contents page no. theory 01 - 10 exercise - 1 11 - 19 exercise - 2 20 - 28 exercise - 3 29 - 33...

Topic Page No.

Theory 01 - 10

Exercise - 1 11 - 19




Answer Key 36 - 40

Contents

Syllabus

REACTION MECHANISM

Organic Reagents, Alkyl halides : Nucleophilic substitution reactions, elimination reactions,Alcohols : dehydration, reaction with sodium, phosphorus halides, ZnCl2/concentrated HCl,Ethers : Preparation by Williamson’s Synthesis; Nucleophilic substitution reactions.

Name : ____________________________ Contact No. __________________

REACTION MECHANISM # 1

A-479 Indra vihar, kotaPh. - 9982433693 (NV Sir) 9462729791(VKP Sir)

Physical & Inorganic By

NV SirB.Tech. IIT Delhi

Organic Chemistry By

VKP SirM.Sc. IT-BHU

REACTION MECHANISM(Alkyl halides, Alcohols & Ethers)

KEY CONCEPTS

Types of solvents

Polar protic solvent Polar aprotic solventCapable of H-bonding Incapable of H-bonding

• even thought polar protic solvents are not the best SN2 and E2, these reactions are often run in these solvents because nucleophiles and bases are often easily prepared in these solvents.






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Solvents Non Polar Polar Protic Aprotic1. H2O × –2. CH3OH × –3. CH3CH2OH × –4. H–COOH × –5. CH3–COOH × –6. NH3 × –7. × ×

8. × × DMSO–Dimethyl sulphoxide

9. × × DMF – Dimethyl formamide

10. × × DMA – Dimethyl acetamide

11. ×

12. ×

13. C–C–C–C–C–C ×






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Organic ReagentsOrganic reagents can be classified in two categories :(1) Electrophile : Electron pair acceptor are electrophile.(2) Nucleophile : Electron pair donor are nucelophile.

(1) ElectrophilesIt can be classified into two categories :(A) Charged electrophiles (E) (B) Neutral electrophiles (E)(A) Charged electrophiles : Positively charged species in which central atom has incomplete octet

is charged electrophile

H , X R , , = O,

Note : Generally All cations are charged electrophiles except cations of A, A group elements,

Al+++ and .(B) Neutral electrophiles : It can be classified into three categories :

(B) Neutral covalent compound in which central atom has incomplete octet is neutral

electrophile, AlX3, 2

••HC ,

2

••XC BF3, BCl3, BBr3, BI3

(B) Neutral covalent compound in which central atom has complete or expended octet and central atom has unfilled -d-shell is neutral electrophile

SnCl4, SiCl4, SbCl5Note :

(i) Cl2, Br2 and I2 also behave as neutral electrophiles.(ii) Electrophiles are Lewis acids.

(2) Nucleophiles

Nucleophiles can be classified into three categories :(A) Charged nucleophiles : Negatively charged species are charged nucleophiles.

, O , R – , C 3, , H, R–

(B) Neutral nucleophiles : It can be classified into two categories :Neutral covalent compound, in which central atom has complete octet, has at least one lonepair of electrons and all atoms present on central atom should not be electronegative, is neutralnucleophile.

, R– , R2 , R3 , –NH2 (Nitrogen nucleophile)

H– –H, R– –H, R– –R (Oxygen nucleophiles)

H– –H, R– –H, R – – R (Sulphur nucleophiles)

H3, R H2, R2 H, R3 (Phosphorus nucleophiles)

(C) Ambident nucleophile : Species having two nucleophilic centres, one is neutral (completeoctet and has at least one lone pair of electrons) and other is charged (negative charge)behaves as ambident nucelophile.

–

Note :(A) Organometallic compounds are nucleophiles.(B) Nucleophiles are Lewis bases.






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Organic compounds which behave as electrophile as well as nucleophile :Organic compound in which carbon is bonded with electronegative atom (O, N, S) by multiple bond/bonds behaves as electrophile as well as nucleophile.

HCR||O

, RCR||O

, OHCR||O

, ClCR||O

ORCR||O

, 2NHCR||O

, R–CN,

R– Note : During the course of chemical reaction electrophile reacts with nucleophile.

NUCLEOPHILIC SUBSTITUTION REACTIONS (SN) AT SATURATED CARBON

NUCLEOPHILIC SUBSTITUTION REACTIONS (SN) :Replacement (displacement) of an atom or group by an other atom or group in molecule is known assubstitution reaction. If substitution reaction is brought about by a nucleophile then it is known as nucleo-philic substitution reaction. Generally substitution takes place at sp3 carbon.

R–g + R – Nu +

UNIMOLECULAR NUCLEOPHILIC SUBSTITUTION REACTIONS (SN1) :Nucleophilic substitution which involves two step process(a) First step : - Slow step involves ionisation to form carbocation

R–g R+ + g –

(b) Second step : - Fast attack of nucleophile on carbocation to result into product .

R+ + Nu – R–Nu

SN1 Reaction of Alkyl halide

Mechanism :

)rds(stepSlowhalidealkyl

ofIonisation

Characteristics of SN1 reactions :1. It is unimolecular, two step process.2. Carbocation intermediate is formed so rearrangement is possible in SN1 reaction.3. It is first order reaction4. Kinetics of the reaction Rate [Alkyl halide]

Rate of SN1 reaction is independent of concentration and reactivity of nucleophile.






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5. Energetics of the SN1

Figure : Free energy diagram for the SN1 reaction.

SN1 Reaction of Alcohols(A) Reaction with hydrogen halides

A common method is to treat the alcohol with a hydrohalic acid, usually HI or HBr. These acids are usedto convert alcohols to the corresponding alkyl halides.

(i) In acidic solution, an alcohol is in equilibrium with its protonated form. Protonation converts thehydroxy group from a poor leaving group to a good leaving group (H2O). If the alcohol isprotonated all the usual substitution and elimination reactions are feasible, depending on the structure(1°, 2°, 3°) of the alcohol.

(ii) Halides are anions of strong acids, so they are weak bases. Solutions of HBr and HI contain nucleo-

philic and ions.

(iii) Concentrated hydrobromic acid rapidly converts t-Butyl alcohol to t-Butyl bromide. The strong acidprotonates the hydroxyl group, converting it to a good leaving group. The hindered tertiary carbonatom cannot undergo SN2 displacement, but it can ionise to a tertiary carbocation. Attack by bromideion gives the alkyl bromide. The mechanism is similar to other SN1 mechanism.

