Question

Draw Lewis structures of these organic molecules: (a) tetrafluoroethylene \(\left(\mathrm{C}_{2} \mathrm{~F}_{4}\right)\) (b) propane \(\left(\mathrm{C}_{3} \mathrm{H}_{8}\right)\) (c) butadiene \(\left(\mathrm{CH}_{2} \mathrm{CHCHCH}_{2}\right.\) ), (d) propyne \(\left(\mathrm{CH}_{3} \mathrm{CCH}\right),\) (e) benzoic acid \(\left(\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{COOH}\right) .\) (Hint: To draw \(\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{COOH}\), replace an \(\mathrm{H}\) atom in benzene with a COOH group.)

Short answer

Lewis structures guides have been provided for tetrafluoroethylene, propane, butadiene, propyne, and benzoic acid. These structures display how carbon, hydrogen, and any other included atoms are arranged and bonded.

Step-by-step solution

Draw the structure of tetrafluoroethylene (\(C_{2}F_{4}\))

Tetrafluoroethylene has two carbon (C) atoms and four fluorine (F) atoms. The carbon atoms are located at the center of the molecule and are connected by a double bond. Each carbon atom is also bonded with two fluorine atoms.

Draw the structure of propane (\(C_{3}H_{8}\))

Propane is a straight chain of three carbon atoms. In respect to hydrogens, the two end carbon atoms are connected to 3 hydrogens each and the middle carbon atom is connected to 2 hydrogens.

Draw the structure of butadiene (\(CH_{2}CHCHCH_{2}\))

Butadiene contains a four carbon chain with alternating single and double bonds. The two end carbon atoms have two hydrogens each and the two middle carbon atoms have one hydrogen each.

Draw the structure of propyne (\(CH_{3}CCH\))

Propyne has three carbon atoms, with a single bond connecting the first two carbon atoms, and a triple bond connecting the second and third carbon atom. The first carbon atom is bonded to 3 hydrogens, the second has no hydrogens, and the third carbon atom is bonded to a single hydrogen.

Draw the structure of benzoic acid (\(C_{6}H_{5}COOH\))

Benzoic acid can be drawn in two parts. The first part is a benzene ring (\(C_{6}H_{5}\)), that is a hexagonal ring of six carbon atoms with alternating single and double bonds, and a hydrogen atom bonded to each carbon atom. The second part is the \(COOH\) group, where the carbon atom is bonded to two oxygen atoms (one by a single bond and one by a double bond), and then the oxygen atom by the single bond is bonded to a hydrogen atom. For benzoic acid, replace one of the hydrogens of the benzene ring by this \(COOH\) group.

Key concepts

Understanding Tetrafluoroethylene Structure

When visualizing the structure of tetrafluoroethylene (C₂F₄), imagine two carbon atoms connected by a strong double bond. This double bond is pivotal as it contributes to the molecule's rigidity and affects its reactivity. Flanking each carbon atom are two fluorine atoms, and these halogen elements are notorious for their high electronegativity, which influences the molecule’s overall polar nature.

Now picture the geometry around each carbon: it's a flat plane since tetrafluoroethylene participates in sp² hybridization due to the double bonding. This planar geometry is why materials made from it, like Teflon, have unique properties such as non-stick surfaces and resistance to chemical attack.

It's crucial to acknowledge that the Lewis structure visually summarizes these bonds as lines (single bonds) or pairs of lines (double bonds) radiating from each carbon symbol, with the chemical symbols for fluorine at the terminus of each single line.

Propane Molecular Structure Dissected

Propane (C₃H₈) is a typical hydrocarbon molecule with a simple, straightforward structure. There are three carbon atoms forming a linear chain. At the ends of this chain, you have two carbon atoms, each attached to three hydrogen atoms, represented as lines stemming from the carbon symbol. The central carbon atom, a communal hub for both its neighbors, holds on to two hydrogen atoms.

This molecular blueprint is the backbone of the energy industry—an alkane with saturated, single bonds connecting the carbon atoms. In propane's Lewis structure, we neatly illustrate how each carbon completes its quartet of bonds (as required by the octet rule) using simple lines for these connections.

The propane molecule's shape, dictated mainly by the sp³ hybridization of its carbon atoms, is not perfectly straight thanks to the tetrahedral angle formed during this hybridization. This structure is central to understanding the physical properties of propane, like its boiling point and energy content.

Navigating Butadiene Bonding

Butadiene's structure (CH₂=CH-CH=CH₂) shows us that it's not just chains and rings that matter in organic chemistry; it's also about the bonds within. Butadiene showcases a pattern of alternating single and double bonds—known formally as conjugation—which is a critical factor in determining the molecule's chemical behavior, especially in polymerization reactions.

In its Lewis structure, we clearly demarcate the single bonds and double bonds. The carbons involved in double bonds undergo sp² hybridization, similar to tetrafluoroethylene, but the overall molecule exhibits an elongated form. This is because butadiene is a diene, meaning it contains two double bonds, influencing its flexibility and the way it can interact with other chemical entities.

Propyne Chemical Structure

With propyne (CH₃C≡CH), we encounter a molecule with a triple bond, a feature that gives it some pretty interesting characteristics. The central carbon atom doesn't have any hydrogens attached, putting the triple-bonded carbons in a straight line due to linear sp hybridization.

The Lewis structure for propyne simplifies this by showing a triple line between the second and third carbon atoms. The first carbon, noticeably different from the others, is bound to three hydrogen atoms, and the third carbon clings to a single hydrogen. Through the lens of a chemist, this structural layout underlines the potential of propyne to engage in reactions that can add groups to the molecule where the triple bond is, a likely point of chemical activity.

Benzoic Acid Lewis Structure Explored

In benzoic acid (C₆H₅COOH), we observe the complex interplay of a benzene ring and a carboxylic acid group. First, imagine the benzene ring, a hexagon with a circle to signify delocalization of electrons across alternate single and double bonds. The beauty and stability come from this resonance, which is why benzene rings serve as keystones in an immense variety of complex organic molecules.

Add to this ring the COOH group, attaching via a single bond to where a hydrogen once was. The double bond of the carboxyl group's carbonyl (C=O) and the single bond to the hydroxyl (O-H) are pivotal in making benzoic acid an acid, capable of donating an H⁺ ion. In the Lewis structure, we lay these connections bare, showing how the carefully arranged atoms enable benzoic acid to fit so neatly into biochemistry and industry.