Wyniki wyszukiwania - BazTech

Ograniczanie wyników

2 Nukleonika

2 2002

Powiadomienia systemowe

Sesja wygasła!

Znaleziono wyników: 2

Liczba wyników na stronie

Wyniki wyszukiwania

Wyszukiwano:
w słowach kluczowych: fluorine-18

Sortuj według:

Ogranicz wyniki do:

Rapid production of 18F fluoride from 2-fluoroaniline via the 19F(n,2n)18F reaction using 14 MeV neutrons

Mikołajczak R., Staniszewska J., Mikołajewski S., Rurarz E.

Nukleonika

2002

Vol. 47, nr 1

13-18

No carrier-added 18F fluoride was produced via the 19F(n,2n)18F reaction by 14 MeV neutron irradiation of 2-fluoroaniline and subsequent extraction of the produced 18F fluoride ion with water. The fluoride was then purified by liquid chromatography on a Chromabond-NO2 column. The time required for all chemical procedures was about 1 h. The average chemical separation yield was about 70%. The 18F activity obtained after 3 hours of irradiation at a flux rate of 108 n cm-2s-1 after a necessary 20-min delay was equal to several kBq per gram of fluorine in a 2-fluoroaniline sample, in accordance with the theoretically expected value. Improvement of the 18F production yield can be achieved by increasing neutron fluxes. Neutron generators with 14 MeV neutron fluxes of the order of 1010 n cm-2s-1 can produce tens MBq of 18F, sufficient for whole-day work in biomedical applications. Our results show that 14 MeV neutron irradiation of 2-fluoroaniline is a low cost alternative for the production of this nuclide in the countries which do not posses either cyclotrons or electron linear accelerator facilities.

Elucidation of reaction mechanisms using kinetic isotope effects of short-lived radionuclides

Matsson O.

Nukleonika

2002

Vol. 47,suppl.1

43-45

The use of the short-lived radionuclides 11C and 18F for the elucidation of organic reaction mechanisms is described. Examples of the different mechanistic problems that are discussed include concerted vs. stepwise base catalysed elimination (E2 or E1cB) and finding the rate limiting step for nucleophilic aromatic substitution (SNAr). The use of radionuclides to learn details about transition state structure for concerted nucleophilic aliphatic substitution (SN2) is also described.