Ethane

Ethane is an alkane with the formula C₂H₆. It is the simplest alkane (1-4 carbons) and the second-most abundant alkane, after methane CH₄. It is an iso olefin with one carbon–carbon triple bond. Ethane is characterised by a characteristic smell, and its solid form is a colourless, pungent gas. Ethane is an important chemical feedstock in industry.

Natural sources of ethane include pyrolysis of biomass, marine biology (bioloading), and biogas formation in anaerobic digesters. It is also produced industrially by steam cracking of ethane, ethylene, or gasoline fractions from petroleum refining.

Ethane is used for a variety of industrial processes, especially in the petroleum industry as a reactant in alkylation, olefins metathesis and cracking processes.

Names and Etymology 

Ethane, or ethyne, is an ethyl (ethylene) compound, but ethene and ethane have two different meanings. "Ethane" is used to mean the name of a compound and is a homologue of ethylene. "Ethene" is the name of a hydrocarbon compound, which is often substituted with a carbonyl group. Thus, both names could refer to the same or a related chemical compound. 

The word "ethene" has a Greek origin from , ethin, ηθην, which can be linked to , etos, "fibre", and , hēs, "breath". The word "ethane" is derived from the Greek prefix, ēthos, that links to  -anous, "pertaining to breath, pertaining to life", so ēthane means breath, life. The name, ``ethane", was first reported by Charles-Marie de La Hire, a French chemist, who was the first to isolate the gas from coal and from natural gas.

Preparation 

The most direct method of manufacturing ethane is to distil and purify crude ethane. It can also be prepared by converting ethane to ethylene and hydrogen by the reaction with hydrogenation and carbon monoxide over an iron catalyst.

Ethane is a colourless, nontoxic gas with a peculiar odour. It is a gas at room temperature but becomes a liquid when cooled below -78.5 °C. The vapour pressure of ethane at 100 °C is 8 mm Hg (28.34 hPa). Ethane is miscible with both oxygen and other hydrocarbons.

Ethane is a versatile organic compound and is easily reacted. It reacts readily with hydrogen to give ethylene, the simplest alkene. This was used as an important precursor in the making of plastic polyethylene. Ethylene is also a key intermediate in the synthesis of alcohols, aldehydes, ketones, and other useful chemicals. It reacts with oxygen or nitric acid to give ethylene oxide. Ethylene can also be polymerized into ethylene polymers.

Ethane can be used in the synthesis of fuel ethanol. Ethylene oxide, on the other hand, is used as a raw material for a variety of products, including epoxy resins, polyvinyl resins, and surfactants. Ethane is used to produce vinyl acetate, a chemical used in resins and other manufacturing processes.

History

The discovery of ethane is associated with the chemist Dmitri Mendeleev, who worked in the 1830s. By looking at the periodic table he realised that the element in the table was missing; it should have a formal oxidation state of −2. However, it was first observed in 1859 by Dmitri Mendeleev.

Its melting point of 62 °C (147.2 °F) was first measured in 1862. In the 19^th century, ethane was called "ether". While there were isolated observations of ethane, it was only in 1897 that Karl Robert Bunsen first reported the discovery of pure ethane.

Isomerism

There are four isomers of ethane. The cis-isomer (in which the groups are in the same plane) and the trans-isomer (in which the groups are perpendicular to one another) exist in a ratio of 60:40. The other two, andro- and tele-isomers (in which the groups are at an angle) are never observed.

Isomers can be distinguished by measuring the mass of a molecule using a mass spectrometer. If a molecule has the same exact mass as another molecule, then the two molecules can be in the same energy state.

Physical Chemistry

Ethane has a tetrahedral carbon atom with 3 sigma orbitals filled, resulting in the four nonbonding electrons. Due to the four covalent bonds between two carbon atoms, ethane is very stable.

Ethane is most reactive towards hydrogen molecules because of the tendency for a two-electron reduction. This happens when two or more carbon atoms share one pair of electrons (covalent bonding). The two electrons tend to be shared equally, so that two or more ethyl groups share a pair of electrons. When this happens, the electrons of the H₂ molecules are donated to the ethyl group, and two hydrogen molecules are formed.

 It is also possible for one ethyl group to gain an electron to create a positive charge, which then attracts the H₂ molecule. Because ethane can lose up to two electrons, this reaction is reversible. When an ethyl group has gained two electrons, they no longer have the tendency to donate their electrons and become unstable.

What is Ethane?

