Position isomerism. Isomerism and its types
Structural isomers- These are compounds that have the same molecular formula, but differ from each other in the order of binding of atoms in the molecule.
Structural isomerism is subdivided into carbon chain isomerism, position isomerism, and functional group isomerism.
Isomerism of the carbon chain. Due to the different sequence of binding of atoms that form the carbon skeleton of the molecule. For example, for an alkane of composition C 4 H 10, two isomers can be written;
For organic compounds with a cyclic structure, chain isomerism can be caused by the size of the cycle.
position isomerism due to different positions of functional groups, substituents or multiple bonds in the molecule.
Isomerism of functional: groups due to the presence in the isomers of the same composition of functional groups of different nature.
SPATIAL ISOMERIA (STEREOISOMERIA)
Spatial isomers- these are compounds that have the same molecular formula, the same order of binding of atoms in a molecule, but differ from each other in the arrangement of atoms in space.
Spatial isomers are also called stereo isomers and (from the Greek stereos - spatial).
Spatial isomerism is subdivided into configurational and conformational.
But before proceeding to the consideration of these types of stereoisomerism, let us dwell on the ways of depicting the spatial structure of the molecules of organic compounds.
To depict the spatial structure of molecules, their configuration or conformation, molecular models and special stereoformulas are used.
Molecular models - a visual representation of the molecules of organic and inorganic compounds, which makes it possible to judge the relative position of the atoms that make up the molecule.
Three main types of models are most often used: spherical (Kekule-Vant-Hoff models), skeletal (Dryding-g models) and hemispherical (Stuart-Briegleb models). Models allow one to judge not only the mutual arrangement of atoms in a molecule, but they are convenient and to consider bond angles and the possibility of rotation around simple bonds. Dryding models also take into account interatomic distances, while Stewart-Briegleb models also reflect the volumes of atoms. The figure below shows the models of ethane and ethylene molecules.
Rice. 3.1. Models of ethane (left) and ethylene (right) molecules; a - ball-and-stick; b - Dryding; in – hemispherical (Stuart-Brigleb)
stereo formulas. To depict the spatial structure of a molecule on a plane, stereochemical and perspective formulas, as well as Newman projection formulas, are most often used.
AT stereochemical formulas chemical bonds located in the plane of the drawing are depicted as a regular line; connections located above the plane - a bold wedge or a bold line, and located pssh plane - a dashed wedge or a dashed line:
Promising Formulas describe the spatial structure on the plane, taking into account the consideration of the molecule along one of the carbon-carbon bonds. In appearance, they resemble sawmill goats:
When building Newman projection formulas the molecule is viewed in the direction of one C–C bond in such a way that the atoms forming this bond obscure each other. From the selected pair, the carbon atom closest to the observer is represented by a dot, and the farthest by a circle. The chemical bonds of the nearest carbon atom with other atoms are represented by lines originating from the point in the center of the circle, and the far one - from the circle:
There are Fisher projection formulas, which are usually used to depict the spatial structure of optical isomers on a plane.
Lecture #5
Theme "Isomerism and its types"
Lesson type: combined
Purpose: 1. To reveal the main position of the theory of structure on the phenomenon of isomerism. Give a general idea of the types of isomerism. Show the main directions in the development of the theory of structure on the example of stereoisomerism.
2. continue to form the ability to build formulas of isomers, give names to substances according to formulas.
3. cultivate a cognitive attitude to learning
Equipment: Stuart-Briegleb molecule models, colored plasticine, matches, a pair of gloves, cumin seeds, mint chewing gum, three test tubes.
Lesson Plan
greeting, roll call
Survey of basic knowledge
Learning new material:
Theory of structure and the phenomenon of isomerism;
Types of isomerism;
Anchoring
Lesson progress
2. Survey of basic knowledge: frontally
According to what criteria organic compounds are classified, explain using a diagram.
What are the main classes of organic compounds, the features of their structure
Perform exercise No. 1 and 2 §6. One student at the blackboard, the rest in notebooks
3. Learning new material: Theory of structure and the phenomenon of isomerism
Recall the definition of isomerism and isomers. Explain the reason for their existence.