(iv) 1-Butanol reacts with sodium bromide in concentrated sulfuric acid to give 1-Bromobutane by an SN2displacement.

oltanbu1OHCH)CH(CH 2223

42SOH,NaBr

%)90(etanbromobu1

BrCH)CH(CH 2223

Protonation converts the hydroxy group to a good leaving group, but ionization to a primary carbocationis unfavourable. The protonated unbranched primary alcohol is well suited for the SN2 displacement.

(v) Secondary alcohols also react with HBr to form alkyl bromides usually by the SN1 mechanism.

e.g. HBr

(vi) HCl (Hydrochloric acid) reacts with alcohols in much the same way that as the hydrobromic acid.

(vii) Chloride ion is a weaker nucleophlile than bromide ion because it is smaller and less polarizable.Lewis acid, such as ZnCl2, is sometimes necessary to promote the reaction of HCl with primary andsecondary alcohols.






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Mechanism :

R –OH 2HOR

RDSO2H–

R R – X

Reactivity of HX : HI > HBr > HCl

Reactivity of ROH : allyl benzyl > 3° > 2° > 1°

SN1 REACTIONS OF ETHERS(A) Reaction with HX

Ethers are unreactive towards most bases, but they can react under acidic conditions. A protonated ethercan undergo substitution or elimination with the expulsion of an alcohol. Ethers react with conc. HBr andHI because these reagents are sufficiently acidic to protonate the ether, while bromide iodide are goodnucleophiles for the substitution.If R or R’ is 3º then mechanism will be SN1 otherwise SN2 .

Mechanism :

R – O – R` ROH–

X

R` – X

SN2 Reaction of Alkyl halide :

Mechanism : +

Characteristic of SN21. It is bimolecular, one step concerted process2. It is second order reaction because in the rds both species are involved3. Kinetics of the reaction rate [alkyl halide] [nucleophile]

rate = k[alkyl halide] [nucleophile]If the concentration of alkyl halide in the reaction mixture is doubled, the rate of the nucleophilicsubstitution reaction is double. If the concentration of nucleophile is doubled the rate of reaction is alsodouble. If the concentration of both are doubled then the rate of the reaction quadriples.

4. Energetics of the reaction :

Figure : A free energy diagrams for SN2 reaction

5. No intermediates are formed in the SN2 reaction, the reaction proceeds through the formation of anunstable arrangment of atoms or group called transition state.






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6. The stereochemistry of SN2 reactions As we seen earlier, in an SN2 mechanism the nucleophileattacks from the back side, that is from the side directly opposite to the leaving group. This modeof attack causes an inversion of configuration at the carbon atom that is the target of nucleophilicattack. This inversion is also known as Walden inversion.

Inversion

SN2 Reaction of Alcohol(A) Reaction with HX : The protonated unbranched primary alcohol is well suited for the SN2 reaction.

Mechanism :

R –OH 2HOR

X

R – X + H2O

e.galcoholPentyln

OHCHCHCHCHCH 22223

chloridePentyln

ClCHCHCHCHCH 22223

(B) Reaction with phosphorus trihalidesSeveral phosphorus halides are useful for converting alcohols to alkyl halides. PBr3, PCl3, & PCl5 workwell and are commercially available.Phosphorus halides produce good yields of most primary and secondary alkyl halides, but none works wellwith tertiary alcohols. The two phosphorus halides used most often are PBr3 and the P4/I2 combination.

3R – OH + PX3 3R – X + H3PO3Mechanism :

Step : 1

Step : 2 RCH2X+ HOPX2

RemarksThe mechanism for the reaction involves attack of the alcohol group on the phosphorus atom, displacinga halide ion and forming a protonated alkyl dihalophosphiteIn second step a halide ion acts as nucleophile to displace HOPX2, a good leaving group due to theelectronegative atoms bonded to the phosphorus.

(C) Reaction with thionyl chloride in presence of pyridineThionyl chloride (SOCl2) is often the best reagent for converting an alcohol to an alkyl chloride. The byproducts (gaseous SO2 and HCl) leave the reaction mixture and ensure that there can be no reversereaction.

R – OH + ClSCl||O

Pyridine

Heat R – Cl + SO2 + HCl






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Mechanism :

H– R – O – S

O

Cl

:..

.. ..

..

Chlorosulphite ester

+ HCl

R – Cl + SO2

In the first step, the nonbonding electrons of the hydroxy oxygen atom attack the electrophilic sulphur atomof thionyl chloride. A chloride ion is expelled a proton and gives test of chloro sulphite ester.Second step is an SN2 mechanism

e.g. PySOCl2

Reaction with thionyl chloride

ROH + SOCl2 RCl + SO2 + HCl

In this mechanism an internal nucleophile attacks from the same side of leaving group , means retensionof configuration . It is an SNi mechanism , where i means internal

Mechanism :

H– R – O – S

O

Cl

:..

.. ..

..

Chlorosulphite ester

+ HCl

R – Cl + SO2

e.g.

SN2 Reaction of Ether(A) Reaction with HX

A protonated ether can undergo substitution reaction. Ether react with conc. HBr and HI because thesereagents are sufficiently acidic to protonate the ether. If R or R’ is 3º then mechanism will be SN1 otherwiseSN2.






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Mechanism :

+ halidealkylRX + HX X – R + X – R

SN Reaction of EpoxideEpoxides are much more reactive than ether because of angle strain in three membered ring thereforeepoxide readily undergo nucleophilic substitution reaction.

In basic medium mechanism is SN2. Nucleophile atacks on less hindered carbon.

Mechanism :

O

|CH—CH—R|Nu

2 H

OH|

CH—CH—R|Nu

2

e.g.

In acidic medium mechanism is SN1 type. Nucleophilic attacks on more substituted carbon.

Mechanism :

H

OH|CH—CH—R

|Nu

2

ELIMINATION REACTIONS :E1 Reaction :

Proton and leaving group depart in two different step.(a) First step : - Slow step involves ionisation to form carbocation(b) Second step : Abstraction of proton

Mechanism :

Step 1 : Formation of the carbocation (RDS)






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Step 2 : Base ( ) abstracts a proton (fast)

+ B – H

E2 Reaction :Dehydrohalogenation is the elimination of a hydrogen and a halogen from an alkyl halide to form analkene.(i) Hot alcoholic solution of KOH, EtO¯/EtOH(ii) NaNH2

(iii) t-BuO¯ K in t-BuOHThis is one step reaction, hydrogen and leaving group depart simultaneouslyMechanism :

+ BH

(iii)E1 cB Reaction (Unimolecular conjugate base reaction)

In the E1 cB, H leaves first and then the X. This is a two step process, the intermediate is acarbanion.Mechanism :

Step - 1: Consists of the removal of a proton, , by a base generating a carbanion

||XCC

||H

Step - 2: Carbanion looses a leaving group to form alkene

||

–CC–

Condition : For the E1 cB, substrate must be containing acidic hydrogens and poor leaving groups.






