A Comparative Study of Homolytic Reactions of Fullerenes with Aldehydes in a Mass Spectrometer under Electron Impact and in Solution under UV Irradiation

Abstract

C(60) was reacted in the ionization chamber of a mass spectrometer under electron impact (EI) with aldehydes, RCHO (R = Ph, p-FC(6)H(4), F(5)C(6), p-MeOC(6)H(4), α-thienyl, o-HOC(6)H(4), o-BrC(6)H(4), m-BrC(6)H(4) and t-Bu), with the transfer of R• radicals and with Me•-transfer from i-PrCHO and t-BuCHO. Paramagnetic fullerene derivatives were stabilized by the addition of the next R• radical or a hydrogen atom, or hydrogen or bromine atom loss. A detailed study showed that the reaction between C(60) and PhCHO occurred via a homolytic mechanism that matches one reported earlier for the reaction with acetone. This suggests the generality of the mechanism for the reactions of fullerenes with other species in ionization chambers under EI at ca 300°C. All aldehydes, except one, had radicals at the carbonyl group which were different from those in the ketones examined earlier in the reactions. This expanded the variety of radicals which can be transferred to fullerenes during reactions in ionization chambers under EI. Due to this and the hydrogen atom at the CO group of aldehydes, some reactions occurred that were not found for the ketones: the formation of cyclic products C(60)COC(6)H(4) and C(60)OC(6)H(4) for PhCHO, o-BrC(6)H(4)CHO and o-HOC(6)H(4)CHO, respectively, and HC(60)Ph for o- and m-BrC(6)H(4)CHO. The reaction with α- formylthiophen gives the first example of transferring an aromatic heterocyclic radical to C(60) in an ionization chamber under EI. C(70) reacted with PhCHO, p-FC(6)H(4)CHO and i- PrCHO similarly to C(60). The results for the reactions of C(60) with PhCHO and with i- PrCHO were compared with those in solution under UV irradiation. Incomplete but reasonable coincidence was found; in both modes, the addition of Ph•, PhCO• and Me• radicals to C(60) occurred, whereas some other products were formed in solution, and the explanation is given as to why this occurred. This conformity supports the hypothesis based on the results of kindred reactions with ketones and organomercurials: the results of EI-initiated homolytic reactions between fullerenes and other compounds in an ionization chamber can predict the reactivity of the fullerenes toward them in solution.

Interaction of Fullerenes with Organosilanes in the Ionization Chamber of a Mass Spectrometer under Electron Impact and the Reaction of C60with Tetraphenylsilane in Solution under UV Irradiation

“…With that, our purpose was not to investigate these reactions in the IC as the end in themselves but to demonstrate that they can predict the reactivity of the fullerenes toward these reagents in solution or the solid phase/state. Actually, it was done by implementing the reactions of C 60 with compounds of each abovementioned class under UV irradiation or thermally [19][20][21][22][23][24][25][26]. The present study continues investigations in this field.…”

“…As for the reactions of fullerenes performed by protocol A with all other compounds studied earlier which belonged to other classes [19,[24][25][26], the mass chromatograms show an interesting feature: the [C 60 ] +• or [C 70 ] +• intensity curves drop significantly when the peaks of silanes appear in the mass chromatograms and return to virtually the same level after the bulk of the peaks has passed. At these points the product traces appear (Figure 2).…”

Mass Spectrometry in Russia

“…In other works, the homolytic reactive mass spectrometry of fullerenes has been investigated using ketones 30,31 and aromatic aldehydes. 32,33 In the case of ketones RCOR 1 the main products were due to the addition of R and R 1 radicals to the fullerenes with hydrogen addition or loss. The same products were obtained in solution under UV irradiation.…”