The phenomenon of isomerism (from the Greek isos - different and meros - share, part) was discovered in 1823 by J. Liebig and F. Wehler using the example of salts of two inorganic acids: cyanic and fulminant. NOSE = N cyan; H-O-N = C rattling
In 1830, J. Dumas extended the concept of isomerism to organic compounds. The term "isomer" appeared a year later, and was suggested by J. Berzellius. Since complete chaos reigned in the field of the structure of both organic and inorganic substances at that time, the discovery was not given much importance.
A scientific explanation for the phenomenon of isomerism was given by A.M. Butlerov within the framework of the theory of structure, while neither the theory of types nor the theory of radicals revealed the essence of this phenomenon. A.M. Butlerov saw the cause of isomerism in the fact that the atoms in the molecules of isomers are connected in a different order. The theory of structure made it possible to predict the number of possible isomers and their structure, which was brilliantly confirmed in practice by A.M. Butlerov himself and his followers.
Types of isomerism: give an example of isomers and suggest a feature by which isomers could be classified?(Obviously, the base will be the structure of the molecules of the isomers). I explain the material using the diagram:
There are two types of isomerism: structural and spatial (stereoisomerism). Structural isomers are those that have a different order of bonding of atoms in a molecule. Spatial isomers have the same substituents on each carbon atom, but differ in their mutual arrangement in space.
Structural isomerism is of three types: interclass isomerism associated with the structure of the carbon skeleton, and isomerism of the position of the functional group or multiple bond.
Interclass isomers contain different functional groups and belong to different classes of organic compounds, and therefore the physical and chemical properties of interclass isomers differ significantly.
The isomerism of the carbon skeleton is already familiar to you, the physical properties are different, and the chemical properties are similar, because these substances belong to the same class.
Isomerism of the position of a functional group or the position of multiple bonds. The physical properties of such isomers are different, but the chemical properties are similar.
Geometric isomerism: have different physical constants but similar chemical properties
Optical isomers are mirror images of each other; like two palms, it is impossible to put them together so that they match.
4. Fixing: recognize isomers, determine the type of isomerism in substances whose formulas: perform exercise 3§ 7
And the Greek μέρος - share, part), a phenomenon consisting in the existence of chemical compounds of the same composition with the same molecular weight, but differing in structure. Such compounds are called isomers. Structural differences cause different mutual influence of atoms in molecules and predetermine different physical and chemical properties of isomers. Isomerism is extremely common in organic chemistry and is one of the main reasons for the diversity and abundance of organic compounds. In inorganic chemistry, isomerism occurs mainly for complex compounds.
The term "isomerism" was introduced by J. Berzelius in 1830, completing the controversy between J. Liebig and F. Wöhler on the existence of two substances that differ sharply in properties and have the same AgCNO composition - silver cyanate and fulminate, and based on the results of research tartaric and tartaric acids. The essence of isomerism was later explained on the basis of the theory of chemical structure.
There are two main types of isomerism: structural and spatial (stereoisomerism). Structural isomers differ in the order of bonds of atoms in a molecule, that is, in their chemical structure. Stereoisomers (spatial isomers) with the same order of bonds of atoms in a molecule differ in the mutual arrangement of atoms in space.
Structural isomerism is subdivided into carbon skeleton isomerism (skeletal isomerism), position isomerism (positional isomerism), metamerism and other types. The isomerism of the carbon skeleton is due to the different order of bonds of the carbon atoms that form the skeleton of the molecule. To specify the structural features of isomers, skeletal isomerism is subdivided into carbon chain isomerism, ring isomerism, and side chain isomerism. For example, carbon chain isomerism is characteristic of alkanes starting from the fourth member of the C 4 H 10 homologous series, which has two structural isomers: n-butane CH 3 -CH 2 -CH 2 -CH 3 and isobutane (2-methylpropane) CH 3 -CH (CH 3)-CH 3. The fifth member of the C 5 H 12 alkane series has three isomers: CH 3 -CH 2 -CH 2 -CH 2 -CH 3 - n-pentane, CH 3 -CH (CH 3) -CH 2 -CH 3 - isopentane (2- methylbutane) and neopentane (2,2-dimethylpropane) CH 3 -C (CH 3) 2 -CH 3. As the chain lengthens, the number of possible isomers increases rapidly. So, for alkanes of the composition C 10 H 22, 75 structural isomers are possible, for C 13 H 28 - 802 isomers, for C 20 H 42 - more than 366 thousand isomers. Alicyclic compounds are characterized by ring isomerism and side chain isomerism. For example, among the skeletal isomers (formulas I-IV), methylcyclopentane (I), cyclohexane (II) and propylcyclopropane (III) are cyclic isomers, and propylcyclopropane (III) and isopropylcyclopropane (IV) are side chain isomers. Differences in the properties of skeletal isomers are manifested in the difference in their boiling points (isomers with a normal carbon chain boil at a higher temperature than isomers with a branched chain), density, and other n-Alkanes, for example, in contrast to branched isomers, they have lower detonation resistance ( see article Octane number), form complexes with urea (clathrates).
