A novel synthesis of branched high-molecular-weight (C40+) long-chain alkanes
2002
Lehmler, H.J. (University of Kentucky, Lexington (USA)) | Bergosh, R.G. | Meier, M.S. | Carlson, R.M.K.
Many biological and geochemical questions remain concerning the structures, functions, and properties of naturally occurring high-molecular-weight (C sub40**+) alkanes with various mid-chain alkylation patterns. Above Csub40, these alkanes are exceedingly difficult to separate and purify, and syntheses can be blocked by the low solubility of intermediates. To overcome these problems, a facile three-step synthesis employing the alkylation of 1,3-dithiane with a suitable alpha, o-dibromoalkane was developed. Bisalkylation of the bis(dithianyl)alkane intermediate with the appropriate 1-bromoalkane and subsequent desulfurization with Raney nickel furnished the desired long-chain alkane. Long-chain alkanes modified at mid-chain and/or symmetrically near the chain termini (or unmodified, i.e., long-chain n-paraffins) are accessible by the selection of appropriate bromoalkanes. Nine mid-chain methylated (C sub38 H sub78 to C sub53 H sub108), one symmetrical terminal-chain dimethylated (C sub40 H sub82), and four linear (C sub44 H sub90 to C sub58 H sub118) long-chain alkanes were synthesized by using this approach. High-temperature gas chromatography (HTGC) was found to have important advantages for evaluating the purity of the synthetic high-molecular-weight alkanes.
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