EntranceOrganic names. Organic chemistry
Based on the type of carbon chain, it is usually divided into cyclic and acyclic; saturated and unsaturated, heterocyclic and carbocyclic. Acyclic, having no cycles in their structure. The carbon atoms in such compounds are arranged sequentially, forming straight or branched open chains.
There are those that have single carbon bonds, as well as compounds with multiple (double, triple) bonds.
Alkanes nomenclature
Systematic nomenclature implies the use of a certain algorithm of actions. Compliance with the rules allows you to name saturated hydrocarbons without errors. If you need the task: “Name the proposed hydrocarbon using systematic nomenclature,” you must first make sure that it belongs to the class of alkanes. Next, you need to find the longest chain in the structure.
When numbering carbon atoms, the proximity of the radicals to the beginning of the chain, their number, and name are taken into account. Systematic nomenclature involves the use of additional prefixes that specify the number of identical radicals. Their position is indicated by numbers, the quantity is determined, and then the radicals are named. At the final stage, the long carbon chain is named by adding the suffix -an. For example, the hydrocarbon CH3-CH2-CH(CH)-CH2-CH3 according to systematic nomenclature is called 3-methylpentane.
Alkene nomenclature
These substances are named according to systematic nomenclature with the obligatory indication of the position of the multiple (double) bond. In organic chemistry, there is a certain algorithm of actions that helps give names to alkenes. To begin with, the longest fragment containing a double bond is determined in the proposed carbon chain. The numbering of carbons in the chain is carried out on the side where the multiple bond is located closer to the beginning. If the task is offered: “Name the substances according to systematic nomenclature,” you need to determine the presence of hydrocarbon radicals in the proposed structure.
If they are absent, name the chain itself, adding the suffix -ene, indicating the position of the double bond with a number. For representatives of unsaturated alkenes, which contain radicals, it is necessary to indicate their position in numbers, add prefixes specifying the amount, and only then proceed to the name of the hydrocarbon chain itself.
As an example, let's give a name to a compound with the following structure: CH2=CH-CH (CH3)-CH2-CH3. Considering that the molecule contains a double bond, a hydrocarbon radical, its name will be as follows: 3-methylpuntene-1.
Diene hydrocarbons
The nomenclature of this class of unsaturated hydrocarbons is characterized by some features. Molecules of diene compounds are characterized by the presence of two double bonds, therefore the position of each of them is indicated in the name. Let's give an example of a compound belonging to this class and give its name.
CH2=CH-CH=CH2 (butadiene -1.3).
If the molecule contains radicals (active particles), then numbers indicate their position, numbering the atoms in the main chain from the side closest to its beginning. If there are several hydrocarbon atoms in a molecule at once, the prefixes di-, tri-, tetra- are used when listing.
Conclusion
Using systematic nomenclature, you can name representatives of any class organic compounds. A general algorithm of actions has been developed that makes it possible to name samples of saturated and For carboxylic acids, which contain a carboxyl functional group, the numbering of the main chain is carried out precisely from it.
Introduction
1. Saturated hydrocarbons
1.1. Saturated straight-chain compounds
1.1.1. Monovalent radicals
1.2. Saturated branched compounds with one substituent
1.3. Saturated branched compounds with several substituents
2. Unsaturated hydrocarbons
2.1. Unsaturated straight hydrocarbons with one double bond (alkenes)
2.2. Unsaturated straight hydrocarbons with one triple bond (alkynes)
2.3. Unsaturated branched hydrocarbons
3. Cyclic hydrocarbons
3.1. Aliphatic hydrocarbons
3.2. Aromatic hydrocarbons
3.3. Heterocyclic compounds
4. Hydrocarbons containing functional groups
4.1. Alcohols
4.2. Aldehydes and ketones 18
4.3. Carboxylic acids 20
4.4. Esters 22
4.4.1. Ethers 22
4.4.2. Esters 23
4.5. Amines 24
5. Organic compounds with several functional groups 25
Literature
Introduction
The scientific classification and nomenclature of organic compounds is based on the principles of the theory chemical structure organic compounds A.M. Butlerov.
All organic compounds are divided into the following main series:
Acyclic - they are also called aliphatic, or fatty compounds. These compounds have an open chain of carbon atoms.
These include:
- Limit (saturated)
- Unsaturated (unsaturated)
Cyclic - compounds with a chain of atoms closed in a ring. These include:
- 1. Carbocyclic (isocyclic) - compounds whose ring system includes only carbon atoms:
a) alicyclic (limited and unsaturated);
b) aromatic. - Heterocyclic - compounds whose ring system, in addition to the carbon atom, includes atoms of other elements - heteroatoms (oxygen, nitrogen, sulfur, etc.)
Currently, three types of nomenclature are used to name organic compounds: trivial, rational and systematic nomenclature - IUPAC nomenclature (IUPAC) - International Union of Pure and Applied Chemistry (International Union of Pure and Applied Chemistry).
Trivial (historical) nomenclature is the first nomenclature that arose at the beginning of the development of organic chemistry, when there was no classification or theory of the structure of organic compounds. Organic compounds were given random names based on their source (oxalic acid, malic acid, vanillin), color or smell (aromatic compounds), and less often, based on their chemical properties (paraffins). Many such names are still often used today. For example: urea, toluene, xylene, indigo, acetic acid, butyric acid, valeric acid, glycol, alanine and many others.
Rational nomenclature - According to this nomenclature, the name of the simplest (usually the first) member of a given homologous series is usually taken as the basis for the name of an organic compound. All other compounds are considered as derivatives of this compound, formed by replacing hydrogen atoms in it with hydrocarbon or other radicals (for example: trimethylacetic aldehyde, methylamine, chloroacetic acid, methyl alcohol). Currently, such nomenclature is used only in cases where it gives a particularly clear idea of the connection.
Systematic nomenclature - IUPAC nomenclature - International Unified Chemical Nomenclature. Systematic nomenclature is based on the modern theory of the structure and classification of organic compounds and attempts to solve the main problem of nomenclature: the name of each organic compound must contain the correct names of the functions (substituents) and the main skeleton of the hydrocarbon and must be such that the name can be used to write the only correct structural formula.
