Appendix J — Laboratory Safety

Working safely in an organic chemistry lab is a skill, not a checklist. This appendix gives the operational discipline that complements Appendix I (reagent hazards) and Ch 40 (green chemistry).

1. Safety Culture

Chemicals do not care about your intentions. They obey their own reactivity. A pyrophoric reagent does not know you are tired, behind schedule, or working solo at 11 PM. The hazard exists when you mishandle it; the hazard is the same whether you "meant to."

The lab is a hazardous workplace. Treat it the way a machinist treats the shop floor, a surgeon treats the OR, or a pilot treats the cockpit. Procedures exist because people died writing them. The 2009 UCLA t-BuLi fire (Sheri Sangji) and the 1996 MIT chromate dust explosion are not anecdotes — they are why your PI insists on a lab coat.

Near misses count. A spill caught in time, a glove change after contact, a hood sash bumped down before an evaporation flask exploded: report and analyze. The next time it will not be a near miss.

The "ask twice" principle. If you are not certain about a procedure, ask before starting. If your first answer feels off, ask someone else. The cost of asking twice is a few minutes. The cost of being wrong can be a finger, an eye, or a life.

Working alone. Do not run hazardous reactions (pyrophorics, high pressure, large scale, energetic intermediates) alone or after hours. Many universities formally prohibit it.

2. PPE Essentials

Glove compatibility (essentials)

Rule: consult the Sigma-Aldrich / Ansell / Showa chemical resistance chart for your specific solvent before assuming a glove is adequate. Double-glove when handling something nasty: outer glove takes the hit, inner gives you time to remove.

3. Hood Discipline

The fume hood is the single most important piece of safety equipment in the organic lab.

• Sash height: working sash at marked safe level (typically 18 inches). Never higher than your shoulders.
• Head out of the hood. If your nose is inside the sash, the hood is not protecting you.
• Airflow visualization. A Kimwipe strip taped at the sash should pull inward. If it droops or fluctuates, the hood is failing — stop work, close sash, alert EHS.
• Decluttering. Reagent bottles, paper, and equipment on the deck disrupt airflow. Keep only what you need.
• Secondary containment. Solvent bottles in trays. Waste containers in trays. A spill should not reach the deck or floor.
• Sash use during evacuation. When leaving an unattended reaction in the hood, lower the sash to the marked "evacuation" level (4-6 inches).
• Hood failure. Loss of airflow alarm: close all open chemicals, lower sash fully, leave the room, post a "DO NOT USE — HOOD FAILED" sign, notify EHS. Do not try to finish "just one thing."

4. Specific Hazards

Pyrophorics (ignite spontaneously in air)

Examples: t-BuLi, n-BuLi, s-BuLi, NaH (oil-free), KH, white phosphorus, Raney Ni (dry), dialkylzinc (Et₂Zn, Me₂Zn), freshly prepared RMgX, PMe₃, LiAlH₄ (dust).

• Handle under inert atmosphere (Ar > N₂ for Li reagents because Li reacts with N₂).
• Cannula transfer or oven-dried gas-tight syringe with bevel-up needle. Never glass-to-glass pour.
• Septum integrity: replace after every few punctures.
• Quench excess reagent slowly, in inert solvent, with i-PrOH or t-BuOH (slower than MeOH; gentler exotherm), then water, then dilute acid.
• t-BuLi: rated highest-hazard; institutional training and PPE protocol required. Never above 1.7 M in pentane unattended.

Reactive metals

Na, K, Li, Cs. Cut under mineral oil. Quench with t-butanol (slow, controllable) or 2-propanol, then methanol, then ethanol, then water — graded sequence. Never drop directly into water. Never wash sodium-contaminated glassware in a sink.

Peroxide formers

Et₂O, THF, 1,4-dioxane, DME, isopropanol, 2-MeTHF, cumene. Aged bottles accumulate peroxides at the meniscus and concentrate when distilled to dryness — they detonate.

• Date bottles when opened.
• Test before use if older than 6 months (KI/starch paper, or commercial peroxide test strips).
• Never distill to dryness. Leave 10-20% in the pot.
• Dispose of suspect bottles via EHS — do not handle a cap that has crystals around it.

Explosive or shock-sensitive

Diazomethane (CH₂N₂), diazo compounds, picric acid (dry), perchlorate salts (organic), azides (especially heavy-metal azides, polyazides, halogen azides), peroxides, nitroaromatics with high N-content.