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PART - I : OBJECTIVE QUESTIONS

* Marked Questions are having more than one correct option.Section (A) Organic reagentA-1. Which of the following molecules can behave both as a nucleophile and an electrophile ?

(A) CH3NH2 (B) CH3Cl (C) CH3CN (D) CH3OH

A-2. Which one of the following statements is not correct for electrophile :(A) Electron deficient species are electrophile (B) Electrophiles are Lewis acids(C) All + ive charged species are electrophile (D) AlCl3 and SO3 are electrophiles

A-3. Which of the following is an electrophilic reagent ?(A) H2O (B) OH– (C) NO2

+ (D) none

A-4. Which of the following reaction intermediates are electrophilic in character ?(a) Carbocation (b) Carbanion (c) Free radicals (d) Carbenes(A) Only b (B) a and c (C) a and d (D) a, b, c and d

A-6. Which one of the following has maximum nucleophilicity ?

(A) (B) (C) (D)

A-7. Which one of the following has maximum nucleophilicity ?

(A) SCH3 (B) (C) Et3N (D)

A-8. Correct arrangement of the following nucleophiles in the order of their nucleophilic strength is -(A) C6H5O– < CH3O– < CH3COO– < OH– (B) CH3COO– < C6H5O– < CH3O– < OH–

(C) C6H5O– < CH3COO– < CH3O– < OH– (D) CH3COO– < C6H5O– < OH– < CH3O–

A-9.* The correct nucleophilicity order is/are :

(A) (CH3)3 O > 3CH (B) CH3S > CH3SH

(C) CH3CH2CH2O > (CH3)3CO (D) (CH3CH2)3N > (CH3CH2)3P

A-10. Which among the following species is an ambident nucleophile ?

(A) CH3 – 2HC

(B) CH2 = CH2 (C) NC

(D) 3

••HN

A-11. Decreasing order of nucleophilicity of the following nucleophile is

(1) CH3O- (2) CN

–(3) (4) 3 2CH CO–

(A) 4 > 3 > 2 > 1 (B) 2 > 1 > 4 > 3 (C) 2 > 1 > 3 > 4 (D) 1 > 2 > 3 > 4






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Section (B) SN1 ReactionsB-1. Following is the list of four halides. Select correct sequence of decreasing order of reactivity for SN1

reaction using the answer codes given below :

(1) H5C6 CH Br

CH3

(2) C6H5–CH2–Br (3) H5C6 CH I

CH3

(4) C6H5–CH2–Cl

Answers codes :

(A) 3, 1, 2, 4 (B) 1,3, 2, 4 (C) 2, 4, 3, 1 (D) 4, 2, 3, 1

B-2. Which one of the following compounds will be most reactive for SN1 reactions:

(A) O

I

(B) O

Cl

(C) O

Br

(D)

O

Cl

B-3. Arrange the following compounds in order of decreasing rate of hydrolysis for SN1 reaction:

(I) CH2–Br (II) H3C CH2–Br

(III) CH3–CH2 CH2–Br (IV) CHCH3

CH3CH2–Br

(A) II > III > IV > I (B) IV > III > II > I (C) III > IV > II > I (D) I > II > III > I

B-4. Among the bromides I–III given below, the order of reactivity in SN1 reaction is:

(I) (II) (III)

(A) III > I > II (B) III > II > I (C) II > III > I (D) II > I > III

B-5. Which of the following compounds is most rapidly hydrolysed by SN1 mechanism.(A) C6H5Cl (B) Cl–CH2–CH = CH2(C) (C6H5)3CCl (D) C6H5CH2Cl

B-6. Which among the following will give SN1 reaction

(1) CH3 CH Br

C6H5

(2) CH3 C Br

CH3

CH3

(3) CH3–CH2–I (4) H5C6 C Cl

CH3

C6H5

Select the correct answer from the codes given below :Codes :(A) 1, 2 and 3 (B) 1, 2 and 4 (C) only 3 (D) 2 and 4






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B-7. What will be the major product of the following reaction ?

BrCHH|||

CH—CH—C—C—CH||CHH

3

33

3

C30,OHCH3

(A)

HHOCH|||

CH—C—C—C—CH|||

HCCHH

3

33

33

(B)

HCHH|||

CH—C—C—C—CH|||OCHCHH

3

33

33

(C)

HOCHH|||

CH—C—C—C—CH|||

CHCHH

3

33

33

(D)

33

23

3

OCHHCHH||||CH—C—C—C—CH

|||HCHH

B-8. Which one of the following compounds will give (d) and () form in SN1 reaction (as major product)

(A) (B) (C) (D)

B-9. Product,

Identify the major product :

(A) (B) (C) (D)

B-10. 3

Aq.AgNO (B)

Which statement is correct about the above reaction ?

(A) Product (B) is (I) by SN1 mechanism.

(B) Product (B) is (II) by SN2 mechanism.

(C) Product (B) is (I) by SN2 mechanism.(D) Product (B) is (II) by SN1 mechanism.






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Section (C) : SN2 ReactionsC-1. The given compound CH3–O–CH2–Br gives which one of the following reactions:

(A) Only SN1 (B) Only SN2(C) SN1 as well as SN2 (D) E1

C-2.* In the given pair in which pair the first compound is more reactive than second to SN2 reaction.

(A) Cl CH Cl2 (B) Cl

Cl

(C) Cl Cl (D)

Cl Cl

C-3. The decreasing order of rate of SN2 reaction is :

CH3–Cl O||

ClCHCCH 23 CH3–CH2–Cl

(I) (II) (III) (IV)

(A) IV > III > II > I (B) II > III > I > IV (C) II > I > IV > III (D) none

C-4. In the following reaction the most probable product will be :

(A) (B) (C) (D)

C-5. 3PBr (X) , X is :

(A) (B) (C) (D)






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C-6. 2SOCl Product,

Identify the product

(A) (B) (C) (D)

C-7. Consider the following reaction.

etherSOCl2

In the above reaction which phenomenon will take place :

(A) Inversion (B) Retention (C) Racemisation (D) Isomerisation

C-8.* Which of the following conditions favour SN2 mechanism ?(A) Strong nucleophile (B) High conc. of nucleophile(C) 3º alkyl halide (D) Polar protic solvent

C-9.* Y

H

OHCH3

H

182OH X, Identify X & Y :Y :

(A) X = (B) Y = (C) X = (D) Y =

vkSj Y gSa %Section (D) : E1 ReactionD-1. Which one of the following compounds undergoes E1 reaction most readily ?

