MaterialdownloadedfrommyCBSEguide.com. 1/42
CBSEClass–12SubjectChemistry
NCERTSolutions
Chapter–11AlcoholPhenolandEther
ChapterEndQuestion
Part-1
1.WriteIUPACnamesofthefollowingcompounds:
(i)
(ii)
(iii)
(iv)
(v)
(vi)
osbincbse.com
OSBINCBSE.COM
OSBINCBSE.COM
OSBINCBSE.COM
MaterialdownloadedfrommyCBSEguide.com. 2/42
(vii)
(viii)
(ix)
(x)
(xi)
(xii)
Ans.(i)2,2,4-Trimethylpentan-3-ol
(ii)5-Ethylheptane-2,4-diol
(iii)Butane-2,3-diol
osbincbse.com
OSBINCBSE.COM
OSBINCBSE.COM
OSBINCBSE.COM
MaterialdownloadedfrommyCBSEguide.com. 3/42
(iv)Propane-1,2,3-triol
(v)2-Methylphenol
(vi)4-Methylphenol
(vii)2,5-Dimethylphenol
(viii)2,6-Dimethylphenol
(ix)1-Methoxy-2-methylpropane
(x)Ethoxybenzene
(xi)1-Phenoxyheptane
(xii)2-Ethoxybutane
2.WritestructuresofthecompoundswhoseIUPACnamesareasfollows:
(i)2-Methylbutan-2-ol
(ii)1-Phenylpropan-2-ol
(iii)3,5-Dimethylhexane-1,3,5-triol
(iv)2,3-Diethylphenol
(v)1-Ethoxypropane
(vi)2-Ethoxy-3-methylpentane
(vii)Cyclohexylmethanol
(viii)3-Cyclohexylpentan-3-ol
(ix)Cyclopent-3-en-1-ol
(x)3-Chloromethylpentan-1-ol.
Ans.(i)
osbincbse.com
OSBINCBSE.COM
OSBINCBSE.COM
OSBINCBSE.COM
MaterialdownloadedfrommyCBSEguide.com. 4/42
(ii)
(iii)
(iv)
(v)
(vi)
(vii)
osbincbse.com
OSBINCBSE.COM
OSBINCBSE.COM
OSBINCBSE.COM
MaterialdownloadedfrommyCBSEguide.com. 5/42
(viii)
(ix)
(x)
3.(i)DrawthestructuresofallisomericalcoholsofmolecularformulaC5H12Oandgive
theirIUPACnames.
(ii) Classify the isomers of alcohols in question 11.3 (i) as primary, secondary and
tertiaryalcohols.
Ans.(i) The structuresofall isomericalcoholsofmolecular formula, are shown
below:
(a)
Pentan-1-ol(1°)
osbincbse.com
OSBINCBSE.COM
OSBINCBSE.COM
OSBINCBSE.COM
MaterialdownloadedfrommyCBSEguide.com. 6/42
(b)
2-Methylbutan-1-ol(1°)
(c)
3-Methylbutan-1-ol(1°)
(d)
2,2-Dimethylpropan-1-ol(1°)
(e)
Pentan-2-ol(2°)
(f)
3-Methylbutan-2-ol(2°)
(g)
osbincbse.com
OSBINCBSE.COM
OSBINCBSE.COM
OSBINCBSE.COM
MaterialdownloadedfrommyCBSEguide.com. 7/42
Pentan-3-ol(2°)
(h)
2-Methylbutan-2-ol(3°)
(ii)Primaryalcohol:Pentan-1-ol;2-Methylbutan-1-ol;
3-Methylbutan-1-ol;2,2-Dimethylpropan-1-ol
Secondaryalcohol:Pentan-2-ol;3-Methylbutan-2-ol;
Pentan-3-ol
Tertiaryalcohol:2-methylbutan-2-ol
4.Explainwhypropanolhashigherboilingpointthanthatofthehydrocarbon,butane?
Ans.PropanolundergoesintermolecularH-bondingduetowhichit'sboilingpointishigher
thanbutanewhichisnon-polarandheldbyweakvanderWall'sforcesofattraction,anditis
sobecauseofthepresenceof-OHgroup.