The process of creating an international nomenclature began in 1892 ( Geneva nomenclature), continued in 1930 ( Liege nomenclature), since 1947, further development is associated with the activities of the IUPAC commission on the nomenclature of organic compounds. The IUPAC rules published over the years were collected in 1979 in “ blue book". The IUPAC Commission considers its task not to create a new, unified system nomenclature, but streamlining, “codification” of existing practice. The result of this is the coexistence in IUPAC rules of several nomenclature systems, and, consequently, several acceptable names for the same substance. IUPAC rules are based on the following systems: substitutive, radical-functional, additive (connective), replacement nomenclature, etc.
IN replacement nomenclature the name is based on one hydrocarbon fragment, and others are considered as hydrogen substituents (for example, (C 6 H 5) 3 CH - triphenylmethane).
IN radical functional nomenclature The name is based on the name of the characteristic functional group that determines the chemical class of the compound to which the name of the organic radical is attached, for example:
C 2 H 5 OH - ethyl alcohol;
C2H5Cl - ethyl chloride;
CH 3 –O–C 2 H 5 - methyl ethyl ether;
CH 3 –CO–CH = CH 2 - methylvinyl ketone.
IN connecting nomenclature the name is composed of several equal parts (for example, C 6 H 5 –C 6 H 5 biphenyl) or by adding the designations of attached atoms to the name of the main structure (for example, 1,2,3,4-tetrahydronaphthalene, hydrocinnamic acid, ethylene oxide, styrene dichloride).
Substitute nomenclature is used when there are non-carbon atoms (heteroatoms) in the molecular chain: the roots of the Latin names of these atoms ending in “a” (a-nomenclature) are attached to the names of the entire structure that would result if there were carbon instead of heteroatoms (for example, CH 3 –O–CH 2 –CH 2 –NH–CH 2 –CH 2 –S–CH 3 2-oxa-8-thia-5-azanonane).
The IUPAC system is generally recognized in the world, and is only adapted according to the grammar of the country's language. The full set of rules for applying the IUPAC system to many less common types of molecules is long and complex. Only the basic contents of the system are presented here, but this allows the naming of the connections for which the system is used.
1. SATURAL HYDROCARBONS
1.1. Saturated unbranched compounds
The names of the first four saturated hydrocarbons are trivial (historical names) - methane, ethane, propane, butane. Starting from the fifth, the names are formed by Greek numerals corresponding to the number of carbon atoms in the molecule, with the addition of the suffix " –AN", with the exception of the number "nine", when the root is the Latin numeral "nona".
Table 1. Names of saturated hydrocarbons
NAME |
NAME |
|||
1.1.1. Monovalent radicals
Monovalent radicals formed from saturated unbranched saturated hydrocarbons by removing hydrogen from the terminal carbon atom are called replacing the suffix " –AN"in the name of the hydrocarbon with the suffix" –IL".
Does the carbon atom with free valence get a number? These radicals are called normal or unbranched alkyls:
CH 3 – - methyl;
CH 3 –CH 2 –CH 2 –CH 2 – - butyl;
CH 3 –CH 2 –CH 2 –CH 2 –CH 2 –CH 2 – - hexyl.
Table 2. Names of hydrocarbon radicals
1.2. Saturated branched compounds with one substituent
The IUPAC nomenclature for alkanes in individual names retains the principle of Geneva nomenclature. When naming an alkane, one starts from the name of the hydrocarbon corresponding to the longest carbon chain in a given compound (the main chain), and then indicates the radicals adjacent to this main chain.
The main carbon chain, firstly, must be the longest, and secondly, if there are two or more chains of equal length, then the most branched one is selected.
*To name saturated branched compounds, choose the longest chain of carbon atoms:
* The selected chain is numbered from one end to the other with Arabic numerals, and the numbering begins from the end to which the substituent is closest:
*Indicate the position of the substituent (number of the carbon atom at which the alkyl radical is located):
*Alkyl radical is named according to its position in the chain:
*Called the main (longest carbon chain):
If the substituent is a halogen (fluorine, chlorine, bromine, iodine), then all nomenclature rules remain the same:
Trivial names are retained only for the following hydrocarbons:
If there are several identical substituents in the hydrocarbon chain, then the prefix “di”, “tri”, “tetra”, “penta”, “hexa”, etc. is placed in front of their names, indicating the number of groups present:
1.3. Saturated branched compounds with several substituents
If there are two or more different side chains, they can be listed: a) in alphabetical order or b) in order of increasing complexity.
a) When listing the different side chains in alphabetical order multiplying prefixes are not taken into account. First, the names of atoms and groups are arranged in alphabetical order, and then multiplying prefixes and location numbers (locants) are inserted:
2-methyl-5-propyl-3,4-diethyloctane
b) When listing side chains in order of increasing complexity, proceed from the following principles:
A less complex chain is one that has fewer total carbon atoms, for example:
less complex than
If the total number of carbon atoms in a branched radical is the same, then the side chain with the longest main chain of the radical will be less complex, for example:
less complex than
If two or more side chains are in equivalent position, then the lower number is given to the chain that is listed first in the name, regardless of whether the order is of increasing complexity or alphabetical:
a) alphabetical order:
b) order of difficulty:
If there are several hydrocarbon radicals in the hydrocarbon chain and they are different in complexity, and when numbering different rows of several numbers are obtained, they are compared by arranging the numbers in the rows in ascending order. “Smallest” are considered to be the numbers of the series in which the first different digit is smaller (for example: 2, 3, 5 is less than 2, 4, 5 or 2, 7, 8 is less than 3, 4, 9). This principle is observed regardless of the nature of the substituents.
