USEFUL TO STUDENTS

1. ORGANICCHEMISTRY RESONINGQUESTIONS
K.G.MALLIKARJUN,VICEPRINCIPAL,JNV,ANANTHAPUR
ORGANIC CHEMISTRY RESONIING QUESTION
1.The bond angle in alcohol isslightlylessthan the tetrahedral bond angle (109.28 ). Whyis it so?
Ans:It isdue to the repulsionbetweenthe unpairedelectronpairsof oxygen.
2. Carbon oxygenbond length in phenol islessthan the alcohol?
Ands:It isdue to the partial double bondcharacterbetweenCandO in phenol.
3. Boilingpointof the alcohol ismore than the alkenes.Comment?
Ans:due to intermolecularhydrogeninalcoholsithashigh boilingpoint.
4. Branched alcoholsare havinglow boilingpointcompare with normal straight chain alcohols?
Explain.
OR
Boilingpoint t-Butyl alcohol is lessthan the n-Butyl alcohol?Explain.
Ans:As branchingincreasessurface areadecreasesandVanderwall’sforce decreases,hence boiling
pointdecreases.Andalsoinbranched alcoholsdue toelectronreleasingeffectstrengthof
hydrogen decreases.
5. Arrange the followingcompoundsin increasingorder of theirboilingpoints?
CH3 -CH2-OH, CH3-CHO, CH3 -O-CH3, CH3 -CH2-CH3,
Ans:molecularof these compoundsare similar;ethanolishavingintermolecularH- bondhence
more boilingpoint.Amongacetaldehyde andether,acetaldehydeHasstrongdi pole attractions
than the ethers.
Propene isweakvanderwaal'sforces.Hence the boilingpointorderis
CH3 -CH2- OH> CH3 -CHO > CH3 -O-CH3 > CH3 -CH2 -CH3
6. Arrange the followinginincreasingorder of theirrelativitytowards nucleophilic addition
reactions. H- CHO, CH3 -CHO, CH3 -CO- CH3
Ans: CH3 -CO-CH3 <CH 3-CHO<H-CHO
Electronreleasingeffect
Stericeffect
7. Ethers have lowboilingpoint compare with correspondingalcohols.Give reasons
Ans: Alcoholscanform intermolecularH-bond,where asethersdonot.Hence alcohols are
having highboilingpointthanethers.
8.Alcoholsare Bronstein basesor Proton acceptors. Explain?
Ans: It is due to presence of unsharedelectronpairoveroxygenatom whichmakes alcoholsproton
acceptors.Protonacceptorsare knownas Bronsteinbases.
9.Alcoholsare weak acids than water. Explain?
Ans:Inboththe cases due to polarO-H bond,behave asacids.But inalcohols due to presence of
alkyl groups,whichare electronreleasinghence O-Hbond islesspolarized,showsweakacidic
character.
10.Arrange the acidity order for 1, 2 & 3 Isomericalcohols (C4H10O)?
Ans:Alwayselectronreleasingeffectdestabilizesthe anionanddecrease the acidity.
11.Phenol is stronger acid than alcohol. Explain.
(Or)
Phenol is weak proton acceptor than alcohol.Explain.
Ans:Acidityof the substance dependsonstabilityof anionafterlosing H+
ion. Since phenoxide ion
undergoesresonancestabilizationcompare toalkoxide, phenol ismore acidicthanalcohol.

2. ORGANICCHEMISTRY RESONINGQUESTIONS
K.G.MALLIKARJUN,VICEPRINCIPAL,JNV,ANANTHAPUR
12.Arrange the followingcompoundsin increasingorder of theiracidic strength. Propan-1-ol,4-Methyl
phenol,Phenol,3,5 dinitrophenol,2,4,6 Trinitrophenol.
