Draw a Lewis structure, and classify each of the following compounds:
(a) CH₃CH₂CONHCH₃
(b) (CH₃CH₂)₂NH

Verified step by step guidance

1. Step 1: Identify the total number of valence electrons for each compound. For compound (a) CH3CH2CONHCH3, count the valence electrons from each atom: Carbon (C) has 4, Hydrogen (H) has 1, Nitrogen (N) has 5, and Oxygen (O) has 6. For compound (b) (CH3CH2)2NH, count the valence electrons similarly.
2. Step 2: Draw the skeletal structure of each compound. For compound (a), arrange the atoms in the order given: CH3CH2CONHCH3, with the carbonyl group (C=O) in the middle. For compound (b), arrange the ethyl groups (CH3CH2) around the nitrogen atom.
3. Step 3: Distribute the valence electrons around the atoms to satisfy the octet rule (or duet for hydrogen). Start by placing electrons to form bonds between atoms, then distribute remaining electrons to complete octets, prioritizing more electronegative atoms like oxygen and nitrogen.
4. Step 4: Check for formal charges to ensure the most stable Lewis structure. Adjust the placement of electrons if necessary to minimize formal charges, ensuring that the overall charge of the molecule is correct.
5. Step 5: Classify each compound based on functional groups. For compound (a), identify the amide group (CONH) and classify it as an amide. For compound (b), identify the amine group (NH) and classify it as a secondary amine due to the two ethyl groups attached to the nitrogen.

Key Concepts

Lewis Structures

Lewis structures are diagrams that represent the bonding between atoms of a molecule and the lone pairs of electrons that may exist. They are essential for visualizing the arrangement of atoms, the distribution of electrons, and predicting the shape and reactivity of the molecule. In drawing Lewis structures, it is important to account for all valence electrons and ensure that each atom satisfies the octet rule, where applicable.

Functional Groups

Functional groups are specific groups of atoms within molecules that have characteristic properties and reactivity. In organic chemistry, recognizing functional groups such as amides (CONH) and amines (NH) is crucial for classifying compounds and predicting their chemical behavior. For example, in CH3CH2CONHCH3, the CONH segment indicates an amide group, while in (CH3CH2)2NH, the NH group signifies a secondary amine.

Molecular Geometry and Hybridization

Molecular geometry refers to the three-dimensional arrangement of atoms in a molecule, which is influenced by the hybridization of atomic orbitals. Understanding the geometry helps predict the molecule's physical and chemical properties. For instance, the sp3 hybridization in amines leads to a tetrahedral geometry around the nitrogen atom, affecting the molecule's polarity and interactions with other compounds.