What is a radical in chemistry an example. "The Nomenclature of Organic Compounds" (study guide)

Radicals in chemistry are atomic particles that have certain features associated with the transition between compounds. In this article we will get acquainted with the representatives of the radicals, their definition and features, and also pay attention to their species diversity.

Introduction

A radical in chemistry is an atom or its group that can transfer, without undergoing changes, from one combination of a compound to another. A similar definition was used by A. L. Lavoisier, who created it himself.

According to Lavoisier, it was assumed that each acid is formed by two simple and indecomposable substances - oxygen and an acid radical. According to this view, it was assumed that sulfuric acids are created by oxygen and sulfur. However, in those days, the difference between acid anhydride and the actual acid was not yet known.

Theory creation

The theory of radicals in chemistry was one of the leading ones in chemistry in the first half of the 19th century. It is based on the idea of \u200b\u200bA. L. Lavoisier on the importance of oxygen atoms in chemical teaching and the dualistic form of chemical composition. compounds. He, using the "radical" as a terminological unit, expressed his thoughts. They affected the structural features of organic and inorganic acids. The latter, in his opinion, were formed from oxygen and simple radicals (from the 1st element). Organic acids are substances combined by the interaction of O 2 and complex radicals (compound C and H).

After cyan was discovered and an analogy was drawn between some cyanides and chlorides, the understanding of complex radicals improved and strengthened. They began to be defined as atoms that did not change during the transition from the 1st compound to the 2nd. I. Bartzelitsus supported this view with his authoritative opinion. Another important step towards understanding these substances was the proposal to consider wine alcohol and ether as the “esterin” hydrate. They admitted a similar point of view of J. Dumas and P. Bull.

Radicals in chemistry are substances that do not undergo changes during transitions. The theory that was created to describe them in the 1840-50s was gradually replaced by type theory. The change was associated with the presence of a considerable number of factors that were contradictory described by TR.

Organism and radicals

Free radicals in the body are particles that have one or more unpaired electrons located on the outer shell of the electrons. In another definition, a free radical is described as a molecule or atom capable of supporting independent existence. It has some stability and 1 - 2 electrons (e -) in an unpaired state. Particles e - occupy the orbital of a molecule or atom in a single form. The presence of paramagnetic properties is characteristic of radicals, which is explained by the interaction of an electron with magnetic fields. There are cases in which the presence of e - in unpaired form entails a significant increase in reactivity.

Examples of free radicals are oxygen molecules (O 2), nitric oxide with different valencies (NO and NO 2), and chlorine dioxide (ClO 2).

Organics

Organic radicals are ionic particles that are characterized by the simultaneous presence of an unpaired electron and charge. Most often, in reactions of organic chemistry, radical ions are created due to the occurrence of one-electron transfers.

If oxidation proceeds in a single-electron form and is applicable to a neutral molecule with an excess of electron density, then it will lead to the creation of a radical cation. The opposite course of the process, during which the neutral molecule is restored, leads to the formation of an anion radical.

A number of aromatic hydrocarbons from the multicore group can independently form both types of radical ions (organic) without much effort.

Free radicals in chemistry are extremely diverse substances, both in their structure and properties. They can be in different states of aggregation, for example, liquid or gas. Their lifespan or the number of electrons that have remained unpaired may also vary. Conventionally, each radical can be attributed to one of two groups: -p- or s-electronic. They differ in the location of the unpaired e -. In the first case, the negative particle occupies a position on the 2p orbitals in the predominant number of cases. The corresponding series of atomic nuclei is in this case located in the nodal orbital plane. In the variant with the s-group, the localization of the electron occurs in such a way that the violation of the electronic configuration practically does not occur.

The concept of hydrocarbon radical

A hydrocarbon radical is an atomic group that forms a bond with a molecular functional group. They are also called hydrocarbon residues. Most often, in the course of chem. radical reactions undergo transitions from one compound to another and do not change. However, such objects of chemical study can carry a number of functional groups. Understanding this forces a person to behave with radicals with extreme caution. Such compounds often include substances that include hydrocarbon residues. The radical itself may be a functional group.

The phenomenon in alkyls

Alkyl radicals are compounds from a number of intermediates that are particles of alkanes. They have free e - in the singular. An example is methyl (CH 3) and ethyl (C 2 H 5). Several types are distinguished among them: primary (for example, methyl - ▪CH 3), secondary (isopropyl - ▪CH (CH 3) 2), tertiary (tert-butyl ▪C (CH 3) 3) and quaternary (neopentyl - ▪CH 2 C (CH 3) 3) a group of alkyl radicals.