(A) (B) CH3 – CH2 – CH2 – Br

(C) CH3 – CH2 – CH2 – I (D)

D-2. Which of the following will be most reactive for E1 reaction ?

(A) (B) (C) (D)






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D-3. In the given reaction,

OHCH3 [X]

[X] as the major product among the elimination products is :

(A) C = CH2

|CH3

(B) (C) (D)

D-4. 42SOH

In the above reaction the major product is shown, which is formed through the intermediate (carbocation)given below :

Which bond will migrate to form the above product ?(A) p (B) q (C) r (D) s

D-5. Major product is :

(A) (B) (C) (D)

Section (E) : E2 ReactionE-1. Which of the following cannot undergo E2 reaction ?

(A) (B) (C) (D) none of these

E-2. Arrange the following in decreasing order of stability of their transition state during elimination by strongbase

(A) II > I > III (B) II > III > I (C) I > III > II (D) I > II > III

E-3. 2-Bromopentane is heated with potassium ethoxide in ethanol. The major product obtained is(A) 2-Ethoxypentane (B) pent-1-ene (C) cis-pent-2-ene (D) trans-pent-2-ene

E-4. In which of the following reaction, regioselectivity can be observed.

(A) CH –C–CH –Cl3 2

H

CH3

/KOH.alc (B) CH –C–CH3 3

Cl

CH3

/KOH.alc

(C) CH –C–CH –CH3 2 3

Cl

CH3

/KOH.alc (D) CH –C–CH –Cl3 2

CH3

CH3

/KOH.alc






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E-5. The most probable product in the following reaction is :

Trans

(A) (B) (C) (D)

E-6. Which one of the following hexachlorocyclohexane is least reactive and which one is most reactive for E2reactions with a strong base for dehydrohalogenation.

(A) I least & II most (B) II least & I most (C) III least & I most (D) III least & II most

Section (F) : E1cB ReactionF-1. E1

cB reaction is given by which of the following :

(A) CF3 – CHCl2 (B) (C) (D) All of these

PART - II : MISLLANEOUS QUESTIONS

Comprehensions Type Questions :

Comprehension # 1Read the following passage carefully and answer the questions.One of the most interesting and useful aspects of stereochemistry is the study of what happens to opticallyacitive molecules when they react. The product isolated from the reaction of a chiral starting material cantell us a great deal about the reaction mechanism . We observeSN2 --------- Inversion of configurationSN1 --------- RacemisationSNi --------- Retention of configuration

1. In the given reaction, mention reaction mechanism respectively

() () +

() (V)

(A) SN2 , SN1 , SN2 , SNi (B) SN2 , SN1 , SNi , SN2

(C) SN1 , SN2 , SNi , SN1 (D) SN2 , SNi , SN1 , SN2






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2. The given reaction is an example of which type of Mechanism ?

Ether + SO + HCl2D Cl

C H3 7

C H6 5

(A) SN2 (B) SN

1 (C) SNi (D) None

3. In which of the following reaction retention of configuration is observed ?

(A) CH3 Br

H

D

acetone/Nal (B)

(C) + HOHCH3 Br

C H2 5

C H3 7

(D) H OTs

CH3

C H2 5

Na

Comprehension # 2Alcohols undergo acid catalysed elimination reactions to produce alkenes. Because water is lost in theelimination , this reaction is called dehydration reaction. Secondary and tertiary alcohols always give E1reaction in dehydration. Primary alcohols whose -carbon is branched also give E1 reaction. The reactivityof alcohol for elimination reaction is tertiary alcohol > Secondary alcohol > Primary alcohol.

4. In the given reaction : 42SOH.conc Alkenes

Total number of alkenes (Including stereo isomers) formed will be(A) Two (B) Three (C) Four (D) Five

5. Which of the following dehydration product (major) is incorrect ?

(A) 42SOH.conc

(B)

42SOH.conc

(C) CH3 CH2 CH2CH2OH

42SOH.conc CH3–CH=CH–CH3

(D) 42SOH.conc

6. Identify the product in the given reaction :

Product

(A) (B) (C) (D)






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Assertion / Reasoning Type Questions

DIRECTIONS :

Each question has 5 choices (A), (B), (C), (D) and (E) out of which ONLY ONE is correct.

(A) Statement-1 is True, Statement-2 is True; Statement-2 is a correct explanation for Statement-1.

(B) Statement-1 is True, Statement-2 is True; Statement-2 is NOT a correct explanation for Statement-1.

(C) Statement-1 is True, Statement-2 is False.

(D) Statement-1 is False, Statement-2 is True.

(E) Statement-1 and Statement-2 both are False.

7. Statement-1 : If the mixture of and reacts with the excess of NaSH in DMF,,

the molecuarity of the SN2 reaction will be two but not three.

Statement-2 : In the SN2 reaction two molecules e.g. R – X and uN..

take part in the formation of transition

state.

8. Statement-1 : Iodide (I–) is the strongest nucleophile (in protic solvent) among the halide anions

Statement-2 : Iodide is the largest halide anion and is the most weakly solvated in a protic solvent

Match the column Type Questions

9. Match the following :






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PART - I : MIXED OBJECTIVE

Single Choice Questions1. Which one is the strongest nucleophilic site in the following species ?

(A) 1 (B) 2 (C) 3 (D) 4

2. Decreasing order of relative nucleophilicity of the following nucleophiles in protic solvent is -

, , , , H2O

(A) > > H2O > > (B) > > > > H2O

(C) > > > H2O > (D) > > > > H2O

3. Which of the following is not expected to be intermediate of the following reaction ?

OH2

(A) (B) (C) (D)

4. Which describes the best stereochemical aspects of the following reaction ?

BrH Product

(A) Inversion of configuration occurs at the carbon undergoing substitution.(B) Retention of configuration occurs at the carbon undergoing substitution.(C) Racemization occurs at the carbon undergoing substitution.(D) The carbon undergoing substitution is not stereogenic.

5. When the concentration of alkyl halide is tripled and the concentration of ion is reduced to half, the rateof SN2 reaction increases by :(A) 3 times (B) 2 times (C) 1.5 times (D) 6 times






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6.

