Reactions of the Acetone Cation. Implications for the Radiolysis of Acetone

• Published in: Radiation research 1972-10, Vol.52 (1), p.47-58
• Main Authors: Sieck, L. W., Ausloos, P.
• Format: Article
• Language: English
• Subjects: Acetone - radiation effects; Cations; Cations, Monovalent; Internal energy; Ionic reactions; Ions; Mass spectra; Mass spectrometers; Mass Spectrometry; Molecules; Photochemistry; Photoionization; Protons; Radiolysis; Space life sciences
• ISSN: 0033-7587; 1938-5404
• DOI: 10.2307/3573587

The reactions of the acetone and acetyl cation with acetone have been investigated in a photoionization mass spectrometer. Reaction of the acetone cation with $\leq 0.3\ {\rm eV}$ internal energy occurs essentially at every collision $(k=8.4\times 10^{-10}\ {\rm ml}/\text{molecule}\ {\rm sec})$, but decreases slightly with an increase in internal energy. Two reaction channels are observed for the acetone cation: (a) ${\rm CH}_{3}{\rm COCH}_{3}{}^{+}+{\rm CH}_{3}{\rm COCH}_{3}\rightarrow ({\rm CH}_{3})_{2}{\rm COH}^{+}+{\rm CH}_{3}{\rm COCH}_{2}$ and (b) ${\rm CH}_{3}{\rm COCH}_{3}{}^{+}+{\rm CH}_{3}{\rm COCH}_{3}\rightarrow {\rm CH}_{3}{\rm COCH}_{3}{\rm COCH}_{3}{}^{+}+{\rm CH}_{3}$. The ${\rm CH}_{3}{\rm CO}^{+}$ ion reacts mainly as follows: ${\rm CH}_{3}{\rm CO}^{+}+{\rm CH}_{3}{\rm COCH}_{3}\rightarrow {\rm CH}_{3}\cdot {\rm COCH}_{3}{\rm COCH}_{3}{}^{+}\ (k\cong 4.6\times 10^{-10}\ {\rm ml}/\text{molecule}\ {\rm sec})$. At pressures above $10^{-3}\ \text{Torr}\ ({\rm CH}_{3})_{2}{\rm COH}^{+}$ and ${\rm CH}_{3}{\rm COCH}_{3}{\rm COCH}_{3}{}^{+}$ reacts further with acetone to produce $({\rm CH}_{3}{\rm COCH}_{3})_{n}{\rm H}^{+}$. It is suggested that in liquid phase radiolysis experiments the acetone cation will react within $10^{-12}-10^{-13}\ {\rm sec}$. Recent radiolysis experiments in which acetone was used as a solvent are discussed in the light of this premise.