Position isomerism is due to the different positions of functional groups, substituents, or multiple bonds. For example, position isomers are 1-propanol CH 3 -CH 2 -CH 2 OH and 2-propanol CH 3 -CH (OH) -CH 3, 1-butene CH 2 \u003d CH-CH 2 -CH 3 and 2-butene CH 3 -CH=CH-CH 3 . Changing the position of the functional group may lead to a change in the class of the compound. For example, the position isomers acetone CH 3 -C(O)-CH 3 and propanal CH 3 -CH 2 -CHO refer to ketones and aldehydes, respectively. Structural isomers with different functional groups differ greatly in chemical properties.
Metamerism is due to the different positions of the heteroatom (O, N, S) in the chain. For example, metamers are methyl propyl ether CH 3 O-CH 2 -CH 2 -CH 3 and diethyl ether CH 3 -CH 2 -O-CH 2 -CH 3, diethylamine CH 3 -CH 2 -NH-CH 2 -CH 3 and CH 3 -NH-CH 2 -CH 2 -CH 3 - methylpropylamine.
Often, differences in isomers are determined by several structural features. For example, methylisopropyl ketone (3-methyl-2-butanone) CH 3 -C (O) -CH (CH 3) 2 and valeric aldehyde (pentanal) CH 3 -CH 2 -CH 2 -CH 2 -CHO differ from each other as the structure of the carbon skeleton, and the position of the functional group.
A special type of structural isomerism is tautomerism (equilibrium dynamic isomerism). In this case, isomers that differ in functional groups easily pass into each other until an equilibrium is reached, at which the substance simultaneously contains tautomer molecules in a certain ratio.
Spatial isomerism is subdivided into geometric (cis, trans and syn, anti-isomerism, or E, Z-isomerism) and optical (enantiomerism). Geometric isomerism is characteristic of compounds containing double bonds or non-aromatic rings, which are structurally rigid fragments of molecules. For cis-isomers, two substituents are located on the same side of the plane of the double bond or cycle, for trans-isomers - on opposite sides. For example, geometric isomers are cis-2-butene (formula V) and trans-2-butene (VI), cis-1,2-dichlorocyclopropane (VII) and trans-1,2-dichlorocyclopropane (VIII).
Characteristic differences between the cis-trans isomers are the lower melting point of the cis-isomers, significantly better solubility in water, and a pronounced dipole moment. Trans isomers are usually more stable. See, for example, the article Maleic and fumaric acids.
The geometric isomerism observed for compounds with double bonds C=N (oximes) and N=N (azo-, azoxy compounds) is often called syn, anti-isomerism. For example, geometric isomers are anti-benzaldoxime (formula IX) and syn-benzaldoxime (X); syn-azobenzene (XI) and anti-azobenzene (XII).
In the general case, the Ε,Z-nomenclature is used. For Z-isomers, senior substituents (having a higher atomic number) are located on one side of the double bond or cycle, for E-isomers - on opposite sides. For example, geometric isomers are (Z)-1-bromo1-iodo-2-chloroethylene (formula XIII) and (E)-1-bromo-1-iodine-2-chloroethylene (XIV).
Optical isomerism is characteristic of compounds whose molecules have elements of chirality, such as an asymmetric (chiral) carbon atom bonded to four different substituents. It was first discovered by L. Pasteur in 1848 using the example of tartaric acids and explained by J. H. van't Hoff and J. A. Le Bel in 1874 based on the concept of the tetrahedral configuration of carbon atoms in saturated compounds. Molecules containing an asymmetric carbon atom can be represented as two optical isomers that cannot be combined in space (i.e., they relate to each other like an object to its mirror image). Such mirror isomers, which differ only in the opposite arrangement of the same substituents at the chiral center, are called enantiomers (from the Greek έναντίος - opposite and μέρος - part). For example, lactic acid enantiomers (XV and XVI) can be represented in 3D or as Fisher formulas (see Chemical Nomenclature).