Phenomenon in methylene

Methylene radical is the simplest form of carbene. Presented as a colorless gas, and the formula is similar to hydrocarbons from a number of alkenes - CH 2. The idea of \u200b\u200bthe existence of methylene was put forward in the thirties of the twentieth century, but it was possible to find irrefutable evidence only in 1959. This was done thanks to the spectral research method.

Obtaining methylene became possible due to the use of diazomethane or ketane substances. They are decomposed by UV radiation. During this process, methylene is formed, as well as nitrogen molecules and carbon monoxide.

A radical in chemistry is also a methylene molecule having one carbon atom in which there is no double bond. This distinguishes methylene from alkenes, and therefore it belongs to carbenes. Extreme chemical activity is characteristic of it. The position of electrons can determine various properties of a chemical nature and geometry. There is a singlet (e - paired) and triplet (electron in a free state - unpaired) form. The triplet form allows one to describe methylene as a biradical.

Hydrophobicity

A hydrophobic radical is a compound having a different polar group. Such molecules and atoms can bond with aminoalkyl sulfo groups via various intermediate bonds.

In accordance with the structure, straight-chain and branched, paraffin (olefin) and perfluorinated radicals are isolated. The presence of a hydrophobic radical allows some substances to easily penetrate through bilayer lipid membranes, as well as integrate into their structures. Such substances are part of non-polar amino acids, which are released due to a certain indicator of the polarity of the side chain.

In the modern method of rational classification of amino acids, radicals are distinguished in accordance with their polarity, i.e., the ability to interact with water in the presence of physiological pH (about 7.0 pH). In accordance with the type of radical contained, several classes of amino acids are distinguished: non-polar, polar, aromatic, negatively and positively charged group.

Radicals with hydrophobic properties cause a general decrease in the solubility of peptides. Analogs with hydrophilic qualitative characteristics determine the formation of a hydration shell around the amino acid itself, and peptides dissolve better when interacting with them.

MOSCOW STATE

UNIVERSITY OF ENGINEERING ECOLOGY

Moscow - 2006

Ministry of Education of the Russian Federation

MOSCOW STATE UNIVERSITY

ENGINEERING ECOLOGY

Department of General and Physical Chemistry

NOMENCLATURE OF ORGANIC COMPOUNDS

Guidelines

Edited by prof. V.S. Pervova

Moscow - 2006

Approved by the Editorial Board

Compiled by G.N. Bespalov, G.S. Isaev, I.V. Yaroshenko, E.D. Streltsova

UDC. 5.4.7.1

The nomenclature of organic compounds. Methodical instructions. / Comp.: G.N. Bespalov, G.S. Isaev, I.V. Yaroshenko, E.D. Streltsova

M .: MGUIE, 2006, 28 p., 2 tab.

The guidelines are intended for students studying in the specialties 1705, 1705.06: 1705.07, 1712.03, studying organic chemistry. The paper considers the basics of the system of names of substances according to the rational nomenclature and nomenclature of IUPAC. To check the assimilation of the material, fifteen task options are offered.

Reviewers: Department of Chemical Technology of Plastic Masses MKhTIim. D.I. Mendeleev.

doctor of Chemical Sciences, Professor, A.L. Rusanov, INEOS RAS.

INTRODUCTION

Nomenclature Is a system of names of substances. The main requirement for the scientific nomenclature is that it unambiguously defines a particular chemical compound, excluding the possibility of mixing this compound with another, would be simple and would allow to construct its structural formula by the name of the compound.

There are several different systems. One of the first is trivial nomenclature. Until now, many organic compounds have random historical names. Some of them are associated with being in nature, others with a method of obtaining, others reflect the physical condition and so on. Benzene, alcohol, methane, explosive acid, formic acid, acetone, ether are the trivial names of organic substances. These names are not integrated in a coherent system into a coherent system and do not reflect the structure of molecules of organic substances. However, many natural and synthetic substances of complex structure still have trivial names due to their brevity and expressiveness.

The emergence of the theoretical foundations of organic chemistry has led to the creation of new classification systems and, therefore, new ways of naming organic compounds that reflect the chemical structure. This means that the name can uniquely compose the structural formula of the substance and the structural formula to give the name of the substance. So it appeared rationalnomenclature and Geneva nomenclature, the further development of which led to the creation of a system IUPAC, proposed by the International Union of Pure Applied Chemistry, recommended for the name of all organic substances. However, in practice, one has to deal with various systems of names of organic substances.