• Diazomethane: smooth glass only, flame-polished joints, no scratches, no ground glass, behind a blast shield.
• Picric acid: store wet (≥10% water).
• Organic azides: avoid C:N ratio ≤3; use behind a blast shield; never use metal spatulas with NaN₃ (sodium azide reacts with copper/brass plumbing).
• Sodium azide: never let aqueous NaN₃ contact heavy-metal pipes — explosive metal azide deposits.

Strong oxidizers

Cr(VI) (Jones, PCC, PDC), MnO₄⁻, peroxyacids (mCPBA), KO₂, Oxone, HNO₃ conc., HClO₄, OsO₄, RuO₄.

• Never with organic paper towels, wood, or sawdust. Spill cleanup: absorb on vermiculite or inert spill granules, not paper.
• HClO₄ work in a dedicated perchloric acid hood with washdown.
• mCPBA: never grind dry; never store next to reductants.

Strong acids and bases

• Acid to water, always. The reverse boils the surface and ejects.
• Never neutralize a large spill with the opposite — use absorbent, then careful neutralization.
• Bases (NaOH, KOH) cause deeper burns than equivalent acids; the soap-feel is the dermis dissolving.

HF (hydrofluoric acid)

A category unto itself. Penetrates skin painlessly; binds Ca²⁺ and Mg²⁺; can cause cardiac arrest hours later.

• Calcium gluconate gel on-site, in date, where HF is used. Apply immediately to any suspected contact.
• Wear butyl gauntlets. Double glove.
• Any contact, even suspected, goes to the ER.
• Anhydrous HF and HF in DCM/MeCN (BF₃·OEt₂, F-TEDA, HF·pyridine) are no less dangerous than aqueous HF.

Toxic gases

Cryogens

• Liquid N₂: frostbite (contact), asphyxiation in enclosed rooms (a Dewar boiling off in a small lab can drop O₂ below safe level — O₂ monitor required for walk-in freezers and cold rooms).
• Dry ice / acetone bath: never seal the container; CO₂ sublimation pressurizes and ruptures.
• Never seal a cryogenic liquid in a closed vessel. Pressure rises catastrophically.

5. Reagent Hazards Quick Reference

Cross-reference Appendix I.

6. Glassware Practice

• Inspect every joint and round-bottom before use. Star cracks at the bottom of an RBF mean it will fail under thermal shock.
• Never apply force to closed systems. Stuck joints: do not pry — heat gently with a heat gun or solvent-soften.
• Pressure considerations: a sealed system heated 30 °C above ambient develops measurable pressure; a hot solvent system above its BP is a bomb. Always vent or use a bubbler.
• Vacuum work behind a blast shield. Use thick-walled flasks rated for vacuum — Erlenmeyers and round-bottom thin-wall flasks implode.
• Round-bottom support with a clamp on the neck, not just a keck clip. Keck clips secure joints, they do not hold flasks.
• Heating mantles sized to the flask. Never use a hotplate directly on an RBF (point-contact thermal stress).
• Stir bar in: put a stir bar in every reaction. Superheated solvent bumping is a common eye-injury cause.

7. Waste Handling

Never combine waste streams without explicit guidance. Mixing nitric acid waste with organic waste, or cyanide with acid, is a classic incident.

Cap every waste container. Open evaporation contaminates the lab atmosphere and is a regulatory violation.

8. Reactive Incidents

Fire

• Small (in flask): smother with watch glass; cut heat; clamp aside.
• Bench fire (small): CO₂ extinguisher (Class B/C for solvents). Avoid water on solvent fires.
• Metal fire (Na, K, Li, Mg): Class D extinguisher (dry sand or graphite powder). Never water, never CO₂ (reacts with Mg).
• Person on fire: stop, drop, roll — or wrap in fire blanket. Safety shower if blanket unavailable.
• LAH workup fire: if t-BuOH/THF residue ignites during quench, smother with sand or vermiculite. Do not pour water on a smoldering LAH residue.

Spills

• Acid: cover with sodium bicarbonate; sweep up with inert absorbent; dispose as solid waste.
• Base: cover with citric acid or sodium bisulfate; absorb; dispose.
• Mercury: never vacuum (aerosolizes). Use a mercury spill kit (sulfur powder amalgamates; specialized aspirator). Report any spill to EHS — federal reporting threshold exists.
• Organic solvent (small): absorb with vermiculite or pad. Dispose in matching waste stream.
• Pyrophoric: smother with sand or vermiculite. Do not use water.

