← Properties of selected organic compounds

Drawing, naming & isomers (every paper)

Longest chain, lowest locants; four isomer types.

Isomer types

• Chain: butane vs 2-methylpropane.
• Positional: butan-1-ol vs butan-2-ol.
• Functional group: C₃H₆O as propanal vs propanone.
• Geometric (cis/trans): but-2-ene's two forms — only possible when BOTH carbons of a C=C have two different groups attached.

✕

Not every C=C can form geometric isomers

Geometric isomerism needs each carbon of the double bond to carry TWO DIFFERENT groups. If either carbon has two IDENTICAL groups attached (e.g. two hydrogens, or a CH₂ end of a chain), rotation around that end makes no visible difference and no cis/trans pair exists. Papers give two candidate molecules and ask you to identify which one qualifies — check BOTH carbons before answering. ✕

Drawing marks

Show ALL bonds and atoms (condensed or full). Missing hydrogens on carbons is the #1 lost mark.

Practice for this standard covers the whole topic — flashcards and quiz.