To compile the names of organic substances both according to the rational nomenclature and the IUPAC system, it is necessary to know the names of hydrocarbon radicals. Hydrocarbon radicals - these are particles that are obtained when one or more hydrogen atoms are separated from a hydrocarbon molecule. In hydrocarbon molecules, primary, secondary, tertiary and quaternary carbon atoms should be distinguished, which is determined by the number of its bonds with neighboring carbon atoms. Primaryhas one bond with a carbon atom, secondary - two bonds with an atom or carbon atoms, tertiary - three, quaternary - four.

When the hydrogen atom is separated from the primary carbon atom, primary radical (i.e., the primary unit of valency is in the primary carbon atom), from the secondary - secondary radical, from tertiary - tertiary radical.

Table 1 shows the formula of saturated hydrocarbons and radicals formed from them, as well as their names. As can be seen from the table, only one radical can be formed from methane and ethane. Two isomeric radicals can already be formed from propane, a hydrocarbon with three carbon atoms - propyl and isopropyl, depending on which carbon atom (primary or secondary) a hydrogen atom breaks off. Starting with butane, hydrocarbons appear isomers. In accordance with this, the number of isomeric radicals also increases: n. Butyl, sec. butyl, isobutyl, tert. butyl.

The name of the subsequent hydrocarbons consists of the Greek numeral corresponding to the number of carbon atoms in the molecule and the suffix "an".

With an increase in the number of carbon atoms in a hydrocarbon, the number of isomers increases, and the number of radicals that can be formed from them increases.

Most isomers have no special names. However, according to the rational nomenclature and nomenclature of IUPAC, any arbitrarily complex compound can be named using the names of simple radicals.

Table 1.

Saturated hydrocarbons and their radicals.

Hydrocarbon


CH 3 —CH 2 —CH 3		CH 3 —CH 2 —CH 2 -	isopropyl (second propyl)
CH 3 - _ CH 2 - CH 2 -CH 3		CH 3 —CH 2 —CH 2 —CH 2 - CH 3 —CH 2 —CH	second butyl
	isobu-tan	CH 3 - CH - CH 2 -	isobutyl tert.butyl

Table 2. shows some unsaturated and aromatic hydrocarbons and their corresponding radicals. Table 2.Unsaturated and aromatic hydrocarbons and their radicals.

Hydrocarbons		Radicals

CH 2 \u003d CH-CH 3	propylene	CH 2 \u003d CH-CH 2 - CH \u003d CH-CH 3 CH 2 \u003d C-CH 3	propenyl isopropenyl
	acetylene		acetylenyl or ethinyl

			p (pair) tolyls

RATIONAL NOMENCLATURE

Rational nomenclature is based on type theory. This system is based on the names of the simplest members of homologous series: methaneif there are no double bonds, ethyleneif one double bond is present, and acetyleneif the connection has one triple bond. All other hydrocarbons are considered as derivatives of these simple hydrocarbons obtained by replacing one or more hydrogen atoms with hydrocarbon radicals. In order to name a particular compound, one must list the substituent radicals, and then name the corresponding hydrocarbon. Enumeration of radicals should be started with the simplest methyl, and then, with increasing complexity, ethyl, propyl, etc. Branched radicals are considered more complex than normal radicals with the same number of carbon atoms. Such
connection can be called methylethylisopropylmethane. If the compound contains several identical radicals, then you should indicate how many of these radicals are contained in the compound, using multiplication prefixes - Greek numerals: 2 - di, 3 - three, 4 - tetra, so the compound will be called trimethylethylmethane.

For the central methane atom, it is better to choose the carbon atom at which the largest number of substituents is located. Depending on which carbon atom is chosen as the central methane atom, several different names can be given to the same substance according to rational nomenclature.

Compounds with double and triple bonds are called in the same way:

In order to distinguish between two isomeric compounds, two methods can be used. In the first compound, substituent radicals are located at two different carbon atoms linked by a double bond, symmetrically with respect to the double bond. In the second compound, both radicals are located on the same carbon atom, i.e. asymmetrically with respect to the double bond.

Therefore, they are called so: the first is symmetrical methyleneand the second is asymmetric methylethyl ethylene. In the second method, one carbon atom of carbon connected to a simpler radical is denoted by the Greek letter , the other - . The name of such compounds indicates at which carbon atom which radical is located. So the first connection will be called  -methyl- ethyleneand the second  -methyl- ethylene.

