Chemistry Reference
In-Depth Information
Fig. 1.4
Adamantane,
diamantane, and triamantane;
red
,
black
, and
blue
denote
quaternary
,
tertiary
, and
secondary
carbon atoms
6-membered rings, and coronamantanes when they have dualists with larger rings
that are not peripheries of condensed 6-membered rings. The dualist of a catamantane
mimics the carbon skeleton of a staggered alkane. In turn, [
n
]catamantanes can be
regular when their molecular formula is C
4
n
+
6
H
4
n
+
12
, or irregular when they have
lower numbers of C and H atoms for a given
n
value. Codes of irregular catamantanes
have one or more repeated digits
a
in a code sequence
...abca...
So far, all possible
[
n
]polymantanes with
n<
8 have been theoretically discussed. Some of them, like
[123]tetramantane, are chiral, and exist as two distinct stable stereoisomers (Fig.
1.5
).
The second fortuitous event was the discovery of large amounts of diamondoids in
petroleum condensates that were blocking pipelines for natural gas from Chevron's
offshore platforms in the Gulf of Mexico. Again, the explanation for this phenomenon
involves volatility, paradoxically associated with high melting point and low solu-
bility. Dahl, Carlson and their associates succeeded in perfecting the technology for
isolating and purifying diamondoids taking advantage of their higher thermal stability
and resistance to oxidation in comparison with other petroleum hydrocarbons (Dahl
et al.
2003
). Reactions of diamondoids were studied by Schreiner and coworkers
C
C
C
C
C
C
C
C
C
C
C
C
Fig. 1.5
Isomeric tetramantanes: [121]tetramantane, [123]tetramantane (one of the two enan-
tiomers), and [1(2)1]tetramantane with branched dualist. Dualists are represented by
red
edges
connectiung the centers of adamanane units indicated by letters C
