Solid state catalytic saturation of double bond with hydrogen, deuterium and tritium is a valid route to incorporate selectively isotopes in specific positions. We studied the best fitting of all parameters that rule the radioactive yield of tritiation of an unsatured substrate, to guarantee the maximum incorporation of labeled atom in the product at room temperature. The wise choice of experimental parameters allowed very high radiochemical yields. The number of tritium exceeded the statistical presence of two atoms. Relative magnitudes for addition and exchange kinetic constants are provided.
The radiolysis of β(−)pinene has been studied at five different radiation dose, namely at 50, 100, 150, 300 and 600 kGy with
a dose rate of 2.2 kGy/h. At lower radiation dose, β(−)pinene showed a reduction of the optical activity, hence, the expected
radioracemization appeared predominant. At higher radiation dose, an opposite and unexpected trend was observed: the optical
activity increased almost linearly with the radiation dose. The increase of [α]D of radiolyzed β(−)pinene was due to the formation oligomers, mainly a dimer and/or a trimer of β(−)pinene which remain soluble
in the monomer but which displayed a higher optical activity than the starting monomer, contributing to the increase in the
specific optical rotation. Simultaneously to the formation of the dimer/trimer the radiolysis of β(−)pinene induced also its
polymerization into a poly(β(−)pinene) resin which was insoluble in the monomer and which was characterized by a high structural
order and by the preservation of the chiral centers so that it showed an enhanced specific optical rotation which is ≈2 times
that of the monomer. It is shown that poly(β(−)pinene) radiopolymer can be easily racemized in presence of a Friedel-Crafts
catalyst. The kinetics of β(−)pinene radiation-induced oligomerization and polymerization can be described by a pseudofirst
order rate constant k = 1.9·10−7·s−1. The radiation chemical yield for the same reaction is G = 1.93·10−6 mol/J. The work shows that also the radiation-induced polymerization of chiral monomers may be a tool for the preservation
and amplification of the optical activity of the monomer with implications for abiotic mechanisms of chiral amplification.
Triazines are a class of molecules which have been found in meteorites such as Orgueil meteorite. Despite their poor resistance
to UV radiation, these molecules survived millions of years inside a meteorite. The present work is dedicated to the examination
of the radiation resistance of the simplest sym-triazine: 1,3,5-triazine. The crystals of this molecule have been irradiated
with γ-radiation at 50 and 350 kGy and were studied by electronic absorption spectroscopy, liquid chromatography, FT-IR spectroscopy
and differential scanning calorimetry (DSC). All the data suggest the relatively low stability of this molecule to high energy
radiation. The resulting products from radiolysis are formamidine together with triazine dimers and oligomers. Other radiolysis
products are H2, CH4, HCN and other gases.
Isoprene polymerizes under the action of γ-radiation from a 60Co source yielding a low molecular weight polyisoprene which remains soluble in the unreacted monomer. The electronic absorption
spectrum of polyisoprene oligomer in isoprene monomer has been explained using squalene, a polyisoprene hexamer, as model
compound. The radiation chemical yield for polyisoprene formation has been estimated from both gravimetric and spectrophotometric
data pertaining the amount of polymer formed. An average G value of 35 molecules/100 eV has been determined suggesting that the polymerization mechanism involves free radicals. The
chemical structure of the resulting polyisoprene radio-oligomer has been determined by FT-IR spectroscopy and found identical
to that of a reference polyisoprene sample prepared by a chemically-initiated free radical polymerization process. The structure
determination by FT-IR spectroscopy has been reported in detail.
Authors:F. Cataldo, O. Ursini, P. Ragni, and A. Rosati
Poly(dimethylbutadiene) (PDMB) was synthesized through the inclusion polymerization technique, by γ-irradiation of a clathrate
of 2,3-dimethyl-1,3-butadiene in deoxycholic acid (DOCA) at 75, 150, 320 and 430 kGy. The resulting inclusion complexes PDMB@DOCA
were studied by FTIR spectroscopy and by thermal analysis (DTA, TGA and DTG). Pure PDMB was isolated by extracting the complex
PDMB@DOCA with ethanol. The best sample in terms of purity was that prepared at 75 kGy, while the other samples prepared at
higher doses suffered of DOCA grafting on PDMB chains. Pure PDMB isolated from PDMB@DOCA complex was studied by FT-IR spectroscopy
and by thermal analysis in comparison to a reference highly crystalline and ≈=100% trans-1,4-PDMB prepared by inclusion polymerization
in thiourea and in comparison to PDMB prepared by emulsion polymerization. A lower degree of regularity and crystallinity
has been found on the PDMB sample prepared as inclusion compound in DOCA in comparison to the reference PDMB obtained by inclusion
polymerization in thiourea.
Authors:F. Cataldo, E. Lilla, O. Ursini, and G. Angelini
C60 fullerene was radiolyzed in toluene solution both in presence of air and in vacuum at four different radiation doses 12,
24, 36, 48 and 96 kGy. Clear evidences of the addition of benzyl radicals to the fullerene cage derive from FT-IR and C13-NMR spectra of the reaction product. In presence of air the interference of oxygen is evident in the FT-IR spectra and from
the elemental analysis. A detailed analysis of the kinetics of the multiple addition of benzyl radicals to the fullerene cage
was made spectrophotometrically with the determination of the addition rate constants at the each addition step and the average
number of benzyl groups added to the fullerene cage as function of the radiation dose.
Authors:F. Cataldo, O. Ursini, E. Lilla, and G. Angelini
Gelatin, the low molecular weight collagen derivative from porcine skin was transformed into a stable permanent hydrogel by
γ-radiation. A series of samples with 3% gelatin solution in water were irradiated at doses of 12, 25, 50, 100, 150, 200 kGy
at room temperature in the absence of air with a dose rate of 2.2 kGy/h. At low dose gelatin hydrogels incorporating all the
available water were obtained. At higher doses above 50 kGy, the gelatin hydrogel samples show a curious shrinking phenomenon
due to the relatively high crosslinking density level achieved, so part of the available water is squeezed out from the gel
cage. The gelatin hydrogel samples were studied by mass fractionation analysis, by spectrophotometric and polarimetric analysis.
Further characterization was made by FT-IR spectroscopy and by thermal analysis (DSC, DTA and TGA) of the dried gelatin samples
after irradiation in comparison to a reference untreated sample.