The name of hydrocarbons, the molecule of which has a symmetrical structure, i.e., consists of two identical radicals, is composed of the names of these radicals and the prefix

Cyclic hydrocarbons in rational nomenclature are considered as polymethylene and are called by the number of methylene groups included in the ring, and Greek numerals are used:

If there are substituents in the cycle, they are listed before the name of the main cycle. Such

the connection will be called methylhexamethylene.

Rational nomenclature is still used to name relatively simple compounds, especially when they want to emphasize the functional type of compounds. However, the name of highly branched hydrocarbons causes difficulties, since there are no names of complex radicals.

IUPAC NOMENCLATURE

The IUPAC nomenclature, proposed by the International Union of Pure and Applied Chemistry, makes it possible to name any arbitrarily complex compound. This nomenclature is the development and streamlining of the Geneva nomenclature, with which it has much in common.

In this nomenclature, the first four saturated hydrocarbons of normal structure have trivial names: methane, ethane, propane and butane. The names of the following normal (unbranched) hydrocarbons are formed from the base of Greek numerals with the addition of the ending -an: С 5 Н 12 - pentane, С 6 Н 14 - hexane, С 7 Н 16 - heptane, etc. (see table 1)

For the name of branched hydrocarbons, you must select the longest normal chain. If several chains of the same length can be distinguished in a hydrocarbon, select the most branched chain. The name of this hydrocarbon, corresponding to the length of the chain, is taken as the basis for the name of this hydrocarbon. Therefore, a hydrocarbon having a structure

will be considered as a derivative of heptane. This is the longest chain number, and the direction of numbering is chosen so that the numbers indicating the position of the side chains would be the smallest. For each side substituent, an Arabic numeral indicates its location in the chain and gives a name. If there are several identical substituents in the compound, then along with indicating the location of each substituent with the help of multiplying prefixes (Greek numerals) di-, tri-, Tatra- and so on, their number is indicated. Side substituents are listed in increasing order of complexity: methyl CH 3 - is less complex than ethyl C 2 H 5 -, i.e. a radical with fewer carbon atoms is less complex than with a large number of atoms. With the same number of carbon atoms, the radical whose main chain is less complex

longer: sec. butyl
less complicated than tert. butyl

Thus, the above connection will be called 2,2,5-trimethyl-3-ethylheptane.

If there are multiple bonds in a hydrocarbon, the longest chain that contains a double or triple bond is taken as the main chain. If a hydrocarbon has one double bond, then the end –An in the name of the saturated hydrocarbon corresponding in this chain is replaced by the end - en and the Arabic numeral indicates the number of the carbon atom at which the double chain begins. So connection

will be called heptin-3.

If the compound contains two double or triple bonds, then the endings of the hydrocarbon names must be - diene or - diine accordingly, indicating the numbers of atoms at which multiple bonds begin:

In the presence of double and triple bonds, the ending in the name of the hydrocarbon will be -In-in indicating the numbers of atoms at which the corresponding multiple bonds begin:

In the case of branched unsaturated hydrocarbons, the main chain is chosen so that the positions of the double and swarm bonds are indicated by the lowest numbers.

The names of cyclic hydrocarbons are formed by adding the prefix to the name of a saturated hydrocarbon with the same number of carbon atoms cyclo-

If there are side substituents, their location, quantity and name are indicated, after which a cyclic hydrocarbon is called.

If the cycle contains multiple connections, then this is reflected in the change in the end to henin the presence of a double bond or at the end of –Inin the presence of one triple bond.

For the simplest monocyclic aromatic compound, the trivial name is preserved - benzene. In addition, the trivial names of some substituted aromatic hydrocarbons are retained.

Monocyclic aromatic hydrocarbons are considered as benzene derivatives obtained by replacing hydrogen atoms with hydrocarbon radicals. In order to name one or another aromatic compound, one should number the carbon atoms of the benzene ring, indicate the positions of the substituents in the ring, indicate how many there are, name these radicals, and then name the aromatic hydrocarbon. The provisions of the substituents should be indicated by the lowest numbers. Thus, the connection

will be called 1,4-dimethyl-2-ethylbenzene.

If in the benzene ring there are only two substituents, then instead of numbers 1,2-, 1,3- and 1,4-we can use the notation ortho (o-), meta (m-) and couple (p-)

The names of some condensed and polycyclic aromatic hydrocarbons and the order of numbering of carbon atoms are given below.

BIBLIOGRAPHIC LIST.

