Aryl halides are extremely less reactive towards nucleophilic substitution. Predict and explain the order of reactivity of the following compounds towards nucleophilic substitution:
After the attachment of the nucleophile at the carbon carrying -Cl, the intermediate compound is stabilised due to resonance. Due to electron withdrawing nature of-NO2, the nucleophile is easily attached to the benzene ring. Greater the number of -NO2 groups in the molecule, greater will be the ease with which the nucleophile will be attached. Hence, the order of reactivity is III > II > I.
Match the structures of compounds given in Column I with the classes of compounds given in Column II.
Chlorobenzene is formed by reaction of chlorine with benzene in the presence of AlCl3. Which of the following species attacks the benzene ring in this reaction?
(a) CP (b) Cl+ (c) AlCl3 (d) [AlCl4]–
Elimination reactions (especially Beta-elimination) are as common as the nucleophilic substitution reaction in case of alkyl halides. Specify the reagents used in both cases.
How will you bring about the following conversions?
(i)Ethanol to but-l-yne . (ii)Ethane to bromoethene
(iii)Propene to 1-nitropropane (iv)Toluene to benzyl alcohol
(v)Propene to propyne (vi)Ethanol to ethyl fluoride
(vii)Bromomethane to propanone (viii)But-l-ene to but-2-ene
(ix)1-Chlorobutane to n-octane (x)Benzene to biphenyl
Which of the following compounds will give racemic mixture on nucleophilic substitution by OH ion?
Alkyl halides are prepared from alcohol by treating with
(a) HCl + ZnCl2 (b) RedP + Br2
(c) H2SO4 + KI (d) all the above
Questions on the basis of the following reaction:
Which of the following statements are correct about the mechanism of this reaction?
(a) Acarbocation will be formed as an intermediate in the reaction.
(b) OH– will attach the substrate (iii) from one side and Cl– will leave it simultaneously from other side.
(c) An unstable intermediate will be formed in which OH– and Cl– will be attached by weak bonds.
(d) Reaction proceeds through SN1 mechanism.
Which of the following are secondary bromides?
(a) (CH3),CHBr (b) (CH3)3C CH2Br
(c) CH3CH(Br)CH2CH3 (d) (CH3)2CBrCH2CH3
Which of the following statements are correct about this reaction?
(a) The given reaction follows SN2 mechanism.
(b) (ii) and (iv) have opposite configuration.
(c) (ii) and (iv) have same configuration.
(d) The given reaction follows SN1 mechanism.
Diphenyls are potential threat to the environment. How are these produced from arylhalides?
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
Some alkylhalides undergo substitution whereas some undergo elimination reaction on treatment with bases. Discuss the structural features of alkyl halides with the help of examples which are responsible for this difference.
Ethylene chloride and ethylidene chloride are isomers. Identify the correct statements.
(a) Both the compounds form same product on treatment with alcoholic KOH
(b) Both the compounds from same product on treatment with aqueous NaOH
(c) Both the compounds form same product on reduction
(d) Both the compounds are optically active
Which of the compounds will react faster in SN1 reaction with the –OH ion?
CH3 – CH2 – Cl or C6H5 – CH2 – Cl
Compound (A) with molecular formula C4H9Br is treated with aq. KOH solution. The rate of this reaction depends upon the concentration of the compound A' only. When another optically active isomer B' of this compound was treated with aq. KOH solution, the rate of reaction was found to be dependent on concentration of compound and KOH both.
(i) Write down the structural formula of both compounds A' and B'.
(ii) Out of these two compounds, which one will be converted to the product with inverted configuration.
Aryl halides are extremely less reactive towards nucleophilic substitution. Predict and explain the order of reactivity of the following compounds towards nucleophilic substitution:
Assertion (A): Hydrolysis of (-)-2-bromooctane proceeds with inversion of configuration.
Reason (R): This reaction proceeds through the formation of a carbocation.
Some halogen containing compounds are useful in daily life. Some compounds of this class are responsible for exposure of flora and fauna to more and more of UV light which causes destruction to a great extent. Name the class of these halo compounds. In your opinion, what should be done to minimize harmful effects of these compounds.
Write the structures and names of the compounds formed when compound ‘A' with molecular formula, C7H8 is treated with Cl2 in the presence of FeCl3.
Why is it necessary to avoid even traces of moisture during the use of a Grignard reagent?
How can you obtain iodoethane from ethanol when no other iodine containing reagent except Nal is available in the laboratory?
In the following questions, a statement of Assertion (A) followed by a statement of Reason (R) is given. Choose the correct option out of the choices given below each question:
(a)Assertion and Reason both are correct and Reason is the correct explanation of Assertion.
(b)Assertion and Reason both are wrong.
(c)Assertion is correct but Reason is wrong.
(d)Assertion is wrong but Reason is correct.
(e)Assertion and Reason both are correct statements but Reason is not the correct explanation of Assertion.
Assertion (A): Phosphorus chlorides (tri and penta) are preferred over thionyl chloride for the preparation of alkyl chlorides from alcohols.
Reason (R): Phosphorus chlorides give pure alkyl halides.
Assertion (A): The boiling points of alkyl halides decrease in the order: RI > RBr > RCl > RF
Reason (R): The boiling points of alkyl chlorides, bromides and iodides are considerably higher than that of the hydrocarbon of comparable molecular mass.
Assertion (A): Presence of a nitro group at ortho or para position increases Reason (R): Nitro gjoup, being an electron withdrawing group decreases the electron density over the benzene ring.
A hydrocarbon C5H10 does not react with chlorine in dark but gives a single monochloro compound C5H9CI in bright sunlight. Identify the hydrocarbon.
Molecules whose mirror image is non superimposable over them are known as chiral. Which of the following molecule is chiral in nature?
(a) 2-Bromobutane (b) 1-Bromobutane
(c) 2-Bromopropane (d) 2-Bromopropan-2-ol
Which of the following statements are correct about the reaction intermediate?
(a) Intermediate (iii) is unstable because in this carbon is attached to 5 atoms.
(b) Intermediate (iii) is unstable because carbon atom is sp2 hybridised.
(c) Intermediate (iii) is stable because carbon atom is sp2 hybridised.
(d) Intermediate (iii) is less stable than the reactant (ii).
Which of the following haloalkanes reacts with aqueous KOH most easily? Explain giving reason.
(i) 1-Bromobutane (ii) 2-Bromobutane
(iii) 2-Bromo-2-methylpropane (iv) 2-Chlorobutane
Discuss the nature of C – X bond in the haloarenes.
C – X bond in haloarenes is extremely less reactive towards nucleophilic
Assertion (A): tert-Butyl bromide undergoes Wurtz reaction to give 2, 2, 3, 3-tetramethylbutane.
Reason (R): In Wurtz reaction, alkyl halides react with sodium in dry ether to give hydrocarbon containing double the number of carbon atoms present in the halide.
Assertion (A): Aryl iodides can be prepared by reaction of arenas with iodine in the presence of an oxidizing agent.
Reason (R): Oxidising agent oxidises I2 into HI.
Write structures of the following compounds:
(i) 2-Chloro-3-methylpentane
(ii) 1-Chloro-4-ethylcydohexane
(iii) 4-tert. Butyl-3-iodoheptane
(iv) 1,4-Dibromobut-2-ene
(v) 1-Bromo-4-sec. butyl-2-methylbenzene.
In the following pairs of halogen compounds, which compound undergoes faster SN1 reaction?
