Reading a scheme

Start with the conditions. A strong base, an acid, a metal, a peroxide: the reagent line narrows the reaction type before you look at a single bond.
Find what changed. Compare starting material and product atom by atom: which bond formed, which left, and whether the carbon count grew.
Substitution vs. elimination vs. addition is a bookkeeping question: same number of σ bonds, fewer, or more.
Mechanism follows structure. A tertiary or benzylic center with a weak nucleophile points to a cation; a primary center with a strong nucleophile does not.
Every example here is a real reaction with a real citation. The yields are the authors’ own.

Alkene isomerization into conjugation

2 real reactions from the literature, on six-membered cycloalkenes and α,β-unsaturated ketones. Each scheme shows starting materials, conditions and products, with the yield and reference where the source reports them.

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Alkene isomerization: 3-cyclohexen-1-one (a six-membered cycloalkene) with NaOH; NaOH gives 2-cyclohexen-1-one (the α,β-unsaturated ketone).

Alkene isomerizationRealOChem worksheet
Alkene isomerization: 5-methylcyclopent-2-en-1-one (an α,β-unsaturated ketone) with NaOH (2 equiv) gives 2-methyl-2-cyclopenten-1-one (the α,β-unsaturated ketone).

Alkene isomerizationRealOChem worksheet