Ans. Propan-1-ol<4-Methoxyphenol<Phenol<3,5 dinitrophenol< 2, 4, 6 Trinitrophenol
Phenol ismore thanalcohol due to resonance stabilityof phenoxide ion.Electronreleasing
groupslike (O-CH3) methoxydecreases acidity.Electronwithdrawinggroupslike(-NO2)
nitrogroupsncreasesacidity.More numberof electronwithdrawinggroupsmore acidity.
13. O- nitro phenol & p-nitrophenol can be separated by distillation?Explain.
Or
Boilingpoint ofp-nitro phenol ismore than the o- nitro phenol.Explain?
Ans:O-nitrophenol isastreamvolatile due tointermolecularHydrogenbondwhere asp-nitro
phenol ishavingintermolecularHydrogenbond.Intermolecularhydrogenbonddecreases
BoilingpointIntermolecularhydrogenbondincreasesBoilingpoint
14. The usual halogenationsofBenzene takesplace of in presence ofLewisacid catalyst like CaCl3,
where as phenol can directlyreact with Bromine?Explain?
Ans:ncase of Halogenationsof benzeneBr2 ispolarizedbyFeBr3, but incase of phenol the
polarizationof Br2 takesplace by phenol due tohighlyactivatingeffect of OH group presenton
the benzene ring.
15. Primary alkyl halide reacts with sodiumalkoxide and forms ethersin good yieldbut t-alkyl halides
yieldfeweramounts of ethers.Explain?
Ans.Since tertiarycarbocationismore stable andit will formalkenesinsteadof ether.
16. Explain the fact that in aryl alkyl ethers(i) alkoxy group activates the
benzene ringtowards electrophilicsubstitutionand(ii) itdirects the incoming substituentsto
ortho & para position?
Ans:Alkoxygroupiselectronreleasingtothe benzene ring (+ve mesomericeffect) and by resonance
-ve charge obtainedat ortho & para positions only.Hence electrophileattractsatortho& para
positions.Anddue to+ve mesomesriceffect ringbecame activated.
17. t- Butyl methyl etherreacts with HI forms methanol & t- butyl iodide explain?
Ans:Since tertiarycarbocationismore stable andreactionisfollowing carbocation mechanism
it givest- Butyl iodide.
18. The commercial ethanol is mixedwithcopper sulphate & pyridine.Explain.
Ans.Commercial ethanol ismixedwithCuSo4&pyridine tomake itunfitfordrinking. Itisknownas
denaturationof alcohol.
19. Explain why are alcohols comparativelymore soluble inwater than the corresponding
hydrocarbons?
Ans:Itisdue to HydrogenBondformationwithwater.
20.Explain the fact that in aryl alkyl ethers(i) alkoxy group activates the benzene ring towards
electrophilic substitutionand (ii) it directs the incomingsubstituentsto ortho & para position?
Ans:Alkoxygroupiselectronreleasingtothe benzene ring(+ve mesomericeffect) andbyresonance
-ve charge obtainedatortho & para positionsonly.Hence electrophileattractsat ortho& para
positions.Anddue to+ve mesomesriceffect ringbecame activated.
21. Unlike phenols,alcoholsare easilyprotanated. Give reason.
Ans:Alcoholsactas proton acceptorsor Bronstedbases.Itisdue to presence of unsharedelectron
pair overoxygen.Incase of phenol lone pairisinvolvingin resonance.Hence,itcannotbe
protanatedeasily.

3. ORGANICCHEMISTRY RESONINGQUESTIONS
K.G.MALLIKARJUN,VICEPRINCIPAL,JNV,ANANTHAPUR
22. Reaction of alcoholswith hydrogenhalides(HX) is of the followingorder.Explain. 3 alcohols
2alcohols 1alcohols
Ans:Thisreactiontakesplace throughcarbocationmechanismsince the stabilityof carbocationis3
2 1. The reactivityorderisalsosame.
23. Anisole react with HI givesphenol & methyl iodide but not iodobenzene and methanol. Explain.
Ans:Nucleophilicsubstitutiononaromaticringisdifficultdue topartial doublebondcharacter
betweenoxygenandcarbonof benzene ring.
