Classify each hydrogen atom in the following compounds as primary (1°), secondary (2°), or tertiary (3°).
a. butane
b. isobutane

Verified step by step guidance

1. Step 1: Understand the classification of hydrogen atoms. In organic chemistry, hydrogen atoms are classified based on the type of carbon atom they are attached to. A primary (1°) hydrogen is attached to a primary carbon, which is bonded to only one other carbon. A secondary (2°) hydrogen is attached to a secondary carbon, bonded to two other carbons. A tertiary (3°) hydrogen is attached to a tertiary carbon, bonded to three other carbons.
2. Step 2: Analyze the structure of butane. Butane is a straight-chain alkane with the molecular formula C₄H₁₀. Draw the structure of butane: CH₃-CH₂-CH₂-CH₃. Identify the types of carbon atoms present in butane.
3. Step 3: Classify the hydrogen atoms in butane. In butane, the terminal CH₃ groups are primary carbons, each bonded to one other carbon. Therefore, the hydrogens attached to these CH₃ groups are primary hydrogens. The CH₂ groups are secondary carbons, each bonded to two other carbons, so the hydrogens attached to these CH₂ groups are secondary hydrogens.
4. Step 4: Analyze the structure of isobutane. Isobutane is a branched alkane with the molecular formula C₄H₁₀. Draw the structure of isobutane: (CH₃)₂CH-CH₃. Identify the types of carbon atoms present in isobutane.
5. Step 5: Classify the hydrogen atoms in isobutane. In isobutane, the central carbon is a tertiary carbon, bonded to three other carbons, so the hydrogens attached to this carbon are tertiary hydrogens. The terminal CH₃ groups are primary carbons, each bonded to one other carbon, so the hydrogens attached to these CH₃ groups are primary hydrogens.

Key Concepts

Hydrogen Atom Classification

In organic chemistry, hydrogen atoms are classified based on the type of carbon atom they are attached to. A primary (1°) hydrogen is attached to a primary carbon, which is bonded to only one other carbon. A secondary (2°) hydrogen is attached to a secondary carbon, bonded to two other carbons, and a tertiary (3°) hydrogen is attached to a tertiary carbon, bonded to three other carbons.

Structure of Butane

Butane is a straight-chain alkane with the molecular formula C4H10. It consists of four carbon atoms connected in a linear sequence. In butane, the terminal carbon atoms are primary, each bonded to three hydrogens, while the two central carbon atoms are secondary, each bonded to two hydrogens.

Structure of Isobutane

Isobutane, also known as methylpropane, is a branched-chain alkane with the molecular formula C4H10. It has a central carbon atom bonded to three other carbon atoms, making it tertiary, and this carbon is bonded to one hydrogen. The remaining carbon atoms are primary, each bonded to three hydrogens.