Mass spectrometry of alcohols and ethers

Towards Perfunctionalized Dodecahedranes—En Route to C20 Fullerene

“…It was understood also that due to the rapidly increasing number of isomers up to C 20 HX 19 , selective product formation, separation, and even reaction control would be highly problematic. As detailed in the preceding paper for oligobrominations, the comparably large increase in strain energy for vicinal disubstitutions does not exert significant steric control.…”

“…[10] In fact, from exploratory experimentation it was learnt that the installation of more than 10-12 chlorine or Abstract: "One-pot" substitution of the twenty hydrogen atoms in pentagonal dodecahedrane (C 20 H 20 ) by OH, F, Cl, and Br atoms is explored. Electrophilic insertion of oxygen atoms with DMDO and TFMDO as oxidizing reagents ended, far off the desired C 20 (OH) 20 , in complex polyol mixtures (up to C 20 H 10 (OH) 10 decols, a trace of C 20 H(OH) 19 ?). Perfluorination was successful in a NaF matrix but (nearly pure) C 20 F 20 could be secured only in very low yield.…”

“…[1] For the replacement of a limited number of tertiary hydrogens in polycyclic (cage) hydrocarbons by OH groups, insertion of oxygen atoms into the CÀH bonds with the use of dimethyldioxirane (DMDO) [16] and the more reactive methyl(trifluoromethyl)dioxirane (TFMDO) [17] are established methods. [18] An analogously patterned "one-pot" transformation of 2 into 3 was tempting yet highly problematic for several reasons: i) The highly strained reagents are thermally labile and are not conducive to forcing reaction conditions, ii) with increasing OH-substitution, the OÀH acidity increases, [19] thus favoring cage-disrupting oxidation processes, iii) the way from C 20 H 20 to C 20 (OH) 20 implies profound solubility changes. Indeed, and not too surprisingly, intensive experimentation fell far from acquiring the target and can be shortly summarized (Scheme 1).…”

“…In sublimates recovered at 200-250 8C, at best traces of 4 were present, possibly due to its thermal decomposition. In the 19 F NMR spectrum, the signal for 4 (d = À163 ppm; CFCl 3 d = 0 ppm; d = À121.9 ppm for C 20 H 19 F [13] ) was accompanied by minor signals between d = À50 to À70 ppm, indicative of CF 3 /CF 2 groups arising from skeletal cleavage. Repeated attempts to purify 4 through crystallization were not successful.…”

“…EI and CI MS spectra differed considerably, in line with the presence of differently polar substances. The highest, very weak signals in the MS spectra (CI) invited an admittedly bold interpretation: m/z 564 corresponds with the C 20 H(OH) 19 [ 21] These signals were no longer observed above 50 % conversion of 2.…”