24. Name the intermediate or electrophile formedduringReimur-Tiemannreaction?
Ans:Dichlorocarbon - CCl2
25. Phenol react with bromine in the presence ofcarbon disulphide givesmonobromophenol whereas
with water givestribromophenol.Explain.
Ans:CS isa non-polarsolventwhereaswaterisapolar solvent.Inthe presence of polarsolvent
phenol polarizesandgivesmole electrophilicsubstitution.
26. Ethers made of similarkind of polar bonds(symmetric) also possessome net dipole moment.
Explain.
Ans.Due to itsbentstructure.
27. Explain why o-nitrophenol is more acidic than o-methoxyphenol?
Ans:Nitrogroupisan electronwithdrawingwhich increasesacidity where asmethoxy groupisan
electronreleasingwhichdecreasesacidity.
28. Phenol is more active towards electrophilicsubstitutionthanbenzene.Explain?
Ans:OHgroup presentonthe phenol iselectronreleasingandactivatesthe benzene ring through
resonance.
29. Preparation of ethersby acid dehydration of secondaryor tertiary alcoholsis not a suitable
method. Give reasons?
Ans:Secondaryandtertiaryalcoholswillgive alkaneseasilybydehydration.
30. Explain why is propanal higherboilingthan butane?
Ans:Due tointermolecularhydrogenbondpresentinalcohols,they possesshighboilingpoint.
31. Explain why are alcoholscomparatively more soluble in water than the corresponding
hydro carbons?
Ans:Due topresence of intermolecularhydrogenbondinalcohols.
32. Aldehydesandketonespossessmore dipole momentthan ethers.Explain?
Ans:Due topresence of double bondmore polaritywhichincreases dipole moment
33. Arrange the following compoundsin increasingorder of theirboilingpoints?
CH3-CHO , CH3-CH2-OH , CH3-O-CH3 , CH3-CH2-CH3
Ans:Theirmolecularmassesare almostall similarbut
CH3-CH2-OH > CH3-CHO > CH3-O-CH3 > CH3-CH2-CH3
Intermolecularmore polarthanpresence of noH-bond& H-bond ethers polarization
34. Why it isnecessary to use sulphuric acid innitration of benzene?
Ans: sulphuricacidishelpinginformationof NO2 electrophilewhichiseasytosubstitute on
benzene.
35. Acetic acid is halogenatedin the presence of red P and Cl2 but formic acid cannot be halogenated
in the same way . Explain?
Ans:There isnoalphahydrogeninformicacid.
36. Carboxylicacid are having more boilingpoint than alcohols ofsame molecularmass. explain
Ans:Incarboxylicacidsstrengthof H bondisstrongerthan alcoholsandformsdimmer in
carboxylicacidswhichincreasesboilingpoint.

4. ORGANICCHEMISTRY RESONINGQUESTIONS
K.G.MALLIKARJUN,VICEPRINCIPAL,JNV,ANANTHAPUR
37. Carboxylicacid can not give characteristic reactions of aldehydesandketonesthough both are
having carbonyl group CO?
Ans:Carbonyl groupincarboxylicacidisresonance stabilizedascarboxyl ate ion.Hence it can
notgive nucleophilicaddition reactionsgivenbycarbonyl group.
38. Formaldehyde givescannizarros reaction but acetaldehyde cannot. Explain
Ans:Cannizarrosreactionisgivenbyanyaldehydeswithoutalpha hydrogenhence acetaldehyde
cannot give thisreaction
39.Why do aldehydesand ketoneshave highdipole moment?
Ans:Due topresence of Polarisable C=Obondinit.
40. Phenol is acidic but do not react with sodium bicarbonate solution.Explain?
Ans.Phenol isaweakacidhence it can not reactwithweakbase like sodium bicarbonate.
41. Boilingpoint of glycol is higherthan alcohol of same molecularmass . Explain?
Ans:Asthe numberof –OH group’s increasesstrengthof H bondincreasesandboiling pointalso
increases.
42. Nitration of phenol iseasierthan benzene .explain?
Ans:Due topresence of –OHgroup whichcauseselectronreleasing effect,ringis activatedand
electrophilicsubstitutioniseasier.
43. Why methyl amine has lower boilingpointthan methanol?
Ans:Aminespossesweakhydrogenbondthanalcohols,hence methanol hashigher boilingpoint.
44. Why isit difficultto prepare pure aminesby ammonalsisof alkyl halides?
Ans:Reactionof alkyl halideswithammoniagivesmixtureof amines because secondary and tertiary
aminesalsobehave as nucleophilicandundergoessubstitutionwith alkyl halides.
45. Electrophilicsubstitutionincase of aromatic aminestakes place more readilythan benzene .
explain?
Ans:NH2 group presentonthe benzene iselectronreleasingandactivatesringhence electrophilic
substitutioniseasy.
46. Why doessilverchloride dissolve inmethyl amine solution?
Ans.Methyl amine formsa complex compoundwithsilverchlorideandthatissoluble inwater
2CH3NH2 + AgCl  [ Ag (CH3NH2)2] Cl
47. Tetiary amines do not undergoacieration .explain?
Ans:Asthese are nothavinghydrogenonnitrogentheycannot give contestation reactionwithacid
chlorides.
48. Why isdiazotizationof aniline carried inice cold solution?
Ans:Diazoniumsaltsare stable atcoldconditionsonly.
49. Why doesamideslessbasic than amines?
Ans:Lone pairpresentinamidesisinvolvedin resonance hence itislessbasicthanamines.
50. Why isethyl amine more basic than amines?
Ans:Inethyl amine lone pairisnotinvolvedinresonance where asinaniline lonepairisinvolvedin
resonance.Hence ethyl aminemore basicthanamines
51. Acid catalyzed dehydrationof t- butanol is faster than n-butanol why?
Ans:Dehydrationistakingplace throughcarboncationmechanism as tertiarycarbo cationis more
stable .hence t- butanol isfasterthann-butanol
52. Hydrazones of acetaldehyde are not prepared in highlyacidic medium?
Ans:Hydrazonesare preparedfromhydrazenesanditisbasicin nature.Inhighlyacidicmediumit
formssalt.

5. ORGANICCHEMISTRY RESONINGQUESTIONS
K.G.MALLIKARJUN,VICEPRINCIPAL,JNV,ANANTHAPUR
53. Why are amidesamphoteric in nature?
Ans:Lone pair presentinN of amidesininvolvinginresonance andlessavailable fordonatinghence
behave as weakbases. andduringresonance itforms +ve charge on nitrogenwhichhas tendency
to loose proton and behave asacidic. So amidesare amphotericinnature.
54.Highly branched carboxylic acids are lessthan unbranched acids .Why?
Ans:Asbranchingincreases,electronreleasingeffectincreases,whichdecreasesacidity.
55.Methyl amine in water reacts with ferric chloride to precipitate ferrichydroxide.Why?
Ans:Methyl amine isa protonacceptor fromwaterand forms hydroxyl ionwhichreactswith
ferricionsformsferrichydroxide.
CH3-NH2 +H2O → CH3-NH3+ + OH-
FeCl3 + 3OH -
→ Fe(OH)3 + 3Cl-
56.Ethers possessa dipole momentevenif the alkyl radicals in the molecule are identical.Explain?
Ans:-Due toSp3
hybridisation,etherspossesbentstructure hencenetdipolemomentisnotzero
and will notcancel.
57.Why di-tertiarybutyl etherscannot be prepared by Williamson’ssynthesis?
Ans:Astertiarycarbocationismore stable,ithaslesstendencyto undergonucleophilic
substitution.Hence itcannotbe prepared.
