INFRARED STUDIES OF ROTATIONAL ISOMERISM IN CF2CL−CF2CLCF_{2}CL-CF_{2}CL AND CF2BR−CF2CLCF_{2}BR-CF_{2}CL

Author Institution: Chemistry Division, Naval Research LaboratoryThe phenomenon of rotational isomerism has been studied in $CF_{2}CL-CF_{2}CL$ and $CF_{2}BR-CF_{2}CL$ by observing the temperature and state dependence of their infrared absorption spectra in the $2-18\mu$ region. In $CF_{2}CL-CF_{2}CL$, the trans isomer persists in the crystalline solid, and is also the more stable form in the liquip and vapor states. The energy difference between the trans ($C_{2}H$) and gauche ($C_{2}$) forms in the vapor was observed to be 500 $\pm$ 200 calories/mole. In $CF_{2}BR-CF_{2}CL$, the selection rules for the two probable isomeric species ($C_{s}$ and $C_{1}$) are not sufficiently different to facilitate a direct determination of the symmetry of the form which persists in the solid state. However, a comparison of the infrared spectrum of $CF_{2}BR-CF_{2}CL$ with those of $CF_{2}CL-CF_{2}CL$ and $CF_{2}BR-CF_{2}BR$ indicates that the persistent isomer is the pseudo-trans form ($C_{s}$ symmetry). This trans form is also the more stable isomer in both the liquid and vapor phases, the energy difference being 520 $\pm$ 200 and 600 $\pm$ 200 calories/mole, respectively

A SIMPLE INTERFEROMETER FOR DISPERSION MEASUREMENTS OF LIQUIDS IN THE 2-22 μ\mu REGION

Author Institution: Chemistry Division, U. S. Naval Research Laboratory“Through the use of crystalline germanium plates it is possible to construct Fabry-Perot etalons which are capable of dispersion measurements in the 2-22 $\mu$ region of the infrared. Moreover, such measurements can be carried out with conventional spectrometers and nominal temperature control. Using the interferometers, the refractive indices of carbon disulfide, carbon tetrachloride, chloroform, cyclohexane and perfluoro 1, 3, 5-trimethylcyclohexane have been measured with an accuracy of $\pm$ 0.003.

INFRARED SPECTRA OF SOME SOAPS OF PHENYLSTEARIC ACID

Author Institution: Chemistry Division, Naval Research LaboratoryThe infrared absorption spectra of solid films of Li, Na, K, Be, Mg, Ca, Sr, and Ba phenylstearate have been studied in the region from 2 to 15 microns. The carbonyl band, which appears at $1712 cm^{-1}$ in phenylstearic acid, disappears in the spectra of the soaps presumably because of ionization effects. Instead, a strong band is observed in the region from 1540 to $1620 cm^{-1}$. The frequency of this band appears to vary linearly with the Pauling electronegativity value of the metal constituent of the various soaps. In addition, the infrared spectra of solutions of lithium phenylstearate in chloroform and benzene have been studied in the region from 5 to 7 $\mu$. In such solutions, the lithium soap exhibits three bands at 1589, 1572, and $1543 cm^{-1}$, rather than a single band at $1587 cm^{-1}$ as observed in solid films. The relative intensities of these three bands are profoundly influenced by the addition of phenylstearic acid, by concentration, or by aging of the solutions. The strength of the band at $1543 cm^{-1}$ appears to be directly proportional and the band at $1572 cm^{-1}$ inversely proportional to the viscosity of the solutions, indicating that the formation of polymeric chains may be responsible for some of the observed spectral changes

ROTATIONAL ISOMERISM IN 1-FLUORO-1,1,2,2-TETRACHLOROETHANE

Author Institution: Chemistry Division, U. S. Naval Research Laboratory“The infrared spectra of liquid, vapor and solid $CHCl_{2}$ $CFCl_{2}$ have been studied in the 2-15 $\mu$ region. Two isomeric species are present in the vapor and liquid whereas only one form persists in the crystalline solid. From the temperature dependence of the band intensities the heat of reaction, $\Delta H^{\circ}$ for the liquid and vapor are found to be 0.42 and 0.82 keal/mole, respectively. On the basis of this observed difference in $\Delta H^{\circ}$ for the two states and calculated dipole moments it is concluded that the more stable isomer, which also persists in the crystalline solid, is the skew isomer ($C_{1}$ symmetry). The less stable or higher energy form is the pseudo-trans form ($C_{1}$ symmetry).