Ethane is one of the simplest hydrocarbons we come across while studying organic chemistry. Hydrocarbons, as the name suggests, are nothing but organic compounds made of only hydrogen (H) and carbon(C) bonds. The first in the family of hydrocarbons is Methane, which is formed by one atom of carbon and four atoms of hydrogen. When two atoms of carbon and six atoms of hydrogen bond together, we get one molecule of Ethane. 

It is second in the family of hydrocarbons after Methane (CH₄) and was created artificially by Michael Faraday in 1834. Ethane is also known as Methyl methane, Bi methyl, Dimethyl, and Ethyl hydride.

The chemical formula or the molecular formula of ethane is C₂H₆. Looking closely at the structure, we can see that two atoms of carbon have bonded together and three hydrogen atoms are attached to each of the two carbon atoms on either side. It is thus structurally represented as or the structure of ethane is CH₃-CH₃.

The Lewis-dot structure of ethane will also represent the single bonding of two carbon atoms with each other, and each of the carbon atoms is bonded by three hydrogen atoms.  The dot structure figure which has dots represents the valence electrons of atoms. 

The atoms of both carbon and hydrogen here are bonded in single bonds. When hydrocarbons are formed by carbon-containing single bonds, they are called saturated hydrocarbons. Saturated hydrocarbons are also called alkanes. 

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Molecular Structure

Its molecular structure is like a straight-chain with only a single carbon-carbon bond. This also makes it the simplest hydrocarbon.

A straight-chain molecule has all the carbon atoms arranged in a straight line appearing as a row of train coaches. It has a tetrahedral geometry shape and its carbon atoms have sp³ hybridization. 

It can also be formed by substituting one hydrogen atom in Methane (CH₄) with another sp³hybridised carbon fragment. Or simply stated, it can be reached by replacing a  CH₃ group, called a methyl group, for one hydrogen of methane. 

The structure of ethane consists of a pair of carbon atoms connected by an ethyl group  CH₃. Carbon atoms share two pairs of valence electrons, one from each, making them highly reactive. The ethyl group has one pair of valence electrons, leaving two spare electrons. These electrons can react with the carbon atoms of the ethyl group to form the double bond of ethane. 

The carbon atoms form two non-bonding, or delocalised, electrons, as well as each of the three covalent bonds. Carbon has the largest electronegativity of the four elements, meaning that it has the greatest tendency to share electrons with its neighbours, making it especially reactive. It is this reactivity that makes it possible for the ethyl group to form bonds to the carbon atoms.

Physical Properties 

Ethane is a natural gas that is found abundantly in nature. Being a greenhouse gas it is found in fossil fuels. In the composition of natural gas, it is found in 5 – 10% concentration. 

Ethane is an important constituent of natural gas and a primary gaseous fuel in the petrochemical industry.

Under normal temperature and pressure conditions, ethane remains colourless, odourless, and is a highly flammable gas. 

The alkane has a melting point of -182.8 °C and a boiling point of 89 °C. Alkanes with a larger number of carbon atoms have higher melting and boiling points. Leaving the first four alkanes, starting from Methane to Propane, as we go higher in the alkanes table, we find the boiling point substantially rises.

Ethane is partially soluble in water and is lighter than air. With changes in the parameters of temperature and pressure, it can be changed into other states of existence like solid. 

Chemical Properties

After methane, ethane is found in the second-largest quantity as the constituent of natural gas. This hydrocarbon is extracted from natural gas and petroleum refining. 

It acts as a raw material for the production of ethylene by the process of pyrolysis. 

⟶    CH₃CH₃ CH₂CH₂ + H₂

In several gas processing plants and units, ethane is separated from the other constituents of natural gas. It can be produced using sodium propionate in the laboratory method. 

The mole of the C atom equals 12.01 g and 1 mol of the H atom equals 1.0079 g. So, upon calculation, 1 molecule of C₂H₆ or the molar mass of C₂H₆ is 30.07 g. 

Plastic crystals start to appear when ethane is cooled under normal pressure. At this state, hydrogen atoms do not have a fixed position and can rotate freely.

Ethane can also be easily created in laboratories using Kolbe electrolysis where a solution of acetate salt is electrolysed. 

Uses of Ethane

The uses of ethane are as follows:

• Ethane is primarily used as the raw material for the production of ethylene for further production of plastics, fruit ripening and detergent making

• In scientific research, it is used in liquid form for vitrifying water-rich materials

• It can also be used for producing ethyl alcohol, acetic acids or other similar organic compounds

• It can also be liquefied for use as fuel for automobiles