The Structure of Ketene Dimer¹

The crystal and molecular structure of diketene

“…Since that time, an ultra-violet study (Calvin, Magel & Hurd, 1941) has been interpreted as fovoring IV; a Raman study (Taufen & Murray, 1945) as favoring V or I; an infra-red study (Whiffen & Thompson, 1946), which considered the Raman data as well, as favoring IV, V or a mixture--some preference being expressed for V; and an electrondiffraction study (Bauer, Bregman & Wrightson, to be published) as favoring IV or V without being able to distinguish between them. Another infra-red study (Miller & Koch, 1948) provided good evidence that diketene was an equilibrium mixture, presumably of IV and V, though perhaps containing some III.…”

UV-Induced Unimolecular Photochemistry of Diketene Isolated in Cryogenic Inert Matrices

“…Prior to 1940, these measurements included determinations of the molecular weight, the refractive index, 7 and the ultraviolet spectrum; 8 the dipole moment was measured, 9 and the Raman spectrum was analyzed. 6,9 An infrared spectrum, first obtained in 1946 by Whiffen and Thompson, 10 established that the "ketene dimer" contained a four-membered ring, and the structure was unequivocally established in 1952 by the X-ray study 4 that showed that crystalline DK had the structure of 4-methyleneoxetan-2-one (Scheme 1), which had been suggested as one of several alternatives in the previous infrared studies. 10,11 This structure was later corroborated by 1 H NMR studies 12−14 showing that, for both crystalline material and liquid between room temperature and 120 °C, this is the only significant form.…”

“…The elucidation of the structure of DK required 45 years, from the time of discovery of the “ketene dimer” (as the molecule was called at that point in time) , until an X-ray diffraction study was completed in 1952. During that period, five different formulas were suggested for the C 4 H 4 O 2 molecule, , and in addition to the chemical reactions that were used to determine the structure of the “ketene dimer”, a variety of physical measurements was undertaken. Prior to 1940, these measurements included determinations of the molecular weight, the refractive index, and the ultraviolet spectrum; the dipole moment was measured, and the Raman spectrum was analyzed. , An infrared spectrum, first obtained in 1946 by Whiffen and Thompson, established that the “ketene dimer” contained a four-membered ring, and the structure was unequivocally established in 1952 by the X-ray study that showed that crystalline DK had the structure of 4-methylene-oxetan-2-one (Scheme ), which had been suggested as one of several alternatives in the previous infrared studies. , …”

“…The elucidation of the structure of DK required 45 years, from the time of discovery of the "ketene dimer" (as the molecule was called at that point in time) 2,3 until an X-ray diffraction 4 study was completed in 1952. During that period, five different formulas were suggested for the C 4 H 4 O 2 molecule, 5,6 and in addition to the chemical reactions that were used to determine the structure of the "ketene dimer", a variety of physical measurements was undertaken. Prior to 1940, these measurements included determinations of the molecular weight, the refractive index, 7 and the ultraviolet spectrum; 8 the dipole moment was measured, 9 and the Raman spectrum was analyzed.…”

Millimeter-Wave Spectroscopy, X-ray Crystal Structure, and Quantum Chemical Studies of Diketene: Resolving Ambiguities Concerning the Structure of the Ketene Dimer

“…Surprisingly, for such a simple molecule, the structure of the dimer was unknown and the subject of controversy for 44 years . There were at least five proposed and seriously considered molecular structures of diketene, one acyclic and four cyclic C 4 H 4 O 2 molecules, as shown in Figure . ,− The first application of infrared spectroscopy to diketene by Miller and Koch in 1948 suggested a possible equilibrium between two or three of the proposed structures ( 1 – 3 , Figure ). The connectivity of the dimer was not firmly established until the 1950s, when the molecular structure of diketene ( 1 ) was determined to be a [2 + 2] cycloaddition dimer of ketene by single-crystal X-ray crystallography − and 1 H NMR spectroscopy .…”