Acyclic Compounds: Acyclic Hydrocarbons Examples

ACYCLIC COMPOUNDS

Organic compounds are a large class of compounds which contain carbon and hydrogen as the main constituent elements. For example, sugar, fatty acids and natural rubber are organic compounds. One important class of organic compounds is acyclic compounds. They are also called open-chain compounds, due to their open-chain structure. Open chain compounds contain long carbon-carbon chains. Branching of such chains is possible. Consequently, more than one structure may be written for the same molecular formulae. Acyclic compounds or open chain compounds can be further classified into saturated and unsaturated hydrocarbons.

Let’s learn what saturated hydrocarbons are. In saturated hydrocarbons, all carbon-carbon bonds are single bonds. When two carbon atoms share one electron each, a single bond is formed. Saturated hydrocarbons, where carbon and hydrogen are linked to each other by single covalent bonds, are known as alkanes. Methane is the first member of alkane family. In the formation of methane, the carbon atom has shared all the four electrons present in its valence shell with the electrons belonging to four hydrogen atoms. Thus, in methane, carbon is linked to four hydrogen atoms by covalent bonds. In methane, the HCH bond angle is 109 degree 28 minutes. Similarly, ethane, the second member of alkane family, has one carbon atom and two more atoms of hydrogen than seen in methane. Therefore, it is clear that one hydrogen atom of carbon in CH4 (methane) is replaced by another carbon atom. The three valences of this carbon atom have been satisfied by hydrogen atoms as a result of electron sharing. In ethane the CCH bond angle is 111 degree 17 minutes. The next two members of the alkane family are propane (C3H8) and butane (C4H10). The general formula representing alkanes is CnH2n+2, n= no. of carbon atoms. So far, we’ve learned about saturated hydrocarbons.

Let’s now discuss unsaturated hydrocarbons. The hydrocarbons in which carbon atoms are linked to each other by at least one carbon-carbon double bond or triple bond are called unsaturated hydrocarbons. There are two types of unsaturated hydrocarbons:alkenes and alkynes. Unsaturated hydrocarbons, with at least one carbon-carbon double bond, are called alkenes. When two carbon atoms share two electrons each, a double bond is formed. Accordingly, the first member of the alkene family is ethene. Its molecular formula is C2H4. Here, each carbon atom is linked to two hydrogen atoms by single bonds. In order to satisfy the remaining valences, the carbon atoms mutually share two electron pairs resulting in a double bond. In Ethene the CCH bond angle is approximately 121 degree and the HCH bond angle is approximately 120 degree. The general formula representing alkenes is CnH2n, n = no. of carbon atoms. Let’s take a look at the other members of the alkene family Within the unsaturated hydrocarbons, we have seen alkene family, now we will learn about alkynes. Hydrocarbons with at least one carbon-carbon triple bond are called alkynes. When two carbon atoms share three electrons each, a triple bond is formed. Let’s introduce the alkyne family members Ethyne is the first member of alkyne family. It is also called acetylene. And the CCH bond angle is 180 degree. Its chemical formula is C2H2 . The general formula representing alkynes is CnH2n-2. Let’s now familiarize ourselves with some of the other members of the alkyne family.

THINGS TO REMEMBER:

1)Organic compounds that contain carbon and hydrogen are called hydrocarbons.

2)One important classification of hydrocarbons is Acyclic compounds or Open chain compounds.

3)There are two types of Acyclic compounds: Saturated hydrocarbons and Unsaturated hydrocarbons.

4)Saturated hydrocarbons have all carbon-carbon single bonds and are called alkanes

5)Unsaturated hydrocarbons with at least one carbon-carbon double bond are called alkenes.

6)Unsaturated hydrocarbons with at least one carbon-carbon triple bond are called alkynes.