1. ORGANIC CHEMISTRY

2. Students should solve this Question Bank by 17th Sept. 2006 positively
Questions No.1 to 6 (6 questions)
Acid strength is measured by the position of equilibrium of ionisation in water. In other words acid
strength is the function ofthe stabilityofconjugate base ofthe acid. More is the stability ofconjugate
base ofthe acid, more is the acidityofacid.
Q.1 Whichoneofthe following isthe most acidic?
(A) (B) (C) (D) CH2=CH–CH3
Q.2 Whichone ofthe following phenols willshow highest acidity?
(A) (B) (C) (D)
Q.3 Arrange thefollowing compounds indecreasingorder ofacidity?
(I) C6H5–OH (II) (III) (IV)
Select the correct answer fromthe codes given below:
(A) III > II > IV > I (B) III > II > I > IV (C) II > III > I > IV (D) II > III > IV > I
Q.4 Whichoneofthe following isstrongest acid?
(A) Cl–CH2–CH2–COOH (B) Cl–CH2–COOH
(C) Cl–CH2–CH2–CH2–COOH (D) CH3 – COOH
Q.5 The correct order ofacidityofthe givenacids:
(I) CH3COOH (II) HOOC–COOH (III) CH2 (IV) HOOC–(CH2)4–COOH
willbe:
(A) II > IV > III > I (B) I > II > III > IV (C) II > III > IV > I (D) II > I > IV > III
Q.6 Which ofthe following is weakest acid?
(A) (B) (C) (D)
Question No. 7 to 9 (3 questions)
Basicityofnitrogencontaining compoundsare determinedbytherealtive availabilityofthenon-bonding
electrons on nitrogen atom to a proton donor or Lewis acid and by the stabilisation of the positive
charged nitrogenatombysolvation or, in some specialcases byresonance.
Q.7 Consider thefollowing bases:
(I) o-nitroaniline (II)m-nitroaniline (III)p-nitroaniline
The decreasing order ofbasicityis:
(A) II > III > I (B) II > I > III (C) I > II >III (D) I > III > II

3. Q.8 Consider thebasicityofthe followingaromatic amines:
(I)aniline (II) p-nitroaniline (III)p-methoxyaniline (IV)p-methylaniline
The correct order ofdecreasing basicityis:
(A) III > IV > I > II (B) III > IV > II > I (C) I > II > III > IV (D) IV > III > II > I
Q.9 Which one ofthe following is least basic in character?
(A) (B) (C) (D)
Q.10 MatchList I with List II andselect the correct answerfromthe codes givenbelow the lists:
List I
(a) 3
2
2
3 CH
CH
CH
C
CH
|
|
O



 and 3
2
2
3 CH
CH
C
CH
CH
|
|
O




(b) and
(c) and
(d) and
List II
(1)Enantiomer (2) Positionisomers
(3) Metamers (4)Tautomers
Codes:
(a) (b) (c) (d) (a) (b) (c) (d)
(A) 3 2 4 1 (B) 3 2 1 4
(C) 1 2 3 4 (D) 2 3 4 1
Q.11 Arrange pH ofthe given compoundsindecreasing order:
(1) Phenol (2)Ethylalcohol (3) Formic acid (4) Benzoic acid
(A) 1 > 2 > 3 > 4 (B) 2 > 1 > 4 > 3 (C)3 > 2 > 4 > 1 (D) 4 > 3 > 1 > 2
Q.12 Arrange acidityofgiven compounds indecreasing order:
(I) CH3–NH–CH2–CH2–OH (II) CH3–NH–CH2–CH2–CH2–OH
(III) OH
CH
CH
N
)
CH
( 2
2
3
3 



(A) III > I > II (B) III > II > I (C) I > II > III (D) II > I > III

4. Q.13 Ineachofthefollowingpairofcompounds, whichismorebasic inaqueoussolution?Giveanexplanation
foryour choice:
(a) CH3NH2 or CF3NH2 (b) CH3CONH2 or H2N NH2
(c) n-PnNH2 or CH3CN (d) C6H5N(CH3)2 or 2,6-dimethyl-N-N-dimethylaniline
(e) m-nitroaniline or p-nitroaniline
Q.14 Answerthefollowing:
(a) Which proton is more rapidlyabstracted byethoxide ion and why?
(b) Which compound is more rapidlyattacked bya nucleophile and why?
or
(i) (ii)
Q.15 Fromthefollowing pair, select thestronger base:
(a) p-methoxyaniline or p-cyanoaniline (b) pyridine or pyrrole
(c) CH3CN or CH3CH2NH2
Q.16 Write equations showing the Lewis acid-base reaction that takes place when
(a) Methylalcoholreacts withBF3. (b) Methylchloride reacts withAlCl3.
(c) Dimethyletherreacts with BF3.
Q.17 Which ofthe following are lewis acids & which are lewis bases?
(a)
3
3
2
3
CH
|
CH
N
CH
CH 



