Rollie J. Myers

Microwave Spectra, Dipole Moment, and Barrier to Internal Rotation of CH3NO2 and CD3NO2

The J = 1 to J = 2 and J = 2 to J = 3 transitions for CH3NO2 and CD3NO2 have been assigned for several internal rotational states. The best values of the rotational constants B and C were found to be 10 542.7 and 5876.7 Mc/sec for CH3NO2 and 8697.1 and 5254.3 Mc/sec for CD3NO2. The rotational constant for the NO2 group about the symmetry axis is 13 277.5 Mc/sec. These constants are determined assuming no inertial defect, slightly different values are calculated if other assumptions are made. Some of the assigned lines are a very sensitive function of the low barrier to internal rotation. The barrier term V6 was determined to be 6.03±0.03 calories/mole for CH3NO2 and 5.19±0.03 calories/mole for CD3NO2. The term V12 is less than 0.05 calorie/mole. The dipole moment of CH3NO2 is 3.46±0.02 Debye units.

THE MICROWAVE SPECTRA, STRUCTURE, DIPOLE MOMENT, AND CHLORINE NUCLEAR QUADRUPOLE COUPLING CONSTANTS OF METHYLENE CHLORIDE

The microwave spectra of CH2Cl235, CH2Cl35Cl37, CH2Cl237, CDHCl235, CDHCl35Cl37, CD2Cl235, and CD2Cl35Cl37 have been examined and effective moments of inertia have been determined for these seven isotopic species. From these data the effective bond distances and angles were determined as C–Cl distance=1.7724±0.0005A, Cl–C–Cl angle=111°47′±1′, C–H distance=1.068±0.005A (average of all species), or 1.082A (extrapolated to infinite hydrogen mass), and H–C–H angle=112°0′±20′ (average of all species) or 112°58′ (extrapolated to infinite hydrogen mass). The best value for the dipole moment of methylene chloride was found from the Stark splitting to be 1.62±0.02×10−18 esu. The chlorine nuclear quadrupole coupling constants were also determined and their relationship to the structure is discussed.

Microwave Spectrum, Structure, and Dipole Moment of Cyclopropene

The microwave spectra of four isotopic species of cyclopropene, CH2(CH)2, CH2CDCH, CH2(CD)2, and CDH(CH)2 were assigned and three rotational constants for each isotopic species were determined. From these data the following structural parameters were evaluated: C–C 1.515 A, C=C 1.300 A, C–H (methylene) 1.087±0.004 A, C–H (vinyl) 1.070 A, H–C–H angle 114°42′±10′ and C=C–H angle 149°55′. The uncertainties in the methylene values are the magnitude of a rotation‐vibration interaction correction. The dipole moment of cyclopropene was found to be 0.455±0.01 debye unit.

Application of Symmetry Principles to the Rotation‐Internal Torsion Levels of Molecules with Two Equivalent Methyl Groups

The set of coordinate transformations, corresponding to symmetry operations, which leave invariant the Hamiltonian operator for a molecule with two equivalent methyl groups, is obtained. These constitute a group which is a direct product of two simple groups, i.e., C3v×C3v. The possible species for the energy levels, their degeneracies, their statistical weights, and the selection rules are worked out by group theory techniques which use only the properties of the smaller groups. The higher symmetry and higher degeneracies given by approximate Hamiltonians are briefly discussed.

Electron spin resonance spectra of the radical anions of pyridine and related nitrogen heterocyclics

The E.S.R. spectra of the radical anions of pyridine, 4-picoline, 3,5-lutidine, 2,6-lutidine, pyrazine, pyrimidine, pyridine N-oxide, 4-picoline N-oxide and 2,6-lutidine N-oxide have been observed in liquid ammonia. The data for pyridine, pyrazine and pyrimidine can be combined to evaluate Q N N = +27·3, Q CN N = -1·7 and Q H = -24·5 gauss independently of molecular orbital spin densities. Good agreement is found for the observed coupling constants for the N-heterocyclics and McLachlans theory with methyl group coupling consistent with both Levys hyperconjugation equations and with Q CH3 eff. = 25·7 gauss. The coupling constants for the N-oxides are in satisfactory agreement with an arbitrary set of molecular orbital parameters.

