Appendix 1 Glossary of Chemical Terms This appendix comprises a glossary of selected chemical terms used in this volume. Many of the definitions included in this glossary were derived from the following sources: (1) Tissot and Welte (1979), Petroleum Formation and Occurrence; (2) Daintith (1990), A Concise Dictionary of Chem- istry; (3) Miles (1989), Illustrated Glossary ofPetroleum Geochemistry; and (4) the glossary in Hunt (1996), Petroleum Geochemistry and Geology. Additional definitions can be found in these refer- ences as well as the chapters of this volume. acyclic compounds: Organic molecules with a chain or and oxygen. They are usually soluble in carbon disul- branched structure and no cyclic subunits. · fide. Asphalts contain heavy oils, resins, asphaltenes, addition: A type of polymerization in which many mole- and high-molecular-weight waxes. cules of a monomer are simply added together. asphaltenes: Asphaltic constituents of crude oil that are sol- alcohols: Alcohols are aliphatic compounds with the gen- uble in carbon disulfide but insoluble in petroleum eral formula ROH, where R is any alkyl or substituted ether or n-pentane. Asphaltenes are agglomerations of alkyl group and OH is an hydroxyl group. molecules with condensed aromatic and naphthenic alginite: See liptinite (see Table 1 in Leventhal and Gior- rings connected by paraffin chains. They have molecular dano, 2000). weights in the thousands. aliphatic compounds: See saturated compounds. asphaltite: Black to dark brown, comparatively hard, solid alkane: Hydrocarbon containing no double or triple bitumens that soften at temperatures above 100°C and bonds, composed only of hydrogen and carbon, and are usually soluble in carbon disulfide. Examples are usually having the formula CnH2n+ 2 (for acyclic struc- gilsonite, glance pitch, and grahamite. tures) or CnH2n (for cyclic structures). biomarker (geochemical fossil or molecular marker): Or- alkyl group: Saturated hydrocarbon group with one less hy- ganic compound whose carbon structure, or skeleton, is drogen than the parent alkane and having the general formed by living organisms and is sufficiently stable to formula CnH2n+l; sometimes denoted by the symbol R be recognized in crude oil or in the organic matter of (e.g., -CH3, methyl group; -C2H 5, ethyl group; etc.). ancient sediments. Typical biomarkers are the por- amphipathic: A term used to define a molecule with a phyrins, pristane, phytane, steranes, carotanes, and pen- polar head and a nonpolar tail. tacyclic triterpanes. API gravity: The density of oil measured with a hydrometer biopolymer: Polymer synthesized in a living organism. having a scale developed by the American Petroleum In- bitumen: Sedimentary liquid or solid substances of variable stitute and given in units of oAPI (degrees API): oo API color, hardness, and volatility, composed principally of gravity= 1.076 g/cm3, 20° API gravity= 0.9340 g/cm3, the elements carbon and hydrogen and soluble in or- 50° API gravity= 0.7796 g/cm3. oAPI is related to the ganic solvents and carbon disulfide. It is derived from density or specific gravity (S.G.) of oil at 60°F by the fol- kerogen during catagenesis and includes crude oil. lowing formula: oAPI = (141.5/S.G. at 60°F)-131.5. branched-alkane: An acyclic alkaQe molecule that has one arenes: Hydrocarbons that contain both aliphatic and aro- or more alkyl groups bonded to a hydrocarbon chain matic units. with three or more other carbon atoms (e.g., iso- aromatic compounds: A general term for compounds con- prenoids). taining one or more benzene or substituted benzene BSR: Bacterial sulfate reduction. Bacteria use sulfate and rings and compounds that resemble benzene in chemi- organic matter to form hydrogen sulfide and carbon cal behavior (see Part 5 in Appendix 2 of this volume). dioxide. aromatic hydrocarbons: Cyclic or polycyclic aromatic com- carbonaceous: Organic-rich, or containing organic matter. pounds consisting of only carbon and hydrogen. Exam- carboxylic acid: A class of compounds which contain the ples include benzene, naphthalene, etc. (see Part 5 in carboxyl group (-COOH) attached to aliphatic (alkyl) Appendix 2 of this volume). or aromatic (aryl) hydrocarbon groups (see Part 1 in aryl group: The aryl group signified by the symbol Ar com- Appendix 2 of this volume). prises the aromatic compounds phenyl and substituted catagenesis: The principal hydrocarbon generation stage of phenyls as well as polynuclear aromatic compounds. organic matter maturation in sedimentary basins and cor- asphalt: Black to dark brown solid or semisolid bitumens responding to temperatures between 50° and 150oC and that gradually liquefy when heated. They are composed pressures from 300 to 1,500 bars. Kerogen evolves during principally of the