Structure and uses of diphenylmethane MCQs With Answer

Structure and uses of diphenylmethane MCQs With Answer

Diphenylmethane is an important organic scaffold for B. Pharm students studying medicinal chemistry and pharmaceutical organic reactions. This short guide focuses on the diphenylmethane structure, benzylic reactivity, synthesis routes (e.g., Friedel–Crafts benzylation), spectroscopy, and pharmaceutical applications of diphenylmethane derivatives. Keywords covered include diphenylmethane structure, benzylic hydrogen, benzophenone formation, Friedel–Crafts alkylation, diphenylmethane uses, and drug scaffolds (e.g., diphenhydramine). The questions emphasize mechanism, functional group transformations, analytical identification, and practical uses in drug synthesis to help reinforce concepts critical for B. Pharm coursework. Now let’s test your knowledge with 50 MCQs on this topic.

Q1. What is the molecular formula of diphenylmethane?

• C12H10
• C13H12
• C14H12
• C13H14

Correct Answer: C13H12

Q2. How is the core connectivity of diphenylmethane best described?

• Two phenyl rings directly bonded to each other
• Two phenyl rings connected by a methylene (-CH2-) bridge
• A phenyl ring fused to a cyclohexane
• A biphenyl with a double bond between rings

Correct Answer: Two phenyl rings connected by a methylene (-CH2-) bridge

Q3. What is the hybridization of the central carbon (methylene) in diphenylmethane?

• sp
• sp2
• sp3
• sp3d

Correct Answer: sp3

Q4. How does the benzylic CH2 in diphenylmethane compare in reactivity to a typical aliphatic CH2?

• Less reactive than aliphatic CH2
• About the same reactivity as aliphatic CH2
• More reactive due to resonance stabilization of intermediates
• Unreactive under most conditions

Correct Answer: More reactive due to resonance stabilization of intermediates

Q5. Which product is commonly formed when diphenylmethane undergoes strong benzylic oxidation?

• Benzhydrol (diphenylmethanol)
• Benzophenone (diphenyl ketone)
• Biphenyl
• Toluene

Correct Answer: Benzophenone (diphenyl ketone)

Q6. Are the two phenyl rings in diphenylmethane conjugated through the central carbon?

• Yes, they are fully conjugated
• No, conjugation is interrupted by the sp3 methylene carbon
• Only under UV irradiation
• Only in the solid state

Correct Answer: No, conjugation is interrupted by the sp3 methylene carbon

Q7. Which reaction is a common laboratory route to synthesize diphenylmethane?

• Nucleophilic aromatic substitution of bromobenzene
• Friedel–Crafts benzylation of benzene with benzyl chloride and AlCl3
• Diels–Alder reaction between benzene and methylene
• Grignard reaction of phenylmagnesium bromide with benzaldehyde followed by elimination

Correct Answer: Friedel–Crafts benzylation of benzene with benzyl chloride and AlCl3

Q8. In electrophilic aromatic substitution of diphenylmethane, how does the CH2–Ph substituent direct incoming electrophiles?

• Meta-directing and deactivating
• Ortho/para-directing and slightly activating
• Strongly deactivating due to -I effect
• Does not affect substitution pattern

Correct Answer: Ortho/para-directing and slightly activating

Q9. Which reagent is commonly used to selectively brominate the benzylic position of diphenylmethane?

• N-bromosuccinimide (NBS) in presence of light or radical initiator
• Br2 in acetic acid under dark conditions
• HBr with peroxide
• SOCl2

Correct Answer: N-bromosuccinimide (NBS) in presence of light or radical initiator

Q10. Which statement about the acidity of benzylic hydrogens in diphenylmethane is correct?

• They are comparable in acidity to phenol OH
• They are more acidic than typical alkane hydrogens due to resonance stabilization of the carbanion
• They are strongly acidic and deprotonate easily in water
• They are less acidic than aliphatic hydrogens

Correct Answer: They are more acidic than typical alkane hydrogens due to resonance stabilization of the carbanion

Q11. Which pharmaceutical scaffold contains a diphenylmethane-like motif?

• Aspirin
• Diphenhydramine (an antihistamine)
• Paracetamol
• Metformin

Correct Answer: Diphenhydramine (an antihistamine)

Q12. Regarding solubility, diphenylmethane is best described as:

• Highly soluble in water
• Moderately soluble in water
• Insoluble in water but soluble in organic solvents
• Soluble in both water and organic solvents equally

Correct Answer: Insoluble in water but soluble in organic solvents

Q13. Which intermediate is stabilized when diphenylmethane forms a carbocation at the benzylic position?