(b)
3
3
3
CH
|
C
CH
|
CH

 (c) (C6H5)3 P:
(d)
—
Br






 (e) (CH3)3B (f) :
H
Q.18 Which would youexpect to be the stronger acid? Explain your reasoning in eachinstance.
(a) CH2ClCO2H or CHCl2CO2H (b) CCl3CO2H or CHCl2CO2H
(c) CH2FCO2H or CH2FCH2CO2H
Q.19 Write equations for the acid base reactionthat would occurwhen each ofthefollowing compounds or
solution are mixed. In each case labelthe stronger acid &stronger base,& the weaker acid & weaker
base.
(a) NaH is added to CH3OH
(b) NaNH2is added to CH3CH2OH
(c) Gaseous NH3 isadded to ethyllithiuminhexane
(d) NH4Cl is added to NaNH2 in liq. NH3
(e) (CH3)3CONa is added to H2O
(f) NaOH is added to (CH3)3 C-OH
(g) C2H5OH is added to a solution of HC  C–Na+ in liquid NH3.

5. Q.20 CH3CH2MgBr + CH3C  CH  A + B
Q.21 Choose the member ofeach ofthe following pairs ofcompunds that is likelyto be the stronger base.
(a) 
2
NH or NH3 (b) OH– or H2O (c) OH– or SH–
(d) CH3CH2O– or (e) OH
C
CH
|
|
O
2 
 or CH3CH2O– (f) NH3 or 
4
NH
Q.22 Choose the member ofeach of the following pairs ofcompunds that is likelyto be the weaker base.
(a) H2O or H3O (b) H2S, HS–, S2– (c) Cl–, SH–
(d) F–, OH–, NH2
–, 
3
CH (e) HF, H2O, NH3 (f) OH–, SH–, SeH–
Q.23 Label the reactants in these acid – base reactions as Lewis acids (electrophiles) or Lewis bases
(nucleophiles). Use curved arrows to show the movement ofelectron pairs inthe recations.
(a)
—
3
3
3
—
3 Cl
CH
O
CH
Cl
CH
O
CH 






























(b)
H
CH
H
CH
|
|
|
|
H
O
CH
O
CH
H
O
CH
O
CH
3
3
3
3
3
3 























(c)
3
3
—
NH
|
H
C
H
NH
H
C
H
|
|
|
O
O
















(d)


























—
3
2
2
3
2
3
2
3 l
C
CH
CH
H
N
CH
l
C
CH
CH
H
N
CH
(e) (CH3)3CCl + AlCl3  (CH3)3C+ + –AlCl4
(f) CH2 = CH2 + BF3  2
2
3
—
H
C
CH
F
B



(g)
(h) 2
2
3
—
H
C
CH
F
B


 + CH2 = CH2  2
2
2
2
3
—
H
C
CH
CH
CH
F
B





(i)
Q.24 Predict theproducts ofthe following acid_base reactions.
H2SO4 + CH3COO– l
Q.25 Methyllithium(CH3Li) is oftenused as a base inorganic reactions.
(a) Predict the products ofthe following acid– base reaction.
CH3CH2 – OH + CH3 – Li 
(b) What istheconjugate acid ofCH3Li?Wouldyou expect CH3Lito bea strong base or aweak base ?
Q.26 Which reagent ineach pair listed here would be the more reactive Nu in a protic solvent ?
(a) CH3NH– or CH3NH2 (b) H2O or H3O
(c) CH3O– or CH3COO– (d) CH3SH or CH3OH
(e) Ph3N or Ph3P (f) CH3COO– or –OH
(g) H2S or HS– (h) NH3 or NH4