,pyridine

2SOCl Product

Product of the above reaction is :

(A) (B) (C) (D)

7. In the given reaction :

CH OH2

42SOH.Conc [X] as major product

[X] will be :

(A) CH2 (B) CH3 (C) CH3 (D)

8.

The product X and Y are respectively :

(A) &

(B) &

(C) &

(D) &

9. Which of the following will undergo fastest elimination reaction with alcoholic KOH.

(A) (B) (C) (D)






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10.

X and Y are respectively :

(A) and (B) and

(C) and (D) and

More than one correct answer11. Which of these statements are correct about nucleophiles :

(A) Nucleophiles have an unshared electron pair and can make use of this to react with an electrondeficient species.

(B) The nucleophilicity of an element (as electron donor) generally increases on going down a group in theperiodic table.

(C) A nucleophile is electron-deficient species(D) All good nucleophiles are good bases when we deal across the period.

12. Which of the following is / are true for SN1 reactions ?(A) They occur through a single step concerted reaction.(B) They are favoured by polar solvents.(C) 3º alkyl halides generally react through this mechanism.(D) Concentration of nucleophile does not affect the rate of such reactions.

13. SN2 reaction will be negligible in

(A) (B) (C)

Br

(D)

14. Rate of SN2 depends on(A) Conc of Nucleophile (B) Conc of substrate(C) Nature of leaving group (D) Nature of solvent

15. Which of the following reaction is correct ?

(A) 1, 4-Dichlorohexane + .eq1

NaI Acetone

ICl||

CHCHCHCHCHCH 22223 + NaCl

(B) 1, 2-Dibromoethane + NaS – CH2 – CH2 – SNa + 2NaBr

(C) 4-Chloro-1-butanol + NaH OEt2 C4H8ClONa

(D) Propyne + NaNH2 3NH

C3H3Na I3CH C4H6






VKP SirM.Sc. IT-BHU

PART - II : SUBJECTIVE QUESTIONS

1. Arrange the given species in decreasing order of their nucleophilicity ?

H2O

2. Write nucleophilicity order in the following compound.

3. Of the following pairs, which is the faster SN1 reactions?

(a) and (b) and CH3(CH2)5Cl

(c) and (d) and

(a) r Fkk (b) r Fkk CH3(CH2)5Cl

(c) r Fkk (d) r Fkk

4. Give the decreasing order of SN1 reactions of the following compounds in H2O.

(a) (i) (ii) (iii)

(b) (i) (ii) (iii)

(c) (i) (ii) (iii)

5. (a) (b)

6. What effect do you expect due to following changes in SN1 reaction of (CH3)3CBr with CH3OH ?

(a) The Concentration of (CH3)3CBr is doubled and that of CH3OH is halved.

(b) The concentration of both (CH3)3CBr and CH3OH are tripled.






VKP SirM.Sc. IT-BHU

7. Which SN1 reaction of each pair would you expect to take place more rapidly ? Explain.

(a) (i) Me3CCl + H2O Me3COH + HCl

(ii) Me3CBr + H2O Me3COH + HBr

(b) (i) Me3CCl + H2O Me3COH + HCl

(ii) Me3CCl + CH3OH Me3COCH3 + HCl

8. Explain how AgNO3 increases the rate of solvolysis in SN1 reactions of alkyl halide

9. Complete the following reactions and predict the nature of solution after product formation.

(a) C25

AcetoneOH2

P + Q (b) R + S

10. Write the mechanism of the following reaction and mention the rate determining step.

(a)

(b)

11. )eq1(

HI A + B,

Identify A and B.

12. Propose a mechanism for the following reaction

(a) CH CH CH CH

Cl

3 2 |

OCH O CH OH3 3

/ CH CH CH CH OCH3 2 3

O + Cl

(b) HO–CH2–CH2–CH2–CH2–OH H

O + HOH

13. How many structural isomers of monobromo cyclohexene are possible. Which will react most readily withNaCN?






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14. Which of the following reactions (a) and (b) would give a better yield of the desired ether as product.

(a)

(b)

15. Explain why thionyl chloride is considered the best reagent for converting alcohols to alkyl chlorides.

16. Predict the product of the following reactions using one equivalent of HI.

(a) (b) (c) (d)

17. Give the products of the following reactions

(i) X (ii) YY

18. Few dialkyl ethers & cyclic ethers were allowed to react with excess of HBr with the following results.Identify the ether in each case.

(P) excessHBr + CH3 – CH2 – CH2 – CH2 – Br

(Q) excessHBr

(R) excessHBr

(S) excessHBr

19. Observe the following reactions.

F–C–CH||O

31

2rOH Cl–C–CH

||O

32

2r

OH

Br–C–CH||O

33

2r

OH I–C–CH||O

34

2r

OH

Identify the order of the rate of reaction r1, r2, r3 and r4, give reason.






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20. Predict the products of the following reactions

(i) + (ii) ClCPh||O

+

21. Explain the order of the rate of esterification of the following acid with MeOH :MeCH2COOH > Me2CHCOOH > Me3CCOOH > Et3CCOOH >> (i-Pr)2CHCOOH

22. Write the correct reactivity order of nucleophilic substitution reaction for the following compounds.

23. Write the correct reactivity order with NaOH of following compounds.

24. When 1-Bromo-1-methylcyclohexane is heated in ethanol for an extended period of time, three productsresult: one ether and two alkenes. Predict the products of this reaction, and propose a mechanism for theirformation. Also, mention the major elimination product.

25. Predict the major product of E1 elimination of the following compounds.

(a) (b) (c) (d)

26. Why dehydration of alcohol takes place in acidic medium but not in basic medium.

27. 1º alcohols are poor starting material for synthesis of 1-Alkene. Explain

28. What happens when ethanol is heated with conc. H2SO4 at 453 K. Explain the mechanism of this reaction.






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29. Predict the major product of the sulphuric acid catalysed dehydration of the following alcohols :

(a) (CH3)2C(OH)CH2CH3 (b) CH3CH2 CH2CH(OH)CH3

(c) (CH3)2C(OH)CH(CH3)2 (d) (CH3)3CCH2OH

30. H Product,

Write the major product of the reaction

31.

43 OH.Conc P A (Major) + B (Minor),

Write structures of A and B

32. Among the various isomers of C4H9Br which would undergo elimination most readily and why ?

33. A halide with formula C6H13I is found to give two isomeric alkenes 2-methyl-2-pentene and 4-methyl-2-pentene on dehydrohalogenation with alcoholic KOH. Suggest its structure.

