Structure and uses of dimethyl phthalate MCQs With Answer

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Dimethyl phthalate (DMP) is a low-molecular-weight phthalate ester important in pharmaceutical science as a plasticizer, solvent and preservative adjunct. B.Pharm students must grasp its chemical structure (phthalate core with two methyl ester groups), synthesis from phthalic anhydride and methanol, physicochemical properties (boiling point, solubility, log P), analytical identification (IR, NMR, GC–MS), pharmaceutical applications, toxicology, metabolism and environmental fate. Emphasis on formulation compatibility, leaching risks, hydrolysis, ester interchange, biodegradation pathways, occupational exposure limits and regulatory aspects prepares students for formulation development and quality control. Understanding these concepts aids safe handling, proper analysis and critical appraisal of DMP-containing products. Now let’s test your knowledge with 50 MCQs on this topic.

Q1. What is the chemical formula of dimethyl phthalate (DMP)?

  • C8H8O4
  • C10H10O4
  • C10H12O4
  • C12H14O4

Correct Answer: C10H12O4

Q2. The structural feature that defines phthalate esters like DMP is:

  • A benzene ring with two adjacent carboxylic acid groups
  • A benzene ring with two esterified ortho-carboxyl groups
  • A linear chain di-ester moiety
  • A cyclic anhydride only

Correct Answer: A benzene ring with two esterified ortho-carboxyl groups

Q3. DMP is commonly synthesized by esterification of phthalic anhydride with which alcohol?

  • Ethanol
  • Methanol
  • Propanol
  • Butanol

Correct Answer: Methanol

Q4. Which reagent is typically used as an acid catalyst in industrial esterification for DMP production?

  • Sodium hydroxide
  • Sulfuric acid
  • Sodium bicarbonate
  • Zinc chloride

Correct Answer: Sulfuric acid

Q5. In IR spectroscopy, which absorption band is characteristic for ester carbonyl in DMP?

  • ~3200 cm−1
  • ~1700–1750 cm−1
  • ~1500 cm−1
  • ~1100 cm−1

Correct Answer: ~1700–1750 cm−1

Q6. Which 1H NMR signal would you expect for the methyl ester protons of DMP?

  • A singlet around 3.7–4.0 ppm
  • A triplet around 0.9 ppm
  • A multiplet around 7.2 ppm
  • A broad signal at 5.5 ppm

Correct Answer: A singlet around 3.7–4.0 ppm

Q7. Which analytical technique is most suitable for quantifying DMP in environmental water samples?

  • UV-visible spectrophotometry
  • Gas chromatography–mass spectrometry (GC–MS)
  • Polarimetry
  • Flame photometry

Correct Answer: Gas chromatography–mass spectrometry (GC–MS)

Q8. The log P (octanol–water partition coefficient) of DMP indicates it is:

  • Highly hydrophilic
  • Relatively hydrophobic
  • Extremely volatile
  • Highly ionic

Correct Answer: Relatively hydrophobic

Q9. One pharmaceutical use of DMP is as:

  • An active pharmaceutical ingredient (API)
  • A plasticizer for polymeric excipients
  • An antibiotic preservative
  • A tablet disintegrant

Correct Answer: A plasticizer for polymeric excipients

Q10. Which property of DMP is most relevant to its function as a plasticizer?

  • High melting point
  • Low molecular mobility
  • Ability to reduce polymer glass transition temperature (Tg)
  • Strong acidity

Correct Answer: Ability to reduce polymer glass transition temperature (Tg)

Q11. DMP hydrolyzes to yield which principal product under acidic or basic conditions?

  • Phthalic acid and methanol
  • Benzoic acid and ethanol
  • Terephthalic acid and water
  • Maleic anhydride and methanol

Correct Answer: Phthalic acid and methanol

Q12. A significant toxicological concern for phthalates like DMP is their potential to:

  • Act as strong oxidizing agents
  • Disrupt endocrine function
  • Cause immediate severe corrosive burns
  • Chemo-selectively reduce ketones

Correct Answer: Disrupt endocrine function

Q13. Which metabolic transformation is commonly observed for DMP in mammals?

  • Formation of catechols
  • Oxidative demethylation to monoester metabolites
  • Direct conjugation without hydrolysis
  • Nitration of the aromatic ring

Correct Answer: Oxidative demethylation to monoester metabolites

Q14. For stability testing of DMP in formulations, which condition is most important to monitor?

  • Exposure to strong reducing agents
  • Exposure to moisture and high temperature
  • Magnetic field exposure
  • Ultraviolet light only

Correct Answer: Exposure to moisture and high temperature

Q15. Which of the following best describes the volatility of DMP compared to higher phthalate esters?

