Carbon chain - Cadena carbonada

Organic compound showing a main chain, in red, of carbon atoms, with two small branches

A carbon chain is the backbone of almost all organic compounds and is formed by a set of several atoms of carbon , linked together by covalent bonds carbon-carbon and that bind or add other atoms such as hydrogen , oxygen or nitrogen , forming varied structures , resulting in countless different compounds. [ 1 ]

The ease of carbon to form long chains is almost specific to this element and is the reason for the high number of known carbon compounds, if we compare it with compounds of other atoms. [ 2 ] Carbon chains are quite stable and do not undergo variation in most organic reactions.

Chain types

The chains can be linear cyclic and in both cases there can be branches, functional groups or heteroatoms. The length of the carbon chains is highly variable or constant, and can contain from only two carbon atoms, which is something more or less like this, up to several thousand in compounds, such as polymers .

Linear chain

no ramifications

Linear chain


Cyclic chain

(can be named using the prefix cycle,
the suffix corresponds to the functional group)

Two condensed cycles
Eicosane3D.png Isocetane3D.png Cycloundecane3D.png 1-Methylnaphthalene 3D.png
Eicosano, C20H42 Isocetano, C16H34
o 2,2,4,4,6,8,8-heptametilnonano
Cicloundecano, C11H22 1-methylnaphthalene, C 11 H 10

Although they are called linear chains, they are actually zigzag shaped, with angles close to 109º, due to the tetrahedral structure of the carbon atom when it only has single bonds. There is the possibility of rotation or spin on the axis of the CC bonds, which gives rise to the existence of different conformational states, also called conformers .

The presence of carbon atoms with double bonds makes this angle close to 120º, with a flat structure and preventing rotation or rotation on the C = C axis. This is the case of alkenes or unsaturated fatty acids .

The presence of carbon atoms with triple C≡C bonds makes said angle close to 180º, with linear geometry and straight sections in the molecule, as in the case of alkynes .

Simple links only Some double bond Some triple bond
Long and complex carbon chains
6 ethyl 3 4 methyloctane numbering PNG Fenbufen-from-xtal-3D-balls.png Cicutoxin.svg Protein.png
Angles close to 109º 28 ' Angle close to 120º Angle close to 180º
Helix- shaped windings in a
protein molecule .
18-bromo-12-butyl-11-chloro-4,8-diethyl-5-hydroxy-15-methoxy-6,13-dien-19-yn-3,9-dione molecule showing the main chain with 23 atoms carbon.

In the case where there are branches, the main chain is the longest. The multiple bonds and most of the functional groups must be in said main chain. The number of carbon atoms in the main chain is used to name these compounds according to the rules of the IUPAC nomenclature .

The atoms or groups of atoms attached to the main chain, other than hydrogen, are the radicals or substituent groups (such as methyl , -CH 3 ; ethyl , -CH 2 -CH 3 ...) and functional groups (such as alcohol group , -OH).

Chain isomerism

The existence of two or more compounds that have the same empirical formula but different form of the chain is one of the cases of structural isomerism, called chain isomerism . This is the case of n-butane (straight chain) and isobutane or methylpropane (branched chain), both of the formula C 4 H 10 .

See also


  1. Biochemistry. Antonio Peña. Editorial Limusa, 1988. ISBN 9681826604 . p. 38
  2. Simplified organic chemistry. Rudolph Macy. Editorial Reverté, 1976. ISBN 8429173315 . Pág. 70

external links