34. Bromocyclodecane on heating with ethanolic KOH, produces two alkenes Write the two products alsomention the major one.

35. A compound (X) [mol formula (C7H13Br)] on dehydrohalogenation gives only vinylcyclopentane, Write thestrucuture of X.

36.

Explain why more alkylated alkene is formed predominatly if base is , while less alkylated alkeneis obtained majorly when base is used.

37. Give the product of elimination reaction with its stereochemistry

(a) (b) ?

38. Which alkyl chloride would yield following pure alkene on reaction with alcoholic KOH ?






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(i) 23

3

CHCCH|

CH

(ii) CH3 – CH2 – CH2 – CH = CH2 (iii)

3

223

CH|

CHCCHCH

39. The sum of molecular weights of the major products P and Q form at the followng reaction is

(i) + CH3I /KOH P (organic product)

(ii) + CH3CH2OH /KOH Q (organic product)

40. What are the essential conditons for any reaction to show E1cB mechanism ?

41. Write down the increasing order of reactivity of following compounds via E1cB mechanism in basic medium

(a) C6H5 – CH2 – CH2 – Br CF3 – CH2 – CF3

(b) NO2 – CH2 – CH2 – Br

42. If ethanol containing EtOD is used as solvent, then deuterium exchange take place in E1cB mechanism.Why?

43. +

Write down the mechanism of the above reaction






VKP SirM.Sc. IT-BHU

PART - I : JEE PROBLEMS (PREVIOUS YEARS)

* Marked Questions are having more than one correct option.

1. An SN2 reaction at an asymmetric carbon of a compound always gives [JEE-2001, 1/135]

(A) an enantiomer of the substrate (B) a product with opposite optical rotation(C) a mixture of diastereomers (D) a single stereoisomer

2. Explain why 7-bromo-1, 3, 5-cycloheptatriene exist as an ion while 5-Bromo-1, 3-cyclopentadiene does notform any ion even in the presence of Ag+ . Explain why ? [JEE 2004, 4/60]

3. Compound (X) is reacted with aqueous acetone it gives following

products. [JEE-(scr.)2005, 3/144]

(A) K, L (B) K, M (C) L only (D) M only

4. Explain the following observations [JEE(M)-05, 1/144]

Acidic solution

Neutral solution

5. Which is the best reagent to convert cyclohexanol into cyclohexene. [JEE-2005, 3/144](A) conc. HCl (B) conc. HBr (C) conc. H3PO4 (D) HCl + ZnCl2

6. H X, Identify X. [JEE-2005, 2/144]






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7. Match the following (one term in column-I may match with more than one terms in column-II)[JEE-2006, 6/184]

8. The major product of the following reaction is [JEE-2008, 3/163]

(A) (B) (C) (D)

9. In the following carbocation; H/CH3 that is most likely to migrate to the positiviely charged carbon is[JEE-2009, 3/160]

(A) CH3 at C-4 (B) H at C-4 (C) CH3 at C-2 (D) H at C-2

10. In the reaction OCH3 HBr the products are : [JEE-2010, 3/163]

(A) Br OCH3 and H2 (B) Br and CH3Br

(C) Br and CH3OH (D) OH and CH3Br

11. The total number of alkenes possible by dehydrobromination of 3-bromo-3-cyclopentylhexane using alcoholicKOH is : [JEE 2011 160/4]

12. The compound that undergoes decarboxylation most readily under mild condition is -[JEE-2012, 3/136]

(A)

COOH

CH2COOH(B)

COOH

O(C)

COOH

COOH(D)

CH2COOH

O






VKP SirM.Sc. IT-BHU

PART - II : AIEEE PROBLEMS (PREVIOUS YEARS)

1. Following reaction(CH3)3CBr + H2O (CH3)3COH + HBr

is an example of : [AIEEE-2002](1) Elimination reaction (2) Free radical substitution(3) Nucleophilic substitution (4) Electrophilic substitution

2. SN1 reaction is feasible in : [AIEEE-2002]

(1) + KOH (aq.) (2) + KOH (aq.)

(3) + KOH (aq.) (4) + KOH (aq.)

3. Maximum dehydration takes place that of : [AIEEE-2002]

(1) (2) (3) (4)

4. Tertiary alkyl halides are practically inert to substitution by SN2 mechanism because of [AIEEE-2005](1) steric hindrance (2) inductive effect (3) instability (4) insolubility

5. The decreasing order of nucleophilicity among the nucleophiles [AIEEE-2005]

(a) (b) (c) (d)

(1) (c), (b), (a), (d) (2) (b), (c), (a), (d) (3) (d), (c), (b), (a) (4) (a), (b), (c), (d)

6. The decreasing order of nucleophilicity among the nucleophiles [AIEEE-2005]

(a) (b) (c) (d)

(1) (c), (b), (a), (d) (2) (b), (c), (a), (d) (3) (d), (c), (b), (a) (4) (a), (b), (c), (d)

7. Fluorobenzene (C6H5F) can be synthesized in the laboratory [AIEEE-2006](1) from aniline by diazotisation followed by heating the diazonium salt with HBF4(2) by direct fluorination of benzene with F2 gas(3) by reacting bromobenzene with NaF solution(4) by heating phenol with HF and KF






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8. CH3Br + Nu– CH3 – Nu + Br–

The decreasing order of the rate of the above reaction with nucleophiles (Nu¯) A to D is :

[Nu¯ = (A) PhO¯, (B) AcO¯, (C) HO¯, (D) CH3O¯] [AIEEE-2006](1) D > C > B > A (2) A > B > C > D (3) B > D > C > A (4) D > C > A > B

9. The structure of the major product formed in the following reaction is [AIEEE-2006]

DMFNaCN

(1) CH Cl2

CN

(2) CH Cl2

CN

(3) CH CN2

(4) CH CN2

CN

10. Reaction of trans 2-phenyl-1-bromocyclopentane on reaction with alcoholic KOH produces : [AIEEE-2006](1) 2–phenylcyclopentene (2) 1–phenylcyclopentene(3) 3-phenylcyclopentene (4) 4-phenylcyclopentene

11.