In some reference books, the sum of digits is used to determine the choice of numbering; numbering begins on the side where the sum of digits indicating the position of the substituents is the smallest:
2, 3 , 5, 6, 7, 9 - the series of numbers is the smallest
2, 4 , 5, 6, 8, 9
2+3+5+6+7+9 = 32 - the sum of the substituent numbers is the smallest
2+4+5+6+8+9 = 34
therefore, the hydrocarbon chain is numbered from left to right, then the name of the hydrocarbon will be:
(2, 6, 9-trimethyl-5,7-dipropyl-3,6-diethyldecane)
(2,2,4-trimethylpentane, but not 2,4,4-trimethylpentane)
If the hydrocarbon chain contains several different substituents (for example, hydrocarbon radicals and halogens), then the substituents are listed either in alphabetical order or in order of increasing complexity (fluorine, chlorine, bromine, iodine):
a) alphabetical order 3-bromo-1-iodo-2-methyl-5-chloropentane;
b) order of increasing complexity: 5-chloro-3-bromo-1-iodo-2-methylpentane.
Literature
- IUPAC rules of nomenclature for chemistry. M., 1979, vol. 2, half volumes 1,2
- Chemist's Handbook. L., 1968
- Banks J. Names of organic compounds. M., 1980
With development chemical science and the appearance large number new chemical compounds, there was an increasing need to develop and adopt a naming system that would be understandable to scientists all over the world, i.e. . Below we provide an overview of the main nomenclatures of organic compounds.
Trivial nomenclature
In the origins of the development of organic chemistry, new compounds were attributed trivial names, i.e. names that have developed historically and are often associated with the method of their receipt, appearance and even taste, etc. This nomenclature of organic compounds is called trivial. The table below shows some of the compounds that have retained their names to this day.
Rational nomenclature
With the expansion of the list of organic compounds, the need arose to associate their names with the basis of the rational nomenclature of organic compounds is the name of the simplest organic compound. For example:
However, more complex organic compounds cannot be named in this way. In this case, the compounds should be named according to the rules of IUPAC systematic nomenclature.
IUPAC systematic nomenclature
IUPAC - International Union of Pure and Applied Chemistry.
In this case, when naming compounds, one should take into account the location of carbon atoms in the molecule and structural elements. The most commonly used is the substitutive nomenclature for organic compounds, i.e. the basic basis of the molecule is highlighted, in which hydrogen atoms are replaced by any structural units or atoms.
Before you start constructing the names of compounds, we advise you to learn the names numerical prefixes, roots and suffixes used in IUPAC nomenclature.
And also the names of functional groups: 
Numerals are used to indicate the number of multiple bonds and functional groups:
Saturated hydrocarbon radicals:
Unsaturated hydrocarbon radicals:
Aromatic hydrocarbon radicals:
Rules for constructing the name of an organic compound according to IUPAC nomenclature:
- Select the main chain of the molecule
Identify all functional groups present and their precedence
Determine the presence of multiple bonds
- Number the main chain, and numbering should begin with the end of the chain closest to the highest group. If several such possibilities exist, the chain is numbered so that either the multiple bond or another substituent present in the molecule receives the minimum number.
Carbocyclic compounds are numbered starting from the carbon atom associated with the highest characteristic group. If there are two or more substituents, they try to number the chain so that the substituents have the minimum numbers.
- Create a name for the connection:
— Determine the basis of the name of the compound that forms the root of the word, which denotes a saturated hydrocarbon with the same number of atoms as the main chain.
— After the base of the name there is a suffix indicating the degree of saturation and the number of multiple bonds. For example, - tetraene, - diene. In the absence of multiple connections, use the suffix - sk.
- Then, the name of the itself is also added to the suffix senior functional group.
— This is followed by a listing of the substituents in alphabetical order, indicating their location in Arabic numerals. For example, - 5-isobutyl, - 3-fluoro. If there are several identical substituents, their number and position are indicated, for example, 2,5 - dibromo-, 1,4,8-trimethyl-.
Please note that numbers are separated from words by a hyphen, and between each other by commas.
As example Let's give the following connection a name:
1. Choose main circuit, which necessarily includes senior group– COUN.
Defining others functional groups: - OH, - Cl, - SH, - NH 2.
Multiple connections No.
2. Number the main circuit, starting with the older group.
3. The number of atoms in the main chain is 12. Name basis
10-amino-6-hydroxy-7-chloro-9-sulfanyl-methyl ester of dodecanoic acid.
10-amino-6-hydroxy-7-chloro-9-sulfanyl-methyl dodecanoate
Nomenclature of optical isomers
- In some classes of compounds, such as aldehydes, hydroxy and amino acids, they are used to indicate the relative position of substituents. D, L– nomenclature. Letter D denote the configuration of the dextrorotatory isomer, L- left-handed.
At the core D,L-nomenclatures of organic compounds are based on the Fischer projection:
- α-amino acids and α-hydroxy acids isolate the “oxyacid key”, i.e. the upper parts of their projection formulas. If the hydroxyl (amino) group is located on the right, then it is D-isomer, left L-isomer.
For example, the tartaric acid shown below has D— configuration according to the oxyacid key: 
- to determine isomer configurations sugars isolate the “glycerol key”, i.e. compare the lower parts (lower asymmetric carbon atom) of the projection formula of sugar with the lower part of the projection formula of glyceraldehyde.
The sugar configuration designation and direction of rotation are similar to that of glyceraldehyde, i.e. D– the configuration corresponds to the location of the hydroxyl group located on the right, L– configurations – on the left.
For example, below is D-glucose.
2) R-, S-nomenclature (Kahn, Ingold and Prelog nomenclature)
In this case, the substituents at the asymmetric carbon atom are arranged in order of seniority. Optical isomers have designations R And S, and the racemate is R.S..
To describe the connection configuration according to R,S-nomenclature proceed as follows:
- All substituents on the asymmetric carbon atom are determined.
- The seniority of the substituents is determined, i.e. compare their atomic masses. The rules for determining the precedence series are the same as when using the E/Z nomenclature of geometric isomers.
- The substituents are oriented in space so that the lowest substituent (usually hydrogen) is in the corner furthest from the observer.
- The configuration is determined by the location of the remaining substituents. If the movement from the senior to the middle and then to the junior deputy (i.e. in decreasing order of seniority) is carried out clockwise, then this is an R configuration, counterclockwise is an S-configuration.
The table below shows a list of deputies, arranged in ascending order of seniority:
Classification of organic substances
Depending on the type of carbon chain structure, organic substances are divided into:
- acyclic and cyclic.
