Foil A. Miller

Infrared spectra of inorganic ions in the cesium bromide region (700–300 cm−1)

Abstract The infrared spectra from 300–880 cm−1 of 208 inorganic substances are reported. Nearly all are salts containing polyatomic ions. Spectral curves are presented for 140 of the compounds, and a list of characteristic frequencies is given for twenty ions. Among other matters discussed are: (a) the non-reproducibility of some of the spectra, and reasons for this, (b) absorption due to the torsional oscillation of water molecules, and (c) some vibrational assignments for MnO4−1 and CrO42−1.

Torsional frequencies in the far infrared—IV. Torsions around the CC single bond in conjugated molecules

Abstract Torsions around the central single bond in conjugated molecules have been studied in the far infrared. Twelve derivatives of butadiene and glyoxal, plus benzaldehyde and styrene, were examined in the gas phase, and the frequency was located for eleven of the compounds. For benzaldehyde and acrolein there are very large frequency increases upon going from gas to liquid, with δv/v equal to 15–20 per cent. Using the potential function 2V = 3Σn=1 Vn (1 - cos nα), the quantity [V1 + 4V2 + 9V3] was evaluated for all eleven compounds. For benzaldehyde, V2 (gas) = 1630 cm−1 or 4·6 kcal/mole; V2, (liquid) = 2340 cm−1 or 6·7 kcal/mole. A method is described for evaluating V1, V2 and V3 separately if appropriate data are available. It is applied to acrolein, and tentative values for these constants are deduced.

Torsional frequencies in the far infrared—V. Torsions around the CC signle bond in some benzaldehydes, furfural, and related compounds☆

Abstract The infrared spectrum between 33 and 400 cm−1 has been examined in the vapor and liquid phases for the following 26 compounds: o-, m-, and p-F, Cl, Br, and CH3 benzaldehydes; pyridine-2-, -3-, and 4-aldehydes; acetophenone and its o-, m-, and p- F derivatives; furan-2-aldehyde; and several monofluorostyrenes and -nitrobenzenes. Torsional frequencies were sought, and have been assigned for all but the last two groups of compounds. For all the meta-substituted benzaldehydes, for a few of the ortho ones, and for furan-2-aldehyde evidence has been found for the presence of two rotational isomers in the vapor. The parameters V1 and V2 of an approximate potential function for the internal rotation have been evaluated. In the meta benzaldehydes the O-cis rotamer is the more stable one, whereas in the ortho compounds and in furan-2-aldehyde it is the O-trans one. For meta-fluorobenzaldehyde a temperature-dependence study of some bands in the mid-infrared has confirmed the existence of two rotamers, and has given 0.5 kcal/mole as an approximate value for their energy difference in CDCl3 solution.

Torsional frequencies in the far infrared—III: The form of the potential curve for hindered internal rotation of a methyl group

Abstract Transitions between excited torsional levels (0 → 1, 1 → 2, 2 → 3, ...) have been measured in the infrared for several compounds. The observed frequencies provide the best test of the potential function for hindered internal rotation which has yet been made. The constants of the usual expression Thus V 6 ⩽ 3 per cent of V 3 and may be either positive or negative. Pitzer and Hollenbergs earlier results for CH 3 CCl 3 could not be confirmed. The spectra for all six compounds were examined from 100 to 435 cm −1 , allowing some bending frequencies to be observed and tabulated.

The Infra‐Red and Raman Spectra of Cyclopentane, Cyclopentane‐d1, and Cyclopentane‐d10

The infra‐red and Raman spectra of cyclopentane, cyclopentane‐d1, and cyclopentane‐d10 have been determined for the purpose of establishing the symmetry of cyclopentane. D5h selection rules are found to hold very well. This does not constitute a rigorous criterion for structure in this case, however, because drastic alteration of the symmetry by substituting groups such as D, OH, CH3, or Cl for a hydrogen atom does not appreciably increase the complexity of the spectra. The data have provided two strong arguments against a D5h structure. (1) An assignment could not be made which simultaneously satisfied the product rule and the expected band contours. (2) The entropy of the vapor demands a low frequency (near 140 cm−1 for the assignment in this paper) if the symmetry is D5h. This is completely incompatible with the heat capacity of the solid.It is concluded that cyclopentane definitely does not have D5h symmetry. The actual geometry of the molecule is still not known. It is shown that a rigid structure of...