Therefore,extraenergyisrequiredtobreakhydrogenbonds.Forthisreason,propanolhasa
higherboilingpointthanhydrocarbonbutane.
osbincbse.com
OSBINCBSE.COM
OSBINCBSE.COM
OSBINCBSE.COM
MaterialdownloadedfrommyCBSEguide.com. 8/42
5.Alcoholsarecomparativelymoresolubleinwaterthanhydrocarbonsofcomparable
molecularmasses.Explainthisfact.
Ans.Alcohols formH-bondswithwater due to the presence of -OH groupwhich prevails
formation of H-bonding with water. However, hydrocarbons cannot form H-bonds with
waterastheyarenon-polar.
As a result, alcohols are comparatively more soluble in water than hydrocarbons of
comparablemolecularmasses.
6.Whatismeantbyhydroboration-oxidationreaction?Illustrateitwithanexample.
Ans.TheadditionofboraneB2H6followedbyoxidationtoformpropan-1-ol,andisknown
as the hydroboration-oxidation reaction. For example, propan-1-ol is produced by the
hydroboration-oxidationreactionofpropene.Inthisreaction,propenereactswithdiborane
(BH3)2 to formtrialkylboraneasanadditionproduct.Thisadditionproduct isoxidized to
alcoholbyhydrogenperoxideinthepresenceofaqueoussodiumhydroxide.
7.GivethestructuresandIUPACnamesofmonohydricphenolsofmolecularformula,
osbincbse.com
OSBINCBSE.COM
OSBINCBSE.COM
OSBINCBSE.COM
MaterialdownloadedfrommyCBSEguide.com. 9/42
.
Ans.
8. While separating a mixture of ortho and para nitrophenols by steam distillation,
nametheisomerwhichwillbesteamvolatile.Givereason.
Ans.IntramolecularH-bonding ispresent ino-nitrophenol.O-Nitrophenol issteamvolatile
because of weak intramolecular H-Bonding. In p-nitrophenol, the molecules are strongly
associated due to the presence of intermolecular bonding. Hence, o-nitrophenol is steam
volatilewhereasp-nitrophenolisnot.
9.Givetheequationsofreactionsforthepreparationofphenolfromcumene.
Ans.To prepare phenol, cumene is first oxidized in the presence of air to form cumene
hydro-peroxide.
osbincbse.com
OSBINCBSE.COM
OSBINCBSE.COM
OSBINCBSE.COM
MaterialdownloadedfrommyCBSEguide.com. 10/42
Then,cumenehydroperoxideistreatedwithdiluteacidtopreparephenolandacetoneasby-
products.
10.Writechemicalreactionforthepreparationofphenolfromchlorobenzene.
Ans.ChlorobenzeneisfusedwithNaOH(at623Kand320atmpressure)toproducesodium
phenoxide,whichgivesphenolonacidificationbynucleophilicsustitutionreaction.
11.Writethemechanismofhydrationofethenetoyieldethanol.
Ans.Themechanismofhydrationof ethene to formcarbocationbyelectrophilicattackof
hydroniumioninvolvesthreesteps.
Step1:
ProtonationofethenetoformcarbocationbyelectrophilicattackofH3O+:
osbincbse.com
OSBINCBSE.COM
OSBINCBSE.COM
OSBINCBSE.COM
MaterialdownloadedfrommyCBSEguide.com. 11/42
Step2:
Nucleophilicattackofwateroncarbocation:
Step3:
Deprotonationtoformethanol:
12. You are given benzene, conc. and NaOH. Write the equations for the
preparationofphenolusingthesereagents.
Ans.
osbincbse.com
OSBINCBSE.COM
OSBINCBSE.COM
OSBINCBSE.COM
MaterialdownloadedfrommyCBSEguide.com. 12/42
13.Showhowwillyousynthesize:
(i)1-phenylethanolfromasuitablealkene.
(ii)cyclohexylmethanolusinganalkylhalidebyanSN2reaction.
(iii)pentan-1-olusingasuitablealkylhalide?
Ans. (i) By acid-catalyzed hydration of ethylbenzene (styrene), 1-phenylethanol can be
synthesized.
(ii)Whenchloromethylcyclohexane is treatedwithsodiumhydroxide,cyclohexylmethanol
isobtained.
(iii)When1-chloropentaneistreatedwithNaOH,pentan-1-olisproduced.
14.Givetworeactionsthatshowtheacidicnatureofphenol.Compareacidityofphenol
withthatofethanol.
