Examples of transition state in the following topics:
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- In a given chemical reaction, the hypothetical space that occurs between the reactants and the products is known as the transition state.
- Transition state theory (TST) describes a hypothetical "transition state" that occurs in the space between the reactants and the products in a chemical reaction.
- The species that is formed during the transition state is known as the activated complex.
- According to transition state theory, between the state in which molecules exist as reactants and the state in which they exist as products, there is an intermediate state known as the transition state.
- The species that forms during the transition state is a higher-energy species known as the activated complex.
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- A mechanism in which two reacting species combine in the transition state of the rate-determining step is called bimolecular.
- If a single species makes up the transition state, the reaction would be called unimolecular.
- The relatively improbable case of three independent species coming together in the transition state would be called termolecular.
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- A cyclic transition state for this rearranged addition is displayed in the second diagram below.
- Two such transition states are drawn in the orange box, the E-reagent state leading to the anti-diastereomer and the Z-reagent state to the syn-isomer.
- An alternative Z-transition state, B would form the syn-isomer.
- Fortuitously, the favored transition state for the E-reagent has a Felkin-Ahn configuration, but the Z-transition state does not.
- Newman projection views of the same transition states are drawn in the orange box.
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- These can most easily occur when the metal is in a high oxidation state.
- In each case the metals (Cr and Mn) have oxidation states of +6 or higher.
- A metal-to ligand charge transfer (MLCT) transition will be most likely when the metal is in a low oxidation state and the ligand is easily reduced.
- The extent of the splitting depends on the particular metal, its oxidation state, and the nature of the ligands.
- In octahedral complexes with between four and seven d electrons, both high spin and low spin states are possible.
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- The d-block elements are commonly known as transition metals or transition elements.
- The formation of compounds in many oxidation states due to the relatively low reactivity of unpaired d electrons.
- These can most easily occur when the metal is in a high oxidation state.
- A metal-to-ligand charge transfer (MLCT) transition will be most likely when the metal is in a low oxidation state and the ligand is an easily reduced d-d transition.
- This activity is attributed to their ability to adopt multiple oxidation states and to form complexes.
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- The Franck-Condon principle requires that excitation occur by a vertical transition, shown by the red line, resulting in the population of higher vibrational levels in the excited state.
- If a higher vibrational level of the excited state is populated, either by the initial Franck-Condon transition or by collisional activation, the molecule may cleave into two X• atoms.
- Nevertheless, Franck-Condon transitions are expected.
- Transitions between electronic states often occur to higher vibrational levels which then relax to lower levels by collisional loss of heat (translational energy).
- The approximate timescales for these transitions are given in the following table.
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- Transition metals typically form several oxidation states and therefore have several oxidation numbers.
- Transition metals are the elements in Groups 3 to 12 representing the d block of the periodic table.
- Unfortunately, there is no simple rule to determining oxidation state possibilities among the transition metals, so it is best simply to memorize the common states of each element.
- The maximum oxidation number in the first row of transition metals is equal to the number of valence electrons from scandium (+3) up to manganese (+7).
- Calculate the oxidation state of a metal in a coordination compound.
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- Sublimation is the phase transition from the solid to the gaseous phase, without passing through an intermediate liquid phase.
- It is an endothermic phase transition that occurs at temperatures and pressures below a substance's triple point (the temperature and pressure at which all three phases coexist) in its phase diagram.
- At a given temperature, most chemical compounds and elements can possess one of the three different states of matter at different pressures.
- In these cases, the transition from the solid to the gaseous state requires an intermediate liquid state.
- But at temperatures below that of the triple point, a decrease in pressure will result in a phase transition directly from the solid to the gaseous.
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- Most transitions that are related to colored metal complexes are either d–d transitions or charge band transfer.
- The Laporte rule states that, if a molecule is centrosymmetric, transitions within a given set of p or d orbitals are forbidden.
- Therefore, transitions are not pure d-d transitions.
- These are most likely to occur when the metal is in a low oxidation state and the ligand is easily reduced.
- These can most easily occur when the metal is in a high oxidation state.
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- It is useful to use the stable eighteen-electron valence shell of the noble gas element that closes each transition element period as a reference when discussing the chemistry of transition metal complexes.
- In their higher oxidation states (usually I, II or III) these metals have proportionately fewer valence electrons.
- When discussing the chemistry of transition metal complexes, it is customary to determine the oxidation state of the metal and the number of valence shell electrons achieved by the covalent and coordinate bonding.
- Because two new metal centered covalent bonds are created, the oxidation state of the metal increases by + 2.
- The oxidation state of the metal remains unchanged throughout the process.