Read the passage given below and answer the following questions:
Nucleophilic substitution reactions are of two types; substitution nucleophilic bimolecular (SN2) and substitution nucleophilic unimolecular (SN1) depending on molecules taking part in determining the rate of reaction. Reactivity of alkyl halide towards SN1 and SN2 reactions depends on various factors such as steric hindrance, stability of intermediate or transition state and polarity of solvent. SN2 reaction mechanism is favoured mostly by primary alkyl halide or transition state and polarity of solvent, SN2 reaction mechanism is favoured mostly by primary alkyl halide then secondary and then tertiary. This order is reversed in case of SN1 reactions.
(i) Which of the following is most reactive towards nucleophilic substitution reaction?
(a) \(C_6\)\(H_5\)Cl
(b) \(CH_2\)=CHCl
(c) \(ClCH_2\)\(CH=CH_2\)
(d) \(CH_3\)CH=CHCl
(ii) Isopropyl chloride undergoes hydrolysis by
(a) SN1 mechanism
(b) SN2 mechanism
(c) SN1 and SN2 mechanism
(d) neither SN1 nor SN2 mechanism
(iii) Tertiary alkyl halides are practically inert to substitution by SN2 mechanism because of
(a) insolubility
(b) instability
(c) inductive effect
(d) steric hindrance
(iv) Which of the following is the correct order of decreasing SN2 reactivity?
(a) \(RCH_2\)X > \(R_2\)CHX > \(R_3\)CX
(b) \(R_3\)CX > \(R_2\)CHX > \(RCH_2\)X
(c) \(R_2\)CHX > \(R_3\)CX > \(RCH_2\)X
(d) \(RCH_2\)X > \(R_3\)CX > \(R_2\)CHX
(v) An organic molecule necessarily shows optical activity if it-
a) contains asymmetric carbon atoms
b) is non-polar
c) is non-superimposable on its mirror image
d) is superimposable on its mirror image
Read the passage given below and answer the following questions:
The replacement of hydrogen atom in a hydrocarbon, aliphatic or aromatic results in the formation of haloalkanes and haloarenes respectively. Haloalkanes contain halogen atom attached to \(sp^3\) hybridised carbon atom of an alkyl group whereas haloarenes contain halogen atom attached to \(sp^2\) hybridised carbon atom of an aryl group. Haloalkanes and haloarenes may be classified on the basis of number of halogen atoms in their structures as mono, di or poly halogen compounds and also on the basis of the state of hybridisation of carbon atom to which the halogen atom is bonded.
(i) Which of the following halide is 2°?
(a) Isopropyl chloride
(b) Isobutyl chloride
(c) n-propyl chloride
(d) n-butyl chloride
(ii) Which of the following is a Gem-dibromide is :
(a) \(CH_3\)\(CH(Br)CH_2\)(Br)
(b) \(CH_3\)\(CBr_2\)\(CH_3\)
(c) \(CH_2\)\((Br)CH_2\)\(CH_2\)
(d) \(CH_2\)\(BrCH_2\)Br
(iii) IUPAC name of (\({\\(CH_3\\)}_3\))CCl is:
(a) 3-Chlorobutane
(b) 2-Chloro-2-methylpropane
(c) t-butyl chloride
(d) n-butyl chloride
(iv) Which of the following is a primary halide?
(a) Isopropyl iodide
(b) Secondary butyl iodide
(c) Tertiarybutylbromide
(d) Neohexylchloride
(v) Which one of the following is not an allylic halide?
(a) 4-Bromopent-2-ene
(b) 3-Bromo-2-methylbut-1-ene
(c) 1-Bromobut-2-ene
(d) 4-Bromobut-1-ene
Read the passage given below and answer the following questions:
Alkyl halides are prepared by the free radical halogenation of alkanes, addition of halogen acids to alkenes, replacement of -OH group of alcohols with halogens using phosphorus halides, thionyl chloride or halogen acids. Aryl halides are prepared by electrophilic substitution to arene. Fluorine and iodides are best prepared by halogen exchange method. These compounds find wide applications in industry as well as in day-to-day life. These compounds are generally used as solvents and as starting material for the synthesis of a large number of organic compounds.