Pavlov B.A., Terentyev A.P. Organic chemistry course. M.-L.

Homework 1

Option 1.16

a) (CH 3) 2 (CH) 2 (C 2 H 5) 2,

b) (CH 3) 2 CCH (CH 3)

a) methylisopropyl tert.butylmethane,

b) methyl ethylacetylene.

a) 2,2,3-trimethylbutane,

b) 3,4-dimethylhexene-3.

Option 2.17

1. Write in expanded form the structural formulas of the following hydrocarbons and name them according to the rational nomenclature and nomenclature of IUPAC. Indicate how many primary, secondary, tertiary and quaternary carbon atoms in each compound:

a) (CH 3) 3 CCH (CH 3) CH (CH 3) (C 2 H 5)

b) (CH 3) (C 2 H 5) C 2 (C 2 H 5) 2.

2. Write the structural formulas of the following compounds

and name them according to the IUPAC nomenclature:

b) -methyl- -ethyl- -second. butylene.

3. Write the structural formulas of the following compounds and name them according to the rational nomenclature:

a) 2,2,3,4-tetramethyl-3-ethylpentane,

b) 2,5-dimethylhexine-3.

: Option 3.18

a) (CH 3) 3 CCH (C 2 H 5) CH (CH 3) (C 2 H 5),

b) (CH 3) 2 CH 2 CH (CH 3) 2.

2. Write the structural formulas of the following compounds and name them according to the IUPAC nomenclature

a) ethyl divider. butylmethane,

b) isopropyl tert.butylacetylene.

3. Write the structural formulas of the following compounds and name them according to rational nomenclature:

a) 2,2-dimethyl-3-ethylpentane,

b) 2,2,5,5-tetramethylhexene-3

Option 4.19

a) (CH 3) 2 (CH) 4 (CH 3) (C 2 H 5),

b) (CH 3) 3 C 2 (CH 3) (C 2 H 5) CH (CH 3) 2.

a) methylisopropyl tert.butylmethane,

b) sim. second butyl tert butyl ethylene.

3. Write the structural formulas of the following compounds and name them according to rational nomenclature:

a) 2,2,4,4-tetramethyl-3-ethylpentane,

b) 2,2,5-trimethylhexine-3.

Option 5.20

a) CH 3 (CH 2) 2 CH (C 2 H 5) CH (CH 3) (C 2 H 5),

b) (CH 3) 3 C 4 (CH 3) 3.

2. Write the structural formulas of the following compounds and name them according to the IUPAC nomenclature

a) ethyl isopropyl isobutylmethane,

b) -ethyl- -isopropyl- -second. butylene.

3. Write the structural formulas of the following compounds and name them according to rational nomenclature:

a) 2-methyl-3,3-diethylpentane,

b) butadiene-1,3

Option 6, 21

a) (CH 3) 3 C (CH 2) 2 CH (CH 3) 2,

b) CH 2 C (CH 3) CHCH 2.

2. Write the structural formulas of the following compounds and name them according to the IUPAC nomenclature

a) methyl ethyl isopropyl tert. butyl methane,

b) ,dimethyl -vorbutylethylene.

Lecture number 1

COMPOUNDS

Structural isomerism.

Lecture number 1

CLASSIFICATION AND NOMENCLATURE OF ORGANIC
COMPOUNDS

Classification of organic compounds.
The nomenclature of organic compounds.
Structural isomerism.

1. Classification of organic compounds.

Organic compounds are classified according to two main characteristics: structure
carbon skeleton and functional groups.

The structure of the carbon skeleton distinguishes between acyclic, carbocyclic and
heterocyclic compounds.

Acyclic compounds - contain an open chain of carbon atoms.

Carbocyclic compounds - contain a closed carbon chain
   atoms and are divided into alicyclic and aromatic. TO alicyclic all carbocyclic compounds except
   aromatic. Aromatic the compounds contain cyclohexatriene
   fragment (benzene core).

Heterocyclic compounds — contain cycles including, along with carbon atoms, one
or several heteroatoms.

By the nature of the functional groups, organic
compounds are divided into classes .

Table 1. The main classes of organic
compounds.