- marginal (saturated) and unsaturated (unsaturated).
- carbocyclic and heterocyclic.
- alicyclic and aromatic.
Acyclic compounds are organic compounds in whose molecules there are no cycles and all carbon atoms are connected to each other in straight or branched open chains.
In turn, among acyclic compounds, saturated (or saturated) ones are distinguished, which contain in the carbon skeleton only single carbon-carbon (C-C) bonds and unsaturated (or unsaturated), containing multiples - double (C=C) or triple (C≡ C) connections.
Cyclic compounds are chemical compounds in which there are three or more bonded atoms forming a ring.
Depending on which atoms form the rings, carbocyclic compounds and heterocyclic compounds are distinguished.
Carbocyclic compounds (or isocyclic) contain only carbon atoms in their rings. These compounds are in turn divided into alicyclic compounds (aliphatic cyclic) and aromatic compounds.
Heterocyclic compounds contain one or more heteroatoms in the hydrocarbon ring, most often oxygen, nitrogen or sulfur atoms.
The simplest class of organic substances are hydrocarbons - compounds that are formed exclusively by carbon and hydrogen atoms, i.e. formally do not have functional groups.
Since hydrocarbons do not have functional groups, they can only be classified according to the type of carbon skeleton. Hydrocarbons, depending on the type of their carbon skeleton, are divided into subclasses:
1) Saturated acyclic hydrocarbons are called alkanes. The general molecular formula of alkanes is written as C n H 2n+2, where n is the number of carbon atoms in the hydrocarbon molecule. These compounds do not have interclass isomers.
2) Acyclic unsaturated hydrocarbons are divided into:
a) alkenes - they contain only one multiple, namely one double C=C bond, the general formula of alkenes is C n H 2n,
b) alkynes – alkyne molecules also contain only one multiple bond, namely a triple C≡C bond. The general molecular formula of alkynes is C n H 2n-2
c) alkadienes – alkadiene molecules contain two double C=C bonds. The general molecular formula of alkadienes is C n H 2n-2
3) Cyclic saturated hydrocarbons are called cycloalkanes and have the general molecular formula C n H 2n.
The remaining organic substances in organic chemistry are considered as derivatives of hydrocarbons, formed by introducing so-called functional groups that contain other chemical elements into hydrocarbon molecules.
Thus, the formula of compounds with one functional group can be written as R-X, where R is a hydrocarbon radical and X is a functional group. A hydrocarbon radical is a fragment of a hydrocarbon molecule without one or more hydrogen atoms.
Based on the presence of certain functional groups, compounds are divided into classes. The main functional groups and the classes of compounds they belong to are presented in the table:
Thus, different combinations of types of carbon skeletons with different functional groups give a wide variety of variants of organic compounds.
Halogenated hydrocarbons
Halogen derivatives of hydrocarbons are compounds obtained by replacing one or more hydrogen atoms in the molecule of a parent hydrocarbon with one or more atoms of a halogen, respectively.
Let some hydrocarbon have the formula C n H m, then when replacing in its molecule X hydrogen atoms per X halogen atoms, the formula of the halogen derivative will be C n H m- X Hal X. Thus, monochlor derivatives of alkanes have the formula C n H 2n+1 Cl, dichloro derivatives CnH2nCl2 etc.
Alcohols and phenols
Alcohols are hydrocarbon derivatives in which one or more hydrogen atoms are replaced by a hydroxyl group -OH. Alcohols with one hydroxyl group are called monatomic, with two - diatomic, with three triatomic etc. For example:
Alcohols with two or more hydroxyl groups are also called polyhydric alcohols. The general formula for saturated monohydric alcohols is C n H 2n+1 OH or C n H 2n+2 O. The general formula for saturated polyhydric alcohols is C n H 2n+2 O x , where x is the atomicity of the alcohol.
Alcohols can also be aromatic. For example:
benzyl alcoholThe general formula of such monohydric aromatic alcohols is C n H 2n-6 O.
However, it should be clearly understood that derivatives aromatic hydrocarbons, in which one or more hydrogen atoms of the aromatic ring are replaced by hydroxyl groups do not apply to alcohols. They belong to the class phenols . For example this this connection is an alcohol:
And this represents phenol:
The reason why phenols are not classified as alcohols lies in their specific chemical properties, which greatly distinguish them from alcohols. As is easy to see, monohydric phenols are isomeric with monohydric aromatic alcohols, i.e. also have the general molecular formula C n H 2n-6 O.
Amines
Aminami are called ammonia derivatives in which one, two or all three hydrogen atoms are replaced by a hydrocarbon radical.
Amines in which only one hydrogen atom is replaced by a hydrocarbon radical, i.e. having the general formula R-NH 2 are called primary amines.
Amines in which two hydrogen atoms are replaced by hydrocarbon radicals are called secondary amines. The formula for a secondary amine can be written as R-NH-R’. In this case, the radicals R and R’ can be either the same or different. For example:
If amines lack hydrogen atoms at the nitrogen atom, i.e. All three hydrogen atoms of the ammonia molecule are replaced by a hydrocarbon radical, then such amines are called tertiary amines. IN general view The tertiary amine formula can be written as:
In this case, the radicals R, R’, R’’ can be completely identical, or all three can be different.
The general molecular formula of primary, secondary and tertiary saturated amines is C n H 2 n +3 N.
Aromatic amines with only one unsaturated substituent have the general formula C n H 2 n -5 N
Aldehydes and ketones
Aldehydes are derivatives of hydrocarbons in which two hydrogen atoms are replaced by one oxygen atom at the primary carbon atom, i.e. derivatives of hydrocarbons in the structure of which there is an aldehyde group –CH=O. The general formula of aldehydes can be written as R-CH=O. For example:
Ketones are derivatives of hydrocarbons in which at the secondary carbon atom two hydrogen atoms are replaced by an oxygen atom, i.e. compounds whose structure contains a carbonyl group –C(O)-.
The general formula of ketones can be written as R-C(O)-R'. In this case, the radicals R, R’ can be either the same or different.
