadiene, i.r. spectroscopy. Poly-2-vinylpyridine produced by Ph₃CMX(THF)_n is rich in isotactic content; the isotacticity is higher for polymer formed in THF than DME solution, falls with change of initiator in the order M = Ca > Sr > Ba and, in DME, is greater when X = Br. The tacticities of poly-4-vinylpyridine and polystyrene are similar to those obtained from related organometallic initiators. The 1,4-content of polybutadiene decreases with initiator Ph₃CMX(THF)_n in the order M = Ba > Sr > Ca; the trans-1,4 structure generally predominates except when M = Ba from which cis-1,4 links are formed in comparable amounts.