The microwave spectrum, structure, and dipole moment of disulfur monoxide☆

Abstract The microwave spectrum of the product resulting from the passage of an electrical discharge through a mixture of sulfur and SO 2 has been examined. This product, usually called “sulfur monoxide”, was found to have a microwave spectrum which was assigned to disulfur monoxide with a bent SSO structure. The ground state rotational constants were established as A = 41,914.4 0 , B = 5,059.0 9 and C = 4,507.1 4 , Mc/sec. Assignments were also made for an excited vibrational state and for the S 34 S 32 O 16 species. The structure of S 2 O was established as SO 1.46 5 ± 0.010 A, SS 1.88 4 ± 0.010 A, and SSO 118°O′ ± 30′. The components of the dipole moment were established as μ A = 0.875 ± 0.01, μ B = 1.18 ± 0.02 with μ (total) = 1.47 ± 0.02 Debye.

Electron Spin Resonance Spectrum of the Radical Anion of 1,3‐Butadiene in Liquid Ammonia

The electron spin resonance spectrum of the radical anion of 1,3‐butadiene has been observed by means of continuous electrolysis in liquid ammonia. The proton coupling constants were observed to be A(CH)=2.791±0.007 Oe and A(CH2)=7.617±0.005 Oe. These values give a Q(av)=20.82±0.02 Oe. The source of this low Q value is discussed together with theoretical spin densities. Simple Huckel theory predicts a spin density ratio of 2.615 which can be compared with the observed coupling constant ratio of 2.729±0.007. The predictions of Parr and Mullikens SCF theory are much less satisfactory and give a low spin‐density ratio. Electrolysis in liquid ammonia appears to be an excellent method for the generation of radical anions.

Infrared Spectrum and Thermodynamic Functions of the NF2 Radical

The three fundamental vibrational frequencies for the NF2 radical have been measured in an N2 matrix at 20°K. They are ν1 = 1069.6±0.5, ν2 = 573.4±1.0, and ν3 = 930.7±0.5, all in cm−1. The infrared spectrum of N2F4 was also examined and good evidence is presented to confirm that N2F4 dissociates into NF2 at low pressures. This dissociation was found under the conditions in our spray‐on line to have a half‐life of 100 sec or more at room temperature and about 1 sec near 100°C. The thermodynamic functions of NF2 are tabulated.

Least squares curve fitting of EPR spectra

Abstract A computer program is described which uses least squares curve fitting for the analysis of electron paramagnetic resonance spectra in solution. The relevant spectroscopic constants are directly determined and their accuracy may be improved by one order of magnitude over that which is obtained from following the usual procedure. In addition, the program gives reliable intensities and works equally well in cases of incompletely resolved absorption lines. The digital apparatus which facilitates the acquisition and subsequent handling of the numerical data for a spectrum is discussed. Finally, two examples are shown to illustrate the great potential of this method for analyzing spectra. It should be easy to adapt this procedure to similar problems in other branches of spectroscopy.

The Microwave Spectra, Structure, and Dipole Moment of Stable Pentaborane

The microwave spectra of several of the naturally occuring boron isotopic species of B5H9 and B5D9 have been observed. These data show that stable pentaborane consists of a tetragonal pyramid of boron atoms and has either C4 or C4v symmetry. The boron‐boron distances are B1–B2=1.687±0.005 and B2–B2=1.800±0.003A. If C4v symmetry and B1–H1 and B2–H2 distances equal to 1.22A are assumed, the following boron‐hydrogen parameters are obtained: B2–H3=1.35±0.02A, ∠B1–B2–H2=136°10′±30′ and ∠B1B2B2–B2B2H3=196±2°. Dipole moment values of 2.13±0.04 and 2.16±0.04 Debye units were measured for B5H9 and B5D9, respectively.