For example:
| propane He | butane He |
As you can see, aldehydes and ketones are very similar in structure, but they are still distinguished as classes because they have significant differences in chemical properties.
The general molecular formula of saturated ketones and aldehydes is the same and has the form C n H 2 n O
Carboxylic acids
Carboxylic acids are derivatives of hydrocarbons that contain a carboxyl group –COOH.
If an acid has two carboxyl groups, the acid is called dicarboxylic acid.
Saturated monocarboxylic acids (with one -COOH group) have a general molecular formula of the form C n H 2 n O 2
Aromatic monocarboxylic acids have the general formula C n H 2 n -8 O 2
Ethers
Ethers – organic compounds in which two hydrocarbon radicals are indirectly connected through an oxygen atom, i.e. have a formula of the form R-O-R’. In this case, the radicals R and R’ can be either the same or different.
For example:
The general formula of saturated ethers is the same as that of saturated monohydric alcohols, i.e. C n H 2 n +1 OH or C n H 2 n +2 O.
Esters
Esters are a class of compounds based on organic carboxylic acids in which the hydrogen atom in the hydroxyl group is replaced by a hydrocarbon radical R. The formula of esters in general can be written as:
For example:
Nitro compounds
Nitro compounds– derivatives of hydrocarbons in which one or more hydrogen atoms are replaced by a nitro group –NO 2.
Saturated nitro compounds with one nitro group have the general molecular formula C n H 2 n +1 NO 2
Amino acids
Compounds that simultaneously have two functional groups in their structure - amino NH 2 and carboxyl - COOH. For example,
NH 2 -CH 2 -COOH
Sodium amino acids with one carboxyl and one amino group are isomeric to the corresponding saturated nitro compounds, i.e. just like they have the general molecular formula C n H 2 n +1 NO 2
IN Unified State Exam assignments For the classification of organic substances, it is important to be able to write general molecular formulas of homologous series of different types of compounds, knowing the structural features of the carbon skeleton and the presence of certain functional groups. In order to learn how to determine the general molecular formulas of organic compounds of different classes, material on this topic will be useful.
Nomenclature of organic compounds
The structural features and chemical properties of the compounds are reflected in the nomenclature. The main types of nomenclature are considered systematic And trivial.
Systematic nomenclature actually prescribes algorithms, according to which a particular name is compiled in strict accordance with the structural features of the molecule of an organic substance or, roughly speaking, its structural formula.
Let's consider the rules for compiling the names of organic compounds according to systematic nomenclature.
When compiling the names of organic substances according to systematic nomenclature, the most important thing is to correctly determine the number of carbon atoms in the longest carbon chain or count the number of carbon atoms in the cycle.
Depending on the number of carbon atoms in the main carbon chain, compounds will have a different root in their name:
|
Number of C atoms in the main carbon chain |
Root name |
|
prop- |
|
|
pent- |
|
|
hex- |
|
|
hept- |
|
|
Dec(c)- |
The second important component taken into account when composing names is the presence/absence of multiple bonds or a functional group, which are listed in the table above.
Let's try to give a name to a substance that has a structural formula:
1. The main (and only) carbon chain of this molecule contains 4 carbon atoms, so the name will contain the root but-;
2. There are no multiple bonds in the carbon skeleton, therefore, the suffix that must be used after the root of the word will be -an, as with the corresponding saturated acyclic hydrocarbons (alkanes);
3. The presence of a functional group –OH, provided that there are no higher functional groups, is added after the root and suffix from paragraph 2. another suffix – “ol”;
4. In molecules containing multiple bonds or functional groups, the numbering of the carbon atoms of the main chain begins from the side of the molecule to which they are closest.
Let's look at another example:
The presence of four carbon atoms in the main carbon chain tells us that the basis of the name is the root “but-”, and the absence of multiple bonds indicates the suffix “-an”, which will follow immediately after the root. Senior group in this compound it is carboxyl, which determines whether this substance belongs to the class of carboxylic acids. Therefore, the ending of the name will be “-ic acid”. At the second carbon atom there is an amino group NH 2—, therefore this substance belongs to amino acids. Also at the third carbon atom we see the hydrocarbon radical methyl ( CH 3—). Therefore, according to systematic nomenclature, this compound is called 2-amino-3-methylbutanoic acid.
Trivial nomenclature, unlike systematic nomenclature, as a rule, has no connection with the structure of a substance, but is determined for the most part by its origin, as well as chemical or physical properties.
| Formula | Name according to systematic nomenclature | Trivial name |
| Hydrocarbons | ||
| CH 4 | methane | marsh gas |
| CH 2 =CH 2 | ethene | ethylene |
| CH 2 =CH-CH 3 | propene | propylene |
| CH≡CH | ethin | acetylene |
| CH 2 =CH-CH= CH 2 | butadiene-1,3 | divinyl |
| 2-methylbutadiene-1,3 | isoprene | |
| methylbenzene | toluene | |
| 1,2-dimethylbenzene | ortho-xylene (O-xylene) |
|
| 1,3-dimethylbenzene | meta-xylene (m-xylene) |
|
| 1,4-dimethylbenzene | pair-xylene (P-xylene) |
|
| vinylbenzene | styrene | |
| Alcohols | ||
| CH3OH | methanol | methyl alcohol, wood alcohol |
| CH3CH2OH | ethanol | ethanol |
| CH 2 =CH-CH 2 -OH | propen-2-ol-1 | allylic alcohol |
| ethanediol-1,2 | ethylene glycol | |
| propanetriol-1,2,3 | glycerol | |
| phenol (hydroxybenzene) |
carbolic acid | |
| 1-hydroxy-2-methylbenzene | ortho-cresol (O-cresol) |
|
| 1-hydroxy-3-methylbenzene | meta-cresol (m-cresol) |
|
| 1-hydroxy-4-methylbenzene | pair-cresol (P-cresol) |
|
| phenylmethanol | benzyl alcohol | |
| Aldehydes and ketones | ||
| methanal | formaldehyde | |
| ethanal | acetaldehyde, acetaldehyde | |
| propenal | acrylic aldehyde, acrolein | |
| benzaldehyde | benzoaldehyde | |
| propanone | acetone | |
| Carboxylic acids | ||
| (HCOOH) | methanoic acid | formic acid (salt and esters- formates) |
| (CH3COOH) | ethanoic acid | acetic acid (salts and esters - acetates) |
| (CH 3 CH 2 COOH) | propanoic acid | propionic acid (salts and esters - propionates) |
| C15H31COOH | hexadecanoic acid | palmitic acid (salts and esters - palmitates) |
| C17H35COOH | octadecanoic acid | stearic acid (salts and esters - stearates) |
| propenoic acid | acrylic acid (salts and esters - acrylates) |
|
| HOOC-COOH | ethanedioic acid | oxalic acid (salts and esters - oxalates) |
| 1,4-benzenedicarboxylic acid | terephthalic acid | |
| Esters | ||
| HCOOCH 3 | methyl methanoate | methyl formate formic acid methyl ester |
| CH 3 COOCH 3 | methyl ethanoate | methyl acetate, acetic acid methyl ester |
| CH 3 COOC 2 H 5 | ethyl ethanoate | ethyl acetate, ethyl acetate |
| CH 2 =CH-COOCH 3 | methylpropenoate | methyl acrylate, acrylic acid methyl ester |
| Nitrogen-containing compounds | ||
| aminobenzene, phenylamine |
aniline | |
| NH 2 -CH 2 -COOH | aminoethanoic acid | glycine, aminoacetic acid |
| 2-aminopropionic acid | alanine | |
Well, to complete our acquaintance with alcohols, I will also give the formula of another well-known substance - cholesterol. Not everyone knows that it is a monohydric alcohol!
