Draw a Lewis structure for each of the following:
a. CH3CHO
b. CH3OCH3
c. CH3COOH
The correct answer and explanation is:
Lewis Structures and Explanation
a. CH₃CHO (Acetaldehyde)
Lewis Structure:
H H
| |
H—C—C=O
|
:
- The first carbon (left) forms 4 bonds: 3 with hydrogen and 1 with the central carbon.
- The second carbon (central) is double bonded to oxygen and single bonded to the first carbon and one hydrogen.
- Oxygen has two lone pairs of electrons.
b. CH₃OCH₃ (Dimethyl ether)
Lewis Structure:
H H
| |
H—C—O—C—H
| |
H H
- Each carbon (CH₃ group) forms 3 single bonds with hydrogen atoms and one bond with oxygen.
- The oxygen atom has two lone pairs and is bonded to both carbon atoms.
- All atoms follow the octet rule.
c. CH₃COOH (Acetic acid)
Lewis Structure:
H O
| ||
H—C—C—O—H
|
H
- The first carbon (CH₃) has 3 hydrogen atoms and bonds to the second carbon.
- The second carbon (carbonyl carbon) is double bonded to one oxygen and single bonded to a hydroxyl group (-OH).
- The carbon makes 4 bonds, and each oxygen has two lone pairs.
Explanation (Approx. 300 Words)
Lewis structures are visual representations that show how atoms in a molecule are bonded and where lone pairs of electrons are located. They are essential in understanding molecular geometry, polarity, and reactivity.
In CH₃CHO, the molecule is composed of a methyl group (CH₃) and an aldehyde group (CHO). The central carbon atom forms a double bond with the oxygen atom, which possesses two lone pairs, and a single bond with the methyl group and one hydrogen. This structure satisfies the octet rule for all atoms.
CH₃OCH₃ is an ether, consisting of two methyl groups (CH₃) connected via an oxygen atom. Each carbon makes four single bonds: three with hydrogen atoms and one with oxygen. Oxygen makes two single bonds with the carbon atoms and has two lone pairs. The structure maintains the octet rule for carbon and oxygen.
CH₃COOH or acetic acid contains a methyl group (CH₃) bonded to a carboxylic acid group (COOH). The carbon in the carboxylic group forms a double bond with one oxygen (carbonyl) and a single bond with a hydroxyl group (-OH). The hydroxyl oxygen is also bonded to hydrogen and holds two lone pairs. This structure allows all atoms to complete their octets and highlights the acidic nature of the molecule due to the OH group attached to a carbonyl carbon.
Each of these molecules demonstrates standard bonding patterns for carbon, hydrogen, and oxygen, reinforcing foundational concepts of chemical bonding and molecular structure.