This blog provides a focused set of multiple-choice questions on hazards encountered in organic synthesis with special emphasis on sulphonation reactions, aimed at M.Pharm students preparing for examinations and lab safety assessments. Questions cover the chemical and physical risks of reagents such as SO3, oleum and chlorosulfonic acid, process hazards like uncontrolled exotherms and pressure rise, materials compatibility, containment, neutralization and waste treatment, and practical controls including calorimetry, vent scrubbing and PPE. Each MCQ is designed to test applied understanding — identifying hazards, appropriate engineering and administrative controls, safe quench and emergency response measures — to strengthen both theoretical knowledge and safe laboratory practice.
Q1. Which hazard is most commonly associated with scale-up of organic reactions in synthesis laboratories?
- Uncontrolled exothermic runaway (thermal runaway)
- Increased microbial contamination
- Enhanced UV radiation exposure
- Noise-induced hearing loss
Correct Answer: Uncontrolled exothermic runaway (thermal runaway)
Q2. Why is SO3 (sulfur trioxide) particularly hazardous during sulphonation?
- It polymerizes spontaneously at room temperature
- It reacts violently with water releasing heat and corrosive aerosols
- It is biologically active and causes mutagenesis
- It is non-flammable but forms explosive peroxides
Correct Answer: It reacts violently with water releasing heat and corrosive aerosols
Q3. What is oleum (fuming sulfuric acid) composed of and why is it hazardous?
- A mixture of H2SO4 and dissolved SO3; it can release SO3 fumes and is highly corrosive
- Aqueous sulfuric acid with peroxide impurities; it is explosive
- Sulfuric acid diluted with methanol; it is flammable
- Sulfuric acid complexed with chloride; it emits chlorine gas
Correct Answer: A mixture of H2SO4 and dissolved SO3; it can release SO3 fumes and is highly corrosive
Q4. Chlorosulfonic acid (ClSO3H) poses which immediate hazard when exposed to moisture?
- It forms hydrogen gas and an explosive atmosphere
- It liberates hydrogen chloride gas and generates heat
- It forms nitrogen oxides
- It decomposes into sulfur dioxide and ozone
Correct Answer: It liberates hydrogen chloride gas and generates heat
Q5. Best engineering control to manage heat release during a sulphonation reaction at pilot scale is:
- Using a fume hood without temperature control
- Ad hoc manual stirring and periodic cooling with ice baths
- Automated jacketed reactor with controlled cooling and calorimetric monitoring
- Performing reaction at ambient without any monitoring
Correct Answer: Automated jacketed reactor with controlled cooling and calorimetric monitoring
Q6. Which personal protective equipment (PPE) is essential specifically for handling oleum or fuming sulfuric acid?
- Cotton lab coat and latex gloves
- Acid-resistant gloves (neoprene or butyl), face shield and acid-resistant apron
- Surgical mask and safety glasses
- Disposable nitrile gloves and cloth apron
Correct Answer: Acid-resistant gloves (neoprene or butyl), face shield and acid-resistant apron
Q7. When quenching a sulphonation reaction containing dissolved SO3, the safest general practice is to:
- Add large volumes of water quickly to the reaction mixture
- Slowly add the acid-containing reaction mixture into an excess of cold water or dilute alkaline quench under vigorous cooling
- Evaporate the solvent to dryness and then add water
- Neutralize with concentrated sulfuric acid
Correct Answer: Slowly add the acid-containing reaction mixture into an excess of cold water or dilute alkaline quench under vigorous cooling
Q8. Which material is most suitable for storage vessels used for concentrated sulfuric acid or oleum?
- Unlined carbon steel
- Glass-lined or PTFE-lined stainless steel
- Plain aluminum tanks
- Polyethylene without chemical resistance rating
Correct Answer: Glass-lined or PTFE-lined stainless steel
Q9. A spill of concentrated sulfuric acid in the lab should initially be managed by:
- Wiping up with dry paper towels and discarding in regular trash
- Containing the spill, neutralizing slowly with a dry neutralizer (soda ash or sodium bicarbonate) while cooling, and collecting the residues
- Adding organic solvent to dilute the acid
- Leaving it to evaporate under the fume hood
Correct Answer: Containing the spill, neutralizing slowly with a dry neutralizer (soda ash or sodium bicarbonate) while cooling, and collecting the residues
Q10. Which monitoring technique is essential to detect incipient thermal runaway in a sulphonation process?
