p-Dichlorobenzene has higher m.p. and lower solubility than those of o-and m-isomers. Discuss.
The p-isomer being more symmetrical fits closely in the crystal lattice and thus has stronger inter-molecular forces of attraction than o- and m-isomers. Since during melting or dissolution, the crystal lattice breaks, therefore, a large amount of energy is needed to melt or dissolve the p-isomer than the corresponding o-and m-isomers. In other words, the melting point of the p-isomer is higher and its solubility lower than the corresponding o-and m-isomers.
Match the structures of compounds given in Column I with the classes of compounds given in Column II.
Which of the following compounds will give racemic mixture on nucleophilic substitution by OH ion?
Diphenyls are potential threat to the environment. How are these produced from arylhalides?
Name the following halides according to IUPAC system and classify them as alkyl, allyl, benzyl (primary, secondary, tertiary), vinyl or aryl halides:
(i)(CH3)2CHCH(Cl)CH3
(ii) CH3CH2CH(CH3)CH(C2H5)CI
(iii) CH3CH2C(CH3)2CH2I
(iv)(CH3)3CCH2CH(Br)C6H5
(v)CH3CH(CH3)CH(Br)CH3
(vi)CH3C(C2H5)2CH2Br
(vii)CH3C(Cl)(C2H5)CH2CH3
(viii)CH3CH=C(CI)CH2CH(CH3)2
(ix)CH3CH=CHC(Br)(CH3)2
(x)P-CIC6H4CH2CH(CH3)2
(xi)m-ClCH2C6H4CH2C(CH3)3
(xii)o-Br -C6H4CH (CH3)CH2CH3
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
Alkyl halides are prepared from alcohol by treating with
(a) HCl + ZnCl2 (b) RedP + Br2
(c) H2SO4 + KI (d) all the above
How can you obtain iodoethane from ethanol when no other iodine containing reagent except Nal is available in the laboratory?
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?
Give the IUPAC names of the following compounds:
(i) CH3CH(CI)CH (Br)CH3 (ii) CHF2CBrCIF (iii) CICH2C=CCH2Br (iv) (CCl3)3CCl
(v)CH3C(p-ClC6H4)2CH(Br)CH3 (vi)(CH3)3CCH=C(CI)C6H4I -p
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]–
Alkyl fluorides are synthesized by heating an alkyl chloride/bromide in presence of or
(a) CaF2 (b) CoF2 (c) Hg,F2 (d) NaF
Draw other resonance structures related to the following structure and find out whether the functional group present in the molecule is ortho, para directing or meta directing.
What are the IUPAC name of the insecticide DDT and benzenehexachloride?
Why is their use banned in India and other countries?
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): 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.
Toluene reacts with a halogen in the presence of iron (III) chloride giving ortho and para halo compounds. The reaction is
(a) electrophilic elimination reaction
(b) electrophilic substitution reaction
(c) free radical addition reaction
(d) nucleophilic substitution reaction
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.
Why is it necessary to avoid even traces of moisture during the use of a Grignard reagent?
Cyanide ion acts as an ambident nucleophile. From which end it acts as a stronger nucleophile in aqueous medium? Give reason for your answer.
How the following conversions can be carried out:
(i) Propene to propan-l-ol (ii) Ethanol to but-l-yne
(iii) l-Bromopropane to 2-bromopropane (iv) Toluene to benzyl alcohol
(v)Benzene to 4-bromonitrobenzene (vi) Benzyl alcohol to 2-phenylethanoic acid
(vii)Ethanol to propanenitrile (viii) Aniline to chlorobenzene
(ix)2-Chlorobutane to 3,4-dimethylhexane (x) 2-Methyl-1 -propene to 2-chk>ro-2-methylpropane.
(xi)Ethyl chloride to propanoic acid (xii) But-1-ene to n-butyliodide
(xiii)2-Chlropropane to 1-propanol (xiv) Isopropyl alcohol to iodoform
(xv)Chlorobenzene to p-nitrophenol (xvi) 2-Bromopropane to 1-bromopropane
(xvii)Chloroethane to butane , (xviii) Benzene to diphenyl
(xix) tert-Butyl bromide to isobutyl bromide (xx) Aniline to phenylisocyanide
Which of the following are secondary bromides?
(a) (CH3),CHBr (b) (CH3)3C CH2Br
(c) CH3CH(Br)CH2CH3 (d) (CH3)2CBrCH2CH3
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.
Identify the products A and B formed in the following reaction:
CH3-CH2-CH=CH-CH3 + HCl–>A+B
Predict all the alkenes that would be formed by dehydrohalogenationof the following halides with sodium ethoxide in ethdnol and identify the major alkene:
(i)1-Bromo-l-methylcyclohexane
(ii)2-Chloro-2-methylbutane.
(ill) 2,2,3-Trimethyl-3-bromopentane.
Explain why
(i)the dipole moment of chlorobenzene is lower than that of cyclohexyl chloride?
(ii)alkyl halides, though polar, are immiscible with water?
(iii)Grignard reagents should be prepared under anhydrous conditions?
What happens when .
(i)n-butyi chloride is treated with alcoholic KOH.
(ii)bromobenzene is treated with Mg in the presence of dry ether.
(iii)chlorobenzene is subjected to hydrolysis.
(iv)ethyl chloride is treated with aqueous. KOH.
(v)methyl bromide is treated with sodium in the presence of dry ether,
(vi) methyl chloride is treated with KCN.
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.
Haloalkanes contain halogen atom(s) attached to sp3 hybridised carbon atom of an alkyl group. Identify haloalkane from the following compounds.
(a) 2-Bromopentane (b) Vinyl chloride (chloroethene)
(c) 2-Chloroacetophenone (d) Trichloromethane
Which of the following compounds can be classified as aryl halides ? (a) p-ClC6H4CH2CH(CH3)2 (b) p-CH3CHCl(C6H4)CH2CH3 (c) o-BrH2CC6H4CH(CH3)CH2CH3 (d) C6H5Cl
Which of the compounds will react faster in SN1 reaction with the –OH ion?
CH3 – CH2 – Cl or C6H5 – CH2 – Cl
Which of the following compounds (a) and (b) will not react with a mixture of NaBr and H2S04. Explain why?