The alkene formed as a major product in the above elimination reaction is : [AIEEE-2006]

(1) (2) CH2 = CH2 (3) (4)

12. Which of the following is the correct order of decreasing SN2 reactivity ? [AIEEE-2007, 3/120](1) RCH2X > R3CX > R2CHX (2) RCH2X > R2CHX > R3CX(3) R3CX > R2CHX > RCH2X (4) R2CHX > R3CX > RCH2X

13. The organic chloro compound, which shows complete stereochemical inversion during an SN2 reaction, is[AIEEE-2008, 3/105]

(1) (CH3)3CCl (2) (CH3)2CHCl (3) CH3Cl (4) (C2H5)2CHCl

14. Which of the following on heating with aqueous KOH, produces acetaldehyde ? [AIEEE-2009, 4/144](1) CH3CH2Cl (2) CH2ClCH2Cl (3) CH3CHCl2 (4) CH3COCl

15. From amongst the following alcohols the one that would react fastest with conc. HCl and anhydrous ZnCl2,is : [AIEEE-2010, 4/144](1) 2-Butanol (2) 2-Methylpropan-2-ol(3) 2-Methylpropanol (4) 1-Butanol

16. Consider the following bromides : [AIEEE-2010, 4/144]

The correct, order of SN1 reactivity is(1) B > C > A (2) B > A > C (3) C > B > A (4) A > B > C






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17. In the chemical reactions : [AIEEE-2010, 4/144]

NH2

K278,HCl

NaNO2 A 4HBF B

the compounds ‘A” and ‘B’ respectively are

(1) nitrobenzene and fluorobenzene (2) phenol and benzene

(3) benzene diazonium chloride and fluorobenzene (4) nitrobenzene and chlorobenzene

18. The main product of the following reaction is : [AIEEE-2010, 4/144]

C6H5CH2CH(OH)CH(CH3)2 42SOH.conc

(1) (2)

(3) (4)

19. An unknown alcohol is treated with the “Lucas reagent” to determine whether the alcohol is primary, secondaryor tertiary. Which alcohol reacts fastest and by what mechanism : [JEE Mains 2013](1) secondary alcohol by S

N1 (2) tertiary alcohol by S

N1

(3) secondary alcohol by SN2 (4) tertiary alcohol by S

N2






VKP SirM.Sc. IT-BHU

NCERT QUESTIONS

1. Write the isomers of the compound having formula C4H9Br.

2. Write the equations for the preparation of 1-iodobutane from(i) 1-butanol (ii) 1-chlorobutane (iii) but-1-ene.

3. What are ambident nucleophiles? Explain with an example.

4. Which compound in each of the following pairs will react faster in SN2 reaction with –OH?(i) CH3Br or CH3I (ii) (CH3)3CCl or CH3Cl

5. Predict all the alkenes that would be formed by dehydrohalogenation of the following halides with sodiumethoxide in ethanol and identify the major alkene:(i) 1-Bromo-1-methylcyclohexane (ii) 2-Chloro-2-methylbutane (iii) 2,2,3-Trimethyl-3-bromopentane.

6. Write the structure of the major organic product in each of the following reactions:

(i) CH3CH2CH2Cl + NaI acetone

heat

(ii) (CH3)3CBr + KOH ethanol

heat

(iii) CH3CH(Br)CH2CH3 + NaOH water

(iv) CH3CH2Br + KCN aq.ethanol(v) C6H5ONa + C2H5Cl (vi) CH3CH2CH2OH + SOCl2

(vii) CH3CH2CH = CH2 + HBr peroxide(viii) CH3CH = C(CH3)2 + HBr

7. Write the mechanism of the following reaction :

nBuBr + KCN 2EtOH H O

nBuCN

8. Arrange the compounds of each set in order of reactivity towards SN2 displacement :(i) 2-Bromo-2-methylbutane, 1-Bromopentane, 2-Bromopentane(ii) 1-Bromo-3-methylbutane, 2-Bromo-2-methylbutane, 2-Bromo-3-methylbutane(iii) 1-Bromobutane, 1-Bromo-2,2-dimethylpropane, 1-Bromo-2-methylbutane, 1-Bromo-3-methylbutane.

9. Out of C6H5CH2Cl and C6H5CHClC6H5, which is more easily hydrolysed by aqueous KOH.

10. p-Dichlorobenzene has higher m.p. and solubility than those of o- and m-isomers. Discuss.

11. The treatment of alkyl chlorides with aqueous KOH leads to the formation of alcohols but in the presenceof alcoholic KOH, alkenes are major products. Explain.

12. Primary alkyl halide C4H9Br(a) reacted with alcoholic KOH to give compound(b).Compound (b) is reacted with HBr to give (c) which is an isomer of (a).When (a) is reacted with sodium metal it gives compound (d),C8H18 which is different from the compound formed when n-butyl bromide is reacted with sodium.Give the structural formula of (a) and write the equations for all the reactions.






VKP SirM.Sc. IT-BHU

13. What happens when(i) n-butyl chloride is treated with alcoholic KOH,(ii) ethyl chloride is treated with aqueous KOH,(iii) methyl chloride is treated with KCN?

14. Explain why propanol has higher boiling point than that of the hydrocarbon, butane?

15. Alcohols are comparatively more soluble in water than hydrocarbons of comparable molecular masses.Explain this fact.

16. Show how will you synthesise:(i) cyclohexylmethanol using an alkyl halide by an SN2 reaction.(ii) pentan-1-ol using a suitable alkyl halide?

17. Give reason for the higher boiling point of ethanol in comparison to methoxymethane.

18. Write the names of reagents and equations for the preparation of the following ethers by Williamson’ssynthesis:(i) 1-Propoxypropane (ii) Ethoxybenzene(iii) 2-Methoxy-2-methylpropane (iv) 1-Methoxyethane

19. Illustrate with examples the limitations of Williamson synthesis for the preparation of certain types of ethers.

20. How is 1-propoxypropane synthesised from propan-1-ol? Write mechanism of this reaction.

21. Preparation of ethers by acid dehydration of secondary or tertiary alcohols is not a suitable method. Givereason.

22. Write the equation of the reaction of hydrogen iodide with :(i) 1-propoxypropane (ii) methoxybenzene and (iii) benzyl ethyl ether.

23. Explain the fact that in aryl alkyl ethers(i) the alkoxy group activates the benzene ring towards electrophilic substitution and(ii) it directs the incoming substituents to ortho and para positions in benzene ring.

24. Write the mechanism of the reaction of HI with methoxymethane.

25. When 3-methylbutan-2-ol is treated with HBr, the following reaction takes place:

Give a mechanism for this reaction.(Hint : The secondary carbocation formed in step II rearranges to a more stable tertiary carbocation by ahydride ion shift from 3rd carbon atom.