Ans.Theacidicnatureofphenolcanberepresentedbythefollowingtworeactions:
(i)PhenolreactswithsodiumtogivesodiumphenoxideandreleaseH2gasasby-product.
osbincbse.com
OSBINCBSE.COM
OSBINCBSE.COM
OSBINCBSE.COM
MaterialdownloadedfrommyCBSEguide.com. 13/42
2phenol+2Na-------->2sodiumphenoxide+H2
(ii)Phenolreactswithsodiumhydroxidetogivesodiumphenoxideandwaterasby-product.
Theacidityofphenolismorethanthatofethanol.Thisisbecauseafterlosingaproton,the
phenoxide ion undergoes resonance and gets stabilized whereas ethoxide ion does not
undergoresonance.Resonance leads todistributionofchargedue towhich thecompound
getsstableunlikeconcentrationofchargeatsinglepointlikeincaseofethoxideionwhich
promotesunstability.
15.Explainwhyisorthonitrophenolmoreacidicthanorthomethoxyphenol?
Ans.
Thenitro-group isanelectron-withdrawinggroup.Thepresenceof thisgroup in theortho
position decreases the electron density in the O-H bond and increase positive charge on
Oxygen.Asaresult,itiseasiertoloseaproton.Also,theo-nitrophenoxideionformedafter
osbincbse.com
OSBINCBSE.COM
OSBINCBSE.COM
OSBINCBSE.COM
MaterialdownloadedfrommyCBSEguide.com. 14/42
thelossofprotonsisstabilizedbyresonance.Hence,orthonitrophenolisastrongeracid.
Ontheotherhand,methoxygroup isanelectron-releasinggroupand itdecreasespositive
chargeonoxygen . Thus, it increases the electrondensity in theO-Hbondandhence, the
protoncannotbegivenouteasily.Itmakesitlessacidic.
Forthisreason,ortho-nitrophenolismoreacidicthanortho-methoxyphenol.
16. Explain howdoes the -OH group attached to a carbon of benzene ring activate it
towardselectrophilicsubstitution?
Ans.The-OHgroupisanelectron-donatinggroup.Thus,itincreasestheelectrondensityin
thebenzeneringasshowninthegivenresonancestructureofphenol.
Asaresult,thebenzeneringisactivatedtowardselectrophilicsubstitution.
17.Giveequationsofthefollowingreactions:
(i)Oxidationofpropan-1-olwithalkaline solution.
(ii)Brominein withphenol.
(iii)Dilute withphenol.
(iv)TreatingphenolwithchloroforminpresenceofaqueousNaOH.
Ans. Propan-1-ol is treated with alcoholic KMnO4 followed by hydrolysis to form
propanoicacidasfollows-
(i)
osbincbse.com
OSBINCBSE.COM
OSBINCBSE.COM
OSBINCBSE.COM
MaterialdownloadedfrommyCBSEguide.com. 15/42
(ii)
(iii)Bytheprocessofnitration,asfollows-
(iv)
18.Explainthefollowingwithanexample.
(i)Kolbe'sreaction.
osbincbse.com
OSBINCBSE.COM
OSBINCBSE.COM
OSBINCBSE.COM
MaterialdownloadedfrommyCBSEguide.com. 16/42
(ii)Reimer-Tiemannreaction.
(iii)Williamsonethersynthesis.
(iv)Unsymmetricalether.
Ans.(i)Kolbe'sreaction:
Whenphenolistreatedwithsodiumhydroxide,sodiumphenoxideisproduced.Thissodium
phenoxidewhen treatedwith carbondioxide, at 400Kunder3-7atm.pressure followedby
acidification,undergoeselectrophilic substitution togiveortho-hydroxybenzoicacidas the
mainproductalsoknownassalicylicacid.ThisreactionisknownasKolbe'sreaction.
(ii)Reimer-Tiemannreaction:
When phenol is treatedwith chloroform (CHCl3) in the presence of sodium hydroxide or
potassiumhydroxide,a -CHOgroupis introducedat theorthopositionof thebenzenering
and3KCland2moleculesofwaterareformedasbyproduct.
ThisreactionisknownastheReimer-Tiemannreaction.