6. Q.27 Arrange thefollowing compounds inorderofincreasing basicity.
(a) CH3NH2, CH3

3
NH , CH3NH– (b) CH3O–, CH3NH–, CH3

2
CH
(c) CH3CH = CH–, CH3CH2

2
CH , CH3CC–
Q.28 Suggest what species would be formed byeach ofthe following combinations :
(a) PhO – + CH3COOH (b) + CH3O –
(c) Pyridiniumion+trifluoroacetate ion
Q.29 Saywhichpka belong to whichfunctionalgroup incase offollowing amino acids :
(i) cysteine : 1.8, 8.3 & 10.8
(ii) glutamic acid : : 2.19, 4.25, 9.67
Q.30 Record the following sets ofcompounds according to increasing pKa ( = – log Ka)
(a) , , cyclohexane carboxylic acid. (b) 1-butyne, 1-butene, butane
(c) Propanoic acid, 3-bromopropanoic acid, 2-nitropropanoic acid
(d) Phenol,o-nitrophenol, o-cresol (e) Hexylamine, aniline, methylamine
Q.31 Explain which compoundis the weaker base.
(a) or (b) CH2 = CH – CH = CH – CH2
– or CH2 = CH – CH2
–
(c) OH
C
C
O
|
|
|
|
O
O




or OH
C
C
HO
|
|
|
|
O
O


 (d) or
Q.32 Rank thefollowing amines inincreasingbasic nature.
(a)
(i) (ii) (iii) (iv)
(b)
(i) (ii) (iii) (iv)
(c)
(i) (ii) (iii)

7. Q.33 Dimethylfurmamide(DMF) is anexample ofpolar aprotic solvent, aprotic meaning it hasno hydrogen
atoms attached to highlyelectronegative atoms.
(a) Draw what you predict to be its most important resonance forms.
(b) DMFwhen usedas the reaction solvent, greatlyenhances the reactivityofnucleophiles. e.g.
NaCN + CH3CH2Br  CH3CH2 C  N + NaBr
Suggest an explanationfor this effects.
Q.34 Arrange thebasic strengthofthe following compounds.
(a) OH– CH3COO– Cl–
(i) (ii) (iii)
(b) CH  C– CH2 = CH– CH3CH2
–
(i) (ii) (iii)
(c) CH2 = CHCH2NH2 CH3CH2CH2NH2 CH  C – CH2NH2
(i) (ii) (iii)
(d)
(i) (ii) (iii)
(e)
(i) (ii) (iii)
(f) Cl– RCOO– OH– RO– NH2
–
(i) (ii) (iii) (iv) (v)
Q.35 Set the following inincreasing order ofpkb :
(i) CH3NH2 , (CH3)2 NH , (CH3)3 N , NH3 [In aqeous medium]
(ii) , (iii) ,
Q.36 Arrangethefollowing inincreasing acidstrength:
(a)
(i) (ii) (iii)
(b) CH3– OH
(i) (ii) (iii)

8. (c) OH
C
CH
|
|
O
3 
 OH
C
C
HO
|
|
|
|
O
O


 OH
C
CH
CH
C
HO
|
|
|
|
O
O
2
2 



(i) (ii) (iii)
Q.37 Set the following inincreasing order ofpka:
(i) Methane sulfonic acid, acetic acid & methanol.
(ii) CH3– CH2 – CH3 , CH2 = CH – CH3 , CH3 – CHO , CHO – CH2 – CHO , CH4
(iii) CH3NO2 , (NO2)2 – CH2 , (NO2)3 – CH
(iv) , , ,
(v) CH3COOH , NO2– CH2 – COOH ,
O
O
|
|
|
|
OH
C
CH
C
CH 2
3 



(vi)
H H
,
H H
,
(vii) CHO – CH2 – CHO ,
O
O
|
|
|
|
CH
C
CH
C
CH 3
2
3 


 ,
O
O
|
|
|
|
Et
O
C
CH
C
O
Et 2 




 ,
O
O
|
|
|
|
CH
C
CH
C
O
Et 3
2 




Q.38 Cyanic acid (HO–CN) & isocyanicacid (H–N=C=O) differ inthe positions oftheirelectrons but their
structure do not represent resonance structures.
(a) Explain
(b) Loss of a proton from cyanic acid yields the same anion as that obtained by loss of a proton from
isocyanic acid. Explain.
Q.39 Arrange the increasingorder ofacidic strength ofthe following compounds.
(a)
(i) (ii) (iii)
(b) CH2=CH–CH2CO2H CH3CH2CO2H
(i) (ii) (iii)
(c) CH3OH CF3OH CCl3–OH
(i) (ii) (iii)