  • Less volatile than high molecular weight phthalates
  • More volatile than high molecular weight phthalates
  • Non-volatile
  • Explosively volatile

Correct Answer: More volatile than high molecular weight phthalates

Q16. In mass spectrometry, a common fragment ion for DMP corresponds to loss of:

  • CH3 radical only
  • One methoxycarbonyl group (–COOCH3)
  • Entire aromatic ring
  • Hydrogen gas

Correct Answer: One methoxycarbonyl group (–COOCH3)

Q17. When assessing excipient compatibility, DMP might interact with which polymeric excipient to cause increased leaching?

  • Polyethylene glycols
  • Polyvinyl chloride (PVC)
  • Lactose monohydrate
  • Silica gel

Correct Answer: Polyvinyl chloride (PVC)

Q18. Which regulatory agency often sets limits and guidelines for phthalate content in consumer and pharmaceutical products?

  • WHO only
  • FDA and EU regulatory bodies
  • International Red Cross
  • WIPO

Correct Answer: FDA and EU regulatory bodies

Q19. For laboratory handling of DMP, the most appropriate PPE includes:

  • Standard clothing only
  • Gloves, goggles and lab coat
  • No protection because it is harmless
  • Lead apron only

Correct Answer: Gloves, goggles and lab coat

Q20. Environmental degradation of DMP is primarily via:

  • Photochemical oxidation only
  • Microbial biodegradation and hydrolysis
  • Spontaneous polymerization
  • Freezing and thawing cycles

Correct Answer: Microbial biodegradation and hydrolysis

Q21. Which chromatographic stationary phase is commonly used for GC analysis of DMP?

  • Polar silica gel normal phase
  • Non-polar capillary column (e.g., 5% phenyl-methylpolysiloxane)
  • Ion-exchange resin
  • Size-exclusion column

Correct Answer: Non-polar capillary column (e.g., 5% phenyl-methylpolysiloxane)

Q22. Which solvent is commonly used to extract DMP from aqueous samples before analysis?

  • Hexane or dichloromethane
  • Water only
  • Acetone with sodium chloride
  • Methanol with acid

Correct Answer: Hexane or dichloromethane

Q23. Compared to diethyl phthalate (DEP), dimethyl phthalate (DMP) has:

  • Lower volatility
  • Higher polarity and slightly higher volatility
  • Greater molecular weight and lower polarity
  • Completely different pharmacology

Correct Answer: Higher polarity and slightly higher volatility

Q24. Which of the following is a reason DMP might be avoided in oral pharmaceutical formulations?

  • Its sweet taste
  • Potential leaching and systemic exposure concerns
  • Excessive solubility in gastric fluid
  • Incompatibility with hard gelatin capsules only

Correct Answer: Potential leaching and systemic exposure concerns

Q25. The presence of DMP in a sample is most directly confirmed by which combination of techniques?

  • TLC and melting point
  • GC–MS with retention time and mass spectral match
  • Colorimetric pH test
  • Conductivity measurement

Correct Answer: GC–MS with retention time and mass spectral match

Q26. In formulation development, a concern about DMP is its tendency to:

  • Enhance tablet hardness permanently
  • Migrate out of polymer matrices (plasticizer migration)
  • Form covalent bonds with APIs
  • Render formulations acidic

Correct Answer: Migrate out of polymer matrices (plasticizer migration)

Q27. Which acute effect may occur after significant inhalation exposure to DMP vapors?

  • Immediate renal failure
  • Respiratory irritation and dizziness
  • Cardiac arrhythmia always
  • Paralysis

Correct Answer: Respiratory irritation and dizziness

Q28. Which of these is a monoester metabolite expected from DMP metabolism?

  • Monoethyl phthalate (MEP)
  • Monomethyl phthalate (MMP)
  • Phthalimide
  • Di-n-butyl phthalate (DBP)

Correct Answer: Monomethyl phthalate (MMP)

Q29. For occupational exposure monitoring to DMP, the biomarker most likely measured in urine is:

  • Unchanged DMP only
  • Monomethyl phthalate (MMP)
  • Phthalic anhydride
  • Benzoic acid

Correct Answer: Monomethyl phthalate (MMP)

Q30. Which pKa is relevant when discussing hydrolysis of DMP?

  • pKa of methyl alcohol
  • pKa of phthalic acid (which influences hydrolysis rate)
  • pKa of benzene
  • DMP does not involve pKa considerations

Correct Answer: pKa of phthalic acid (which influences hydrolysis rate)

Q31. Which storage condition minimizes degradation of DMP in raw material stores?

  • High humidity and high temperature
  • Cool, dry, well-ventilated area away from sunlight
  • Open containers at room temperature
  • Storage with strong oxidizers

Correct Answer: Cool, dry, well-ventilated area away from sunlight

Q32. Which of the following is a common industrial application of DMP outside pharmaceuticals?

  • Flavoring agent in foods
  • Insect repellent solvent and plasticizer in cosmetics
  • Primary fuel additive
  • Explosive binder

Correct Answer: Insect repellent solvent and plasticizer in cosmetics

Q33. Which safety data sheet (SDS) hazard class is most relevant to DMP?