- Periodic visual inspection only
- Reaction calorimetry and continuous temperature/pressure monitoring with automated shutdown
- Measuring pH in the vapor phase
- Subjective operator smell tests
Correct Answer: Reaction calorimetry and continuous temperature/pressure monitoring with automated shutdown
Q11. The primary environmental concern for gaseous emissions from sulphonation plants is:
- Release of volatile organic compounds (VOCs) only
- SOx emissions (SO2, SO3) leading to acidification and respiratory hazards
- Chlorofluorocarbon emissions
- Emission of inert nitrogen gas
Correct Answer: SOx emissions (SO2, SO3) leading to acidification and respiratory hazards
Q12. Which scrubber medium is most effective for neutralizing SO3/SO2 exhaust from sulphonation vents?
- Water only without caustic
- Alkaline scrubber solution (e.g., sodium hydroxide or sodium carbonate solution)
- Pure organic solvent scrubber
- Activated carbon without wet scrubbing
Correct Answer: Alkaline scrubber solution (e.g., sodium hydroxide or sodium carbonate solution)
Q13. Sulfonation of an activated aromatic ring typically proceeds by which mechanism and why can this be a hazard?
- Nucleophilic aromatic substitution; hazard is formation of stable toxins
- Electrophilic aromatic substitution; hazard is strong acid medium, high exotherm and possible resinification/charring
- Free radical polymerization; hazard is explosive radical chain reactions
- Pericyclic rearrangement; hazard is UV exposure requirement
Correct Answer: Electrophilic aromatic substitution; hazard is strong acid medium, high exotherm and possible resinification/charring
Q14. Which storage incompatibility is most critical for concentrated sulfuric acid and sulfonating reagents?
- Storage with noble metals like gold and platinum
- Storage with reactive organics and reducing agents that can char or ignite
- Storage next to inert gases like nitrogen
- Storage with glassware
Correct Answer: Storage with reactive organics and reducing agents that can char or ignite
Q15. For laboratory-scale sulphonation, what administrative control reduces human error during reagent addition?
- Allowing untrained personnel to perform additions quickly
- Use of written procedures, staging checks, buddy system and pre-approved addition rates
- Relying solely on operator memory
- Adding reagents without any protective shields to speed up process
Correct Answer: Use of written procedures, staging checks, buddy system and pre-approved addition rates
Q16. During a sulphonation reaction, sudden rise in pressure accompanied by acid fume release likely indicates:
- Onset of vapor-phase polymerization of solvent
- Rapid desorption of inert gas only
- Decomposition or release of gaseous SOx due to overheating or overpressure
- Harmless condensation of water vapor
Correct Answer: Decomposition or release of gaseous SOx due to overheating or overpressure
Q17. Which neutralization endpoint is generally acceptable for aqueous waste containing sulfuric acid from sulphonation before discharge (subject to local regulations)?
- pH 1–2
- pH 6–8
- pH 12–13
- Unadjusted highly acidic pH
Correct Answer: pH 6–8
Q18. If a worker receives skin contact with concentrated sulfuric acid or chlorosulfonic acid, first aid should be:
- Neutralize immediately with strong alkali like concentrated NaOH
- Flush with copious running water for at least 15 minutes and seek medical attention
- Cover with cotton and wait for medical personnel without flushing
- Apply organic solvent to the affected area
Correct Answer: Flush with copious running water for at least 15 minutes and seek medical attention
Q19. Which analytical/diagnostic practice helps predict safe addition rates for sulfonating reagents during process development?
- Trial-and-error at full batch scale
- Reaction calorimetry (e.g., RC1) to measure heat release and maximum temperature rise
- Relying only on literature without testing
- Measuring only final product purity
Correct Answer: Reaction calorimetry (e.g., RC1) to measure heat release and maximum temperature rise
Q20. Which waste handling practice is appropriate for solids contaminated with strong sulfonating acids?
- Incinerate immediately without controls
- Collect in compatible containers, neutralize carefully, and dispose through licensed hazardous waste routes
- Pour onto the general sewer
- Burn in an open area to remove acids
Correct Answer: Collect in compatible containers, neutralize carefully, and dispose through licensed hazardous waste routes
I am a Registered Pharmacist under the Pharmacy Act, 1948, and the founder of PharmacyFreak.com. I hold a Bachelor of Pharmacy degree from Rungta College of Pharmaceutical Science and Research. With a strong academic foundation and practical knowledge, I am committed to providing accurate, easy-to-understand content to support pharmacy students and professionals. My aim is to make complex pharmaceutical concepts accessible and useful for real-world application.
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