• Primary carbocation with no resonance stabilization
• Benzylic carbocation stabilized by resonance with both phenyl rings
• Carbanion stabilized by inductive withdrawal
• Radical cation localized only on one ring

Correct Answer: Benzylic carbocation stabilized by resonance with both phenyl rings

Q14. In 1H NMR spectroscopy, where would you expect the benzylic CH2 protons of diphenylmethane to appear relative to typical aliphatic CH2 protons?

• Far upfield (0–1 ppm)
• At a similar chemical shift as alkane CH2 (1–2 ppm)
• Downfield (higher ppm) compared to aliphatic CH2 due to benzylic deshielding
• They are NMR-silent

Correct Answer: Downfield (higher ppm) compared to aliphatic CH2 due to benzylic deshielding

Q15. Which of the following transformations converts diphenylmethane to a carbonyl-containing compound?

• Hydrogenation over Pd/C
• Benzylic oxidation with chromic acid or KMnO4
• Radical chlorination at the ring
• Electrophilic aromatic nitration

Correct Answer: Benzylic oxidation with chromic acid or KMnO4

Q16. Does diphenylmethane exhibit significant conjugation between the two phenyl rings across the methylene bridge?

• Yes; the rings are strongly conjugated through the methylene
• No; conjugation is disrupted by the sp3 carbon making rings electronically separated
• Only at high temperatures
• Only when protonated

Correct Answer: No; conjugation is disrupted by the sp3 carbon making rings electronically separated

Q17. Which of the following best explains why benzylic radicals formed from diphenylmethane are stabilized?

• Inductive donation from the methylene group
• Hyperconjugation only
• Resonance delocalization over the adjacent aromatic rings
• Steric hindrance preventing reaction

Correct Answer: Resonance delocalization over the adjacent aromatic rings

Q18. Which spectroscopic feature is most useful to confirm the presence of aromatic rings in diphenylmethane?

• A strong IR absorption near 1700 cm-1
• Characteristic aromatic C–H stretch and C=C ring vibrations in IR and aromatic proton signals in 1H NMR
• A carbonyl stretch in IR
• A single sharp peak in mass spectrometry at m/z 16

Correct Answer: Characteristic aromatic C–H stretch and C=C ring vibrations in IR and aromatic proton signals in 1H NMR

Q19. In mass spectrometry of diphenylmethane, a common fragment corresponds to which species?

• Hydrogen gas
• Benzyl cation (C7H7+)
• Carbon dioxide
• Methane radical

Correct Answer: Benzyl cation (C7H7+)

Q20. Which statement about diphenylmethane’s use in pharmaceutical synthesis is correct?

• It is rarely used as a synthetic intermediate in drug molecules
• Diphenylmethane derivatives serve as core scaffolds in many drug classes and intermediates in synthesis
• It is exclusively used as an active pharmaceutical ingredient
• It is only used in formulation, not synthesis

Correct Answer: Diphenylmethane derivatives serve as core scaffolds in many drug classes and intermediates in synthesis

Q21. During nitration of diphenylmethane, where does nitration predominantly occur?

• At the benzylic carbon
• On the aromatic rings at ortho/para positions
• At the central carbon to form a nitrile
• No reaction occurs under nitration conditions

Correct Answer: On the aromatic rings at ortho/para positions

Q22. Which reagent would most likely convert diphenylmethane into a benzylic anion under laboratory conditions?

• Sodium chloride in water
• Strong non-nucleophilic base like LDA at low temperature
• Mild base like sodium bicarbonate
• Acetic acid

Correct Answer: Strong non-nucleophilic base like LDA at low temperature

Q23. Which of the following best describes diphenylmethane’s polarity?

• Highly polar due to two phenyl rings
• Nonpolar to weakly polar, favoring organic solvents
• Ionic
• Amphiphilic like surfactants

Correct Answer: Nonpolar to weakly polar, favoring organic solvents

Q24. What happens when diphenylmethane undergoes Friedel–Crafts acylation under typical conditions?

• The methylene carbon is acylated directly
• The aromatic rings undergo acylation at ortho/para positions
• The molecule polymerizes exclusively
• No reaction since diphenylmethane is inert to acylation

Correct Answer: The aromatic rings undergo acylation at ortho/para positions

Q25. Which property makes benzylic hydrogens amenable to radical halogenation?

• High bond dissociation energy compared to alkanes
• Resonance stabilization of the resulting benzylic radical
• Steric shielding preventing radical attack
• Complete absence of hydrogen atoms on the benzylic carbon

Correct Answer: Resonance stabilization of the resulting benzylic radical

Q26. Which product results from hydrogenolysis (hydrogenation) of diphenylmethane?

• Cyclohexylmethane
• Diphenylmethane remains unchanged under mild hydrogenation
• Benzhydrol formation
• Benzene

Correct Answer: Diphenylmethane remains unchanged under mild hydrogenation

Q27. Which synthetic transformation would introduce a leaving group at the benzylic carbon of diphenylmethane?

