Draw the structure and give the systematic name for a compound with molecular formula C₅H₁₂ that has
(a) only primary and secondary hydrogens.

Verified step by step guidance

1. Step 1: Understand the molecular formula C5H12. This formula represents an alkane, which is a saturated hydrocarbon containing only single bonds between carbon atoms.
2. Step 2: Recognize the requirement for the compound to have only primary and secondary hydrogens. Primary hydrogens are attached to primary carbons (carbons bonded to only one other carbon), and secondary hydrogens are attached to secondary carbons (carbons bonded to two other carbons). This means the structure cannot contain tertiary hydrogens (attached to tertiary carbons).
3. Step 3: Begin by constructing a straight-chain alkane with five carbons (pentane). In this structure, all hydrogens are either primary or secondary because the terminal carbons have primary hydrogens, and the internal carbons have secondary hydrogens.
4. Step 4: Verify the structure by counting the hydrogens on each carbon atom to ensure the molecular formula matches C5H12. Each carbon should follow the valency rule of forming four bonds.
5. Step 5: Assign the systematic name to the compound. Since the structure is a straight-chain alkane with five carbons, the name is 'pentane'.

Key Concepts

Hydrocarbon Structure

Hydrocarbons are organic compounds consisting solely of carbon (C) and hydrogen (H) atoms. The structure of a hydrocarbon can vary significantly based on the arrangement of these atoms, leading to different types of isomers. In the case of C5H12, understanding the structural possibilities, including straight-chain and branched forms, is essential for identifying the correct compound that meets the criteria of having only primary and secondary hydrogens.

Primary and Secondary Hydrogens

Hydrogens in organic compounds are classified based on the type of carbon atom they are attached to. Primary hydrogens are attached to a primary carbon (a carbon bonded to only one other carbon), while secondary hydrogens are attached to secondary carbons (a carbon bonded to two other carbons). For the compound C5H12, recognizing which hydrogens are primary or secondary is crucial for determining the correct structure and ensuring it meets the specified criteria.

Systematic Naming (IUPAC Nomenclature)

IUPAC nomenclature is a systematic method for naming organic compounds based on their structure. The name reflects the number of carbon atoms, the type of bonds, and the presence of functional groups. For the compound C5H12, understanding how to apply IUPAC rules will help in accurately naming the compound, ensuring that the name corresponds to the structure drawn, particularly when distinguishing between different isomers.