Test: 35 Year JEE Previous Year Questions: Haloalkanes & Haloarene- 2
18 Questions MCQ Test Chemistry for JEE | Test: 35 Year JEE Previous Year Questions: Haloalkanes & Haloarene- 2
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Chlorobenzene can be prepared by reacting aniline with : (1984 - 1 Mark)
The reaction of toluene with chlorine in presence of ferricchloride gives predominantly : (1986 - 1 Mark)
TIPS/Formulae :
The given reaction is an example of electrophilic substitution. Further, CH3 group in toluene is o, p-directing
The reaction conditions leading to the best yields of C2H5Cl are : (1986 - 1 Mark)
Chlorination beyond monochlorination during the preparation of alkyl halides in presence of UV light can be suppressed by taking alkane in excess.
NOTE : For isomeric alkanes the one having largest straight chain has highest b.p. because of large surface area.
n-Propyl bromide on treatment with ethanolic potassiumhydroxide produces (1987 - 1 Mark)
Further dehydrohalogenation of CH3CH = CH2 can be done only by strong base like NaNH2
The number of structural and configurational isomers of abromo compound, C5H9Br, formed by the addition of HBr to 2-pentyne respectively are (1988 - 1 Mark)
Addition of HBr of 2-pentyne gives two structural isomers (I) and (II)
Each one of these will exist as a pair of geometrical isomers. Thus, there are two structural and four configurational isomers
1-Chlorobutane on reaction with alcoholic potash gives (1991 - 1 Mark)
NOTE : Alkyl halides give alcohols with aq. KOH, which is a substitution reaction.
The chief reaction product of reaction between n-butane and bromine at 130ºC is : (1995 S)
TIPS/Formulae :
The reaction proceeds via free radical mechanism.
As 2º free radical is more stable than 1º, so
CH3CH2CH(Br)CH3 would be formed.
Isobutyl magnesium bromide with dry ether and ethyl alcohol gives : (1995S)
(CH3)3 CMgCl on reaction with D2O produces :
(CH3 )3C -MgCl + D2O → (CH3)3C -D +Mg(OD)Cl
A solution of (+) –2–chloro–2–phenylethane in tolueneracemises slowly in the presence of small amount of SbCl5,due to the formation of (1999 - 2 Marks)
Occurrence of racemization points towards the
formation of carbocation as intermediate, which being planar can be attacked from either side.
Identify the set of reagent / reaction conditions 'X' and 'Y' in the following set of transformations (2002S)
Dehydrobromination by strong base (alc. NaOH) followed by Markownikoff addition of HBr.
How many structures for F are possible? (2003S)
So F can have three possible structures
What would be the product formed when 1-bromo-3- chlorocyclobutane reacts with two equivalents of metallic
sodium in ether? (2005 S)
TIPS/Formulae :
It is an example of intramolecular Wurtz reaction.
NOTE : Br– is a better leaving group than chloride. In this reaction alkali metal (Na) is electron donor.
When phenyl magnesium bromide reacts with tert -butanol, the product would be (2005S)
Grignard reagents react with compounds containing active hydrogen to form hydrocarbons corresponding to alkyl (or aryl) part of the Grignard reagent.
C6H5MgBr + Me3COH →C6H6 + Me3COMgBr
The reagent(s) for the following conversion,
NOTE : Elimination of HBr from CH2= CHBr requires a stronger base because here, Br acquires partial double bond character due to resonance.
The major product of the following reaction is – (2008)
The product (a) will be formed.
Nucleophilic substitution of an alkyl halide is easier as compared to that of an aryl halide.
PhS– is a strong nucleophile and dimethyl formamide 
is a highly polar aprotic solvent.
These reagent favour SN2 reactions at 2° benzylic carbon.
NOTE : In a SN2 reaction, the major product formed is inversion product.
Aryl halides are less reactive towards nucleophilicsubstitution reaction as compared to alkyl halides due to :(1990 - 1 Mark)
TIPS/Formulae :
Aryl halides are stable due to resonance stabilization.
The resonating structures
stabilise the aryl halide. These structures include a double bond between C and Cl which is shorter and thus stronger than the usual C – Cl single bond. The sp2 hybridised carbon, being electronegative, makes the C – Cl bond shorter and stronger.
Benzyl chloride (C6H5CH2Cl) can be prepared from toluene by chlorination with (1998 - 2 Marks)
SOCl2,SO2Cl2 both give chlorination by nucleophilic substitution on an electrophilic carbon.
In toulene ,there is no electrophilic centre
oxidation occur by controlled free radical reaction using Cl2 in presence of high.
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