Cuts (broken glass)

• Treat as biohazard if blood involved (other lab members' samples are unknown risk).
• Wash with water; pressure to stop bleeding; bandage; seek medical for embedded glass.
• Document; broken glass with chemical exposure goes to sharps in a contaminated stream.

Chemical splash to eye

• Eyewash for 15 minutes minimum. No exceptions. Hold lids open. Roll eye in all directions.
• After eyewash, go to medical. Always. Even if it "feels fine now."

Chemical contact to skin

• Remove contaminated clothing before rinsing if necessary. Some chemicals (HF, phenol, dimethyl sulfate) penetrate fabric and concentrate against skin.
• Rinse 15 minutes with cool running water.
• HF, phenol, alkylating agents — go to ER even if the area looks clean.

9. Procedure Templates (High-Hazard)

Grignard prep: 1. Glassware oven-dried, cool under N₂. 2. Mg turnings (1.1 equiv), I₂ crystal or 1,2-dibromoethane (activation). 3. Few drops of alkyl halide + a little solvent; warm to initiate. 4. Add halide as solution at rate that maintains gentle reflux. Do not add all at once — induction period is dangerous. 5. Quench excess: saturated NH₄Cl, then dilute HCl if needed for product workup.

LiAlH₄ quench (Fieser method, for n grams LAH): 1. Add n mL water dropwise (most violent step — slow, behind shield). 2. Add n mL 15% aqueous NaOH dropwise. 3. Add 3n mL water. 4. Stir until granular white precipitate (Al(OH)₃-like), then filter. 5. This produces a filterable solid instead of a gel; far cleaner workup than direct aqueous quench.

Ozonolysis: 1. Cool substrate in MeOH/DCM to −78 °C (dry ice/acetone). 2. Bubble O₃ until pale blue color persists (or Sudan III indicator turns). 3. Purge with N₂ to remove excess O₃. 4. Add reductive workup: PPh₃ (1.5 equiv) or Me₂S (excess) or Zn/AcOH. Warm slowly to rt. Never warm an ozonide without quench — peroxide decomposition.

Distillation: - Never to dryness, especially ethers (peroxide concentration). - Boiling chips or stir bar in pot. - Vent every distillation head — never seal. - Vacuum distillation: gradual application; thick-wall flasks; blast shield.

Hydrogenation (H₂ balloon, Parr shaker, autoclave): - No flames, no sparks, no static in the area. - Leak-test the system before charging. - Pd/C and Pt are oxidatively reactive; add to degassed solvent, then introduce H₂. Reverse order can ignite filter paper. - After reaction, vent H₂ before opening; filter Pd/C wet (do not let cake dry on the filter — pyrophoric). - Quench filter cake by wetting with water before disposal.

10. SDS Literacy

The Safety Data Sheet (SDS, formerly MSDS) is required by law to be accessible for every chemical in the lab. Sixteen GHS-harmonized sections. The four you read before every new reagent:

GHS pictograms (memorize):

• Flame — flammable
• Flame over circle — oxidizer
• Exploding bomb — explosive / self-reactive / peroxide
• Skull & crossbones — acute toxicity
• Health hazard — carcinogen, mutagen, reproductive toxin, respiratory sensitizer
• Exclamation mark — irritant, acute toxicity (lower category)
• Corrosion — corrosive to skin or metal
• Gas cylinder — compressed gas
• Environment — aquatic toxicity

Hazard statements (H-codes) and precautionary statements (P-codes) are standardized — H200s explosives, H300s toxicity, H400s environment.

11. Emergency Contacts

• Building EHS / Safety officer — post number at every phone.
• Poison Control (US): 1-800-222-1222
• Local emergency: 911 (US), 112 (EU), 999 (UK).
• Chemical Spill / HazMat: institutional EHS first; CHEMTREC (1-800-424-9300, US) for transport-related.
• SDS access: Sigma-Aldrich, MilliporeSigma, Fisher, TCI all maintain free online SDS by CAS number.

12. Closing Principle

The best piece of safety equipment in the lab is critical thinking. PPE protects you from accidents; thinking protects you from creating them.

Before you start:

• Read the procedure end to end.
• Know what each reagent does, what the exotherm looks like, and what the quench is.
• Set up your quench before you set up your reaction.
• Identify the worst plausible failure mode and what you would do.
• If something feels off — the bottle, the smell, the color, your gut — stop.

You will spend a career in this lab if you do it right. Do it right.

Lab safety is not paranoia. It is the operating discipline that lets you do your best science for forty years instead of forty days. Inherit the habit; pass it on.