Theintermediateishydrolyzedinthepresenceofalkalistoproducesalicyldehyde.
osbincbse.com
OSBINCBSE.COM
OSBINCBSE.COM
OSBINCBSE.COM
MaterialdownloadedfrommyCBSEguide.com. 17/42
(iii)Williamsonethersynthesis:
Williamson ether synthesis is a laboratory method to prepare symmetrical and
unsymmetricalethersbyallowingalkylhalidestoreactwithsodiumalkoxides.
Thisreaction involvesSN2attackof thealkoxide iononthealkylhalide.Betterresultsare
obtainedincaseofprimaryalkylhalides.
Ifthealkylhalideissecondaryortertiary,theneliminationcompetesoversubstitution.
(iv)Unsymmetricalether:
Anunsymmetricaletherisanetherwheretwogroupsonthetwosidesofanoxygenatom
differ(i.e.,haveanunequalnumberofcarbonatoms).Forexample:ethylmethylether(CH3-
O-CH2CH3).
19.Writethemechanismofacid-catalyseddehydrationofethanoltoyieldethene.
Ans.Themechanismofaciddehydrationofethanol toyieldethene involves the following
threesteps:
Step1:
Protonationofethanoltoformethyloxoniumion:
osbincbse.com
OSBINCBSE.COM
OSBINCBSE.COM
OSBINCBSE.COM
MaterialdownloadedfrommyCBSEguide.com. 18/42
Step2:
Formationofcarbocation(ratedeterminingstep):
Step3:
Eliminationofaprotontoformethene:
Theacidconsumedinstep1isreleasedinStep3.Aftertheformationofethene,itisremoved
toshifttheequilibriuminaforwarddirection.
20.Howarethefollowingconversionscarriedout?
(i)Propene→Propan-2-ol
(ii)Benzylchloride→Benzylalcohol
(iii)Ethylmagnesiumchloride→Propan-1-ol.
(iv)Methylmagnesiumbromide→2-Methylpropan-2-ol.
Ans.(i)Ifpropeneisallowedtoreactwithwaterinthepresenceofanacidasacatalyst,then
osbincbse.com
OSBINCBSE.COM
OSBINCBSE.COM
OSBINCBSE.COM
MaterialdownloadedfrommyCBSEguide.com. 19/42
propan-2-olisobtained.
(ii)IfbenzylchlorideistreatedwithNaOH(followedbyacidification)thenbenzylalcoholis
produced.
(iii)When ethylmagnesium chloride is treatedwithmethanal, an adduct is theproduced
whichgivespropan-1-olandMgClOHonhydrolysis.
(iv)Whenmethylmagnesium bromide is treatedwith propane, an adduct is the product
whichgives2-methylpropan-2-olonhydrolysis.
osbincbse.com
OSBINCBSE.COM
OSBINCBSE.COM
OSBINCBSE.COM
MaterialdownloadedfrommyCBSEguide.com. 20/42
21.Namethereagentsusedinthefollowingreactions:
(i)Oxidationofaprimaryalcoholtocarboxylicacid.
(ii)Oxidationofaprimaryalcoholtoaldehyde.
(iii)Brominationofphenolto2,4,6-tribromophenol.
(iv)Benzylalcoholtobenzoicacid.
(v)Dehydrationofpropan-2-oltopropene.
(vi)Butan-2-onetobutan-2-ol.
Ans.(i)Acidifiedpotassiumpermanganate
(ii)Pyridiniumchlorochromate(PCC)
(iii)Brominewater
(iv)Acidifiedpotassiumpermanganate
(v)85%phosphoricacidorconc.Sulphuricacidat443K.
(vi)NaBH4orLiAlH4orH2/Ni
22. Give reason for the higher boiling point of ethanol in comparison to
methoxymethane.
osbincbse.com
OSBINCBSE.COM
OSBINCBSE.COM
OSBINCBSE.COM
MaterialdownloadedfrommyCBSEguide.com. 21/42
Ans. Ethanol undergoes intermolecular H-bonding due to the presence of -OH group,
resultingintheassociationofmolecules.Extraenergyisrequiredtobreakthesehydrogen
bonds. On the other hand,methoxymethane does not undergo intermolecular H-bonding.
Hence,theboilingpointofethanolishigherthanthatofmethoxymethane.
