Synthesis of [1‐¹³C]‐para‐xylene and [2‐¹³C]‐para‐xylene

Abstract

SummaryAn efficient synthesis of [1-13 C]-para-xylene (1a) and [2-13 C]-para-xylene (1b) is described. Dehydration of these alcohols followed by dehydrogenation of the intermediate dimethylcyclohexenes furnished the title compounds in 32 and 40% overall yield, respectively.

From Fragmentation to Construction—from Void to Massive: Fascination with Organic Mass Spectrometry and the Synthesis of Novel Three‐Dimensional Polycyclic Aromatic Hydrocarbons

“…The trick to generate arenium ions by EI‐induced dissociation of dihydrobenzoic acids, or the corresponding esters, was particularly fruitful. We ourselves applied it also to simpler cases such as, for example, toluenium and xylenium ions,[33–35] to gain a deeper insight into the complex skeletal isomerization processes preceding the loss of H 2 , CH 4 , and C 2 H 4 from such apparently simple species. This also led us to the determination of intrinsic gas‐phase properties of neutral molecules, such as the proton affinities and gas‐phase basicities (GB) of cycloheptatrienes [36,37].…”

Intermediates in the Methanol-to-hydrocarbons (MTH) Reaction: A Gas Phase Study of the Unimolecular Reactivity of Multiply Methylated Benzenium Cations

“…A number of reports on the gas-phase reactivity of protonated methylbenzenes already exist and have been reviewed [25][26][27][28]. Of particular relevance to the present study are those on metastable toluenium ions [29] and, more recently, para-xylenium [30,31] ions and protonated cycloheptatrienes [32], carried out besides those on various methyl-substituted a, x-diphenylalkanes [33]. Also, Arstad et al recently published a detailed theoretical study on xylenium ions [34].…”

Toluenium and Other Gaseous Methylbenzenium Ions: Complex Interplay of Protonated Arenes and Cyclo‐olefins

“…Our own work on the composite scrambling of gaseous xylenium ions, [15+H] + , published in 2002, had also revealed this trend but, on the whole, confirmed the various isomerization channels found for toluenium ions. Nevertheless, extended isotope labeling, including the synthesis of four site-specifically 13 C-labeled precursors, the methyl esters, 18a and 18b, and the two deuterium-labeled para-xylenes, 15c and 15d, as well as the synthesis of the deuterium-labeled acids 19a and 19b was necessary to understand the rather complex reactions preceding the elimination dihydrogen, methane, and ethene from these C 8 H 11 + ions (Scheme 8) (Mormann & Kuck, 2002a, 2002b. The MIKE spectra of the [M-COOH] + ions of the latter two precursors, 1-trideuteromethyl-4-methyl-1,4-dihydrobenzoic acid, 19a, and its 1-methyl-4-trideuteromethyl regioisomer, 19b, are reproduced in Figure 6 (Mormann & Kuck, 2002a).…”