SELF-EVALUATION TEST — 1 1. RCH,Br+ Nal" pi-+ NaBr Which of the following statement is correct? (@) Reaction can take place in acetic acid (2) ‘This reaction is called Swartz reaction (c) The reaction shifts to forward direction using Le Chatellier's principle (@ The reaction will take place even if Bris replaced by 2. Flaorobenzene can be synthesised by (a) Phenol + HF + KF—*> (&) CH NICr— (Coe Es Br @ +NaF — 3. 100 mL of C,H.MgBr, on treatment with CH,OH produces 2,24 mL of gas at STP, the mass of gas produced is (a) Smg (b) 4mg (ce) Img (d) 6 mg 4. (CH,),CCI reacts with C,H,ONa by (@) Sy @) Se (o) (@) £, mechanism 5. Assertion (A): Alkyl iodide can be prepared by treated RCV/RBr with Nal in Acetone. ‘Reason (R): NaCl/NaBr are soluble in acetone while Nal is not, 6. Assertion (A): Sy! reaction is generally carried out in polar protic solvent like H,O, alcohol, acetic acid etc. Reason (R): CgH,CH(C,H,)Br is less reactive than C(H,CH(CH,)Br in Sy1 reaction, 7. What happens when (a)_1-Chloro butane is treated with alc. KOH. (4) Chlorobenzene is treated with Na in dry ether, 8. Why haloarenes are not reactive towards nucleophilic substitution reaction? Give two reasons. 9. (a) Which isomer of C,H, give 2 single mono chloro product CHCl in bright sunlight? (b) Arrange the following compounds in increasing order of reactivity towards S,2 reaction 2-Bromo pentane, 1-Bromo pentane, 2-Bromo-2-methyl butane. (c) Identify ‘A’ and ‘B" in the following: Br Mg #0 Dry ether A B 10. u. (a) Out of (CH,),C—Br and (CH,),C—I, which one is more reactive towards Syl and why? (6) Why dexiro and laevo—rotatory isomers of Buter-2-0l are difficult to separate by fractional distillation? () Owor (a mi on 1, Which one is more reactive towards $2 reaction and way? which one is more reactive towards S,2 reaction and why? (©) Out role moe Which one is optically active and why? Read the following passage and answer the questions that follow: ‘The substitution reaction of alkyl halides occurs in Syl or $2 mechanism whatever mechanism alkyl halide follow for substitution reaction to occur, the polarity of the carbon-halogen bond is responsible for the substitution reaction, The rate of S,1 reactions are governed by the stability of carbocation where as for 8,2 reactions sterie factor is the deciding factor. If the starting material is a chiral compound, we may end up with an inverted product orracemic mixture depending ‘upon the type of mechanism followed by alkyl halide. Cleavage of ethers with HI is also governed by steric factor and stability of carbocation which indicates that in organic chemistry, these two major factors help us in deciding the kind of product formed, (a) Why do optically active tert. halides undergo recemisation? () Name the instrument used for measuring optical rotation, (©) 2-Bromo butane on heating with ale KOH gives 81% 2-Butcne. Give reason, Name the type of reaction. Or How is Anilsole prepared from Williamson synthesis? What produets will it give on reaction with HI?[Ne i tions 1. Which of the following reaction will yield 2, 2-dibromo propane? (@ HC=C—CH, + 24D —> () CHy—CH=CH—B:——> (¢) HC=CH+2HBr—> (d) CH,—CH+CH, + HBr—> 2, Toluene reacts with Cl, in presence of sunlight to give (a) Benzyl chloride (6) ¢-chlorotoluene (©) petiorotolueac (a) Both (b) and (c) NO, HNOJHCI KI 3. Spa A Be (a) p-iodo aniline (c) p-dinitro benzene (6) p-nitto iodobenzene (@) none of these Bia ap a Gaon? “X's Bi A OCH, (a) @ ec Br Br Br Br “Ch, «Ch OH ocH, 5, Assertion (A): 4-Nitro chlorobenzene undergoes nucleophilic substitution reaction more readily. Reason (2); NO, group is electron withdrawing and destablises intermediate carbocation. 6. Assertion (A); Bromobenzene, on reaction with Bry Fe gives 1, 4-dibromobenzene. Reason (R): —I is dominating over +R effect 7. (@) Which alkyl halide from the following pairs would you expect to react more rapidly by an 8,2 mechanism and why? cH,—cH, an —CH,; CH,—CH,—CH,—CH,—Br Br (0) Inversion occurs in S,2 reactions. Why? 8. (8) Arrange the following in increasing order of their boiling points: 1 -chloropropane, 2-chloropropane, I-chlorobutane (ii) What is an ambjdent nucleophile? Give one example. 9, Justify and arrange the following in increasing order of reactivity towards asked displacement. (a) 1-Bromo butane, 2-Bromo butane, 2-Bromo-2- methyl propane (S,1 reaction) (6) 1-Bromo butane, 2-Bromo butane, 2-Bromo-2- methyl propane (S,2 reaction) 10, Compound ‘A’ with molecular formula C,H,Br is treated with aq. KOH solution. The rate of this reaction depends upon the concentration of the compound A EVALUATI u EST-2 only, When anather 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. () Write down the struetural formula of both compounds ‘A’ and ‘B’. (i) Out of these two compounds, which one will be converted to the product with inverted configuration. Read the following passage and answer the questions that follow: Influences of halogen : No matter which mechanism the nucleophilic substitution reaction is based on, the leaving group always leave the central carbon stom with electron pair. