What is the rational nomenclature

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2018-03-27 02:13:30

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The Name of his rational nomenclature derived from Latin ratio "reason". This system was first allowed to give a logical name organic compounds based on their belonging to a particular class. She was replaced by trivial names, which in no way reflect the structural features of molecules. And to remember the structural formulas of many organic compounds on forces not to everyone.

A New item that is called radical or functional, the basis began to take the simplest matter in the homological series of any class. And the remaining compounds were considered as substituted derivatives of them. There are clear requirements to name compounds. In the 19th century these rules were innovative, and their occurrence became possible thanks to the theory of radicals, the theory of types and a number of scientific treatises.

old book

General rules of rational nomenclature

For a starting point of names, take the first or second member of the homologous series of the class of organic substances. The rest of the hydrocarbon skeleton of the molecule is recorded as the radicals attached to it.

The Names themselves of alternate form, based on homologous series of alkanes by replacing the suffix -EN in Il for example, methyl, ethyl, etc. To name a branched radical, to a penultimate carbon atom of which is attached two groups-CH3, add the prefix Trying with-. for Example, isopropyl, isobutyl.

Another common way to show the branching of the substituents is the addition of the prefixes Second and Tert-. This entry indicates that a free valence at a secondary or tertiary carbon atom. If the free valency is at the end of unbranched remainder of the molecule, then add a letter N (from the word "normal"), but in fact it is recorded rarely.

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the names of some of the hydrocarbon radicals

In order to reflect the position of the radical relative to the main fragment of the molecule, there are several ways:

  • Numbers;
  • Letters of the Greek alphabet;
  • Consoles SIMM. or Nesim., characterizes the symmetry of the molecules;
  • The addition of the letters Is (ortho), M (meta) or P (pair) in the description of cyclic compounds;
  • Letters corresponding to the name of the heteroatoms (N - nitrogen, O - oxygen S - sulphur, etc.).

The Number of the same substituents indicate using prefix Di-, tri-, Tetra-, Penta- etc.

Examples of rational nomenclature of organic compounds:

  • 3-SΗ2-SΗ2-S(CΗ3)2-SΗ(SΗ3)-Zn3 - dimethylpropyleneurea;
  • 3-SΗ2-SΗ(SΗ3)-SΗ2-Zn3 - methylethyl-second-butelman;
  • C6AndΗ5-Η (Η3)-CH3 - isopropyl;
  • N32-ΗBr-Η2-CH2-CH3 - ethylpropylamine;
  • BUT-C6N4-C2H5 - o-acetylbenzo.

Alkanes

According to the rules of rational nomenclature of alkanes is considered as methane or ethane, hydrogen atoms which are substituted by various hydrocarbon radicals. Moreover, in complex molecules the remainder of the methane is considered the least gidrogenizirovannye a carbon atom, that is, one that is associated with a large number of deputies.

The names of the radicals are recording in order of seniority, that is, to increase the complexity of their structure, thus multiplying prefix to this order are not affected.

If the molecule contains non-hydrocarbon substituents, e.g., Halogens, their names are mentioned after the rest of the radicals.

Homologous series of alkanes
Molecular formula

A Simplified structural formula

Name according to IUPAC Rational name Name of the radical is
Η4 Η4 Metan Metan Methyl
C2Η6 Η3-CH3 Ethan Metalmetal Ethyl
C3Η8 CH32-CH3 Propane Dimethylmethane Propyl
C4Η10 CH3-Η2Η23 Bhutan Demethylated Butyl
C5AndΗ12 CH3-(Η2)33 Pentane Methylethylketon Pentyl
C6Η14 CH3-(Η2)43 Hexane Titilate Exil
C7AndΗ16 CH3-(Η2)53 Heptane Ethylpropylamine UDMH
C8Η18 CH3-(Η2)63 Octane DIPROPYLENE Octyl
C9AndΗ20 CH3-(Η2)73 Noonan Propinball-Ethan Neil
C10Η22 CH3-(Η2)83 Dean Dbutility Decyl

Alkenes

The Hydrocarbons with C=C double bond is usually considered as substituted ethylene. The location of the radicals at this point words of SIMM. (nesim.) or Greek letters. If similar substituents are connected to different carbon atoms at the double bond, suchalken is called symmetric, and if the same, it is symmetrical.

In cases when the substituents have a strongly branched structure, and to make the name of the alkene on the rational nomenclature is problematic, the connection is considered as derivatives of methane. In this case the double bond is part of one of the deputies, and based on the names choose the least hydrogenated carbon atom.

nomenclature of alkenes

Dienes

Features of compilation of the names of diene hydrocarbons by rational nomenclature depend on the relative placement of the multiple bonds in the molecule. If the double carbon-carbon bonds in the compound are kemuliaanmu or paired, the substance is considered to be a derivative of Allen or butadiene, respectively. If the double bonds are isolated, that is, if there are two or more single, substances referred to as derivatives of methane or ethane. And multiple bonds in this case are deputies.

Rational name dienes

A Simplified structural formula

Name
SN2=C=CH2 Allen
Η3-Η=C=CH2 Matiello
Η2=Η CΗ=CH2 Butadiene
Η32-Η=C=CH2 Atralin
Η3-Η=Η-SN=SN2 α-merdiveni
Η2=Η CΗ2-Η=CH2 Diphenylmethan
Η3-Η==Η-CH3 SIMM.dimethylallyl
Η3-(Η3)=C=CΗ2 Nasim.dimethylallyl
Η2=(Η3)-Η=Η2 β-merdiveni

Alcina

Rational nomenclature considers alkyne as substituted acetylene. In contrast to the ethylene hydrocarbons the molecules of the hydrocarbons with C≡communication cannot be the two radicals linked to the same carbon atom in front of her. Therefore, to specify the mutual position of them is not necessary. It is only necessary to list the names of the radicals in the order of increasing complexity.