9. Q.40 Explainwhich isa stronger acid.
(a) CH3CH3 BrCH2NO2 (b) 3
3 CH
C
CH
|
|
O

 & CN
CH
C
CH
|
|
O
2
3 

(c)
OH
O=C–CH3
or (d)
OH
O=C–CH3
or
(e) or
Q.41 Which ofthe following would you predict to be the stronger acid ?
(a) or
(b) CH3 – CH2 – CH2 – OH or CH3 – CH = CH – OH
(c) CH3 – CH = CH – CH2 – OH or CH3 – CH = CH – OH
Q.42 Which is a stronger base? & Why.
(a) ethylamineor aniline (b) ethylamine or ethoxide ion
(c) phenoxide ionor ethoxide ion (d) cyclohexylamineor aniline
Q.43 The Ka ofphenylacetic acid is 5.2 × 10–5, and the pKa ofpropionic acid is 4.87.
(a) Calculate the pKa ofphenylacetic acid and the Ka ofpropionic acid.
(b) Which oftheseis the stronger acid?
(c) Predict whetherthe following equilibriumwillfavor the reactants orthe products.
Q.44 Whichofthe following systemshowH–bonding during tautomerism.
(a) (b) (c) (d)
Q.45 What is theattacking siteofconjugatebase oftriketo formofphloroglucinolinprotic&aprotic solvent.
Q.46 In eachofthe following pairs which is more stable :
(a) l (b) l

10. (c) l (d) l
(e) l
Q.47 In each ofthe following pairs which is less stable :
(a) l (b) l
(c) l (d) l
(e) l
Q.48 In eachofthe following pairs which is more stable :
(a)
(b) (c) l
(d) l (e) l
Q.49 In each ofthe following pairs which is less stable :
(a) l (b) l

11. (c) l (d) l
Q.50 Ineachofthe following pairswhichwillhave higher enolcontent :
(a) and
(b) and
(c) and
(d) and
Q.51 In eachofthe following pairswhichwillhave lessenolcontent :
(a) and (b) and
(c) and (d) and
(e)
Cl
|
CHO
CH2  and CHO
CH3 
Q.52 Ineachofthe following pairswhichwillhave higher enolcontent :
(a)
2
2
NO
|
CHO
CH  and
Cl
|
CHO
CH2  (b) and
(c) and
(d) and

12. Q.53 In eachofthe following pairswhichwillhave lessenolcontent :
(a) and (b) and
(c) and (d) and
(e) and
Q.54 Whichofthe following compounds canexhibit tautoimerism:
(a) CH2 = C = O (b) CH2 = CH – OH (c) HO – CH = CH – OH
(d) CH3CN (e)
Q.55 Whichofthefollowing compounds cannot exhibit tautoimerism:
(a) (b) (c)
(d) (e)
Q.56 Whichofthe following compounds canexhibit tautoimerism:
(a) (b) (c) (d) (e)
Q.57 Whichofthefollowing compounds cannot exhibit tautoimerism:
(a) (b) (c)
(d) (e) CH3 – NO
Q.58 What isthe relationship betweenthesetwo molecules? Discuss the structure ofthe anionthat wouldbe
formed bythe deprotonation ofeachcompound.

13. Q.59 Write down tautomericstructure of5,5 – dimethylcyclohexane –1,3 –dione (dimedone).
Q.60 Draw enolforms ofthese carbonylcompounds and comment onthe stabilityofthe enolforms.
(a) (b)
Q.61 (a) and (b)
Shows tautomeric forms of(a) & (b).
Q.62 Isatinwas the first compound to show tautomerism.
What is thetautomeric formofisatin.
Q.63 1, 3 – dicarbonyl compounds such as (A) are usually mostly enolized. Why is this ? Draw the enols
available to compoundsA&B comment onthe different pattern ofenolization.
(A) (B)
Q.64 In eachofthe following sets ofcompounds write the increasing order of% enolcontent
(a)
(b)
(c)
(d)
(e)

14. Q.65 In eachofthe following setsofcompounds write thedecreasing order of% enolcontent.
(a)
(b)
(c)
(d)
(e)
Q.66 Out ofenolform ofcyclobutanone and enol formoftriketocyclobutane, which is more stable? Give
reason also.
Q.67 has lowerboiling point than evenwhenformer has –OH group. Explain.
Q.68
Among these giveease ofenolization.
Q.69 % enolcontent ofacetylacetone infollowing solvents is foundas :
Solvent % enolcontent
H2O 15
Liquid state 76
hexane 92
gas phase 92
Explainthe observation.

