Structural isomerism, also known as structural isomerism, refers to the fact that compounds have different atomic connection ordersIsomerismPhenomenon, andStereoisomerismrelative.Compounds with structural isomerism are mutually symmetricIsomer,They can be divided into chain isomerism, position isomerism andfunctional group isomerism Three types.
Chain isomerism usually refers to carbon chain isomerism, which refers to the different connection modes of atomic skeletons in compound molecules. It is generally used to describe hydrocarbons.It can be regarded as the isomerization between linear and branched chain compounds with the same molecular formula.
Take pentane for example, it has three isomers: common names are "n-pentane", "isopentane" and "neopentane".The latter two are obtained by treating some carbon atoms of the first type as branch chains, as shown in Figure 1:
Figure 1 Example of chain isomerism
Heterogeneous location
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The substituents or functional groups (including carbon carbon double bonds and triple bonds) with the same composition have different positions on the carbon frame (carbon chain or carbon ring). These compounds are called positional isomers.This phenomenon is called position isomerism.
Positional isomerism only refers to the position of substituents or functional groups, usually for compounds with the same carbon frame structure.When deriving the isomer of an organic substance, the carbon frame isomer can be derived first, and then the possible positional isomer can be derived according to various carbon frame isomers.[1]
1. Functional group isomerization involves the combination mode of carbon atoms in the molecule (single bond, double bond or triple bond), the basic structure of the carbon frame (chaining or looping), and the position of other atoms in or on the carbon chain.
2. Common functional group isomers include alkenes and cycloalkanes, alkynes and dienes, alcohols and ethers, aldehydes and ketones, carboxylic acids and esters, amino acids and nitro compounds, phenols and aromatic alcohols.
3. Functional group isomerism is very different from carbon frame isomerism and position isomerism, and there are often essential differences in chemical properties between functional group isomers.
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Coordination Chemistry:Structural isomers refer to different atom atom bonding orders, that is, different molecular topologies.Therefore, structural isomers always have different chemical and physical properties.Coordination compoundThe structural isomerism phenomena of CdTe include: bonding, hydration, coordination and ionization isomerism.[2]
1. Bonded isomerism
[Co(CN)sixHCS]3-CyanothioCoordination compoundThe N - and S-bonds of provide examples of bonds and isomerism, as shown in Figure 2:
Fig. 2 Bonding isomerism
2. Hydroisomerism
The classic example isChromium trichlorideHydrate, the empirical formula is CrCl3·6HtwoO。The green form of the compound is: [Cr (HtwoO)fourCltwo]Cl·2HtwoO。However, when this compound is dissolved in water, it will cause chloride ions closely bound to metals to be replaced by water molecules one by one. After replacement, the blue-green isomer [Cr (HtwoO)fiveCl]Cltwo·HtwoO，Followed by purple isomer [Cr (HtwoO)]Clthree。
3. Coordination isomerism
Examples are [Co (NHthree)six][Cr(CN)six]And [Cr (NHthree)six][Co(CN)six]。In the first isomer, the ammonia ligand coordinates with the cobalt atom, while in the second isomer, it coordinates with the chromium atom.Only the following cases can be considered as coordination isomerism, that is, compounds must exist in the form of salts, where cations and anions are both transition metalsCoordination compoundConsists of.
4. Ionization isomerization
An example of this isomerism is the compound [Co (NHthree)sixBr]SOfourAnd [Co (NHthree)sixSOfour]Br。The former is a bromine ligand coordinated with cobalt atom, while the latter is a free anion.
