25th International Meeting on Organic Geochemistry IMOG 2011

P-075
Bicadinanes extend to C39 in oils from Southeast Asia
Hans Peter Nytoft 1 , Geir Kildahl-Andersen 2 , Jon Eigill Johansen 3 , Håkon Midtaune 3 ,
Herbert Volk 4
1 Geological Survey of Denmark and Greenland (GEUS), Copenhagen, Denmark, 2 Department of Chemistry,
University of Oslo, Oslo, Norway, 3 Chiron AS, Trondheim, Norway, 4 CSIRO Petroleum, North Ryde,
Australia (corresponding author:hpn@geus.dk)
Bicadinanes are pentacyclic C30H52 hydrocarbons
derived from thermal breakdown products of
polycadinene, a polymer present in dammar resins
(van Aarssen 1992a,b). Bicadinanes are abundant in
Tertiary oils from Southeast Asia but low
concentrations can be found in Tertiary oils from other
parts of the world (Nytoft et al., 2010). Oils with
bicadinanes also contain C31 bicadinanes.
Bicadinanes up to C35 have been noted (van Aarssen,
personal communication). In this study we show that
bicadinanes extend to C39 but not any further. A
biodegraded Malaysian oil had a particularly high
content of bicadinanes. Analysis in MRM mode using
the m/z 412 → 369 and 426 → 383 transitions etc.
showed one dominating isomer in all cases (Fig. 1).
The C38 and C39 compounds appeared as partly
resolved doublets. Clean EI mass spectra and MS-
MS daughter spectra were obtained of the whole
series from HPLC purified fractions. EI and M+ .
daughter spectra of all major compounds indicated a
trans-trans-trans-bicadinane structure like bicadinane
T. Most of the late eluting bicadinanes had similar
spectra and could have structures similar to the C30
bicadinanes T1 and R, whereas the major early
eluting bicadinanes (e.g. 33W) appear to have a ciscis-trans
structure like bicadinane W. Compounds
having EI mass spectra with an intense m/z 411
fragment but almost no molecular ion were also
observed from C33 and up. The MS-MS daughter
spectrum of such a C33 compound (33*) is shown in
Fig. 2. Its response using the m/z 454 → 411
transition is lower than that of isomeric C33
bicadinanes. These mass spectral features suggest
the loss of a C3 side-chain from a quaternary carbon
atom. The structure of the higher bicadinanes may be
a bicadinane moiety and a partly degraded cadinane
moiety linked by one carbon-carbon bond. The
relative abundance of the major C30-C39 bicadinanes
(―T-series‖) in the Malaysian oil was 100; 20; 1.0; 2.5;
0.5; 0.5; 0.1; 0.04; 0.4; 0.08 respectively. Oils from
Assam, India and the Kutei Basin, Indonesia showed
similar distributions of C30-C39 bicadinanes.
W
T
T1 R
33W
33T
33*
3.6
454 411
42 44 46 48
Retention time (min)
Fig. 1. C30 and C33 bicadinanes in a Malaysian oil
33W
151
233
383411
343
439
454
100 200 300 400 500
W
191
301
273
33*
397
341
369
412
100 200 300 400 500
315 355
33T
151
205
259
315
355
100
412 369
411
439
454
100 200 300 400 500
T
411
151
454
100 200 300 400 500
205
313
273
369
397
412
100 200 300 400 500
Fig. 2. MS-MS daughter spectra of C30 and C33
bicadinanes in a Malaysian oil
References
[1] Van Aarssen et al., 1992a. Organic Geochemistry
18, 805-812.
[2] Van Aarssen et al., 1992b. Geochimica et
Cosmochimica Acta 56, 1231-1246.
[3] Nytoft et al., 2010. Organic Geochemistry 41,
1104-1118
219