23.GiveIUPACnamesofthefollowingethers:
(i)
(ii)
(iii)
(iv)
(v)
(vi)
osbincbse.com
OSBINCBSE.COM
OSBINCBSE.COM
OSBINCBSE.COM
MaterialdownloadedfrommyCBSEguide.com. 22/42
Ans.(i)1-Ethoxy-2-methylpropane
(ii)2-Chloro-1-methoxyethane
(iii)4-Nitro-1-methoxybenzene
(iv)1-Methoxypropane
(v)1-Ethoxy-4,4-dimethylcyclohexane
(vi)Ethoxybenzene
24.Write the names of reagents and equations for the preparation of the following
ethersbyWilliamson'ssynthesis:
(i)1-Propoxypropane
(ii)Ethoxybenzene
(iii)2-Methoxy-2-methylpropane
(iv)1-Methoxyethane
Ans. (i)
(ii)
osbincbse.com
OSBINCBSE.COM
OSBINCBSE.COM
OSBINCBSE.COM
MaterialdownloadedfrommyCBSEguide.com. 23/42
(iii)
(iv)
25.IllustratewithexamplesthelimitationsofWilliamsonsynthesisforthepreparation
ofcertaintypesofethers.
Ans. The reaction of Williamson synthesis involves SN2 attack of an alkoxide ion on a
primary alkyl halide because tertiary halide undergoes elimination reaction instead of
substitutionreaction.
That'swhyifsecondaryortertiaryalkylhalidesaretakeninplaceofprimaryalkylhalides,
theneliminationwouldcompeteoversubstitution.Asaresult,alkeneswouldbeproduced.
This is because alkoxides arenucleophiles aswell as strongbases.Hence, they reactwith
alkylhalides,whichresultsinaneliminationreaction.
26.How is1-propoxypropanesynthesised frompropan-1-ol?Writemechanismof this
reaction.
osbincbse.com
OSBINCBSE.COM
OSBINCBSE.COM
OSBINCBSE.COM
MaterialdownloadedfrommyCBSEguide.com. 24/42
Ans.1-propoxypropanecanbesynthesizedfrompropan-1-olbydehydration.
Propan-1-olundergoesdehydrationinthepresenceofproticacids(suchasH2SO4,H3PO4)to
give1-propoxypropane.
Themechanismofthisreactioninvolvesthefollowingthreesteps:
Step1:Protonation
Step2:Nucleophilicattack
Step3:Deprotonation
27.Preparationofethersbyaciddehydrationofsecondaryortertiaryalcoholsisnota
suitablemethod.Givereason.
Ans. The formation of ethers by dehydration of secondary or tertiary alcohol is a
bimolecular reaction (SN2) involving the attack of an alcohol molecule on a protonated
alcoholmoleculeveryquickly.Inthemethod,thealkylgroupshouldbeunhindered.Incase
of secondary or tertiary alcohols, the alkyl group is hindered. As a result, elimination
dominatessubstitution.Hence,inplaceofethers,alkenesareformed.
osbincbse.com
OSBINCBSE.COM
OSBINCBSE.COM
OSBINCBSE.COM
MaterialdownloadedfrommyCBSEguide.com. 25/42
28.Writetheequationofthereactionofhydrogeniodidewith:
(i)1-propoxypropane
(ii)Methoxybenzeneand
(iii)Benzylethylether
Ans.(i)
(ii)
(iii)
29.Explainthefactthatinarylalkylethers
(i)Thealkoxygroupactivatesthebenzeneringtowardselectrophilicsubstitutionand
(ii)Itdirectstheincomingsubstituentstoorthoandparapositionsinbenzenering.
Ans.(i)Inarylalkylethers,duetothe+Reffectofthealkoxygroup,theelectrondensityin
thebenzeneringincreasesasshowninthefollowingresonancestructure.
Thus, benzene is activated towards electrophilic substitution by the alkoxy group and
electrophilewillattackatO-andp-positions.
osbincbse.com
OSBINCBSE.COM
OSBINCBSE.COM
OSBINCBSE.COM
MaterialdownloadedfrommyCBSEguide.com. 26/42
(ii)Itcanalsobeobservedfromtheresonancestructuresthattheelectrondensityincreases
more at the ortho andpara positions than at themeta position.As a result, the incoming
substituentsaredirectedtotheorthoandparapositionsinthebenzenering.
30.WritethemechanismofthereactionofHIwithmethoxymethane.
