Q8P - Organic Chemistry (Mcmurry)

Question

Draw a line-bond structure for propane, $\mathbf{CH}\mathbf{3}\mathbf{CH}\mathbf{2}\mathbf{CH}\mathbf{3}$. Predict the value of each bond angle, and indicate the overall shape of the molecule.

Step-by-Step Solution

Answer

                                              Each bond angle is  ${109.5}^{°}$

Step 1: Line bond structure

The line bond structure is used to indicate covalent bonds by using a line to represent two electrons shared between two atoms. Line bond structure is done in a step-by-step process by starting with the first carbon and attached hydrogen atoms followed by other carbon and hydrogens.

Step 2: Propane line bond structure

To draw the line bond structure of propane, ${\mathrm{CH}}_3{\mathrm{CH}}_2{\mathrm{CH}}_3$, draw the first C atom bonded to three H atoms as shown:

First carbon bonded to three hydrogen atoms

Then we should draw a bond connecting the first C atom to a second C atom, followed by drawing bonds between the second C atom and two H atoms.

A bond connecting the second C atom to a third C atom is drawn, and bonds between the third C atom and three H atoms are connected.

Propane line bond structure

Step 3: Bond angle of propane

Each C atom makes 4 equivalent bonds by hybridizing its 2s and three 2p orbitals to form four equivalent atomic orbitals called ${\mathrm{sp}}^3$ hybrids. Because the ${\mathrm{sp}}^3$ hybrids are equivalent, they are arranged about the C atom in a tetrahedral orientation. This means that they are separated by angles of approximately ${109.5}^{°}$.  The arrows in the ${\mathrm{CH}}_3{\mathrm{CH}}_2{\mathrm{CH}}_3$ figure indicate the different tetrahedral bond angles.

Each bond angle is approximate ${109.5}^{°}$. The shape of each C atom of propane, resembles the shape of methane,  ${\mathrm{CH}}_4$.

                                            Each bond angle is ${109.5}^{°}$