  • Explosive
  • Flammable liquid
  • Non-hazardous under all classes
  • Oxidizer

Correct Answer: Flammable liquid

Q34. In an HPLC method for DMP, which detector would give selective structural information with a prior MS interface?

  • Refractive index detector
  • UV detector without MS
  • Mass spectrometric detector (LC–MS)
  • Evaporative light scattering detector only

Correct Answer: Mass spectrometric detector (LC–MS)

Q35. Which intermolecular force contributes significantly to DMP’s physicochemical behavior?

  • Hydrogen bonding as donor
  • Dipole–dipole interactions and London dispersion
  • Strong ionic bonding
  • Metal coordination

Correct Answer: Dipole–dipole interactions and London dispersion

Q36. Which degradation product of DMP is commonly monitored in environmental studies?

  • Phthalic acid
  • Toluene
  • Acetone
  • Benzaldehyde

Correct Answer: Phthalic acid

Q37. Which factor increases the rate of ester hydrolysis of DMP in aqueous media?

  • Neutral pH and low temperature
  • High ionic strength only
  • Strong acidic or basic conditions and elevated temperature
  • Presence of inert gases

Correct Answer: Strong acidic or basic conditions and elevated temperature

Q38. In risk assessment for pharmaceuticals, the principal concern with DMP leaching from packaging is:

  • Loss of tablet color
  • Patient exposure and systemic toxicity over time
  • Increase in active drug potency
  • Reduction of tablet weight only

Correct Answer: Patient exposure and systemic toxicity over time

Q39. Which phase of drug development most requires knowledge of DMP compatibility with polymers?

  • Discovery target validation
  • Formulation development and stability testing
  • Clinical pharmacodynamics only
  • Patent drafting

Correct Answer: Formulation development and stability testing

Q40. What is a typical physical appearance of dimethyl phthalate at room temperature?

  • Colorless oily liquid
  • White crystalline solid
  • Dark brown resin
  • Gas

Correct Answer: Colorless oily liquid

Q41. Which method best separates DMP from other phthalates for analysis?

  • Simple gravimetric analysis
  • High-resolution GC with appropriate column and temperature program
  • Titration with NaOH
  • Paper chromatography only

Correct Answer: High-resolution GC with appropriate column and temperature program

Q42. A formulation scientist is concerned about DMP’s effect on drug permeability. How might DMP alter permeability?

  • By decreasing membrane fluidity and reducing permeability
  • By acting as a plasticizer and potentially increasing membrane permeability
  • By chemically reacting to form impermeable layers
  • By precipitating the drug

Correct Answer: By acting as a plasticizer and potentially increasing membrane permeability

Q43. Which occupational exposure route is most relevant for workers handling DMP powder or liquid?

  • Solar radiation
  • Inhalation and dermal contact
  • Hearing damage
  • Prolonged fasting

Correct Answer: Inhalation and dermal contact

Q44. Which of the following is true about DMP’s biodegradability?

  • It is completely persistent and non-biodegradable
  • It can be biodegraded by microorganisms under aerobic conditions
  • It only degrades via photolysis
  • It instantaneously vaporizes and disappears

Correct Answer: It can be biodegraded by microorganisms under aerobic conditions

Q45. In environmental monitoring, DMP would most likely be detected in which matrix?

  • Deep space samples
  • Surface waters and sediments
  • Pure distilled water with no exposure
  • Solid metals only

Correct Answer: Surface waters and sediments

Q46. Which concept explains why DMP can migrate from packaging into pharmaceuticals?

  • Chemical bonding to polymer chains
  • Concentration gradient-driven diffusion and solubility in the formulation
  • Gravitational attraction
  • Electrostatic repulsion

Correct Answer: Concentration gradient-driven diffusion and solubility in the formulation

Q47. Which laboratory waste disposal method is appropriate for small quantities of DMP-contaminated organic solvents?

  • Pour down the sink
  • Collect in labeled hazardous organic waste and dispose per institutional guidelines
  • Incinerate in an open area
  • Neutralize with baking soda and discard as regular trash

Correct Answer: Collect in labeled hazardous organic waste and dispose per institutional guidelines

Q48. Which spectroscopic technique will provide direct information about the aromatic substitution pattern in DMP?

  • UV-visible only
  • 1H and 13C NMR spectroscopy
  • Polarimetry
  • Conductivity measurement

Correct Answer: 1H and 13C NMR spectroscopy

Q49. When preparing a calibration curve for GC–MS quantification of DMP, which standard is essential?

  • A blank solvent and a series of known concentration standards of DMP
  • Only one high concentration standard
  • An unrelated compound as internal standard only
  • No standards are required

Correct Answer: A blank solvent and a series of known concentration standards of DMP

Q50. For a B.Pharm student evaluating literature on DMP, which interdisciplinary topics should be consulted?

  • Only organic synthesis textbooks
  • Toxicology, environmental chemistry, analytical methods and formulation science
  • Astronomy and geology
  • Music theory

Correct Answer: Toxicology, environmental chemistry, analytical methods and formulation science

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