Lucy W. Pickett

Effect of Ring Size on the Far Ultraviolet Absorption and Photolysis of Cyclic Ethers

Absorption curves, tabulated extinction coefficients, and oscillator strengths are given for trimethylene oxide, ethylene oxide, and formaldehyde vapor in the spectral range 2000–1550 A. A comparison is made of the spectra and photochemical stability of these compounds with those of previously determined five‐ and six‐membered ring ethers.

The Ultraviolet Absorption Spectra of 1–3 Cyclohexadiene

The intense absorption of 1–3 cyclohexadiene in the region 35,000–45,000 cm—1 has been measured in the vapor and in hexane solution, and characteristic frequency differences of the band maxima noted. Values of oscillator strength obtained from these data are consistent with theoretical predictions, but the f value found from the solution agrees better with that from the vapor if the correction for Lorenz‐Lorentz forces is not applied.

The Far Ultraviolet Absorption Spectra of the Isomeric Butenes

Measurements of the intensity and position of absorption from 45 000 to 64 000 cm—1 of butene‐1, cis‐butene‐2, trans‐butene‐2, and 2‐methylpropene were made on flowing vapors. All show a broad intense band which is most intense in the case of the cis‐isomer, and superimposed systems of narrow bands, both at shorter and longer wavelengths. Whereas the position of the last named is dependent on the number of alkyl groups adjacent to the double bond, the broad band maximum is not similarly displaced but rather depends on the molecular shape and seems related to the dipole moment vector. The vibrational structure of the bands is consistent with infrared and Raman data.

Absorption of Bicycloheptane and Bicycloheptene in the Vacuum Ultraviolet

The vacuum ultraviolet absorption spectra of bicycloheptane and bicycloheptene have been investigated in the region from 45 000 to 65 000 cm—1. Two distinct band systems with maxima at 51 125 and 59 715 cm—1 were noted in the case of bicycloheptene, each with an oscillator strength of 0.15. The first observed absorption of bicycloheptane was near 55 000 cm—1 while that of the unsaturated hydrocarbon was displaced more than 8000 cm—1 toward lower frequencies. In both compounds, sharp narrow bands were superimposed on the continuous absorption. In a study of the photodecomposition, it was shown that cyclopentadiene and ethylene were formed as photodecomposition products of bicycloheptane and also of bicycloheptene.

Far Ultraviolet Absorption Spectra of Small Ring Hydrocarbons

Molar extinction coefficients for the far ultraviolet absorption of cyclobutene, 1‐methylcyclobutene, and methylenecyclobutane were measured between 40 000 cm—1 and 64 000 cm—1. These spectra show the characteristic absorption of π electrons with oscillator strengths of 0.3 and with band positions which are explicable on the basis of molecular structure. Photodecomposition to give ethylene was observed in the case of methylenecyclobutane and 1‐methylcyclobutene.

The Infra‐Red Spectrum of Furan

The infra‐red spectrum of furan vapor has been investigated in the region from 500 to 35,000 cm−1 with a prism spectrograph using potassium bromide, rocksalt, and fluorite prisms. The data have been compared with those of other investigators and the frequency assignments proposed by Lord and Miller for pyrrole were applied to these data.

The vacuum ultraviolet spectra of ethyleneimine and trimethyleneimine

Experimental studies of the vacuum ultraviolet absorption spectrum of ethyleneimine in the region 40 000–60 000 cm−1 yield maxima at 6.32 and 7.15 eV, with oscillator strengths of 0.003 and 0.086, respectively. Trimethyleneimine has in the same region a band maximum at 6.44 eV with an oscillator strength of 0.047. Semiempirical SCF–CI calculations using the CNDO method with Sichel–Whitehead parameters are reported on 3‐, 4‐, and 5‐membered ring compounds in the series of saturated alkanes, ethers, and amines and the predicted transitions are compared with experimental interpretations of the nature of the excitations.