William West

The Infrared Absorption Spectrum of Hydrogen Chloride in Solution

The near infrared absorption bands of HCl in nonionizing solvents in the neighborhood of 3.5μ and 1.8μ, measured with a 3600 line per inch grating, have the following characteristics; they show no rotational structure; they usually have two components of unequal intensities; the absorption region is displaced towards lower frequencies compared with the gas. The displacement is independent of concentration up to mole fraction 0.1, but increases with diminishing temperature in certain solvents. The interval between the components varies directly with the dielectric constant of the solvent. In solution, the relative displacement of the more intense component from the origin of the gas band is approximately the same for the 3.5μ and 1.8μ bands, as is also the interval between components. A simple relation exists approximately between the frequency displacement from the gas origin and the dielectric constant of the solvent, of the form Δv/v=C[(D—1)/(2D+1)], a deduction of which formula has been made by J. G. K...

The Influence of Temperature and Pressure on the Infra‐Red Absorption Spectrum of Gaseous and Liquid Hydrogen Chloride up to the Critical State

The absorption spectra, near 1.7μ, of liquid HCl from — 100°C to the critical temperature of 52°C, and of gaseous HCl from one atmosphere to the critical pressure of 82 atmospheres, have been measured. The spectrum of the gas retains P and R branches about an origin undisplaced from its low pressure value up to just below the critical pressure, although discreet rotational lines are not recognizable after the density of 0.1 g/cc has been reached. At all temperatures, the transition of gas to liquid is accompanied by the replacement of the P—R branched type of spectrum by a single maximum displaced to low frequencies from the gas origin by an amount increasing from 48 to 117 cm—1 as the temperature is lowered from the critical temperature to — 100°. This band is asymmetric, with a tail to the short wave side, and above 20°C shows signs of being resolved into two bands, one in the position of the gas band. It is concluded that liquid HCl contains two types of molecules, one gas‐like, the other, with the vib...

The Vibration Spectra and Electric Moments of Azomethane, N–N′ Dimethylhydrazine and Acetaldazine

The investigations reported here on azomethane, CH3·N=N·CH3, N–N′ dimethylhydrazine, (CH3)HN·NH(CH3), and acetaldazine (CH3)HC=N–N=CH(CH3) were carried out primarily to obtain information on the general form and some of the structural properties of these molecules, which are of a type whose chemical behavior with respect to thermal and photodecomposition is of considerable current interest. The properties examined have included the Raman spectra, with the state of polarization of the stronger lines, in the liquid state, and the electric moment in solution of the three compounds; the infrared absorption spectrum of azomethane vapor has also been investigated to the degree possible with the resolution ordinarily obtained from a rocksalt prism spectrometer.

Photosensitization and Fluorescence by Aromatic Hydrocarbons

Benzene, naphthalene, related hydrocarbons and some of their derivatives act as optical sensitizers towards the decomposition of alkyl iodides in hexane solution. Within this group, the sensitizing power of a substance towards an acceptor runs parallel with the ability of the acceptor to quench the fluorescence of the sensitizer; this is demonstrated quantitatively and in detail. The quantum yield of the naphthalene‐sensitized decomposition of ethyl iodide follows an equation of the form 1/φ=a+b(1/[EtI]), and detailed analysis of the quenching and sensitization shows that while sensitization and fluorescence are alternative processes, they are not completely reciprocal, in that more molecules may sensitize than may potentially fluoresce. All of the observed features of the sensitization are consistent with its being the result of a resonative transfer of energy at collision from the excited sensitizer to the acceptor.

The Vibration Spectra and Structure of the Cyanogen Halides

The Raman spectra of the cyanogen halides in the liquid state or in alcoholic solution contain 3 frequencies v1, v2, and v3. In the order chloride, bromide, iodide, v1 = 2201, 2187, 2158 cm—1; v2 = 729, 580, 470; v3 = 397, 368, 321; the order of intensities of Raman transitions is v1>v2>v3. The relative values of the frequencies indicate a linear arrangement of the nuclei in the lowest electronic state of these molecules, and the data are in accord with the structure X–C≡N rather than X–N=C.

The Raman Spectra of Some Simple Molecules in Solution

The Raman spectra of HCl, HBr, SO2 and NH3 in various nonionizing solvents indicate vibrational frequencies in the solute molecules of lower value than in the corresponding gaseous states, the relative diminution amounting, in the hydrogen halides dissolved in some solvents, to 3 percent of the gas frequencies. The frequency shift is smaller for the two polyatomic molecules. There seems to be a definite relation between the relative frequency displacement and the dielectric constant of the solvent for the dissolved molecules of HCl and HBr. Δv/v increases with solvent dielectric constant to a limiting value of 0.03. A similar trend is shown in SO2 and for NH3 it seems that other factors than the dielectric constant of the solvent are effective in determining the frequency displacement. Concentrated solutions of HCl and HBr in several ionizing solvents have no features in their Raman spectra which can be identified as vibrations in HCl or HBr molecules. The bearing of these results on the dissociation proc...