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Lecture

Polymerization Mechanisms of Thiophene Derivatives

Related concepts (25)

Reaction mechanism

In chemistry, a reaction mechanism is the step by step sequence of elementary reactions by which overall chemical reaction occurs. A chemical mechanism is a theoretical conjecture that tries to describe in detail what takes place at each stage of an overall chemical reaction. The detailed steps of a reaction are not observable in most cases. The conjectured mechanism is chosen because it is thermodynamically feasible and has experimental support in isolated intermediates (see next section) or other quantitative and qualitative characteristics of the reaction.

Cross-coupling reaction

In organic chemistry, a cross-coupling reaction is a reaction where two different fragments are joined. Cross-couplings are a subset of the more general coupling reactions. Often cross-coupling reactions require metal catalysts. One important reaction type is this: (R, R' = organic fragments, usually aryle; M = main group center such as Li or MgX; X = halide) These reactions are used to form carbon–carbon bonds but also carbon-heteroatom bonds. Cross-coupling reaction are a subset of coupling reactions.

Homo rhodesiensis

Homo rhodesiensis is the species name proposed by Arthur Smith Woodward (1921) to classify Kabwe 1 (the "Kabwe skull" or "Broken Hill skull", also "Rhodesian Man"), a Middle Stone Age fossil recovered from Broken Hill mine in Kabwe, Northern Rhodesia (now Zambia). In 2020, the skull was dated to 324,000 to 274,000 years ago. Other similar older specimens also exist. H. rhodesiensis is now widely considered a synonym of H. heidelbergensis. Other designations such as Homo sapiens arcaicus and Homo sapiens rhodesiensis have also been proposed.

Zinc

Zinc is a chemical element with the symbol Zn and atomic number 30. Zinc is a slightly brittle metal at room temperature and has a shiny-greyish appearance when oxidation is removed. It is the first element in group 12 (IIB) of the periodic table. In some respects, zinc is chemically similar to magnesium: both elements exhibit only one normal oxidation state (+2), and the Zn2+ and Mg2+ ions are of similar size. Zinc is the 24th most abundant element in Earth's crust and has five stable isotopes.

Lindemann mechanism

In chemical kinetics, the Lindemann mechanism (also called the Lindemann–Christiansen mechanism or the Lindemann–Hinshelwood mechanism) is a schematic reaction mechanism for unimolecular reactions. Frederick Lindemann and J. A. Christiansen proposed the concept almost simultaneously in 1921, and Cyril Hinshelwood developed it to take into account the energy distributed among vibrational degrees of freedom for some reaction steps. It breaks down an apparently unimolecular reaction into two elementary steps, with a rate constant for each elementary step.