Ethylene, Lewis structures

Multiple bonds are very common m organic chemistry Ethylene (C2H4) contains a carbon-carbon double bond m its most stable Lewis structure and each carbon has a completed octet The most stable Lewis structure for acetylene (C2H2) contains a carbon-carbon triple bond Here again the octet rule is satisfied... 

Many of the Lewis structures in Chapter 9 and elsewhere in this book represent molecules that contain double bonds and triple bonds. From simple molecules such as ethylene and acetylene to complex biochemical compounds such as chlorophyll and plastoquinone, multiple bonds are abundant in chemistry. Double bonds and triple bonds can be described by extending the orbital overlap model of bonding. We begin with ethylene, a simple hydrocarbon with the formula C2 H4. 

Every description of bonding starts with a Lewis structure. Ethylene has twelve valence electrons. The bond framework of the molecule has one C—C bond and four C—H bonds, requiring ten of these electrons. We place the final two electrons as a lone pair on one of the carbon atoms, leaving the second carbon atom with only six electrons. Making a double bond between the carbon atoms gives both carbon atoms octets and completes the Lewis structure. 

Sigma and pi NBOs of hydrocarbons ethane, ethylene, acetylene Let us turn now to the actual NBOs for the classical cases of equivalent sp" hybridization acetylene (n = 1), ethylene (n = 2), and methane (n = 3). In each case, the NBO results are in excellent agreement with the expected Lewis structures,... 

Dative bonding can also occur in pi-type interactions, particularly involving the BH2 group. A good example is H2B=NH2, isoelectronic to ethylene, which is well described by a double-bonded NBO Lewis structure with dative 7Tb n bond ... 

The leading NBO Lewis structure of the less strongly bound Au(HCCH)+ complex does indeed correspond to separated Au+ HCCH reactants. Figure 4.89 illustrates the principal NBO donor-acceptor interactions for the Au(HC=CH)+ complex, which are seen to be rather similar to those for the long-range Ti(H2C=CH2) complex (Fig. 4.72). Thus, for a transition metal with only one vacant valence orbital, acetylene and ethylene 7tCc bonds function rather similarly as two-electron donors, and the p2, two-electron complex description is apt. 

When there is more than one central atom, the bonding about each atom is considered independently. For example, let s predict the shape of an ethene (ethylene) molecule, CH2=CH2. There are two centers in ethene to consider—the two carbon atoms. The first step is to write the Lewis structure (13). Each carbon atom has three regions of electron concentration on it two single bonds and one double bond. There are no lone pairs. The arrangement around each carbon atom is therefore trigo-... 

The ethylene molecule will illustrate construction of a model containing both a and 77 bonding. The Lewis structure (22) shows that each carbon should be approximately trigonal. Therefore we need sp2 hybrids on each carbon. Figure... 

Next, let s see what happens with a compound that has a double bond A simple organic compound with a double bond is ethene (ethylene), QFL,. Again, we should start by looking at the Lewis structure, which is shown in Figure 3.9a. All the atoms of ethene... 

In a Lewis structure, the double bond of an alkene is represented by two pairs of electrons between the carbon atoms. The Pauli exclusion principle tells us that two pairs of electrons can go into the region of space between the carbon nuclei only if each pair has its own molecular orbital. Using ethylene as an example, let s consider how the electrons are distributed in the double bond. 

Ethylene (C2H4) is an organic compound with a double bond. When we draw a Lewis structure for ethylene, the only way to show both carbon atoms with octets is to draw them sharing two pairs of electrons. The following examples show organic compounds with double bonds. In each case, two atoms share four electrons (two pairs) to give them octets. A double dash (=) symbolizes a double bond. 

Ethylene (C2H4) is an important starting material in the manufacture of plastics. The C2H4 molecule has 12 valence electrons and the following Lewis structure ... 

Now we will see how these orbitals can be used to account for the Lewis structure of ethylene. The three sp2 orbitals on each carbon are used to share electrons, as shown in Fig. 14.11. In each of these bonds the electron pair is shared in an area centered on a line running between che atoms. This type of... 

We can now completely specify the orbitals used to form the bonds in the ethylene molecule. As shown in Fig. 14.13, the carbon atoms are described as using sp2 hybrid orbitals to form the a bonds to the hydrogen atoms and to each other, and using p orbitals to form the 7t bond with each other. Note that we have accounted fully for the Lewis structure of ethylene with its carbon-carbon double bond and carbon-hydrogen single bonds. 

Multiple carbon-carbon bonds result when hydrogen atoms are removed from alkanes. Hydrocarbons that contain at least one carbon-carbon double bond are called alkenes and have the general formula C H2 . The simplest alkene (C2H4), commonly known as ethylene, has the Lewis structure... 

Draw a Lewis structure for each compound. Assume the atoms are arranged as follows a. ethylene, C2H4... 

This uses all 12 electrons, each C has an octet, and each H has two electrons. The Lewis structure is valid. Ethylene contains a carbon-carbon double bond. 

Antifreeze Research ethylene glycol, an antifreeze-coolant, to learn its chemical formula. Draw its Lewis structure and identify the sigma and pi bonds. 

Ans. The Lewis structure for ethylene is H—C=C—H. The VSEPR theory treats double and triple bonds as though they were single bonds. Therefore we can conclude that there are three bonding pairs around each carbon atom to be accommodated in some symmetrical structure. That structure is the equilateral triangle. VSEPR theory predicts that ethylene consists of two equilateral triangles connected at one corner. The carbon atoms are connected by a single line which we know to be the double bond. The angles between all atoms are equal, and are 120 °. Because of the symmetry of the molecule, it has no dipole moment. 

Fig. 5. Schematic description of hybrids and VB Lewis structures used for the study of the electrophilic attachment of chlorine to ethylene in aqueous solution (see text for details).

Now we will see how these orbitals can be used to account for the Lewis structure of ethylene. The three sp orbitals on each carbon are used to share... 

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