Functional Group	Connection class	General formula
Missing	Hydrocarbons	R-h
Halogen F, -Cl, -Br, -I (–Hal)	Halogen derivatives	R-hal
Hydroxyl IT	Alcohols and phenols	R-OH
Alkoxyl	Ethers	R-OR
Amino NH 2,\u003e NH,\u003e N-	Amines	RNH 2, R 2 NH, R 3 N
Nitro	Nitro compounds	RNO 2
Carbonyl	Aldehydes and Ketones
Carboxylic	Carboxylic acids
Alkoxycarbonyl	Esters
Carboxamide	Amides carboxylic acids
Tiola	Thiols	R-sh
Sulpho	Sulfonic acids	R-SO 3 H

2. Nomenclature of organic
compounds.

Currently, in organic chemistry, it is generally accepted systematic nomenclature developed by International Union of Pure and Applied Chemistry
(IUPAC) Along with it survived and
are used trivial and rational nomenclature.

Trivial nomenclature composed
   from historically established names that do not reflect the composition and structure
   substances. They are random and reflect the natural source of the substance.
   (lactic acid, urea, caffeine), characteristic properties (glycerin, detonating
   acid), production method (pyruvic acid, sulfuric ether), name
   discoverer (Michler's ketone, Chichibabin hydrocarbon), scope
   (vitamin C). The advantage of trivial names is their
   conciseness, so the use of some of them is allowed by the rules
   IUPAC.

Systematic nomenclature is scientific and reflects the composition, chemical and spatial structure
   connections. The name of the compound is expressed using a compound word, compound
parts of which reflect certain structural elements of a substance’s molecule. IN
   IUPAC nomenclature rules are based on principles replacement
   nomenclaturesaccording to which the molecules of the compounds are considered as
   hydrocarbon derivatives in which hydrogen atoms are replaced by other atoms or
   groups of atoms. When constructing a name in a molecule of a compound, the following
   structural elements.

Parent structure - main chain
carbon chain or cyclic structure in carbo and heterocycles.

Hydrocarbon radical - balance
formula for hydrocarbon with free valencies (see table
2).

Characteristic group –
functional group associated with or included in the parent structure
composition (see table 3).

When compiling a title sequentially
comply with the following rules.

Determine the highest characteristic
group and indicate its designation in the suffix (see table 3).
The parent structure is determined by
   the following criteria in order of precedence: a) contains senior
   characteristic group; b) contains the maximum number of characteristic
   groups; c) contains the maximum number of multiple bonds; d) has a maximum
   length. The original structure is indicated at the root of the name in accordance with
   chain length or loop size: C 1 - “meth”, C 2 - “et”, C 3 - “prop”, C 4 - “but”, C 5 and further - the roots of the Greek numerals.
Determine the degree of saturation and reflect
its suffix: “an” - no multiple bonds, “en” - a double bond, “in” -
triple bond.
Set the remaining deputies
(hydrocarbon radicals and lower characteristic groups) and list
their names are prefixed in alphabetical order.
Set multiplying prefixes - “di”,
“Three”, “tetra”, indicating the number of identical structural elements (for
listing alternates in alphabetical order are not counted).
Numbering the parent structure
   so that the highest characteristic group has the least ordinal
   number. Locants (numbers) put before the name of the parent structure, before
   prefixes and before suffixes.

Table 2. Names of alkanes and alkyl
radicals adopted by the systematic nomenclature of IUPAC.

Alkan	Title	Alkyl radical	Title
CH 4	Methane	CH 3 -	Methyl
CH 3 CH 3	Ethane	CH 3 CH 2 -	Ethyl
CH 3 CH 2 CH 3	Propane	CH 3 CH 2 CH 2 -	Propyl
CH 3 CH 2 CH 3	Propane		Isopropyl
CH 3 CH 2 CH 2 CH 3	n-Butane	CH 3 CH 2 CH 2 CH 2 -	n-Butyl
CH 3 CH 2 CH 2 CH 3	n-Butane		sec-Butyl
	Isobutane		Isobutyl
	Isobutane		tert-butyl
CH 3 CH 2 CH 2 CH 2 CH 3	n-Pentane	CH 3 CH 2 CH 2 CH 2 CH 2 -	n-Pentyl
	Isopentane		Isopentyl
	Neopentane		Neopentyl

Table 3. Names of characteristic
groups(listed in descending order of seniority).

Group	Title
Group	in prefix	in suffix
- (C) OOH *	—	hydrochloric acid
-COOH	carboxy	carbon acid
-SO 3 H	sulfo	sulfonic acid
- (C) HO	oxo	al
-CHO	formed	carbaldehyde
\u003e (C) \u003d O	oxo	it
-IT	hydroxy	ol
-SH	mercapto	thiol
-NH 2	amino	amine
-OR **	alkoxy, aroxy	—
-F, -Cl, -Br, -I	fluorine, chlorine, bromine, iodine	—
-NO 2	nitro	—

* Carbon atom
enclosed in parentheses is part of the parent structure.