|`/`\\`|<`|w>`\`/|<`/w$color(red)HO$color()>\/`|0/`|/\<`|w>|_q_q_q<-dH>:a_q|0<|dH>`/<`|wH>`\|dH; #a_(A-72)<_(A-120,d+)>-/-/<->`\
I marked the hydroxyl group in it in red.
Carboxylic acids
Any winemaker knows that wine should be stored without access to air. Otherwise it will turn sour. But chemists know the reason - if you add another oxygen atom to an alcohol, you get an acid.Let's look at the formulas of acids that are obtained from alcohols already familiar to us:
| Substance | Skeletal formula | Gross formula | ||
|---|---|---|---|---|
| Methane acid (formic acid) |
H/C`|O|\OH | HCOOH | O//\OH | |
| Ethanoic acid (acetic acid) |
H-C-C\O-H; H|#C|H | CH3-COOH | /`|O|\OH | |
| Propanic acid (methylacetic acid) |
H-C-C-C\O-H; H|#2|H; H|#3|H | CH3-CH2-COOH | \/`|O|\OH | |
| Butanoic acid (butyric acid) |
H-C-C-C-C\O-H; H|#2|H; H|#3|H; H|#4|H | CH3-CH2-CH2-COOH | /\/`|O|\OH | |
| Generalized formula | (R)-C\O-H | (R)-COOH or (R)-CO2H | (R)/`|O|\OH |
Distinctive feature organic acids is the presence of a carboxyl group (COOH), which gives such substances acidic properties.
Anyone who has tried vinegar knows that it is very sour. The reason for this is the presence of acetic acid in it. Typically table vinegar contains between 3 and 15% acetic acid, with the rest (mostly) water. Consumption of acetic acid in undiluted form poses a danger to life.
Carboxylic acids can have multiple carboxyl groups. In this case they are called: dibasic, tribasic etc...
Food products contain many other organic acids. Here are just a few of them:
The name of these acids corresponds to those food products in which they are contained. By the way, please note that here there are acids that also have a hydroxyl group, characteristic of alcohols. Such substances are called hydroxycarboxylic acids(or hydroxy acids).
Below, under each of the acids, there is a sign specifying the name of the group of organic substances to which it belongs.
Radicals
Radicals are another concept that has influenced chemical formulas. The word itself is probably known to everyone, but in chemistry radicals have nothing in common with politicians, rebels and other citizens with an active position.
Here these are just fragments of molecules. And now we will figure out what makes them special and get acquainted with a new way of writing chemical formulas.
Generalized formulas have already been mentioned several times in the text: alcohols - (R)-OH and carboxylic acids - (R)-COOH. Let me remind you that -OH and -COOH are functional groups. But R is a radical. It’s not for nothing that he is depicted as the letter R.
To be more specific, a monovalent radical is a part of a molecule lacking one hydrogen atom. Well, if you subtract two hydrogen atoms, you get a divalent radical.
Radicals in chemistry received their own names. Some of them even received Latin designations similar to the designations of the elements. And besides, sometimes in formulas radicals can be indicated in abbreviated form, more reminiscent of gross formulas.
All this is demonstrated in the following table.
| Name | Structural formula | Designation | Brief formula | Example of alcohol | ||
|---|---|---|---|---|---|---|
| Methyl | CH3-() | Me | CH3 | (Me)-OH | CH3OH | |
| Ethyl | CH3-CH2-() | Et | C2H5 | (Et)-OH | C2H5OH | |
| I cut through | CH3-CH2-CH2-() | Pr | C3H7 | (Pr)-OH | C3H7OH | |
| Isopropyl | H3C\CH(*`/H3C*)-() | i-Pr | C3H7 | (i-Pr)-OH | (CH3)2CHOH | |
| Phenyl | `/`=`\//-\\-{} | Ph | C6H5 | (Ph)-OH | C6H5OH | |
I think everything is clear here. I just want to draw your attention to the column where examples of alcohols are given. Some radicals are written in a form that resembles the gross formula, but the functional group is written separately. For example, CH3-CH2-OH turns into C2H5OH.
And for branched chains like isopropyl, structures with brackets are used.
There is also such a phenomenon as free radicals. These are radicals that, for some reason, have separated from functional groups. In this case, one of the rules with which we began studying the formulas is violated: the number of chemical bonds no longer corresponds to the valence of one of the atoms. Well, or we can say that one of the connections becomes open at one end. Free radicals usually live for a short time as the molecules tend to return to a stable state.
Introduction to nitrogen. Amines
I propose to get acquainted with another element that is part of many organic compounds. This nitrogen.
