Synthetic approaches to large diamondoid hydrocarbons

Isolation and Structural Proof of the Large Diamond Molecule, Cyclohexamantane (C26H30)

“…[22] The 1 H-decoupled 13 C NMR spectrum of cyclohexamantane ( Figure 5 a) shows three of the expected four signals with the signal for the two equivalent quaternary carbon atoms (atoms 11 and 12; Figure 5 This corresponds with the value of d = 38.6 ppm reported for the structurally related triamantane. [23] Similarly, the CH resonance at d = 37.8 ppm can be assigned to the twelve equivalent CH carbon atoms (atoms 1, 3,5,7,9,14,16,18,20,22,24, and 25; Figure 5 c) and that at d = 47.3 ppm to the six equivalent CH carbon atoms (atoms 2, 6, 10, 13, 17, 21; Figure 5 c) on the basis of the similarities in chemical environment with carbon atom 2 (d = 46.9 ppm) and atom 3 (d = 38.1 ppm) in triamantane. [23] The 1 H NMR spectrum ( Figure 5 c) is characterized by three second-order multiplets (indicating the presence of long-range couplings), which could be assigned on the basis of integration and homonuclear decoupling experiments.…”

“…Only one of the tetramantanes (anti-tetramantane) has been prepared by an elegant, complex, but low-yielding alternative synthetic pathway devised by McKervey's research group. [9] Diamondoids occur naturally in virtually all petroleum. [10] In most crude oils, diamondoid concentrations are in the order of 1-100 ppm, and occur predominantly as substituted and unsubstituted adamantanes and diamantanes.…”

“…Spectra were recorded using C 6 D 6 as solvent. In the 1 H NMR spectrum, "X" corresponds to impurities; the approved IUPAC numbering for cyclohexamantane is shown, namely, dodecacyclo-[12.12.0 2,11 .0 3,16 .0 5,18 .0 6,11 .0 7,20 .0 9,22 .0 10,25 …”

Confined adamantane molecules assembled to one dimension in carbon nanotubes

“…Diamondoids are well known for their outstanding thermal stability, light weight, and rigidity [1][2][3]. Few experimental studies have been reported on the diamondoids due to the difficulty to synthesize them [4]. Recently 11 different diamondoids could however be extracted from sludge formed in oil industry [1].…”

Reaction yields of diamondoid synthesis by plasmas generated in supercritical xenon

“…Many attempts have been undertaken to obtain diamondoids synthetically, but with the exception of triamantane [13] and anti-tetramantane [14], no other diamondoids have been obtained by conventional organic synthesis. The reason is that with increasing diamondoid size, the number of possible reaction pathways and reaction intermediates increases exponentially [15], making such approaches impractical or even impossible. Therefore, other, alternative methods are needed to synthesize diamondoids.…”