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Alkane Functional Group with Examples || What is the use of Alkanes?

Alkane is an open-chain saturated hydrocarbon chain (saturated group), the carbon atoms in a molecule are a single bond connected to, the remaining valences are bonded hydrogen compounds. The general formula is CnH2n+2, (Alkane Functional Group).

Which is the simplest organic compound? The main sources of alkanes are oil and natural gas, which are important chemical raw materials and energy materials.

Alkane Definition

A compound consisting of only two elements, hydrocarbons, is called a hydrocarbon, or simply a hydrocarbon. According to the different molecular structure of hydrocarbons, hydrocarbons can be divided into two types: Chain hydrocarbons ( aliphatic hydrocarbons ) and Cyclic hydrocarbons ( alicyclic hydrocarbons ).

Chain hydrocarbons can be divided into saturated hydrocarbons and unsaturated hydrocarbons. Most of the overall configuration of carbon only hydrogen atoms to carbon-carbon single bond and an organic compound consisting of a hydrocarbon bond, and means a saturated carbon atom bound to other atoms in the molecule reaches the maximum.

Strictly speaking, alkanes do not include naphthenes, so this entry focuses on cyclic alkanes.

In addition, the alkane is a kind of saturated hydrocarbon, and saturated hydrocarbon includes cycloalkane and alkane.

Physical Properties

1. When the number of carbon atoms is less than or equal to 4, the alkanes are gaseous at normal temperature, and other alkanes are solid or liquid at normal temperatures.

2. Not soluble in water, easily soluble in organic solvents.

3. As the number of carbon atoms increases, the boiling point
gradually increases.

4. As the number of carbon atoms increases, the relative density
gradually increases. The density of alkanes is generally less than the
density of water.

Alkane Structure

The alkane is not a planar structure drawn by the structural formula, but a three-dimensional shape. All carbon atoms are sp3 hybrids.

Each atom is connected by a σ bond, and the bond angle is close to 109°28 ‘. The length is 154 pm, and the average bond length of the CH bond is 109 pm.

Since the σ-bond electron cloud is distributed along the axis of the axis, the two bonding atoms can “freely” rotate about the axis of the bond.

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Alkane Chemical Formula

Starting from methane, two carbon atoms are added for each carbon atom. Therefore, the general formula of an alkane is CnH2n + 2, where n is the number of carbon atoms (n = 1,2,3, ···) In theory, n can be large, but the known alkane n is within about 100.

A series of compounds with the same molecular formula and
structural characteristics are called homologous series. The homologue of
alkane is CH2, and alkanes with different numbers of C atoms are
homologous to each other. The homologs in the same series have similar
structures, similar chemical properties, and regular changes in physical
properties with increasing carbon atoms.

Common Nomenclature

Ordinary nomenclature, also known as customary nomenclature, is applicable to simpler alkanes. Alkanes with a carbon number of less than 10 are represented by the number of carbon atoms using the names of A, B, C, D, P, P, H, G, S, N, and Dec.

For example, CH4 is called methane, and C2H6 It is called ethane, C3H8 is called propane, and the rest can be deduced by analogy when the number of carbon atoms is 10 or more, it is represented by Chinese numerals. For example, C11H24 is called undecane, and C18H38 is called octadecane.


CH3—CH2—CH2—CH 2—CH2—CH3

Iso- hexyl alkoxy


New hexyl alkyl








Derivative nomenclature

Derivative nomenclature

Derivative nomenclature uses methane as the parent and treats
other alkanes as alkyl derivatives of methane. When naming, choose the
carbon atom with the most alkyl groups. The alkyl groups are arranged in order
of size, with the smaller ones in front. E.g:

CH 3 — CH —CH 2 —CH 3
  CH 3
  dimethyl ethyl methane

Dimethyl ethyl isopropyl methane

Although this nomenclature can reflect the molecular structure
of alkanes, it is still not suitable for the construction of more complex

System Nomenclature

This is a systematic nomenclature formulated by adopting the universal IUPAC naming principles and combining the characteristics of Chinese characters.

The naming of straight-chain alkanes is basically the same as that of ordinary nomenclature, except that the word “normal” is omitted and branched-chain alkanes are regarded as alkyl derivatives of straight-chain alkanes, and are named according to the following rules:

(1) The longest carbon chain in the molecule is selected as the main chain, and the branched alkyl group is regarded as a substituent on the main chain. The alkane is called according to the number of carbon atoms contained in the main chain.

(2) Starting from the end closest to the branch chain, the carbon atoms of the main chain are numbered with Arabic numerals, and the position of the branch chain is indicated by the number of the carbon atom to which it is connected.

(3) Write the name of the substituent in front of the name of the alkane. If the main chain contains several different substituents, they are arranged in ascending order; if they contain several identical substituents, they can be listed in The name is indicated by two, three, four …

If the position of the first substituent is the same from either end of the carbon chain, the sum of the numbers representing the positions of all substituents is required to be the smallest number.

Alkane Preparation

The main sources of hydrocarbons are natural gas and petroleum. Although the natural gas composition varies from place to place, almost all of them contain 75% methane, 15% ethane, and 5% propane, and the rest are higher-level alkanes. 

The most alkane-containing types are petroleum. Petroleum contains chain alkane and some cyclic alkanes with 1 to 50 carbon atoms. Cyclopentane, cyclohexane and their derivatives are the main types of petroleum. It contains aromatic hydrocarbons. 

The petroleum produced in different parts of world has different compositions, but they can be fractionated into different fractions and applied as required. Alkanes are not only an important source of fuel but also a feed stock for the modern chemical industry. In addition, alkanes can also be used as food for some bacteria.

After the alkanes are consumed by the bacteria, many useful compounds are secreted, that is, the alkanes can become more useful compounds after being “processed” by the bacteria.

Although petroleum is rich in various alkanes, this is a complex mixture. Except for C1 to C6 alkanes, it is difficult to completely separate them into extremely pure alkanes due to the small molecular weight differences between the components and similar boiling points. 

Alkane Preparation

The physical properties of alkanes change regularly with the increase in the number of carbon atoms in the molecule.

At room temperature 25°, alkanes containing 1 to 4 carbon atoms are gases. Alkanes containing 5 to 17 carbon atoms are liquid.

However, alkanes containing 10 to 19 carbon atoms can be solid at normal temperatures. Containing 18 or more carbon atoms as solid n-alkanes, but then-alkanes containing up to 60 carbon atoms (melting point of 99 deg.] C) melting point (melting point) does not exceed 100 .

Alkane is non-polar molecules (non-polar molecule), dipole moments (dipole moment) is zero, but the molecular charge distribution is not uniform, may be generated in the movement transient dipole moment, the dipole moment has between instantaneous Interaction force ( dispersion force ).

In addition, there are Van der Waals forces between the molecules.

These intermolecular forces are one or two orders of magnitude smaller than chemical bonds. The energy required to overcome these forces is also low. Therefore, the melting point and boiling point of organic compounds rarely exceed 300°C.

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