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¹¹C-Acetylene

Ohio State University, Columbus, Ohio

Correspondence: For reprints contact: William G. Myers, Dept. of Radiology, Ohio State University, 410 W. 10th Ave., Columbus, Ohio 43210.

ABSTRACT

¹¹C-acetylene formed directly and rapidly in a one-step synthesis when water or 5 N H₂SO₄ dropped on calcium carbide, following bombardment of it with ³He ions. After 2 µA of 15–18-MeV ³He²⁺ had struck 0.5 mmole of CaC₂ for 12 min, the yield of ¹¹C was 1.2 mCi. The calculated yield per microampere for 60 min (3 half-lives) is 1.6 mCi, and the specific activity is 3.2 mCi/mmole.

The cross sections of the ¹²C(³He,⁴He)¹¹C reaction are sufficiently large at the energies of ³He ions provided by modern biomedical cyclotrons that bombardment of CaC₂ with 50 µA for 1 hr might provide as much as 150 mCi of ¹¹C-acetylene, with specific activity as great as 300 mCi/mmole (12 mCi/mg of ¹¹C-HCCH).

The ready availability of the highly reactive two-carbon reagent, ¹¹C-acetylene, provides new opportunities to exploit the usefulness of 20-min ¹¹C. Projections are made for facile syntheses of randomly labeled two-carbon ¹¹C molecules of potential interest in biomedicine, e.g., acetaldehyde, acetate, and ethanol. Using ¹¹C-acetylene for random labeling of vital acids such as alanine, lactate, and succinate in positions other than carboxyl may be advantageous for applications in nuclear medicine.