• Direct substitution with NaOH
• Benzylic radical bromination followed by nucleophilic displacement
• Nitration of the aromatic ring
• Hydrogenation of aromatic rings

Correct Answer: Benzylic radical bromination followed by nucleophilic displacement

Q28. Which statement about the UV–Vis absorption of diphenylmethane is accurate?

• It shows very strong long-wavelength absorption due to extended conjugation across the methylene
• It has weak to moderate absorption typical of isolated aromatic rings because rings are not conjugated through the methylene
• It is completely transparent in the UV region
• It absorbs exclusively in the infrared

Correct Answer: It has weak to moderate absorption typical of isolated aromatic rings because rings are not conjugated through the methylene

Q29. Which reagent would convert diphenylmethane into the corresponding benzhydrol (diphenylmethanol)?

• Hydrogenation with Pd/C
• Oxidation with KMnO4
• Hydroxylation of the benzylic position using appropriate oxidants followed by reduction of intermediate
• Treatment with strong acid only

Correct Answer: Hydroxylation of the benzylic position using appropriate oxidants followed by reduction of intermediate

Q30. In comparison to biphenyl, diphenylmethane differs because:

• It has a saturated methylene linker between rings, preventing direct conjugation
• It has a double bond linking the rings
• Both compounds are identical structurally
• Diphenylmethane is an ionic compound while biphenyl is not

Correct Answer: It has a saturated methylene linker between rings, preventing direct conjugation

Q31. Which functional group transformation is commonly used to convert a benzylic bromide (derived from diphenylmethane) into a carbonyl compound?

• Grignard formation followed by hydrolysis
• Hydrolysis of the benzylic bromide to alcohol followed by oxidation to ketone
• Direct substitution with cyanide gives ketone
• Alkene formation then ozonolysis

Correct Answer: Hydrolysis of the benzylic bromide to alcohol followed by oxidation to ketone

Q32. Which factor most contributes to the stabilization of a benzylic carbanion formed from diphenylmethane?

• Inductive withdrawal by the methylene group
• Resonance delocalization into aromatic rings
• Hydrogen bonding to water
• Formation of a stable carbene

Correct Answer: Resonance delocalization into aromatic rings

Q33. Which description best fits diphenylmethane’s appearance and state at room temperature (general organic lab context)?

• Highly volatile gas
• Colorless to pale liquid/low-melting crystalline solid, typical of many simple diarylalkanes
• Inorganic salt solid
• Brightly colored dye

Correct Answer: Colorless to pale liquid/low-melting crystalline solid, typical of many simple diarylalkanes

Q34. Which reaction condition should be avoided if the goal is to keep the benzylic CH2 intact?

• Mild, non-oxidizing conditions
• Strong oxidative conditions like KMnO4 or chromic acid
• Neutral solvent at room temperature
• Inert atmosphere with no radical initiator

Correct Answer: Strong oxidative conditions like KMnO4 or chromic acid

Q35. Which type of mechanism commonly explains electrophilic aromatic substitution on diphenylmethane rings?

• Nucleophilic aromatic substitution
• Electrophilic aromatic substitution via arenium ion intermediate
• Free radical chain addition across the ring
• Pericyclic cycloaddition only

Correct Answer: Electrophilic aromatic substitution via arenium ion intermediate

Q36. Which statement about diphenylmethane derivatives and dye chemistry is most accurate?

• Diphenylmethane is itself a triphenylmethane dye
• Diphenylmethane derivatives can be precursors to triphenylmethane dyes by further electrophilic substitution
• Diphenylmethane derivatives are never used in dye synthesis
• All diphenylmethane derivatives are fluorescent dyes

Correct Answer: Diphenylmethane derivatives can be precursors to triphenylmethane dyes by further electrophilic substitution

Q37. Which analytical technique would best distinguish diphenylmethane from benzophenone?

• Thin-layer chromatography only
• Infrared spectroscopy showing carbonyl stretch in benzophenone but not in diphenylmethane
• Paper chromatography
• Simple visual inspection under daylight

Correct Answer: Infrared spectroscopy showing carbonyl stretch in benzophenone but not in diphenylmethane

Q38. Which reagent selectively oxidizes a benzylic methylene to a ketone without affecting aromatic rings under controlled conditions?

• Potassium permanganate under vigorous reflux in all cases
• Chromium(VI) reagents under controlled conditions or milder oxidants tailored for benzylic oxidation
• Sodium chloride in water
• Hydrochloric acid only

Correct Answer: Chromium(VI) reagents under controlled conditions or milder oxidants tailored for benzylic oxidation

Q39. Which statement about chlorination of diphenylmethane under radical conditions is true?