It is denoted by the Latin letter N and has a valency of three.
Let's see what substances are obtained if nitrogen is added to the familiar hydrocarbons:
| Substance | Expanded structural formula | Simplified structural formula | Skeletal formula | Gross formula |
|---|---|---|---|---|
| Aminomethane (methylamine) |
H-C-N\H;H|#C|H | CH3-NH2 | \NH2 | |
| Aminoethane (ethylamine) |
H-C-C-N\H;H|#C|H;H|#3|H | CH3-CH2-NH2 | /\NH2 | |
| Dimethylamine | H-C-N<`|H>-C-H; H|#-3|H; H|#2|H | $L(1.3)H/N<_(A80,w+)CH3>\dCH3 | /N<_(y-.5)H>\ | |
| Aminobenzene (Aniline) |
H\N|C\\C|C<\H>`//C<|H>`\C<`/H>`||C<`\H>/ | NH2|C\\CH|CH`//C<_(y.5)H>`\HC`||HC/ | NH2|\|`/`\`|/_o | |
| Triethylamine | $slope(45)H-C-C/N\C-C-H;H|#2|H; H|#3|H; H|#5|H;H|#6|H; #N`|C<`-H><-H>`|C<`-H><-H>`|H | CH3-CH2-N<`|CH2-CH3>-CH2-CH3 | \/N<`|/>\| |
As you probably already guessed from the names, all these substances are united under the general name amines. The functional group ()-NH2 is called amino group. Here are some general formulas of amines:
In general, there are no special innovations here. If these formulas are clear to you, then you can safely engage in further study of organic chemistry using a textbook or the Internet.
But I would also like to talk about the formulas in inorganic chemistry. You will see how easy it will be to understand them after studying the structure of organic molecules.
Rational formulas
It should not be concluded that inorganic chemistry is easier than organic chemistry. Of course, inorganic molecules tend to look much simpler because they don't tend to form complex structures like hydrocarbons. But then we have to study more than a hundred elements that make up the periodic table. And these elements tend to combine according to their chemical properties, but with numerous exceptions.
So, I won’t tell you any of this. The topic of my article is chemical formulas. And with them everything is relatively simple.
Most often used in inorganic chemistry rational formulas. And now we’ll figure out how they differ from those already familiar to us.
First, let's get acquainted with another element - calcium. This is also a very common element.
It is designated Ca and has a valency of two. Let's see what compounds it forms with the carbon, oxygen and hydrogen we know.
| Substance | Structural formula | Rational formula | Gross formula |
|---|---|---|---|
| Calcium oxide | Ca=O | CaO | |
| Calcium hydroxide | H-O-Ca-O-H | Ca(OH)2 | |
| Calcium carbonate | $slope(45)Ca`/O\C|O`|/O`\#1 | CaCO3 | |
| Calcium bicarbonate | HO/`|O|\O/Ca\O/`|O|\OH | Ca(HCO3)2 | |
| Carbonic acid | H|O\C|O`|/O`|H | H2CO3 |
At first glance, you can see that the rational formula is something between a structural and a gross formula. But it is not yet very clear how they are obtained. To understand the meaning of these formulas, you need to consider the chemical reactions in which substances participate.
Calcium in its pure form is a soft white metal. It does not occur in nature. But it is quite possible to buy it at a chemical store. It is usually stored in special jars without access to air. Because in air it reacts with oxygen. Actually, that’s why it doesn’t occur in nature.
So, the reaction of calcium with oxygen:
2Ca + O2 -> 2CaO
The number 2 before the formula of a substance means that 2 molecules are involved in the reaction.
Calcium and oxygen produce calcium oxide. This substance also does not occur in nature because it reacts with water:
CaO + H2O -> Ca(OH2)
The result is calcium hydroxide. If you look closely at its structural formula (in the previous table), you can see that it is formed by one calcium atom and two hydroxyl groups, with which we are already familiar.
These are the laws of chemistry: if a hydroxyl group attaches to organic matter, it turns out alcohol, and if it is applied to a metal, it turns out to be hydroxide.
But calcium hydroxide does not occur in nature due to the presence of carbon dioxide in the air. I think everyone has heard about this gas. It is formed during the respiration of people and animals, the combustion of coal and petroleum products, during fires and volcanic eruptions. Therefore, it is always present in the air. But it also dissolves quite well in water, forming carbonic acid:
CO2 + H2O<=>H2CO3
Sign<=>indicates that the reaction can proceed in both directions under the same conditions.
Thus, calcium hydroxide, dissolved in water, reacts with carbonic acid and turns into slightly soluble calcium carbonate:
Ca(OH)2 + H2CO3 -> CaCO3"|v" + 2H2O
A down arrow means that as a result of the reaction the substance precipitates.
Upon further contact of calcium carbonate with carbon dioxide in the presence of water, a reversible reaction occurs to form an acidic salt - calcium bicarbonate, which is highly soluble in water
CaCO3 + CO2 + H2O<=>Ca(HCO3)2
This process affects the hardness of the water. When the temperature rises, bicarbonate turns back into carbonate. Therefore, in regions with hard water, scale forms in kettles.
Chalk, limestone, marble, tuff and many other minerals are largely composed of calcium carbonate. It is also found in corals, mollusk shells, animal bones, etc...
But if calcium carbonate is heated over very high heat, it will turn into calcium oxide and carbon dioxide.
This short story about the calcium cycle in nature should explain why rational formulas are needed. So, rational formulas are written so that the functional groups are visible. In our case it is:
In addition, individual elements - Ca, H, O (in oxides) - are also independent groups.Ions
I think it's time to get acquainted with ions. This word is probably familiar to everyone. And after studying the functional groups, it doesn’t cost us anything to figure out what these ions are.
In general, the nature of chemical bonds is usually that some elements give up electrons while others gain them. Electrons are particles with a negative charge. An element with a full complement of electrons has zero charge. If he gave away an electron, then its charge becomes positive, and if he accepted it, then it becomes negative. For example, hydrogen has only one electron, which it gives up quite easily, turning into a positive ion. There is a special entry for this in chemical formulas:
H2O<=>H^+ + OH^-
Here we see that as a result electrolytic dissociation
water breaks down into a positively charged hydrogen ion and a negatively charged OH group. The OH^- ion is called hydroxide ion. It should not be confused with the hydroxyl group, which is not an ion, but part of some kind of molecule. The + or - sign in the upper right corner shows the charge of the ion.
