Structure of double bond (ethene)

Introduction

Ethene has the chemical formula C2H4and is an unsaturated organic molecule. It is the simplest member of the alkene class of hydrocarbons, with only one double bond.

Ethene, often known as C2H4, is the most basic alkene. Ethene, Polyethene, and Etileno are some of the other names for it. As a plant hormone, a refrigerant, and a food ingredient, it is widely utilised.

Ethene is a colourless gas with a pleasant aroma and flavour. When compared to air, it is combustible and lighter. The containers can explode if they are exposed to heat or fire for an extended period of time.

Bonding in Ethene (double bond)

Valence bond theory has only been able to describe the bonding in molecules with single bonds so far. When molecules have double or triple bonds, however, the model requires more information. The simplest chemical with a carbon-carbon double bond is ethene (often known as ethene), CH2=CH2. Ethene has one carbon-carbon double bond and four carbon-hydrogen single bonds, according to its Lewis structure.

The four carbon-hydrogen bonds in the ethene molecule have been proved to be similar in an experiment. The molecule should have a trigonal planar geometry, according to VSEPR theory, because each carbon is surrounded by three electron groups. Despite the fact that each carbon has met its tetravalent criterion, one bond appears to be different. Clearly, this is a different form of orbital overlap.

A different type of hybrid orbital participates in the formation of sigma bonds in ethene. The 2s, 2px, and 2py atomic orbitals on each carbon unite to produce three sp2 hybrids, leaving the 2pz orbital unhybridized. Three of each carbon’s four valence electrons are dispersed among the three sp2 hybrid orbitals, with the fourth electron remaining in the unhybridized pz orbital.

“Sp2-hybridized carbon” describes each carbon in ethene. There are four unpaired electrons to form bonds in the electron configuration of the sp2 hybridised carbon. However, because the unpaired electrons are trapped in two different sorts of orbitals, two different types of bonds are expected to form.

Mathematically, the form of the sp2-hybridized orbital is essentially the same as that of the sp3-hybridized orbital. The three sp2-hybridized orbitals are placed in a trigonal planar layout to reduce electron repulsion. Each orbital lobe points to the three corners of an equilateral triangle, forming a 120-degree angle between them. Geometry and hybridization can be linked once more. Trigonal planar geometry and sp2 hybridization are attributes of atoms surrounded by three electron groups.

The plane of the trigonal planar sp2 hybrid orbitals is perpendicular to the unhybridized 2pz orbital.

Each carbon atom in the ethene molecule is linked to two hydrogen atoms. For the C-H sigma bonds in ethene (sp2(C)-1s), overlap two sp2-hybridized orbitals with the 1s orbitals of two hydrogen atoms (H). As a result, the four carbon-hydrogen bonds in ethene are identical, as predicted by the data.

The overlap of a sp2 hybrid orbital from each carbon forms the C-C sigma bond in ethene. The ethene molecule’s sigma bond framework is formed by the overlap of hybrid orbitals or a hybrid orbital and a 1s orbital from hydrogen. On each carbon, however, the unhybridized Pz orbital persists.

Each carbon’s unhybridized Pz orbitals overlap to form a bond (pi). Pz(C)-1pz is a typical notation for orbital overlap (C). In most chemical compounds, numerous bonds are created by the overlap of unhybridized p orbitals. It’s worth noting that ethylene’s carbon-carbon double bond is made up of two separate sorts of bonds: sigma and pi.

Ethene is stated to have five sigma bonds and one pi bond in total. Pi bonds are weaker than sigma bonds because the p orbitals overlap side-by-side, resulting in a less effective orbital overlap when compared to a sigma bond’s end-to-end orbital overlap. This makes breaking the pi, which is one of the most fundamental concepts in organic chemistry reactions, considerably easier.

Five sigma bonds and one pi bond are said to make up an ethene molecule. The basic trigonal planar geometry is created by the three sp2 hybrid orbitals on each carbon. In ethene, the H-C-C bond angle is 121.3 degrees, which is extremely close to the 120 degrees predicted by VSEPR. In ethene, there are four C-H sigma bonds. In comparison to the carbon-carbon single bond in ethene (154 pm & 377 kJ/mol), the carbon-carbon double bond in ethene is both shorter (133.9 pm) and nearly twice as strong (728 kJ/mol). Each of ethene’s four carbon-hydrogen bonds is equal, with a length of 108.7 pm.

Hardness in Ethene

Pi bonds are not free to spin since they are the result of side-by-side overlap (rather than end-to-end overlap like a sigma bond). Rotation around this bond would cause the side-by-side overlap between the two 2pz orbitals that make up the pi bond to be disrupted. The p-orbitals would have to go through a phase where they are 90° apart if free rotation occurred, which would break the pi bond because there would be no overlap. Because the pi bond is so important to ethene’s structure, it can’t break, hence there can’t be any free rotation around the carbon-carbon sigma bond. The presence of the pi bond binds the six atoms together.

Uses of ethene

Many essential polymers, such as polyethene and polyvinyl chloride, are made in this way (PVC). Raincoats, shoe soles, pipelines, and floor tiles are all made with these polymers.

Ethene is primarily used in the production of polymers. Poly(ethene) accounts for approximately 60% of global ethene demand (HDPE 28%, LLDPE 18%, LDPE 14%), with dichloro-1,2-ethane, the precursor for chloroethene and hence PVC, accounting for the remaining 11%. Another 5% is used to make ethylbenzene, which is used to make poly(phenylene).

Epoxyethane is made from about 16 per cent of ethene globally (ethene oxide).

Conclusion

Ethene consist of at least one double bond present in the structure and has a general formula C2H4. Ether is an unsaturated organic compound and is the simplest hydrocarbon of the alkene class. Most Ethene are purchased as Ethene can be rarely prepared in laboratories due to its complex formation. Ethene appears to be colourless and consist of light smell and taste. Due to zero dipole moment and linear geometry Ethene is non polar in nature.