Enantiomers have different biological activities; they are also characterized by optical activity - the ability to act on plane-polarized light (rotate the plane of polarization). Enantiomers rotate the plane of polarization by the same angle but in the opposite direction, which is why they are called optical antipodes.
For a long time, the configuration of enantiomers was determined relative to the configuration of a known standard, which was the enantiomers of glyceraldehyde (D, L-steric series). More universal is the R, S-nomenclature (proposed by R. Kahn, K. Ingold and V. Prelog), which establishes the absolute configuration of spatial isomers. In accordance with the rules of R, S nomenclature, lactic acid enantiomers (XV, XVI) are respectively (R)-lactic and (S)-lactic acids. There are no rules for translating the D, L-nomenclature into the R, S-system, since these nomenclatures use different principles. No connection has been established between the absolute configuration and optical rotation parameters.
For compounds having n chiral centers in the molecule, the number of possible stereoisomers is 2 ". However, at n ≥ 2, there are stereoisomers that differ from each other in part of the chirality elements they contain. Such stereoisomers that are not enantiomers are called diastereomers (from the Greek δια ... - through, between, stereo... and μέρος - part). and XX are enantiomers, the remaining pairs (XVII and XIX, XVII and XX, XVIII and XIX, XVIII and XX) are diastereomers.
With the appearance of additional symmetry elements (plane, axis, or center of symmetry), the total number of stereoisomers, as well as the number of optically active forms, may decrease. For example, tartaric acids have three stereoisomers, of which two are optically active: D-tartaric acid, or (2R,3R)-tartaric acid (formula XXI), and L-tartaric acid, or (2S,3S)-tartaric acid (XXII ), which are enantiomers. Their diastereomer - mesotartaric acid, or (2R,3S)-tartaric acid (formula XXIII, or identical configuration XXIV), due to the presence of a plane of symmetry (indicated by a dotted line) is optically inactive - is the so-called intramolecular racemate.
The process of interconversion of enantiomers is called racemization. A mixture of equal amounts of optical antipodes - a racemic mixture, or racemate, does not have optical activity. Stereoisomerism is given great attention in the study of natural compounds and the synthesis of biologically active substances. Substances of natural origin containing elements of chirality have a certain stereoconfiguration, as well as optical activity. When a chiral center is formed under the conditions of chemical synthesis (with the exception of asymmetric synthesis), a racemate is formed; isolation of enantiomers requires the use of complex methods for separating the racemate into optically active components.
As a result of the internal rotation of molecules, conformational isomers, or conformers, arise that differ in the degree of rotation of molecular fragments about one or more simple bonds. In some cases, individual conformers, sometimes also called rotational isomers, can be isolated. Conformational analysis is used to study the formation, differences in properties and reactivity of conformers.
Isomers can be converted into each other by isomerization reactions.
Lit .: Potapov V. M. Stereochemistry. 2nd ed. M., 1988; Traven VF Organic chemistry. M., 2004. T. 1.
ἴσος - equal + μέρος - share, part) - a phenomenon consisting in the existence of chemical compounds - isomers, - identical in atomic composition and molecular weight, but differing in the structure or arrangement of atoms in space and, as a result, in properties.Encyclopedic YouTube
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Isomerism and nomenclature of saturated hydrocarbons
1.1. Alkanes: Structure, nomenclature, isomerism. Preparation for the exam in chemistry
Types of isomerism
Stereoisomers, Enantiomers, Diastereomers, Structural isomers, Meso compounds
No. 42. Organic chemistry. Topic 12. Halogen derivatives. Part 1. Nomenclature, isomerism
Subtitles
Historical information
This type of isomerism is subdivided into enantiomers(optical isomerism) and diastereomerism.
Enantiomerism (optical isomerism)
The process of interconversion of enantiomers is called racemization: it leads to the disappearance of optical activity as a result of the formation of an equimolar mixture of (−)- and (+)-forms, that is, a racemate. The interconversion of diastereomers leads to the formation of a mixture in which the thermodynamically more stable form predominates. In the case of π-diastereomers, this is usually the trans form. The interconversion of conformational isomers is called conformational equilibrium.