** Alkoxy groups and all
those following them are listed in a prefix alphabetically and have no order
seniority.

Rational (radical-functional)
   nomenclature used for simple mono- and
   bifunctional compounds and some classes of natural compounds. Basis
   name is the name of this class of compounds or one of the members
   homologous series indicating substituents. As locants, as a rule,
   Greek letters are used.

3. Structural isomerism.

Isomers Are substances having the same composition and molecular
mass, but different physical and chemical properties. Differences in the properties of isomers
due to differences in their chemical or spatial structure.

Under chemical structure understand the nature and sequence of relationships
between atoms in a molecule. Isomers whose molecules differ in chemical
structure, called structural isomers.

Structural isomers may vary:

on the structure of the carbon skeleton

by the position of multiple bonds and
functional groups

by type of functional groups

It is well known that in organic molecules (including those that make up our body), the electrons on the outer electron shell are arranged in pairs: one pair on each orbital ( fig. one) Free radicals differ from ordinary molecules in that they have an unpaired (single) electron ( fig. 2and 3 ).

An unpaired electron in radicals is usually denoted by a dot. For example, a hydroxyl radical is designated as HO ·, a hydrogen peroxide radical as HOO ·, a superoxide radical as · OO - or O 2 · -. The following are the formulas of the three radicals of ethyl alcohol:

CH 3 CH 2 O ·; CH 3 · C HOH; CH 3 CH 2 O

A free radical is a particle - an atom or molecule that has on the outer shell one or more unpaired electrons.

This makes the radicals chemically active, because the radical seeks either to regain the missing electron by taking it from the surrounding molecules, or to get rid of the "excess" electron, giving it to other molecules.

The oxygen (dioxigen) molecule, which contains two unpaired electrons on the outer shell, turned out to be in a special position. Thus, dioxigen is a biradical and, like other radicals, has a high reactivity.

It is important to emphasize that unpaired electrons must be on the outer shell of an atom or molecule. The concept of a free radical does not include metal ions of variable valency, unpaired electrons in which are located on the inner shells. Since both radicals and ions of metals such as iron, copper or manganese (as well as complexes of these metals) give signals of electron paramagnetic resonance (EPR), these particles, in combination, are often called paramagnetic centers.

The formation of radicals from stable molecules is, therefore, due to the appearance of a new electron on the free, valence orbital, or vice versa, the removal of one electron from an electron pair. These processes usually occur as a result of single electron oxidation or reduction reactions. In such reactions, it is usually involved, along with the molecule from which the radical is formed, a metal ion of variable valency, which once serves as a donor or acceptor of one electron (and not two at once, as happens in reactions between two organic molecules or between an organic molecule and oxygen). A typical example of a reaction in which a radical is formed is the Fenton reaction: the interaction of hydrogen peroxide with a ferrous ion:

Fe 2+ + H 2 O 2  Fe 3+ + OH - + · OH (hydroxyl radical)

At high temperatures or under the influence of ultraviolet radiation, radicals can also form as a result of breaking a chemical bond (homolytic cleavage). Under normal conditions, such reactions in normal living cells practically do not occur.

Nomenclature of radicals

More recently, the Commission on the Nomenclature of Inorganic Chemistry formulated the basic rules for the nomenclature of radicals (see (Koppenol, 1990 # 7)) ( tab. one) Let us dwell on some of these recommendations. First of all, there is no need to write "free" before the word radical. The radical nature of the particle under consideration is indicated by the ending "silt". So the radicals RO · and HO · have the name, respectively, "alkoxyl" and "hydroxyl".

The recommendation not to abuse derivatives of “peroxide” and “hydroperoxide” can be considered as essentially new. A group of two interconnected oxygen atoms is called "dioxide". Accordingly, the radical ROO · is recommended to be called an “alkyldioxyl” (Koppenol, 1990 # 7). The alternative name “alkyl peroxyl” may also be retained, but this is worse (Koppenol, 1990 # 7). Molecular oxygen is called “dioxigen” and ozone is called “trioxygen”.

The name with the ending "silt" is very convenient, but nothing burns about what the charge of the particle is. Therefore, in necessary cases, it is recommended to use the systematic name of the radical, where after the name of the group a charge is given in parentheses. For example, the radical O 2 · - has the name "dioxide (l–)". In this work, we will use the shorter name "dioxide".