58.Treatment ofC6H5-CHO with HCN givesa mixture of two isomers which cannot be separated evenby
very careful fractional distillation?
Ans:Thisreactiongivesracemicmixtureof twooptical isomerswhichgare havingalmostall same
boilingpointandsimilarchemical properties.Hencetheycannotbe separatedbyfractional
distillation.
59.Electrophilicsubstitutionon nitro benzene isdifficultcompare with benzene.explain?
Ans.Nitrogrouppresentonthe benzeneiselectronwithdrawinganddeactivatesthe ringfor
substitution.Hence itisdifficult.
60.The presence ofelectronwithdrawinggroups on benzene facilitatesnucleophilicsubstitution.
Explain?
Ans:Due toelectronwithdrawingeffectitwill stabilize the carbanion intermediate.
61.Tertiary aminesare having low boilingpointcompare with primary and secondary amines.Explain?
Ans:Due toabsence of Hydrogenbondintertiaryamines,theypossesslowboilingpointascompare
withprimaryandsecondary.
62.In solutions,basicstrengthof aminesis secondary>tertiary >primary .Explain?
Ans:.Basicstrengthof aminesdependsonammoniumcationinsolutions.Ammoniumstabilitynot
only dependsonelectronreleasingeffectbutalsoH-bonding,stearicfactor.Hence the above
orderof basicstrengthiscorrect .
63 .Acid chloridesgive pungentsmell in air.Explain?
Ans:AcidchloridesundergohydrolysiswithatmosphericmoistureandgivesHCl fumes,whichare
pungent
64.In gas phase,basicstrength of aminesis tertiary> secondary> primary. Explain?
Ans:Ingasphase,there isnosalvationeffect.Itonlydependsonelectronreleasingeffect.Hence the
above orderiscorrect for basic strengthingas phase.

6. ORGANICCHEMISTRY RESONINGQUESTIONS
K.G.MALLIKARJUN,VICEPRINCIPAL,JNV,ANANTHAPUR
65.Acylation on amines and phenolstakes place directly,whereasacylationon benzene requiresAlCl3
catalyst.Give reasons?
Ans:Reactionof aminesandphenol withacidchloridesisnucleophilic substitution,whichtakesplace
directlydue topresence of lone paironbothoxygen andNitrogen.Whereasacidchloride on
reactionwith benzene iselectrophilicsubstitutionwhichrequiresacatalystlike AlCl3 catalystto
forman electrophile.
.66.Nitration of benzene givessubstantial amount of metaproduct,though –NH2 is o-pdirectinggroup?
Ans:Nitrationtakesplace inthe presence of H+ ionswhichprotanatesonAmine andformswhich
behavesaselectronwithdrawinggroup,hence itformssome amountof metaproduct.
67.Before nitration,Aneline isacylated.Explain?
Ans:Toprotect -NH2 groupfrom oxidationandto preventmetaproduct.
68.Reactivity order of carbpxylic acid derivativesare Acid chlorides>
Anhydrides>Esters>Amides.Explainthe reason?
Ans.I) Basisityof leaving groupResonance effect
69.Explain cyanidesare soluble inwater whereasisocyanidesare insoluble.
Ans:CyanidescanformhydrogenbondwithwaterwhereasIsocyanidescannot.
70.Preparation ofAlkyl halidesfrom alcoholsby using SOCl2 ispreferable.Explain?
Ans:WhenSOCl2 isused,side productsare gasesandformspure alkyl halides.
R-OH+SOCl2 → R-Cl + SO2+ HCl
71.Alkyl halidesreact with nitriteswhereasAgNO2 givesNitro alkanes. Explain?
Ans:KNO2 isanioniccompound andformsNO2- whichisan ambidentate nucleophile.Itcanformbond
withnitrogenandoxygen.Since C-Obondisstable,itformsalkyl nitriteswhereasAgNO2 is
covalentcompound.Here oxygenisnot free.only bondingtakesthroughnitrogenandforms
nitroalkanes.
