ACIDITY, BASICITY, H-BONDING & TAUTOMERISM
Q.1 Write equations showing the Lewis acid-base reaction that takes place when
(a) Methylalcoholreacts withBF3.
(b) Methyl chloride reacts with AlCl3.
(c) Dimethyl ether reacts with BF3.
Q.2 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.3 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.4 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 is added to ethyl lithium in hexane
(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.
Q.5 CH3CH2MgBr + CH3C  CH  A + B
Q.6 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.7 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.13 Eachofthese molecules is nucleophile. Identifythe nucleophilic atom&draw a mechanismfor reaction
witha generalised electrophile E+, giving the product ineachcase.
(a) R – C  C– (b) (c) NH2 – NH2
(d) (e)
Q.14 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.15 Neither ofthese methods of making pentan-1,4 diol will work. Explain why not – what will happen
instead?
(i) CHO–CH2–CH2–CH2–OH



 

H
by
followed
MeMgBr
OH
OH
|
|
CH
CH
CH
CH
CH 2
2
2
3 



(ii) Br–CH2–CH2–CH2–OH
O
Et
Mg
2


 MgBr–CH2–CH2–CH2–OH 


 

H
by
followed
CHO
CH3
OH
OH
|
|
CH
CH
CH
CH
CH 2
2
2
3 



Q.16 Suggest what species would be formed byeach ofthe following combinations :
(a) PhO – + CH3COOH
(b) + CH3COO –
(c) Pyridiniumion+trifluoroacetate ion
Q.17 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.18 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

(d)
(i) (ii) (iii)
(e)
(i) (ii) (iii)
(f) Cl– RCOO– OH– RO– NH2
–
(i) (ii) (iii) (iv) (v)
Q.23 Set the following inincreasing order ofpkb :
(i) ,
(ii) CH3NH2 , (CH3)2 NH , (CH3)3 N , NH3 [In aqeous medium]
(iii) ,
(iv) ,
Q.24 Arrangethefollowing inincreasing acidstrength:
(a)
(i) (ii) (iii)
(b) CH3– OH
(i) (ii) (iii)
(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.29 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.30 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.31 Which is a stronger base? & Why.
(a) ethylamine or aniline (b) ethylamine or ethoxide ion
(c) phenoxide ion or ethoxide ion (d) cyclohexylamine or aniline
Q.32 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.33 Explainwhythe2-methylpyrrolidineboilsat ahigher temperature thanitsisomers N- methylpyrrolidine.
Q.34 Although nitration usuallycauses elevation of B.P. yet the nitration ofresorcinolto 2-nitroresorcinol
decreases their B.P. thentheir parent compound.
Q.35 o-nitrophenolissparinglysoluble in water& has lower B.P. but p-nitrophenolis completelysolublein
water &hashigh boiling point.
Q.36 When 30 mlof ethanol and 5 ml of water are mixed the volume of the resulting solution is less than
35 ml. Explain.

Q.50 In each ofthe following pairs which is less stable :
(a) l (b) l
(c) l (d) l
(e) l
Q.51 In eachofthe following pairs which is more stable :
(a)
(b) (c) l
(d) l (e) l
Q.52 In each ofthe following pairs which is less stable :
(a) l (b) l
(c) l (d) l

Q.56 In eachofthe following pairswhichwillhave lessenolcontent :
(a) and (b) and
(c) and (d) and
(e) and
Q.57 Whichofthe following compounds canexhibit tautoimerism:
(a) CH2 = C = O (b) CH2 = CH – OH (c) HO – CH = CH – OH
(d) CH3CN (e)
Q.58 Whichofthefollowing compounds cannot exhibit tautoimerism:
(a) (b) (c)
(d) (e)
Q.59 Whichofthe following compounds canexhibit tautoimerism:
(a) (b) (c) (d) (e)
Q.60 Whichofthefollowing compounds cannot exhibit tautoimerism:
(a) (b) (c)
(d) (e) CH3 – NO
Q.61 What isthe relationship betweenthesetwo molecules? Discuss the structure ofthe anionthat wouldbe
formed bythe deprotonation ofeachcompound.

(c)
(d)
(e)
Q.69 In eachofthe following setsofcompounds write thedecreasing order of% enolcontent.
(a)
(b)
(c)
(d)
(e)

ANSWER KEY
Q.2 LA b,e LB acdf
Q.3 (a) 2; (b) 1; (c) 1
Q.5 CH3CH3 + CH3C  CMgBr
Q.6 (a) 1; (b) 1; (c) 1; (d) 1; (e) 2; (f) 1
Q.7 (a) 2; (b) 1; (c) 1; (d) 1; (e) 1; (f) 3
Q.11 (a) 1; (b) 1; (c) 1; (d) 1; (e) 2; (f) 2; (g) 2; (h) 1
Q.14 (a) 2<1<3; (b) 1<2<3; (c) 3<1<2
Q.18 (a) 3<2<1; (b) 1<2<3; (c) 3<2<1; (d) 2<1<3; (e) 2<3<1
Q.19 (a) 2; (b) 1; (c) 2; (d) 2
Q.20 (a) 3<2<1<4; (b) 1<2<3<4; (c) 3<1<2
Q.22 (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.23 (i) 1>2; (ii) 4>3>1>2; (iii) 1<2; (iv) 1<2
Q.24 (a) 1<2<3; (b) 3>1>2; (c) 1<3<2
Q.25 (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.28 (a) 3>1>2; (b) 1>2>3; (c) 2>3>1
Q.29 (a) 2; (b) 2; (c) 1; (d) 1; (e) 1
Q.30 (a) 2; (b) 2; (c) 2
Q.31 (a) 1; (b) 2; (c) 2; (d) 1
Q.32 4.25, 1.34×10–5
Q.49 (a) 2; (b) 2; (c) 1; (d) 1; (e) 1
Q.50 (a)2; (b) 2; (c) 2; (d) 2; (e) 1
Q.51 (a) 2; (b) 2; (c) 1; (d) 2; (e) 1
Q.52 (a) 2; (b) 1; (c) 1; (d) 1
Q.53 (a) 1; (b)1; (c) 2; (d)1; (e) 2
Q.54 (a) 1; (b) 1; (c) 2; (d) 1; (e) 2
Q.55 (a) 1; (b) 1; (c) 1; (d) 1
Q.56 (a) 2; (b) 2; (c) 2; (d) 1; (e) 2
Q.57 a, b, c, d, e
Q.58 a, c, d
Q.59 b
Q.60 b
Q.68 (a) 2>1>4>3; (b) 3>2>1; (c) 3>2>1; (d) 3>1>2; (e) 3>1>2
Q.69 (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.72 3>1>2