15. Q.70
Explainthe observation.
Q.71 l
This tautomeric system exist almost exclusivelyin favour of phenoland it is insensitive to changein
solvent.

16. ANSWER KEY
Q.1 B Q.2 C Q.3 D Q.4 B Q.5 C Q.6 B Q.7 A
Q.8 A Q.9 A Q.10 A Q.11 B Q.12 A
Q.13 (a) i, (b) ii, (c) i, (d) ii, (e) i Q.14 (a) Hb, (b) ii Q.15 (a) i, (b) i, (c) ii
Q.17 LA b,e LB acdf Q.18 (a) 2; (b) 1; (c) 1
Q.20 CH3CH3 + CH3C  CMgBr Q.21 (a) 1; (b) 1; (c) 1; (d) 1; (e) 2; (f) 1
Q.22 (a) 2; (b) 1; (c) 1; (d) 1; (e) 1; (f) 3 Q.26 (a) 1; (b) 1; (c) 1; (d) 1; (e) 2; (f) 2; (g) 2; (h) 1
Q.27 (a) 2<1<3; (b) 1<2<3; (c) 3<1<2
Q.28 (a) PhOH + 
AcO , (b) MeOH + , (c) no reaction
Q.29 (i) cysteine : (ii) glutamic acid:
Q.30 (a) 3<2<1; (b) 1<2<3; (c) 3<2<1; (d) 2<1<3; (e) 2<3<1 Q.31 (a) 2; (b) 1; (c) 2; (d) 2
Q.32 (a) 3<2<1<4; (b) 1<2<3<4; (c) 3<1<2
Q.34 (a) 1>2>3; (b) 1<2<3; (c) 3<1<2; (d) 2<1<3; (e) 1<2<3; (f) 1<2<3<4<5
Q.35 (i) 4>3>1>2; (ii) 1<2; (iii) 1<2 Q.36 (a) 1<2<3; (b) 3>1>2; (c) 1<3<2
Q.37 (i) 1<2<3; (ii) 1>5>2>3>4; (iii) 1>2>3; (iv) 1>3>4>2; (v) 1>3>2; (vi) 2>1>3;
(vii) 3>4>2>1
Q.39 (a) 3>1>2; (b) 1>2>3; (c) 2>3>1 Q.40 (a) 2; (b) 2; (c) 1; (d) 1; (e) 1
Q.41 (a) 2; (b) 2; (c) 2 Q.42 (a) 1; (b) 2; (c) 2; (d) 1
Q.43 (a) 4.25, (b) 1.34×10–5, (c) reactant Q.46 (a) 2; (b) 2; (c) 1; (d) 1; (e) 1
Q.47 (a)2; (b) 2; (c) 2; (d) 2; (e) 1 Q.48 (a) 2; (b) 2; (c) 1; (d) 2; (e) 1
Q.49 (a) 2; (b) 1; (c) 1; (d) 1 Q.50 (a)1; (b) 2; (c)1; (d) 2
Q.51 (a) 2; (b) 1; (c) 2; (d) 1; (e) 2 Q.52 (a) 1; (b) 1; (c) 1; (d) 1
Q.53 (a) 2; (b) 2; (c) 2; (d) 1; (e) 2 Q.54 a, b, c, d, e
Q.55 a, c, d Q.56 b
Q.57 b Q.58 Tautamers
Q.59 Q.60 (a) (b) both are more stable
Q.61 (a) (b)
Q.62 Q.63 (A) (B)
Q.64 (a) 2>1>3>4; (b) 3>2>1; (c) 3>2>1; (d) 3>1>2; (e) 3>1>2
Q.65 (a) 3>1>2; (b) 4>2>1>3; (c) 4>3>1>2; (d) 1>3>4>2; (e) 3>2>4>1
Q.66 enolformoftriketocyclobutane
Q.68 3>1>2