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.

Dehydration of amides to nitriles

6 real reactions from the literature, on amides. Each scheme shows starting materials, conditions and products, with the yield and reference where the source reports them.

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Amide dehydration to nitrile: fumaramide with P2O5; Δ gives fumaronitrile.

Amide dehydration to nitrileOrg. Synth. Coll. Vol. 4, p. 486
Amide dehydration to nitrile: isobutyramide with P2O5; Δ gives isobutyronitrile.

Amide dehydration to nitrileOrg. Synth. Coll. Vol. 3, p. 493
Amide dehydration to nitrile: nicotinamide with P2O5; Δ gives 3-cyanopyridine (the nitrile).

Amide dehydration to nitrileOrg. Synth. Coll. Vol. 4, p. 706
Amide dehydration to nitrile: cyanoacetamide with PCl5, Δ gives malononitrile.

Amide dehydration to nitrileOrg. Synth. Coll. Vol. 2, p. 379
Amide dehydration to nitrile: cyanoacetamide with POCl3, Δ; ethylene dichloride gives malononitrile.

Amide dehydration to nitrileOrg. Synth. Coll. Vol. 3, p. 535
Amide dehydration to nitrile: chloroacetamide with P2O5, Δ; trimethylbenzene gives chloroacetonitrile.

Amide dehydration to nitrileOrg. Synth. Coll. Vol. 4, p. 144