Ans.The mechanism of the reaction of HI with methoxymethane involves the following
steps:
Step1:Protonationofmethoxymethane:
Step2:NucleophilicattackofI-:
Step3:When HI is in excess and the reaction is carried out at a high temperature, the
methanolformedinthesecondstepreactswithanotherHImoleculeandgetsconvertedto
methyliodide
31.Writeequationsofthefollowingreactions:
(i)Friedel-Craftsreaction-alkylationofanisole.
(ii)Nitrationofanisole.
osbincbse.com
OSBINCBSE.COM
OSBINCBSE.COM
OSBINCBSE.COM
MaterialdownloadedfrommyCBSEguide.com. 27/42
(iii)Brominationofanisoleinethanoicacidmedium.
(iv)Friedel-Craft'sacetylationofanisole.
Ans.(i)
(ii)
(iii)
(iv)
osbincbse.com
OSBINCBSE.COM
OSBINCBSE.COM
OSBINCBSE.COM
MaterialdownloadedfrommyCBSEguide.com. 28/42
32.Showhowwouldyousynthesisethefollowingalcoholsfromappropriatealkenes?
(i)
(ii)
(iii)
(iv)
Ans.ThegivenalcoholscanbesynthesizedbyapplyingMarkovnikov'sruleofacid-catalyzed
hydrationofappropriatealkenes.
(i)
osbincbse.com
OSBINCBSE.COM
OSBINCBSE.COM
OSBINCBSE.COM
MaterialdownloadedfrommyCBSEguide.com. 29/42
(ii)
(iii)
Acid-catalyzedhydrationofpent-2-enealsoproducespentan-2-olbutalongwithpentan-3-ol.
Thus,thefirstreactionispreferredoverthesecondonetogetpentan-2-ol.
(iv)
33.When3-methylbutan-2-olistreatedwithHBr,thefollowingreactiontakesplace:
osbincbse.com
OSBINCBSE.COM
OSBINCBSE.COM
OSBINCBSE.COM
MaterialdownloadedfrommyCBSEguide.com. 30/42
Giveamechanismforthisreaction.(Hint:ThesecondarycarbocationformedinstepII
rearrangestoamorestabletertiarycarbocationbyahydrideionshiftfrom3rdcarbon
atom.
Ans.Themechanismofthegivenreactioninvolvesthefollowingsteps:
Step1:Protonation
Step2:Formationof2°carbocationbytheeliminationofawatermolecule
Step3:Re-arrangementbythehydride-ionshift
Step4:Nucleophilicattack
osbincbse.com
OSBINCBSE.COM
OSBINCBSE.COM
OSBINCBSE.COM
MaterialdownloadedfrommyCBSEguide.com. 31/42
In-textquestion
1.Classifythefollowingasprimary,secondaryandtertiaryalcohols:
(i)
(ii)
(iii)
(iv)
(v)
(vi)
osbincbse.com
OSBINCBSE.COM
OSBINCBSE.COM
OSBINCBSE.COM
MaterialdownloadedfrommyCBSEguide.com. 32/42
Ans.Primaryalcohol→(i),(ii)(iii)
Secondaryalcohol→(iv),(v)
Tertiaryalcohol→(vi)
2.Identifyallylicalcoholsintheaboveexamples.
Ans.Thealcoholsgivenin(ii)and(vi)areallylicalcohols.
3.NamethefollowingcompoundsaccordingtoIUPACsystem.
(i)
(ii)
(iii)
(iv)
(v)
osbincbse.com
OSBINCBSE.COM
OSBINCBSE.COM
OSBINCBSE.COM
MaterialdownloadedfrommyCBSEguide.com. 33/42
Ans.(i)3-Chloromethyl-2-isopropylpentan-1-ol
(ii)2,5-Dimethylhexane-1,3-diol
(iii)3-Bromocyclohexanol
(iv)Hex-1-en-3-ol
(v)2-Bromo-3-methylbut-2-en-1-ol
4.ShowhowarethefollowingalcoholspreparedbythereactionofasuitableGrignard
reagentonmethanal?