• Chlorination will exclusively occur on aromatic rings
• Benzylic chlorination is feasible due to radical stabilization
• Chlorination is impossible on benzylic positions
• Chlorination converts diphenylmethane to benzene

Correct Answer: Benzylic chlorination is feasible due to radical stabilization

Q40. In the context of drug design, why is the diphenylmethane motif valuable?

• It confers ionic character that improves renal clearance
• It provides a rigid aromatic framework that can modulate lipophilicity and receptor interactions
• It always increases water solubility
• It prevents any metabolic transformation

Correct Answer: It provides a rigid aromatic framework that can modulate lipophilicity and receptor interactions

Q41. Which pathway best describes conversion of diphenylmethane into benzophenone?

• Benzylic reduction followed by dehydrogenation
• Benzylic oxidation of the methylene group to a carbonyl
• Direct substitution on the aromatic ring to introduce an oxygen atom
• Photochemical rearrangement of rings

Correct Answer: Benzylic oxidation of the methylene group to a carbonyl

Q42. Which of the following is a correct statement about the benzylic C–H bond strength in diphenylmethane?

• It generally has lower bond dissociation energy than a tertiary alkane C–H due to resonance stabilization of the radical
• It is the strongest C–H bond found in organic chemistry
• It is not susceptible to homolytic cleavage
• Its bond strength is identical to methane C–H

Correct Answer: It generally has lower bond dissociation energy than a tertiary alkane C–H due to resonance stabilization of the radical

Q43. For selective functionalization at the benzylic position, which approach is most commonly used?

• Direct electrophilic aromatic substitution at the ring
• Radical halogenation followed by nucleophilic substitution
• Hydrogenation of aromatic rings
• Electrochemical substitution at the ring

Correct Answer: Radical halogenation followed by nucleophilic substitution

Q44. Which statement about thermal stability of diphenylmethane under mild laboratory heating is accurate?

• It decomposes explosively at low temperatures
• It is relatively thermally stable under mild heating without strong oxidants
• It spontaneously polymerizes at room temperature
• It sublimes immediately at ambient conditions

Correct Answer: It is relatively thermally stable under mild heating without strong oxidants

Q45. In retrosynthetic analysis, diphenylmethane can be disconnected into which simple fragments?

• Two benzyl anions
• Benzyl cation and benzene (electrophilic benzylation of benzene)
• Carbon dioxide and benzene
• Methane and biphenyl

Correct Answer: Benzyl cation and benzene (electrophilic benzylation of benzene)

Q46. Which of the following is a likely metabolic transformation of a diphenylmethane-containing drug in the body?

• Benzylic oxidation to give corresponding carbonyl or hydroxyl metabolites
• Conversion to inorganic salts immediately
• Complete resistance to any metabolic process
• Instant polymerization in plasma

Correct Answer: Benzylic oxidation to give corresponding carbonyl or hydroxyl metabolites

Q47. Which reagent combination would promote Friedel–Crafts benzylation of benzene to form diphenylmethane?

• Benzyl chloride and AlCl3
• Benzyl alcohol and NaOH only
• Benzene and water
• Benzyl bromide and weak base at cold temperature

Correct Answer: Benzyl chloride and AlCl3

Q48. Why are benzylic positions often sites of metabolic oxidation in drugs?

• Benzylic C–H bonds are extremely strong and inert
• Benzylic C–H bonds are relatively weak and radicals or cations are resonance-stabilized, facilitating enzymatic oxidation
• Because aromatic rings block all metabolic enzymes
• They are always protonated in vivo making them reactive

Correct Answer: Benzylic C–H bonds are relatively weak and radicals or cations are resonance-stabilized, facilitating enzymatic oxidation

Q49. Which structural feature differentiates diphenylmethane from diarylmethenes?

• Diphenylmethane contains a saturated methylene (CH2) between rings, diarylmethenes contain an sp2 carbon (C=) linking rings
• Diphenylmethane has a double bond between rings
• Diarylmethenes have an sp3 carbon between rings
• They are identical in every structural aspect

Correct Answer: Diphenylmethane contains a saturated methylene (CH2) between rings, diarylmethenes contain an sp2 carbon (C=) linking rings

Q50. For B. Pharm students, which concept about diphenylmethane is most important to link chemical structure to pharmaceutical behavior?

• That it is ionic and water-soluble
• That the benzylic position’s reactivity affects metabolic stability and synthetic functionalization of drug candidates
• That it cannot be modified chemically
• That it always confers antibacterial activity

Correct Answer: That the benzylic position’s reactivity affects metabolic stability and synthetic functionalization of drug candidates

G S Sachin

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.

Mail- Sachin@pharmacyfreak.com