Crocetane

Crocetane

Names
IUPAC name 2,6,11,15-Tetramethylhexadecane[1]
Identifiers
CAS Number	504-44-9
3D model (Jmol)	Interactive image
ChemSpider	120105
EC Number	211-332-2
PubChem	136331
InChI InChI=1S/C20H42/c1-17(2)11-9-15-19(5)13-7-8-14-20(6)16-10-12-18(3)4/h17-20H,7-16H2,1-6H3 Key: KKFZXXATNGJPJS-UHFFFAOYSA-N
SMILES CC(C)CCCC(C)CCCCC(C)CCCC(C)C
Properties
Chemical formula	C20H42
Molar mass	282.56 g·mol^−1
Related compounds
Related alkanes	Phytane
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Crocetane, or 2,6,11,15-tetramethylhexadecane, is an isoprenoid hydrocarbon compound. Unlike its isomer phytane, crocetane has a tail-to-tail linked carbon skeleton. Crocetane has been detected in modern sediments and geological records as a biomarker, often associated with anaerobic methane oxidation.

Research

Crocetane was first studied^[2] in the late 1920s and early 1930s for the structural identification of crocetin, which is its polyunsaturated diacid analogue. The infrared spectrum was reported in 1950,^[3] the mass spectrum was described in 1968^[4] and the ¹H and ¹³C NMR spectra was obtained in 1990s.^[2]

In 1994, Liangqiao Bian^[5] first reported strong ¹³C depletion in crocetane from anoxic sediments in the Kattegat. Such low ¹³C content is thought to originate from microbes harvesting biogenic methane, which is always ¹³C depleted,^[6] as a carbon source. Years later several groups^[7][8][9] made similar observations in either modern or ancient sediments near methane seeps. Crocetane was found in environments with anaerobic methane oxidizing consortium, comprised of methanotrophic archea and sulfate-reducing bacteria. These work makes crocetane the first biomarker^[10] of anaerobic methanotrophy.

In 2009, Erchin Maslen and his colleagues detected crocetane in highly-mature Devonian sediments and crude oils of the Western Canada Sedimentary Basin.^[11] They propose that natural product precursor for this crocetane is green sulfur bacteria derived isorenieratene and palaerernieratene, which means that crocetane can also be related to photic zone euxinia in highly matured samples.

References

1. "Hexadecane, 2,6,11,15-tetramethyl-". webbook.nist.gov.
2. Robson, J. N.; Rowland, S. J. (1993-09-01). "Synthesis, chromatographic and spectral characterisation of 2,6,11,15-tetramethylhexadecane (crocetane) and 2,6,9,13-tetramethyltetradecane: reference acyclic isoprenoids for geochemical studies". Organic Geochemistry. 20 (7): 1093–1098. doi:10.1016/0146-6380(93)90117-T.
3. Pliva, Josef; Sorensen, Andreas (1950). "Studies Related to Pristane: IV. InfraRed Spectra" (PDF). ACTA CHEMICA SCANDINAVICA. 4: 846–849.
4. McCarthy, E. D.; Han, Jerry; Calvin, Melvin (1968-08-01). "Hydrogen atom transfer in mass spectrometric fragmentation patterns of saturated aliphatic hydrocarbons". Analytical Chemistry. 40 (10): 1475–1480. doi:10.1021/ac60266a021. ISSN 0003-2700.
5. Bian, Liangqiao (1994). "Isotopic biogeochemistry of individual compounds in a modern coastal marine sediment (Kattegat, Denmark and Sweden).". M.Sc. thesis. Dept. of Geological Sciences, Univ. Indiana.
6. Whiticar, Michael J. (1999-09-30). "Carbon and hydrogen isotope systematics of bacterial formation and oxidation of methane". Chemical Geology. 161 (1–3): 291–314. doi:10.1016/S0009-2541(99)00092-3.
7. Thiel, Volker; Peckmann, Jörn; Seifert, Richard; Wehrung, Patrick; Reitner, Joachim; Michaelis, Walter (1999-12-01). "Highly isotopically depleted isoprenoids: molecular markers for ancient methane venting". Geochimica et Cosmochimica Acta. 63 (23–24): 3959–3966. doi:10.1016/S0016-7037(99)00177-5.
8. Hinrichs, Kai-Uwe; Summons, Roger E; Orphan, Victoria; Sylva, Sean P; Hayes, John M (2000-12-01). "Molecular and isotopic analysis of anaerobic methane-oxidizing communities in marine sediments". Organic Geochemistry. 31 (12): 1685–1701. doi:10.1016/S0146-6380(00)00106-6.
9. Elvert, Marcus; Suess, Erwin; Whiticar, Michael J. "Anaerobic methane oxidation associated with marine gas hydrates: superlight C-isotopes from saturated and unsaturated C20 and C25 irregular isoprenoids". Naturwissenschaften. 86 (6): 295–300. doi:10.1007/s001140050619. ISSN 0028-1042.
10. Hinrichs, K.-U.; Boetius, A. (2002-01-01). Wefer, Professor Dr Gerold; Billett, Dr David; Hebbeln, Dr Dierk; Jørgensen, Professor Dr Bo Barker; Schlüter, Professor Dr Michael; Weering, Dr Tjeerd C. E. van, eds. Ocean Margin Systems. Springer Berlin Heidelberg. pp. 457–477. doi:10.1007/978-3-662-05127-6_28. ISBN 9783642078729.
11. Maslen, Ercin; Grice, Kliti; Gale, Julian D.; Hallmann, Christian; Horsfield, Brian (2009-01-01). "Crocetane: A potential marker of photic zone euxinia in thermally mature sediments and crude oils of Devonian age". Organic Geochemistry. 40 (1): 1–11. doi:10.1016/j.orggeochem.2008.10.005.