SOP: LiAlH₄ quench (Fieser) template

Standard operating procedure for quenching a lithium aluminium hydride reduction by the Fieser work-up (n mL H₂O, n mL 15% NaOH, 3n mL H₂O per n g LiAlH₄): document control, apparatus, the n:n:3n rule worked for 1.0 g, step list, hazard table and emergency actions.

What the template shows

• Standard operating procedure
• Quenching a LiAlH₄ reduction: the Fieser work-up (n : n : 3n)
• ⚠ Always check the supplier SDS; this is an example. Adapt this SOP to your scale and get it approved locally.
• Document control
• Fieser quench of LiAlH₄ (≤ 5 g)
• Apparatus and the Fieser rule
• Dropping funnel: H₂O, then 15% NaOH, then H₂O
• N₂ in / out to an oil bubbler (H₂ vents through it)
• 3-neck flask, stir bar, reaction in THF
• Ice–water bath: internal T < 15 °C
• For n g of LiAlH₄, add in order, dropwise at 0 °C:
• For 1.0 g LiAlH₄
• LiAlH₄ + 4 H₂O → LiOH + Al(OH)₃ + 4 H₂: 1.0 g (26 mmol) can release ~2.5 L of H₂. The NaOH makes the aluminium salts granular and easy to filter instead of a gel.
• Before you start: reduction complete (TLC); ice bath, N₂ line with bubbler, dry sand / Class D extinguisher and a second person in the lab.
• Dilute the mixture with dry THF or Et₂O (≥ 25 mL per g LiAlH₄) and cool to 0 °C with stirring under N₂.
• Fill the dropping funnel with water. Add n mL H₂O (n = g LiAlH₄ used) dropwise; wait for each drop to stop fizzing. Keep the internal T < 15 °C.
• Add n mL 15% aq. NaOH dropwise.
• Remove the ice bath, warm to rt and stir 15–30 min until the salts are white and granular (add a little anhydrous MgSO₄ to help).
• Filter through Celite or a sinter; wash the cake with THF / Et₂O. Combine and evaporate the filtrate.
• Let the filter cake stand in the hood (residual hydride); then dispose of it as solid waste. Never put unquenched hydride in a bin.
• Hydride fire: dry sand, Class D powder or a dry-powder extinguisher. NO water, CO₂ or foam.
• Solvent fire away from hydride: CO₂ extinguisher; if it spreads, close the sash, alarm, evacuate.
• Runaway (violent fizzing, solvent boiling): stop addition, more ice, lower sash; do not leave the hood unattended.
• Skin/eye contact with LiAlH₄ or NaOH: brush off solid, then water ≥ 15 min (shower / eyewash); medical attention.

Drawn with 69 shapes – every one editable in MolDraw.

Sources

• UN GHS Rev.10, United Nations 2023 Database
• Prudent Practices in the Laboratory, National Research Council 2011 Textbook
• Fieser & Fieser, Reagents for Organic Synthesis, Vol. 1, Wiley 1967, p. 584 Textbook