The phenomenon of isomerism greatly contributes to the growth of the number of known (and even more - the number of potentially possible) compounds. So, the possible number of structural isomeric decyl alcohols is more than 500 (of which about 70 are known), there are more than 1500 spatial isomers.
In the theoretical consideration of problems of isomerism, topological methods are becoming more and more widespread; mathematical formulas have been derived to calculate the number of isomers.
Another example was tartaric and tartaric acids, after the study of which J. Berzelius introduced the term isomerism and suggested that the differences arise from the "different distribution of simple atoms in a complex atom" (i.e., a molecule). The true explanation of isomerism was received only in the 2nd half of the 19th century. based on the theory of the chemical structure of A. M. Butlerov (structural isomerism) and the stereochemical theory of J. G. van't Hoff (spatial isomerism).
Structural isomerism
Structural isomerism is the result of differences in chemical structure. This type includes:
Isomerism of the hydrocarbon chain (carbon skeleton)
Isomerism of the carbon skeleton, due to the different bonding order of carbon atoms. The simplest example is butane CH 3 -CH 2 -CH 2 -CH 3 and isobutane (CH 3) 3 CH. Dr. examples: anthracene and phenanthrene (formulas I and II, respectively), cyclobutane and methylcyclopropane (III and IV).
Valence isomerism
Valence isomerism (a special type of structural isomerism), in which isomers can be converted into each other only by redistributing bonds. For example, the valence isomers of benzene (V) are bicyclohexa-2,5-diene (VI, "Dewar's benzene"), prisman (VII, "Ladenburg's benzene"), benzvalene (VIII).
Functional group isomerism
It differs in the nature of the functional group. Example: Ethanol (CH 3 -CH 2 -OH) and Dimethyl ether (CH 3 -O-CH 3)
position isomerism
A type of structural isomerism characterized by a difference in the position of the same functional groups or double bonds with the same carbon skeleton. Example: 2-chlorobutanoic acid and 4-chlorobutanoic acid.
Spatial isomerism (stereoisomerism)
Enantiomerism (optical isomerism)
Spatial isomerism (stereoisomerism) arises as a result of differences in the spatial configuration of molecules that have the same chemical structure. This type of isomer is subdivided into enantiomers(optical isomerism) and diastereomerism.
Enantiomers (optical isomers, mirror isomers) are pairs of optical antipodes of substances characterized by opposite in sign and equal in magnitude rotations of the plane of polarization of light with the identity of all other physical and chemical properties (with the exception of reactions with other optically active substances and physical properties in a chiral medium ). A necessary and sufficient reason for the appearance of optical antipodes is the assignment of a molecule and one of the following point symmetry groups C n, D n, T, O, I (Chirality). Most often we are talking about an asymmetric carbon atom, that is, an atom associated with four different substituents, for example:
Other atoms can also be asymmetric, such as silicon, nitrogen, phosphorus, and sulfur atoms. The presence of an asymmetric atom is not the only reason for enantiomers. So, derivatives of adamantane (IX), ferrocene (X), 1,3-diphenylallene (XI), 6,6"-dinitro-2,2"-diphenic acid (XII) have optical antipodes. The reason for the optical activity of the latter compound is atropisomerism, that is, spatial isomerism caused by the lack of rotation around a single bond. Enantiomerism also appears in the helical conformations of proteins, nucleic acids, hexahelycene(XIII).
(R)-, (S)- nomenclature of optical isomers (naming rule)
The four groups attached to the asymmetric carbon atom C abcd are assigned different seniority corresponding to the sequence: a>b>c>d. In the simplest case, seniority is established by the serial number of the atom attached to the asymmetric carbon atom: Br(35), Cl(17), S(16), O(8), N(7), C(6), H(1) .
For example, in bromochloroacetic acid:
The seniority of the substituents at the asymmetric carbon atom is as follows: Br(a), Cl(b), C of the COOH group (c), H(d).
In butanol-2, oxygen is the senior substituent (a), hydrogen is the junior substituent (d):
It is required to resolve the issue of substituents CH 3 and CH 2 CH 3 . In this case, the seniority is determined by the serial number or numbers of other atoms in the group. The primacy remains with the ethyl group, since in it the first C atom is bonded to another C(6) atom and to other H(1) atoms, while in the methyl group carbon is bonded to three H atoms with the atomic number 1. In more complex cases continue to compare all the atoms until they reach atoms with different serial numbers. If there are double or triple bonds, then the atoms attached to them are considered to be two and three atoms, respectively. Thus, the -COH group is considered as C (O, O, H), and the -COOH group is considered as C (O, O, OH); the carboxyl group is older than the aldehyde group, since it contains three atoms with a serial number of 8.