(i)
(ii)
Ans.(i)
(ii)
osbincbse.com
OSBINCBSE.COM
OSBINCBSE.COM
OSBINCBSE.COM
MaterialdownloadedfrommyCBSEguide.com. 34/42
5.Writestructuresoftheproductsofthefollowingreactions:
(i)
(ii)
(iii)
Ans.(i)
(ii)
osbincbse.com
OSBINCBSE.COM
OSBINCBSE.COM
OSBINCBSE.COM
MaterialdownloadedfrommyCBSEguide.com. 35/42
(iii)
6.Givestructuresoftheproductsyouwouldexpectwheneachofthefollowingalcohol
reactswith(a) (b)HBrand(c) .
(i)Butan-1-ol
(ii)2-Methylbutan-2-ol
Ans.(a)(i)
Primary alcohols do not react appreciably with Lucas' reagent (HCl-ZnCl2) at room
temperature.
(ii)
TertiaryalcoholsreactimmediatelywithLucas'reagent.
(b)
(i)
osbincbse.com
OSBINCBSE.COM
OSBINCBSE.COM
OSBINCBSE.COM
MaterialdownloadedfrommyCBSEguide.com. 36/42
(ii)
(c)
(i)
(ii)
7.Predictthemajorproductofacidcatalyseddehydrationof
(i)1-Methylcyclohexanoland
(ii)Butan-1-ol
Ans.(i)
osbincbse.com
OSBINCBSE.COM
OSBINCBSE.COM
OSBINCBSE.COM
MaterialdownloadedfrommyCBSEguide.com. 37/42
(ii)
8. Ortho and para nitrophenols are more acidic than phenol. Draw the resonance
structuresofthecorrespondingphenoxideions.
Ans.
Resonancestructureofthephenoxideion
osbincbse.com
OSBINCBSE.COM
OSBINCBSE.COM
OSBINCBSE.COM
MaterialdownloadedfrommyCBSEguide.com. 38/42
Resonancestructuresofp-nitrophenoxideion
Resonancestructuresofo-nitrophenoxideion
It can be observed that the presence of nitro groups increases the stability of o-and p-
nitrophenoxideionorphenolateionascomparedtophenoxideion.
9.Writetheequationsinvolvedinthefollowingreactions:
osbincbse.com
OSBINCBSE.COM
OSBINCBSE.COM
OSBINCBSE.COM
MaterialdownloadedfrommyCBSEguide.com. 39/42
(i)Reimer-Tiemannreaction
(ii)Kolbe'sreaction
Ans. (i) Reimer-Tiemann reaction: when phenol reacts with CHCl3 and KOH at 60`C,
salicylaldehydeisformed.
(ii) Kolbe's reaction: when sodium phenoxide reacts with CO2 at high pressure, on
heatingsodiumsalicylateisformedwhichonacidificationgivessalicylicacid.
10.Write the reactions ofWilliamson synthesis of 2-ethoxy-3-methylpentane starting
fromethanoland3-methylpentan-2-ol.
Ans.InWilliamsonsynthesis,analkylhalidereactswithanalkoxideion.Also,itisanSN2
reaction.Inthereaction,alkylhalidesshouldbeprimaryhavingtheleaststerichindrance.
Hence,analkylhalideisobtainedfromethanolandalkoxideionfrom3-methylpentan-2-ol.
osbincbse.com
OSBINCBSE.COM
OSBINCBSE.COM
OSBINCBSE.COM
MaterialdownloadedfrommyCBSEguide.com. 40/42
11.Whichofthefollowingisanappropriatesetofreactantsforthepreparationof1-
methoxy-4-nitrobenzeneandwhy?
(i)
(ii)
Ans. Set (ii) is an appropriate set of reactants for the preparation of 1-methoxy-4-
nitrobenzene.
osbincbse.com
OSBINCBSE.COM
OSBINCBSE.COM
OSBINCBSE.COM
MaterialdownloadedfrommyCBSEguide.com. 41/42
Inset(i),sodiummethoxide(CH3ONa)isastrongnucleophileaswellasastrongbase.Hence,
aneliminationreactionpredominatesoverasubstitutionreaction.
12.Predicttheproductsofthefollowingreactions:
(i)
(ii)
(iii)
(iv)
Ans.(i)
(ii)
osbincbse.com
OSBINCBSE.COM
OSBINCBSE.COM
OSBINCBSE.COM
MaterialdownloadedfrommyCBSEguide.com. 42/42
(iii)
(iv)
osbincbse.com
OSBINCBSE.COM
OSBINCBSE.COM
OSBINCBSE.COM
