Properties and reactions of ketene in the gas phase by ion cyclotron resonance spectroscopy and photoionization mass spectrometry. Proton affinity, site specificity of protonation, and heat of formation of ketene

Journal Article · Wed May 24 04:00:00 EDT 1978 · J. Am. Chem. Soc.; (United States)

DOI:https://doi.org/10.1021/ja00479a032· OSTI ID:6650423

Vogt, J; Williamson, A D; Beauchampt, J L

The properties and reactions of ketene and ketene-d/sub 2/ are investigated using the techniques of ion cyclotron resonance spectroscopy and photoionization mass spectrometry. The major reaction sequence initiated by the ketene molecular ion in its ground vibrational state at thermal energies involves sequential incorporation of CH/sub 2/ into the ionic product with loss of CO. The species C/sub 2/H/sub 3/O/sup +/ (presumably the acyl cation) is a major product at long times or high pressure and does not react further with ketene neutrals. The energetics of ionization of ketene and ketene-d/sub 2/ and the effect of vibrational energy on reactivity are examined using photoionization mass spectrometry and photoelectron spectroscopy. The threshold determined for the endothermic process CH/sub 2/CO/sup +/ + CH/sub 2/CO ..-->.. C/sub 2/H/sub 4//sup +/ + 2CO provides confirmation of the recently redetermined heat of formation of ketene (..delta..H/sub f/ = -11.4 +- 0.4 kcal/mol). Equilibrium proton transfer reactions in a number of mixtures lead to a determination of the proton affinity of ketene, PA(CH/sub 2/CO) = 195.9 +- 2 kcal/mol, relative to PA(NH/sub 3/) = 202.3 +- 2 kcal/mol. The site of protonation is shown to be the methylene carbon. These results yield ..delta..H/sub f/(CH/sub 3/CO/sup +/) = 159.9 +- 2 kcal/mol, which is discussed in light of other measurements of the heat of formation of the acyl cation. With sufficiently acidic species (e.g., CH/sub 5//sup +/), oxygen protonation occurs. 5 tables, 4 figures, 48 references.

• Research Organization: California Inst. of Tech., Pasadena
• OSTI ID: 6650423
• Journal Information: J. Am. Chem. Soc.; (United States), Journal Name: J. Am. Chem. Soc.; (United States) Vol. 100:11; ISSN JACSA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400104 -- Spectral Procedures-- (-1987)
400301 -- Organic Chemistry-- Chemical & Physicochemical Properties-- (-1987)
400302* -- Organic Chemistry-- Isotope Effects-- (-1987)
DEUTERIUM
DEUTERIUM COMPOUNDS
ELECTRON SPECTROSCOPY
ENERGY LEVELS
ENTHALPY
EXCITED STATES
FLUIDS
FORMATION HEAT
GASES
HYDROGEN COMPOUNDS
HYDROGEN ISOTOPES
ION CYCLOTRON RESONANCE SPECTROSCOPY
ION SPECTROSCOPY
IONIZATION
ISOTOPE EFFECTS
ISOTOPES
KETENES
LIGHT NUCLEI
MASS SPECTROSCOPY
NUCLEI
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
ORGANIC OXYGEN COMPOUNDS
PHOTOELECTRON SPECTROSCOPY
PHYSICAL PROPERTIES
REACTION HEAT
SPECTROSCOPY
STABLE ISOTOPES
THERMODYNAMIC PROPERTIES
VIBRATIONAL STATES