The infrared spectrum of carbon suboxide

Abstract The infrared spectrum of gaseous and solid C 3 O 2 has been examined from 70 to 4000 cm −1 . Because impurity bands have been a problem in the past, strenuous efforts were made to obtain an authentic spectrum. Samples were prepared by three different methods. (1) by dehydration of malonic acid with P 2 O 5 , (2) by dehydration of malonic acid-d 4 with P 2 O 5 , and (3) by pyrolysis of diacetyl tartaric anhydride. All three gave samples whose infrared spectra were quantitatively identical. In addition only traces of impurities were found by gas chromatography. The spectrum reported here is therefore surely that of pure C 3 O 2 . The range 70–400 cm −1 was examined with very thick gas and solid samples in an effort to locate the lowest fundamental. It was not observed, and is surely outside this region. The spectrum of the gas from 400 to 4000 cm −1 was examined with a resolution of 0·5–1 cm −1 . Six of the seven fundamentals for the linear form are known with certainty, and the seventh is believed to be below 70 cm −1 . Nonetheless there are many features of the spectrum which are still unexplained, and the analysis is far from satisfactory.

Notes on the Practice of Infrared Spectroscopy

Miscellaneous techniques for infrared prism spectroscopy are described in detail. These include: techniques for cleaving, cutting, and polishing alkali halide crystals for absorption cell windows; construction of absorption cells for liquids and gases, including some suitable for high and low temperatures and one of long path; the measurement of cell thickness; removal of atmospheric absorption; techniques useful for wavelengths above twenty-five microns; formulas for recording inks. A modified source-optical system and a method of calibration adjustment for Perkin-Elmer Model 12 instruments are also discussed.

Infrared and Raman spectra of chromyl chloride

Abstract The infrared spectrum of CrO 2 Cl 2 , a deep red liquid, has been measured from 120–3000 cm −1 . Six Raman lines have been obtained by excitation with the D -lines of potassium. The fundamental frequencies are, for C 2v symmetry: a 1 = 981, 465, 356, 140; a 2 = 224; b 1 = 995, 211; b 2 = 496, 257. The results agree well with the very recent work on the Raman spectrum by Stammreich et al . Thermodynamic properties have been calculated at four temperatures.

Vibrational spectra of fumaronitrile, maleonitrile and tetracyanoethylene

Abstract Infrared and Raman spectra are reported for fumaronitrile, maleonitrile, and tetracyanoethylene. The infrared observations extend from 4000 to at least 100 cm −1 . The Raman data include polarizations, although they are incomplete for tetracyanoethylene. The data and assignment for fumaronitrile agree very well with the recent results of Devlin , Overend and Crawford . Two fundamentals which they inferred have been confirmed by direct observation. All fundamentals are now known except for two a u modes. Values are given for all but one of the fundamentals of maleonitrile. For tetracyanoethylene the assignment of the planar vibrations has been aided by comparison with frequencies calculated from Urey-Bradley force constants. The latter were obtained from an overlay treatment of three other cyanoethylenes. The assignments for the out-of-plane fundamentals are still unsatisfactory.

Vibrational spectra of CF3CCH, CF3CCD, and CF3CCCF3

Abstract The infrared spectra of gaseous CF3CCH and CF3CCD have been measured from 75 to 4000 cm−1. The Raman spectrum of liquid CF3CCH is given with polarizations. The fundamental frequencies for the latter compound are, for C3v symmetry: a1: 3330, 2165, 1254, 810 and 535; e: 1182, 686, 611, 452 and 171 cm−1. The infrared spectrum of CF3CCCF3 has been extended to 60 cm−1 to locate two postulated fundamentals. The entire spectrum has also been examined at a resolution of better than 1 cm−1. Kopelman has suggested that for an ethane-like molecule with free internal rotation, the effective symmetry of the potential function is D6h. Consideration of the shapes of certain combination bands in the spectrum of CF3CCCF3 suggests that the actual point group is D3d. This is interpreted as evidence against Kopelmans suggestion. The fundamental frequencies for CF3CCCF3 are, for D3d symmetry: a1g: 2300, 1245, 771, 291; a2u: 1294,900,639; eg: 1181,624,464,186; eu: 1198,603,434,75cm−1. The a1u torsion was not evaluated; it is presumed to be small.