Flashcards · 7405 · A Level Topic 32

Organic synthesis (A Level) flashcards

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Percentage atom economy: (Mr of the desired product ÷ sum of Mr of all reactants) × 100.
Why do chemists aim for processes that need no solvent?: Solvents must be made, transported and separated from the product (often by energy-intensive distillation), become waste unless recycled, and are often flammable or toxic.
Why do chemists aim for fewer steps?: Product is lost at every step, so the overall yield falls; each step also needs its own reagents, separation, energy and time.
Overall yield of a three-step route with step yields 80%, 70% and 50%: 0.80 × 0.70 × 0.50 = 0.28, so 28%. Multiply the yields; never add or average them.
Which reactions in the course make a new C–C bond?: KCN with a halogenoalkane; KCN with an aldehyde or ketone; Friedel–Crafts acylation (and addition polymerisation).
Atom economy of an addition reaction: Exactly 100%: there is only one product. Substitution and elimination are always below 100%.
Route: 1-bromopropane to butylamine: KCN in aqueous ethanol, reflux → butanenitrile; then reduce (e.g. LiAlH₄, or H₂ with Ni) → butylamine.