When writing radical formulas in a superscript, a dot is first set up indicating the presence of an unpaired electron for a given atom, and then the sign of the ion charge. For example, "O 2 · – ". In the structural formulas, the point should be exactly at the atom where the unpaired electron is localized. For example, to emphasize that dioxigen has two unpaired electrons, you can write its formula in this way" O 2. " table 1a list of recommended radical names is given; in square brackets are the names that will be primarily used in this book.

Alkanes (methane and its homologues) have the general formula C nH 2 n+2. The first four hydrocarbons are called methane, ethane, propane, butane. The names of the highest members of this series consist of the root - the Greek numeral and the suffix -an. The names of alkanes form the basis of the IUPAC nomenclature.

Rules for systematic nomenclature:

The rule of the main chain.

The main chain is selected, guided sequentially by the following criteria:

The maximum number of functional substituents.
The maximum number of multiple bonds.
The maximum extent.
The maximum number of side hydrocarbon groups.

The rule of the smallest numbers (locants).

The main chain is numbered from one end to the other in Arabic numerals. Each substituent receives the number of the carbon atom of the main chain to which it is attached. The numbering sequence is chosen so that the sum of the numbers of substituents (locants) is the smallest. This rule also applies to the numbering of monocyclic compounds.

The rule of the radicals.

All hydrocarbon side groups are considered as monovalent (simply connected) radicals. If the side radical itself contains side chains, then according to the above rules, an additional main chain is selected in it, which is numbered starting from the carbon atom attached to the main chain.

The rule of alphabetical order.

The name of the compound begins with a listing of the substituents, indicating their names in alphabetical order. The name of each substituent is preceded by its number in the main chain. The presence of several substituents is indicated by numerator prefixes: di-, tri-, tetra-, etc. After this, the hydrocarbon corresponding to the main chain is called.

In the table. 12.1 shows the names of the first five hydrocarbons, their radicals, possible isomers, and the corresponding formulas. The names of the radicals end with the suffix -il.

Formula		Title
hydrocarbon	radical	coal hydrogen	radical


			Isopropyl
		Methylpropane (iso-butane)	Methylpropyl (isobutyl) Tert-butyl

		methylbutane (isopentane)	methylbutyl (isopentyl)
		dimethylpropane (neopentane)	dimethylpropyl (neopentyl)

Table 12.1.

Alkanes of the acyclopical series C n H 2 n +2 .

Example. Name all hexane isomers.

Example. Name the alkane of the following structure

In this example, one of the two twelve-atom chains is selected in which the sum of the numbers is the smallest (rule 2).

Using the names of branched radicals given in table. 12.2

Radical	Title	Radical	Title
	isopropyl		isopentyl
	isobutyl		neopentyl
	sec-butyl		tert-pentyl
	tert-butyl		isohexyl

Table 12.2.

Names of forged radicals.

the name of this alkane is somewhat simplified:

10-tert-butyl-2,2- (dimethyl) -7-propyl-4-isopropyl-3-ethyl-dodecane.

When a hydrocarbon chain is closed in a cycle with the loss of two hydrogen atoms, monocycloalkanes with the general formula C are formed nH 2 n. The cyclization begins with C 3, the names are formed from C n with cyclo prefix:

Polycyclic alkanes. Their names are formed by the prefix bicyclo-, tricyclo-, etc. Bicyclic and tricyclic compounds contain two and three cycles in a molecule, respectively, to describe their structure in square brackets indicate in decreasing order the number of carbon atoms in each of the chains connecting nodal atoms ; under the formula the name of the atom:

This tricyclic hydrocarbon is usually called adamantane (from the Czech adamant - diamond), because it represents a combination of three condensed cyclohexane rings in a form that leads to the arrangement of carbon atoms in the crystal lattice, which is typical for diamond.

Cyclic hydrocarbons with one common carbon atom are called spirals, for example, spiro-5,5-undecane:

Flat cyclic molecules are unstable, therefore various conformational isomers are formed. In contrast to configurational isomers (spatial arrangement of atoms in a molecule without regard to orientation), conformational isomers differ only by the rotation of atoms or radicals around formally simple bonds while maintaining the configuration of the molecules. The formation energy of a stable conformer is called conformational.

Conformers are in dynamic equilibrium and are transformed into each other through unstable forms. The instability of plane cycles is caused by a significant deformation of the valence angles. While maintaining the tetrahedral bond angles for C 6H 12 cyclohexane, two stable conformations are possible: in the form of a chair (a) and in the form of a bath (b):