INFRARED STUDY OF THE COMPLEXING OF ACETONE WITH CDl3.CDCl2BrCDl_{3}. CDCl_{2}Br AND CDBr3CDBr_{3}

Author Institution: Chemistry Division, U. S. Naval Research LaboratoryThe well-known interaction which occurs between acetone and haloforms has been studied by observing the resulting intensity changes in the C-D stretching band of the haloforms. The interacting components were dissolved in a relatively inert solvent, n-hexane, in order to reduce the complicating effects of self-association and of higher order complex formation. The absorptivities of the C-D bands in the free molecules and in the 1:1 complexes have been determined together with equilibrium constants. In addition, heats of formation have been measured by studying the temperature dependence of the equilibrium constants. On the basis of these measurements it is concluded that the strength of the interaction of a given haloform with acetone decreases in the order, $CDCl_{2}>CDCl_{2}Br>CDBr_{2}$

VIBRATIONAL SPECTRA OF SYMMETRICAL TERACHLORO-AND TETRABROMOETHANE

Author Institution: Pennsylvania State CollegeThe Raman and infrared spectra of liquid 1,1,2,2-tetrachloro- and 1,1,2,2-tetrabromoethane have been investigated. Using a grating spectrograph of 3.8 \AA/mm dispersion, we have observed the chlorine isotope effect for the $\Delta \nu = 353$ and $366 cm^{-1}$ line pair, and have verified the previous results of Rank, Sheppard, and Szasz concerning the anomolous intensity contour exhibited by the $353 cm^{-1}$ vibration. From temperature intensity measurements in the Raman effect and Raman-infrared correspondences, we conclude that the two forms posses $C_{2h}$ and $C_{2}$ symmetry, with the $C_{2}$ form being the more stable one. On the basis of this conclusion we are able to explain the intensity contours observed in the chlorine isotope effect. The value of $\Delta H$ for the reaction $C_{2}\to C_{2h}$ in s-tetrabromoethane was found to be 910 cal/mole

THE EFFECT OF SOLVENT-SOLUTE INTERACTIONS ON THE INFRARED CARBONYL STRETCHING VIBRATION

Author Institution: U.S. Naval Research LaboratoryThe effect of solvent-solute interactions on the carbonyl stretching vibration of several ketones, amides and esters has been studied. The compounds examined include acetone, cyclohexanone, n-acetyl pyrrolidine, ethyl acetate, ethyl trichloroacetate and ethyl trifuloroacetate. Changes in the frequency and shape of the carbonyl band were produced by varying the composition of two-component solvent systems and/or by varying the temperature of the solutions. The results clearly suggest that the observed variations in frequency and intensity are due to specific interactions between solvent and solute rather than to bulk dielectric effects. Moreover, these interactions can result in the formation of a number of solvent-solute complexes which are in equilibrium with each other

VIBRATIONAL SPECTRA OF THE ACETONE MOLECULE

Author Institution: Pennsylvania State CollegeWe have prepared acetone$-d_{6}$ in high purity and have obtained Raman and infrared spectra and polarizations. We have also obtained the infrared spectrum of the gas and liquid in the rock-salt region. We have taken some low-temperature Raman spectra of the acetone which gives rise to some interesting results. We have performed a vibrational analysis which is quite complete for certain classes of vibrations since in these cases we can unequivocally apply the Teller-Redlich product rule