VKP SirM.Sc. IT-BHU

Exercise # 1PART - I

A-1. (C) A-2. (C) A-3. (C) A-4. (C) A-6. (A) A-7. (A) A-8. (D)A-9.* (BC) A-10. (C) A-11. (B) B-1. (A) B-2. (A) B-3. (A) B-4. (A)B-5. (C) B-6. (B) B-7. (C) B-8. (B) B-9. (A) B-10. (D) C-1. (C)C-2.* (BD) C-3. (C) C-4. (B) C-5. (A) C-6. (A) C-7. (B) C-8.* (AB)C-9.* (AD) D-1. (D) D-2. (A) D-3. (C) D-4. (B) D-5. (C) E-1. (C)E-2. (A) E-3. (D) E-4. (C) E-5. (C) E-6. (B) F-1. (D)

PART - II

1. (B) 2. (C) 3. (B) 4. (C) 5. (B) 6. (C) 7. (A)8. (A) 9. (A) - p, r, s ; (B) - r, s ; (C) - r, s ; (D) - p, q


1. (D) 2. (B) 3. (A) 4. (C) 5. (C) 6. (A) 7. (B)

8. (A) 9. (A) 10. (A) 11. (ABD) 12. (BCD) 13. (ABC)

14. (ABCD) 15. (ABCD)PART - II

1. > > > H2O 2. III > II > I > IV 3. (a) (i), (b) i, (C)i (d) i

4. a. (iii) > (ii) > (i) b. (iii) > (i) > (ii) c. (ii) > (i) > (iii) (allylic > 3° > 1°)

5. (a) (b)

6. (a) Rate - doubled ; (b) Rate - tripled

7. (a) ii, (b) i

8. Ag+ ion has strong affinity for X– than a solvent molecule, the precipitation of AgX accelerates the dissociationof R–X bond.

9. (a) P = , Q = pH is less than seven because acid HBr is formed.

(b) R = , S = pH is less than seven because acid HCl is formed






VKP SirM.Sc. IT-BHU

10. (a)

oltanbu2Methyl3OH|

CHCHCHCH|CH

33

3

rds

Slow

(b) rdsOH2

11. + CH3OH

12. (a) CH O CH OH

SN

3 3

2

/ CH CH CH CH OCH

Cl OH

SN3 2 3

2 | |

CH –CH–CH–CH –O–CH3 2 3

O

H

CH –CH–CH–CH –O–CH3 2 3

O

(b) HO–(CH2)3–CH2OH H

H O CH CH O– ( )

2 3 2

H

H

H O2 O

H

H

O

13. Three will react most readily with NaCN.

14. (a) Give better yield, because in the (b) nucleophile attacks on more hindered 2° carbon. So along withsubstitution, elimination also posible in the (b).

15. ROH + SOCl2 R–Cl + HCl + SO2 gases

Pure RCl is obtained, as the by products (HCl and SO2) are gases and get evaporated from the reactionmixture.

16. (a) I–H2C – CH2 – CH2 – CH2 – CH2–OH (b) + CH3I

(c) (d)

17. (i) X = CH3CH(OH)CH2OH (ii) Y = CH3CH(OH)CH2OMe






VKP SirM.Sc. IT-BHU

18. P = Q = CH2OCH2

R = S =

19. r4 > r3 > r2 > r1 rate of SN2 Th is inversly proportional to basicity of leaving group.

20. (i) (ii)

21. As the size of the substituents on the C increases, the tetrahedrally bonded intermediate becomes morecrowded. The greater the crowding, the larger is H+ of the TS and the slower is the reaction.

22. II > I > IV > III 23. II > III > I 24. +

25. (a) (b) (c) (d)

26. In basic condition very poor leaving group –OH will eliminate but in acidic medium –OH will be converted

into 2HO– which is very good leaving group.

27. 1º carbocation

2CH–R would rearrange and 2-alkene would result. Even if 1-alkene is also formed but, it

would tend to rearrange in acidic medium to 2-alkene.

28. What happens when ethanol is heated with conc. H2SO4 at 453 K. Explain the mechanism of this reaction.

Ans. (a) CH3—CH2—O.... —H + H+ CH3—CH2— —H

Ethanol Oxonium ion

(b) slow CH2=CH2 + H2O

29. (a) CH3 C CH

CH3

CH3(b) CH3 – CH2 – CH = CH – CH3

(c) C CCH3

CH3CH3

CH3

(d) CH3 C CH

CH3

CH3

30. OH2 H C3

+

CH3

H

H–

31. A : B :






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32. Tert-butyl bromide would undergo elimination most readily as the alkene formed from it would be morestable.

33. 34. +

35. HBr

2E

The product is formed only by E2 elimination.

36. t- is bulky base so Hoffmann product is formed as major product.

37. (a) (b)

38. (i) or ; (ii) CH3CH2CH2CH2CH2Cl ; (iii)

3

223

CH|

ClCHCHCHCH

39. 196

P = O

CH3

CH3

[M.F. C7H14O M.W. 84+14+16 = 114]

Q = CH3 [M.F. C6H10 M. W. 72 + 10 = 82]

M.W. (P + Q) = 114 + 82 = 196

40. Reactant should have acidic -hydrogen and poor leaving group.

41. (a) C6H5 – CH2 – CH2 – Br < CF3 – CH2 – CF3 (b) NO2 – CH2 – CH2 – Br <

42. In E1cB mechanism carbanion is formed as intermediate and 1st step is reversible.

43.

2nd step

In E1cB 1st step is reversible step so deuterium exchange take place






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1. (D)

2. 7-bromo-1, 3, 5-cycloheptatriene on ionisation gives tropylium ion which is aromatic & highly stable,

but ionisation of 5-bromo-1, 3-cyclopentadiene gives 1, 3-cyclopentadienyl cation which is anti aromatic

& unstable. (non existent)

3. (A)

4. + HBr (strong acid) + (SN1 product)

No reaction.

Because aryl halide have resonance stabilized C – X bond, and do not give SN reaction.

5. (C) 6. 7. (A) - q ; (B) - q ; (C) - r, s ; (D) - p, s

8. (A) 9. (D) 10. (D) 11. 5 alkenes including stereoisomers 12. (B)

PART - II

1. (3) 2. (1) 3. (2) 4. (1) 5. (1) 6. (1) 7. (1)

8. (4) 9. (3) 10. (3) 11. (2) 12. (2) 13. (3) 14. (3)

15. (2) 16. (1) 17. (3) 18. (1) 19. (2)

contents page no. theory 01 - 10 exercise - 1 11 - 19 exercise - 2 20 - 28 exercise - 3 29 - 33...

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