elements carbon and hydrogen but this stage to produce the first liquid petroleum. Both liq- also contain appreciable quantities of nitrogen, sulfur, uid oil and condensates are accompanied by significant 315 Downloaded from http://pubs.geoscienceworld.org/books/book/chapter-pdf/3807892/9781629490168_backmatter.pdf by guest on 29 September 2021 316 APPENDIX.l amounts of methane. The end of catagenesis is reached in hard base: An electron donor atom of low polarizability the range where the disappearance of aliphatic carbon and high electronegativity. Hard bases are usually small chains in kerogen is complete. The equivalent vitrinite re- and highly charged and tend to bond ionically. flectance range would be 0.5 to 2.0 percent. HC: Refers to (1) Hydrogen, carbon or (2) hydrocarbon. CHO: Carbon, hydrogen, oxygen. heteroatoms: Atoms in organic compounds other than car- complex ion: See metal complex. bon and hydrogen; for example, nitrogen, oxygen, and condensation: A type of polymerization in which monomer sulfur. molecules combine by the loss of some simple mole- heterocompounds: Organic compounds that contain a het- cules, usually water. eroatom such as nitrogen, oxygen, or sulfur. CPI: Carbon preference index. The ratio of odd to even heterocyclic compounds: Cyclic compounds in which one normal alkanes in a specific molecular weight range or more of the carbon atoms in the ring is replaced by (usually c25 to c34) . an atom of another element such as nitrogen, oxygen, CSIA: Compound specific isotope analysis. or sulfur. cyclic compounds: Organic compounds with ring structures. HI: See hydrogen index. dalton: Measure of atomic mass of molecules in terms of homologous series: Compounds (homologs) having similar atomic mass units (i.e., molecular weight). structure but differing in the addition or subtraction of dealkylation: The loss of an alkyl group from an organic aCH2 group. compound. HPLC: High-performance liquid chromatography. decarboxylation: The loss of a carboxyl group from an or- HRMS: High-resolution mass spectrometry. ganic compound, for example, the conversion of alkyl humic acid: See humic substances. acids to alkanes. humic (type) organic matter: A general term, not to be con- dehydration: The loss of H20 from an organic compound. fused with humic substances or materials. It is the decom- DOC: Dissolved organic carbon. position and polymerization product of the lignin, tan- DOP: Degree of pyritization (see Leventhal and Giordano, nins, and cellulose of plant-cell and -wall material, plus 2000). carbonized organic matter deposited in swamps and soils EPR: Electron paramagnetic resonance spectroscopy. under aerobic conditions with lower than normal oxygen equilibrium state: A state of thermodynamic equilibrium at- content. Kerogen types III and N are humic in nature. tained for a system or chemical species if its properties humic substances (humic material): Humic substances are do not change with time and if it returns to that state geopolymers formed in soil and sediment. They are after having one or more of its properties slightly amorphous, brown or black colored, acidic, and poly- changed and then change back spontaneously. disperse (i.e., consisting of a number of ill-defined com- ESR: Electron spin resonance spectroscopy. pounds), with molecular weights in the range of several EXAFS: Extended X-ray absorption fine structure. hundreds to tens of thousands. Humic substances gen- extract: Oil or oil-like products which are removed from erally contain subequal portions of C, H, and 0. They rock samples by using organic solvents. are generally divided into three fractions: ( 1) humic fatty acids: Aliphatic carboxylic acids (alkanoic acid). acid (HA), which is soluble in dilute alkaline solutions free radical: An atom or molecule possessing an odd ( un- but precipitates upon acidification; (2) fulvic acid (FA), paired) electron. which is soluble in alkaline solutions and remains solu- fulvic acid: See humic substances. ble in acid; and (3) humin, which is insoluble in acid functional group: Group of two or more atoms that has a and base. Typically, fulvic acids have molecular weights specific structure and characteristic chemical proper- less than 5,000 while humic acids have molecular ties, e.g., hydroxyl, -OH-; carboxyl, -COOH; amino, weights greater thari 5,000. -NHx; methyl, -CH3; sulfhydryl, -SH. humin: See humic substances. GC: Gas chromatography. hump: See UCM. GC-MS: Gas chromatography-mass spectrometry. hydrocarbon: A compound composed of only the elements geochemical fossil: See biomarker. hydrogen and carbon. Bituminous material such as pe- geopolymer: Polymer or macromolecule synthesized in soil troleum is composed principally, but not exclusively, of and sediments (e.g., humic substances).