But carbonic acid never exists as an independent substance. In fact, it is a mixture of hydrogen ions and carbonate ions (or bicarbonate ions):
H2CO3 = H^+ + HCO3^-<=>2H^+ + CO3^2-
The carbonate ion has a charge of 2-. This means that two electrons have been added to it.
Negatively charged ions are called anions. Typically these include acidic residues.
Positively charged ions - cations. Most often these are hydrogen and metals.
And here you can probably fully understand the meaning of rational formulas. The cation is written in them first, followed by the anion. Even if the formula does not contain any charges.
You probably already guess that ions can be described not only by rational formulas. Here is the skeletal formula of the bicarbonate anion:
Here the charge is indicated directly next to the oxygen atom, which received an extra electron and therefore lost one line. Simply put, each extra electron reduces the number of chemical bonds depicted in the structural formula. On the other hand, if some node of the structural formula has a + sign, then it has an additional stick. As always, this fact needs to be demonstrated with an example. But among the substances familiar to us there is not a single cation that consists of several atoms.
And such a substance is ammonia. His water solution often called ammonia and is included in any first aid kit. Ammonia is a compound of hydrogen and nitrogen and has the rational formula NH3. Let's consider chemical reaction which occurs when ammonia is dissolved in water:
NH3 + H2O<=>NH4^+ + OH^-
The same thing, but using structural formulas:
H|N<`/H>\H + H-O-H<=>H|N^+<_(A75,w+)H><_(A15,d+)H>`/H + O`^-# -H
On the right side we see two ions. They were formed as a result of one hydrogen atom moving from a water molecule to an ammonia molecule. But this atom moved without its electron. The anion is already familiar to us - it is a hydroxide ion. And the cation is called ammonium. It exhibits properties similar to metals. For example, it may combine with an acidic residue. The substance formed by combining ammonium with a carbonate anion is called ammonium carbonate: (NH4)2CO3.
Here is the reaction equation for the interaction of ammonium with a carbonate anion, written in the form of structural formulas:
2H|N^+<`/H><_(A75,w+)H>_(A15,d+)H + O^-\C|O`|/O^-<=>H|N^+<`/H><_(A75,w+)H>_(A15,d+)H`|0O^-\C|O`|/O^-|0H_(A-15,d-)N^+<_(A105,w+)H><\H>`|H
But in this form the reaction equation is given for demonstration purposes. Typically equations use rational formulas:
2NH4^+ + CO3^2-<=>(NH4)2CO3
Hill system
So, we can assume that we have already studied structural and rational formulas. But there is another issue that is worth considering in more detail. How do gross formulas differ from rational ones?
We know why the rational formula of carbonic acid is written H2CO3, and not some other way. (The two hydrogen cations come first, followed by the carbonate anion.) But why is the gross formula written CH2O3?
In principle, the rational formula of carbonic acid may well be considered a true formula, because it has no repeating elements. Unlike NH4OH or Ca(OH)2.
But an additional rule is very often applied to gross formulas, which determines the order of elements. The rule is quite simple: carbon is placed first, then hydrogen, and then the remaining elements in alphabetical order.
So CH2O3 comes out - carbon, hydrogen, oxygen. This is called the Hill system. It is used in almost all chemical reference books. And in this article too.
A little about the easyChem system
Instead of a conclusion, I would like to talk about the easyChem system. It is designed so that all the formulas that we discussed here can be easily inserted into the text. Actually, all the formulas in this article are drawn using easyChem.
Why do we even need some kind of system for deriving formulas? The thing is that the standard way to display information in Internet browsers is hypertext markup language (HTML). It is focused on processing text information.
Rational and gross formulas can be depicted using text. Even some simplified structural formulas can also be written in text, for example alcohol CH3-CH2-OH. Although for this you would have to use the following entry in HTML: CH 3-CH 2-OH.
This of course creates some difficulties, but you can live with them. But how to depict the structural formula? In principle, you can use a monospace font:
H H | | H-C-C-O-H | | H H Of course it doesn’t look very nice, but it’s also doable.
The real problem comes when trying to depict benzene rings and when using skeletal formulas. There is no other way left except connecting a raster image. Rasters are stored in separate files. Browsers can include images in gif, png or jpeg format.
To create such files, a graphic editor is required. For example, Photoshop. But I have been familiar with Photoshop for more than 10 years and I can say for sure that it is very poorly suited for depicting chemical formulas.
Molecular editors cope with this task much better. But with a large number of formulas, each of which is stored in a separate file, it is quite easy to get confused in them.
For example, the number of formulas in this article is . From them are derived the form graphic images(the rest using HTML tools).
The easyChem system allows you to store all formulas directly in an HTML document in text form. In my opinion, this is very convenient.
In addition, the gross formulas in this article are calculated automatically. Because easyChem works in two stages: first the text description is converted into an information structure (graph), and then various actions can be performed on this structure. Among them are the following functions: calculation molecular weight, conversion to a gross formula, checking for the possibility of output as text, graphic and text rendering.
Thus, to prepare this article, I only used a text editor. Moreover, I didn’t have to think about which of the formulas would be graphic and which would be text.
Here are a few examples that reveal the secret of preparing the text of an article: Descriptions from the left column are automatically turned into formulas in the second column.
In the first line, the description of the rational formula is very similar to the displayed result. The only difference is that the numerical coefficients are displayed interlinearly.
In the second line, the expanded formula is given in the form of three separate chains separated by a symbol; I think it is easy to see that the textual description is in many ways reminiscent of the actions that would be required to depict the formula with a pencil on paper.
The third line demonstrates the use of slanted lines using the \ and / symbols. The ` (backtick) sign means the line is drawn from right to left (or bottom to top).
There is much more detailed documentation on using the easyChem system here.
Let me finish this article and wish you good luck in studying chemistry.