If the molecule has a complex structure, in the preparation of its name treated as alkynes. The triple bond in this case is reflected in the composition of the Deputy, for example, acetylenyl and based on taking methane or ethane. In this first recording of the ultimate radicals, unsaturated and then with the same number of carbon atoms. Examples:

  • N3≡C-CH3 - dimethylacetate;
  • Η3S-SΗ2-S≡S-SΗ2-SΗ2-SΗ3 - ethylpropylamine;
  • NS≡S-S(SΗ3)(C2Η5)-SΗ(SΗ3)-Zn3 - метилэтилацетиленилизопропилметан.
structure of ethylene

Aromatic compounds

Mononuclear aromatic hydrocarbons are considered as rational nomenclature of substituted benzene compounds. The mutual arrangement of the radicals denoted by the letters Oh, M or P

In molecules with complex hydrocarbon skeleton, the presence of benzene ring is reflected in the name of the corresponding radical. The presence of the hydroxyl groups of phenols is indicated by the prefix Oxy-, for example, oxybenzone.

nomenclature of aromatic hydrocarbons

Alcohol

Rational nomenclature of alcohols has its own characteristics for each of the compounds of this class. Monohydric alcohols take derivatives of carbinol (methyl alcohol). The names of the radicals written in the increasing order in their carbon atoms:

  • CH3-CH2-metilkarbinolom;
  • Η3-Η (Η)-C≡CΗ - methylacetanilide.

Diatomic alcohols, whose molecules hydroxyl group -OhΗ located at the neighboring carbon atoms, are called glycol:

  • Η3-Η (Η)-Η2(Η) - methylaminophenol.

But if the hydroxyl is connected with the neighboring carbon atoms, in the names record the number of methylene groups -CH2-in between:

  • Η CΗ2222-Η - tetraethyleneglycol;
  • AΗ-SΗ2-SΗ2-SΗ2-SΗ2-SΗ2-SΗ2-OΗ - hexamethyleneimine.

Aldehydes and ketones

The names of the aldehydes on the rational nomenclature are based on the structure of ethanal, in this case called acetaldehyde. For example:

  • CH3-SLEEP - acetaldehyde;
  • Η322-Η - acyloxy aldehyde;
  • CH3-Η (Η3) is a SLEEP - dimethyluracil aldehyde.

If the join has multiple functional groups, the group -SON designated by adding the prefix Aldo-:

  • NOSE-SN2-COOH - Algarrobina acid.

The Ketones referred to, listing the substituents linked to the carbonyl group >C=O and adding the word Ketone:

  • CH3-co-CH3 - dimethylketone;
  • Η2=Η-WITH-WITHΗ3 - methylvinylketone.

With the Greek letters denote not only the mutual location of several carbonyl groups, but also substituents in the main hydrocarbon chain:

  • N3-CO-co-CH3 - α-diketone;
  • Η323 - β-diketone;
  • The
  • Br-N2-co-CH2-CH3 - (α-bromomethyl)ethylketone.
structure of formaldehyde

Carboxylic acids

For monobasic carboxylic acids with unbranched hydrocarbon chain used trivial names (butyric, acetic, etc.). If the molecule has a branched structure, its name for the sound item is composed of the corresponding radicals, United with acetic acid or its homologues. Thus, one and the same acid may have several rational names:

  • N3CH(CH3)-COOH - dimethyloctane, or methylpropionate acid;
  • Η32-Η (Η3)-sooΗ - methylethylacetate, or α-matlakala acid.

If the position of Deputy noted by Greek letters, beginning the countdown to the carbonyl carbon and followed. According to a rational nomenclature, the names of unsaturated acids get, based on the molecule of acrylic acid, if the double bond is located between the α and β carbons. In other cases, a multiple connection is indicated in the composition of the deputies. Examples:

  • N2C=CH-COOH acrylic acid;
  • N3-HC=CH-COOH - β-methylacrylate acid;
  • Η2=Η CΗ (Η3)-sooΗ - methylisoleucine acid.

Esters

According to a rational nomenclature, the names of esters are composed of two balances: the trivial name of the acid and alcohol radical. For example:

  • CH3-WO-CH3 - uksousnokisloy live
  • Η32-WO-CH3 - propiononitrile live
  • 3-SΗ2-SΗ2-Sao-SΗ(SΗ3)-SΗ3 - maslanopodobnaya live
  • CH3-soo-C5H11 - exploitability the air.

Cycloalkane

Limit cyclic hydrocarbons are called based on the number of methylene groups -CH2-, which form a ring. Their number indicate prefixes Three, Tetra-, Penta-, hexa-, hepta-, etc. If the cycle is connected with one or more substituents, they first list their names.

item cycloalkanes

In modern chemistry, a rational nomenclature is not as widespread as Geneva. However, at the time its principles laid the Foundation for the modern system names for different connections.

The Main drawback of a rational nomenclature is the ambiguity of the requirements for the selection of substances, which is based on the building name. This leads to the fact that compounds with a very complex branched structure can have several names. And in particularly difficult cases, they build and do it is impossible. However, for some classes of organic substances such as alkanes or alcohols, and today the names, chosen according to its rules, are used quite often.


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Alin Trodden - author of the article, editor
"Hi, I'm Alin Trodden. I write texts, read books, and look for impressions. And I'm not bad at telling you about it. I am always happy to participate in interesting projects."

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