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.

Halogenation of silyl enol ethers

1 real reaction from the literature, on silyl enol ethers. Each scheme shows starting materials, conditions and products, with the yield and reference where the source reports them.

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Silyl enol ether halogenation: trimethyl-(2-methyl-1-methylene-propoxy)-silane (a silyl enol ether) with Br2; Hexane (solvent) gives 1-bromo-3-methylbutan-2-one (the α-halo ketone). 79% yield.

Silyl enol ether halogenationEur. J. Org. Chem. 2005, 4141