The Use of Carbon-14 in the Determination of the Structures of Aldoketene Dimers

Electron-Impact Spectroscopy Investigation of Diketene

“…Electron-impact spectroscopy has been employed to study electronic transitions in a wide variety of molecules, , and the measured differential cross sections have been utilized to aid in assignment of transitions. − In this work, low-energy variable-angle electron-impact spectroscopy has been used to investigate both optically forbidden and optically allowed electronic transitions in the spectrum of diketene. Previous optical studies , of diketene in solution extended to 250 nm (about 5 eV) and showed only a weak, ultraviolet, absorption band at 313 nm (3.96 eV). The present gas-phase work shows four new, higher energy loss, electronic transitions including a spin-forbidden one.…”

Uses of isotopes in organic chemistry

“…A useful technique for detecting the (IH3CH2C1 '02C2H3 -f-CH3(CH2)6C02C2IL (5) Concerted mechanism: X-C-C:H + OH slow Although infrared absorption and electron diffraction analyses of organic azides support the linear chain formulation for the azide nitrogens, the formerly accepted cyclic structure for phenylazide has only recently been excluded by isotopic analysis (7). A N "-labeled phenylazide was made by the reaction shown in equation (6). (6) presence of the carbanion is to carry out the reaction in a deuterated solvent and determine whether or not exchange to give the deuterated halide is more rapid than elimination.…”

“…A N "-labeled phenylazide was made by the reaction shown in equation (6). (6) presence of the carbanion is to carry out the reaction in a deuterated solvent and determine whether or not exchange to give the deuterated halide is more rapid than elimination. Generally, such exchange is not found with the simple alkyl halides (9).…”

“…for 0.15 m. e. v. particles. 6 Annihilation of the 0® particle by reaction with j3e gives a y-ray of 0.5 m. e. v. energy. c Natural carbon which is, or was within 10= years, in equilibrium with atmospheric carbon dioxide contains a small but detectable amount of C14 (2).…”

Mass Spectra and Appearance Potentials of Ketene Monomer and Dimer; Relation to Structure of Dimer1

“…At various times the following structures have been seriously considered2 Recently several lines of evidence have tended to eliminate A and D and to suggest that the most likely structure is either B, vinylaceto-/3-lactone or C, ß-crotonolactone or perhaps a mixture of the two. Thus both the infrared spectra3 and electron diffraction studies4 are incompatible with A and D and favor B and C. The results of investigation of infrared spectra at various temperatures suggested to Miller and Koch that there is probably an equilibrium mixture of B and C. 6 The work of Roberts, Armstrong, Trimble and Burg6 on reaction of ketene dimers containing carbonyl labeled C14 and also the fact that a non-zero dipole moment was observed,7 tend to eliminate the symmetrical structure, D. Results which favor structure B have been reported by Blomquist and Baldwin, 8 Hurd and Blanchard,9 and Johnson and Shiner.10 Finally a very recent report on the X-ray studies of the crystalline solid at low temperatures11 show that in this state the molecule is definitely vinylaceto-/3lactone (B). This paper reports a study of the products obtained by electron bombardment of ketene and ketene dimer in a conventional analytical mass spectrometer and discusses the bearing of these dissociation patterns on molecular structure.…”