Lecture 7
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Lecture 7 - Marcador
Lecture 7 - Detalles
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36 preguntas
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| What are the six types of diagenetic reactions? | 1. Oxidation/mineralisation 2. Sulphurisation 3. Aromatisation 4. Defunctionalisation 5. Isomerisation 6. Catagenesis (e.g. C-C bond cleavage) |
| Diagenesis can alter ... and ... of biomarker lipids in different ways depending on the structure of the original biomarker lipids | Abundances & structure |
| The concentrations of “marine” biomarkers in the oxidized S1sapropel are significantly .... | Decreased |
| The concentrations of “terrestrial” n-alkanes in the oxidized S1sapropel are .... compared to marine bimarkers | Decreased much less than |
| Post depositional oxidation = | As oxygen came back the upper part of the sapropel + biomarkers was burned away (this is why the decrease is super sharp) |
| Post depositional oxidation may be recognized when comparing Corg to ... | Ba/Al -> shows old (not burned away) sapropel |
| What happened to this biomarker and what can the ratio between the two signify? What is it and who makes these? | Poster-depositional oxidation & shows a spike at the oxidation front. they are longchail diols made by algae. |
| The position of the sulphur indicated? | Position of past functional groups |
| Sulphurisation takes mainly place ... | In the sediments (not watercolumn) as it is a relatively slow process (100-1000 years) -> dependent on structure of organic component however |
| Intramolecular S incorporation can result in the formation of... | Low molecular weight molecules |
| Intermolecular s incorporation can result in the formation of ... | High molecular weight molecules (polymerisation) |
| Labrotary desulphurisation is needed because ... | Sulphurisation lead to the lss of many biomarkers from our common analytical window |
| Sulphurisation results in archiving “labile” functional group information by the ... | Position of sulphur incorporation. |
| During late diagenesis/early catagenesis labile S-C bonds are preferentially broken resulting in release of biomarkers from HMW substances... | This process results in loss of information since functional group information is lost. |
| Aromatization is the process of converting a chains & nonaromatic rings into .... and is catalysed by aromatase, a P450 enzyme. | An aromatic rings |
| Aromatization happens relatively fast, especially if .... are already present. Aromatization towards thermodynamically stable products. | Rings and double bonds |
| Aromatization leads to the..... However, basic features of carbon skeletons can still be recognized and related to original biomarker lipids | Loss of functional groups, addition of rings and ring cleavage |
| Wha tis a PAH and what diagentic reaction can make them | Polycyclic aromatic hydrocarbons - aromatisationS |
| Anthropogenic sources of PAH? | Mainly produced by combustion processes, dominated by parent (non-substituted) PAHs |
| Natura sources of PAHs? | Forest and prairie fires, natural seepage of petroleum & diagenesis of natural products |
| What is this molecule called and what is its precursor? | Perylene -> quinone pigments in fungi and insects |
| What happened to these molecules and what might be their origin? | Aromatisation - abietc acid (gymnosperms) -> diterpenoid precursor |
| What happened to these molecules and what might be their origin? | Aromatisation- b-amyrin (angiosperms) ((pentacyclic) triterpenoid) |
| What does this figure show? | Cyclisation and aromatisation of isorenieratene |
| This was likely a? | Bacteriohopanetetrol |
| Defunctionalisation is the .... | Loss of functional groups |
| What are the four typical defunctionalisation reactions? | 1. Dehydration (removal of hydroxy groups -OH) 2. Reduction of double bonds (removal of double bonds) – form saturated equivalent, could also aromatize instead though – both take place! 3. Decarboxylation (removal of acid groups -COOH) 4. Reduction of keto groups R-C(=O)-R |
| Isomerisation = | Change of original stereochemistry into its isomer -> can be used to determine maturity of sample/oil as heat and pressure will result in more of the diagenetic isomer (vs natural isomer) |
| Catagenesis = | Breaking of bonds |
| Catagenesis of c-C bonds | May result in product(s) that can still be used as biomarkers |
| Catagenesis often results in | Substatial loss of information |
| What happned to this molecule and what is its precursor | Catagenesis & isorenieratene |