(i) The best method for the conversion of an alcohol into analkyl chloride is by treating the alcohol with
(a) \(PCl_5\)
(b) dry HCl in the presence of anhydrous \(ZnCl_2\)
(c) \(SOCl_2\) in presence of pyridine
(d) None of these
(ii) The catalyst used in the preparation of an alkyl chloride bythe action of dry HCl on an alcohol is
(a) anhydrous \(AlCl_3\)
(b) \(FeCl_3\)
(c) anhydrous \(ZnCl_2\)
(d) Cu
(iii) An alkyl halide reacts with metallic sodium in dry ether. The reaction is known as :
(a) Frankland’sreaction
(b) Sandmeyer’sreaction
(c) Wurtz reaction
(d) Kolbe’s reaction
(iv) Fluorobenzene (\(C_6\)\(H_5\)F) can be synthesized in the laboratory
(a) by direct fluorination of benzene with \(F_2\) gas
(b) by reacting bromobenzene with NaF solution
(c) by heating phenol with HF and KF
(d) from aniline by diazotisation followed by heating thediazonium salt with \(HBF_4\)
(v) When 2-bromobutane reacts with alcoholic KOH, thereaction is called
(a) halogenation
(b) chlorination
(c) hydrogenation
(d) dehydrohalogenation
Read the passage given below and answer the following questions:
The polarity of carbon-halogen bond of alkyl halides is responsible for their Nucleophilic substitution, elimination and their reaction with metal atoms to form organ metallic compounds. Nucleophilic substitution reactions are categorized into SN1 and SN2 on the basis of their kinetic properties. Chirality has a profound role in understanding the reaction mechanisms of SN1 and SN2 reactions. SN2 reactions of chiral alkyl halides are characterized by the inversion of configuration while SN1 reactions are characterized by racemisation.
ASSERTION -REASON TYPE
A statement of assertion is followed by a statement of reason. Mark the correct choice from the options given below:
(a) Both assertion and reason are true and reason is the correct explanation of assertion.
(b) Both assertion and reason are true but reason is not the correct explanation of assertion.
(c) Assertion is true but reason is false.
(d) Assertion is false but reason is true.
(i) Assertion : SN2 reactions do not proceed with retention of configuration.
Reason : SN2 reactions proceed in a single step.
(ii) Assertion : Tertiary alkyl halides show high reactivity in SN1 reaction.
Reason : Tertiary carbocation has more stability.
(iii) Assertion : Nucleophilic substitution reaction in an optically active alkyl halide gives a mixture of enantiomers.
Reason : Reaction occurs by SN1 mechanism.
(iv) Assertion : Primary allylic halides show higher reactivity in SN1 reactions than other primary alkyl halides.
Reason : Intermediate carbocation is stabilized by resonance.
When Benzene diazonium chloride is treated with cuprous chloride in HCl, Chlorobenzene is formed, This reaction is known as –
a) Etard Reaction
b) Perkin’s Reaction
c) Gattermann’s Reaction
d) Sand Meyer’s Reaction
Which is the most reactive towards SN1 reaction –
a) \(C_6\)\(H_5\)\(CH_2\)Cl.
b) \(C_6\)\(H_5\)CH(\(C_6\)\(H_5\))Br.
c) \(C_6\)\(H_5\)CH(\(CH_3\))Br.
d) \(C_6\)\(H_5\)C(\(CH_3\))(\(C_6\)\(H_5\))Br.
The reaction R-Br + NaCN → R – CN + NaBr is an example of –
(a) Elimination Reaction.
(b) Nucleophilic Substitution.
(c) Electrophilic Substitution.
(d) Oxidation Reduction.
The reaction \({\\(CH_3\\)}_2\)CHCl + NaI → \({(\\CH_3\\)}_2\)CHI + NaCl is known as –
a) Finkelstein’s reaction.
b) Stephen’s reaction.
c) Kolbe’s reaction.
d) Wurtz reaction.
The Addition of HBr to 2—Pentene gives –
a) 2-Bromopentane only.
b) 3-Bromopentane only.
c) 2-Bromopentane and 3-Bromopentane.
d) 1-Bromopentane and 3-Bromopentane.
Which of the following is an example of vic-dihalide?
(a) Dichloromethane.
(b) 1,2-dichloroethane.
(c) Ethylidene chloride.
(d) Allyl chloride.
Chlorobenzene is formed by reaction of chlorine with benzene in the presence of \(AlCl_3\). Which of the following species attacks the benzene ring in this reaction?
(a) \(Cl^+\)
(b) \(Cl^-\)
(c) \(AlCl_3\)
(d) \({[\\(AlCl_4\\)]}^-\)
Molecules whose mirror image is non-superimposable over them are known as chiral. Which of the following molecules is chiral in nature?
(a) 2-Bromobutane.
(b)1-Bromobutane.
(c) 2-Bromopropane.
(d) 2-Bromopropan-2-ol.
Which is the correct increasing order of boiling points of the following compounds?
1-Iodobutane, 1-Bromobutane, 1-Chlorobutane, Butane
(a) Butane < 1-Chlorobutane < 1-Bromobutane < 1-Iodobutane.
(b) 1-Iodobutane < 1-Bromobutane < 1-Chlorobutane < Butane.
(c) Butane < 1-Iodobutane < 1-Bromobutane < 1-Chlorobutane.
(d) Butane < 1-Chlorobutane < 1-Iodobutane < 1-Bromobutane.