In D-glyceraldehyde, the OH(a) group is the highest, followed by CHO(b), CH 2 OH(c) and H(d):
The next step is to determine whether the arrangement of the groups is right, R (lat. rectus), or left, S (lat. sinister). Moving on to the corresponding model, it is oriented so that the minor group (d) in the perspective formula is at the bottom, and then viewed from above along the axis passing through the shaded face of the tetrahedron and group (d). In the D-glyceraldehyde group
located in the direction of right rotation, and therefore, it has an R-configuration:
(R)-glyceraldehyde
In contrast to the D,L nomenclature, the designations for (R)- and (S)-isomers are enclosed in brackets.
diastereomerism
σ-diastereomerism
Any combination of spatial isomers that do not form a pair of optical antipodes is considered diastereomeric. There are σ and π-diastereomers. σ-diasteriomers differ from each other in the configuration of some of the chirality elements they contain. So, diasteriomers are (+)-tartaric acid and meso-tartaric acid, D-glucose and D-mannose, for example:
For some types of diastereomerism, special designations have been introduced, for example, threo- and erythro-isomers are a diastereomerism with two asymmetric carbon atoms and spaces, the arrangement of substituents at these atoms, reminiscent of the corresponding threose (related substituents are on opposite sides in Fisher's projection formulas) and erythrose ( deputies - on one side):
Erythro isomers whose asymmetric atoms are bonded to the same substituents are called meso forms. They, unlike the other σ-diastereomers, are optically inactive due to the intramolecular compensation of the contributions to the rotation of the light polarization plane of two identical asymmetric centers of the opposite configuration. Pairs of diastereomers that differ in the configuration of one of several asymmetric atoms are called epimers, for example:
The term "anomers" refers to a pair of diastereomeric monosaccharides differing in the configuration of the glycosidic atom in the cyclic form, for example, α-D- and β-D-glucose are anomeric.
π-diastereomerism (geometric isomerism)
π-diasteriomers, also called geometric isomers, differ from each other in the different spatial arrangement of substituents relative to the plane of the double bond (most often C=C and C=N) or the ring. These include, for example, maleic and fumaric acids (formulas XIV and XV, respectively), (E)- and (Z)-benzaldoximes (XVI and XVII), cis- and trans-1,2-dimethylcyclopentanes (XVIII and XIX).
conformers. Tautomers
The phenomenon is inextricably linked with the temperature conditions of its observation. So, for example, chlorocyclohexane at room temperature exists in the form of an equilibrium mixture of two conformers - with the equatorial and axial orientations of the chlorine atom:
However, at minus 150 °C, an individual a-form can be isolated, which behaves under these conditions as a stable isomer.
On the other hand, compounds that are isomers under normal conditions may turn out to be tautomers in equilibrium with increasing temperature. For example, 1-bromopropane and 2-bromopropane are structural isomers, however, as the temperature rises to 250 °C, an equilibrium is established between them, which is characteristic of tautomers.
Isomers that transform into each other at temperatures below room temperature can be considered as non-rigid molecules.
The existence of conformers is sometimes referred to as "rotational isomerism". Among dienes, s-cis- and s-trans isomers are distinguished, which, in essence, are conformers resulting from rotation around a simple (s-single) bond:
Isomerism is also characteristic of coordination compounds. So, compounds that differ in the way of coordination of ligands (ionization isomerism) are isomeric, for example, are isomeric:
SO 4 - and + Br -
Here, in essence, there is an analogy with the structural isomerism of organic compounds.
Chemical transformations, as a result of which structural isomers are converted into each other, is called isomerization. Such processes are important in industry. So, for example, isomerization of normal alkanes into isoalkanes is carried out to increase the octane number of motor fuels; pentane isomerized to isopentane for subsequent dehydrogenation to isoprene. Intramolecular rearrangements are also isomerizations, of which, for example, the conversion of cyclohexanone oxime to caprolactam, a raw material for the production of capron, is of great importance.
