Isoprenoid Hydrocarbons in Petroleum Isolation of 2,6,10,14-Tetra methylpentadeca ne by High Temperature Gas-Liquid Chromatography J. G. BENDORAITIS, 6. L. BROWN, and
L. S.
HEPNER
Research Department, Socony Mobil Oil Co., Inc., Paulsboro, N. 1.
b
A
saturated isoprenoid residue, tetramethylpentadecane (pristane), was isolated from petroleum b y high temperature gas-liquid chromatography and identified by mass, infrared, and proton magnetic resonance spectroscopy. On a total crude basis, this hydrocarbon represents 0.5% of the East Texas and 0.2y0 of the Mid-Continent crudes from which it was isolated. The occurrence of pristane at an abnormally high concentration level in petroleum corroborates current theories regarding the origin of petroleum from natural source material. The most likely precursor of pristane i s the phytol component of chlorophyll.
2,6,10,14
-
T
fact that isoprenoids are a fundamental group of compounds synthesized by nature has caused much speculation on their possible role in the hypothesized transformation of natural source material into petroleum. It has been pointed out (d,S, 7 ) that many isoprenoids-e.g., carotenes-undergo low temperature reactions to produce naphthenic and aromatic hydrocarbons such as those found in petroleum. Curphey (I) has postulated similar geosynthetic reactions involving the diterpenic alcohol, phytol, derived from the chlorophylls. The predominance in petroleum of methyl-branched alkanes along with HE
was initially selected for this study on the basis of its anomalous properties, in contrast to those of adjacent fractions of a series. This fraction (nominally labeled Cis) had an unusually low density and refractive index and a high isoparaffin content, as shown in Table I. The marked discontinuity in the density and refractive index curves is shown in Figure 1. In addition, a prominent m/e 183 alkane fragment peak occurred in its mass spectrum. ,411 of these factors suggested the presence of a branched alkane in high concentration. In view of the unexpected nature of the East Texas Ci7 distillation cut, a similar nonaromatic 295' to 310' C./760 mm. fraction from a Mid-Continent straight-run gas oil was also examined by mass spectrometry. The mass spectrum of this fraction, likewise, revealed
evidence for the presence of tetracyclic naphthenes (steranes) which are biochemically related to isoprenoids, has also been cited by RIeinschein (8) as an indication that isoprenoid substrates may have been a significant source material in the formation of petroleum. In so far as could be determined, there has been no report of the isolation or identification in petroleum of a specific hydrocarbon retaining sufficient structural detail to permit classification as an isoprenoid. This paper describes the isolation of one such hydrocarbon2,6,10,14-tetramethylpentadecane. EXPERIMENTAL
Isolation of 2,6,10,14-Tetramethylpentadecane. A nonaromatic 294' t o
309' C . j i 6 0 mm. distillate fraction of an East Texas straight-run gas oil
i.8100
350'
I4550
18200
Rn x
I
Table 1. Properties of C17 Nonaromatic Distillate Fractions from East Texas and Mid-Continent Gas Oils
East Texas
iB u
g
I.4500
2
5
1.8100
250
LL
e
m
MidContinent
Boiling rang: at 294309" 295-3100 760 mm. C. Total gas oil, vol. % 11.6 11.8 Total crude, vol. % 3.6 2.4 Specific gravity (20O /.4) 0.8073 0.8145 Refractive index, no: 1.44795 1.45098 Isoparaffi content by mass spec39.8 trometry, vol. yo 39.2 Converted from 20 mm.
1.4150
).800b
,
I50
0
IO
20
10
40
50
MI
70
00
90
1.4400
0.7900 I
VOL. 91: TAKEN OVERHEAD
(1
Figure 1.
Properties of East Texas nonaromatic distillate fractions VOL. 34, NO. 1, JANUARY 1962
49
1
He: 125 mlJmin. Temp: 2 1 0 ° C .
FRACTION
l
A
I
“I7
62
48
80
TIME MINUTES
-
IO0
I20
(01 EAST TEXAS DISTILLATE FRACTION 1211.309 Q ON CARBOWAX 20M
I
I FQACT13Ni
40
n-C,,
100
83
60
120
TIME MIVUTEI(b)
MID CONTINENT DISTILLATE FRACTIOY ‘295 110