72.During preparation of estersby reaction ofcarboxylic acids and alcohols, the ester formedis
distilledoutas soon as it is formed.Explain?
Ans:Formation of esterisa reversible reaction.Toprevent backward reaction,itis distilledout
immediately.
73.Electrophilicsubstitutionon Benzoic acid takes place at meta position?
Ans:Since COOH groupis electronwithdrawing group,itactsas metadirectinggroupinresonance,it
createspositive charge on orthoandpara position.And electrophile ispositiveandfeel
repulsionatorthoand para position.Hence itgoestothe metaposition.
74.Aneline dissolvesinaq.HCl,why?
Ans.Aneline isbasicinnature.hence,itissoluble inacidslike HCl.
75.Why are aryl diazoniumionmore stable than diazoniumion?
Ans.Aryl diazoniumionisstabilizedbyresonance butinalkyl diazoniumion,noresonance for
stabilization
76. Althoughphenoxide ionhas more number ofesonatingstructure than carboxylate ion,carboxylic
acid is a stronger acid than phenol.Why.?
Ans: In the resonatingstructure of phenoxide ionthe negative charge isdispersedononly oxygen
atomwhere as inthe carboxylate ionthe charge getsdispersedontwooxygenatoms.Thus,the
dispersal of charge ismore inthe case of carboxylate ionandhence the resonance stabilizationis
more.Thisiswhy the carboxylicacidsare more strongerthan phenol
77. Cloroaceticacid has lowerpKa value than acetic acid. Why?
Ans:Chloroaceticacidis strongerthan aceticacid because Cl groupis electron withdrawingand
chlroacetate ionismore stabilizedthanacetate ion.

7. ORGANICCHEMISTRY RESONINGQUESTIONS
K.G.MALLIKARJUN,VICEPRINCIPAL,JNV,ANANTHAPUR
78. Carboxylicacid have higher boilingpointsthan alcohols to comparable molecularmasses.Explain
Why ?
Ans:Carboxylicgroupinacidsis highlypolarandcarboxylicacidgenerallyexistsasdimmers
containingtwohydrogenbonds.These hydrogenbondsincarboxylicacidsare strongerthanthose of
alcohols.
79.pKb of aniline ismore than that of methylamine,Why?
Ans:In Methylamine the +Ieffectof methyl groupincreasesthe electrondensityaroundN atomand it
increasesthe electronreleasingtendencyof the molecule .InAniline the resonanceeffectcauses
delocalizationof lone pairoverthe ringandtherebydecrease itsbasiscstrengthsinceaniline is
lessbasicthanmethylamine,itspKb value issmallerthanthat of methylamine.
80. Aniline doesnot undergo Friedel Craft’sreaction. Why?
Ans:Aniline isabase due to electrondonatingnature of lone paironN atom of NH3 group.Aniline
therefore,formsaltwithAlCl3 whichisLewisacidanda catalystusedinFriedel Craft’sreaction.
C6H5NH2 + AlCl3 → C6H5N +
H2 − AlCl3
–
In the salt N atomdevelopspositivecharge andtherefore,becomesaverystrongdeactivating
group.This preventsaniline toundergoFriedelCraft’sreacting.
81. Diazoniumsaltsof aromaticaminesare more stable thanof aliphaticamines.Why?
Ans:Arenediazoniumionisresonance stabilizedwherenoresonance stabilizationoccursinalkyl
diazoniumion.
82. Gabriel phthalimide synthesisispreferred forsynthesizingprimaryamines.Why?
Ans:Gabriel synthesis involvesthe conversionof alkylhalid(R –X) to10
amine (R– NH2).
Ammonolysisof R– X on the otherhandgive 20
, 30
and quaternarysaltas otherside products.
Hence,,forthe productionof pure 10
amines,Gabriel synthesis ispreferredtoammonolysis
reaction.
.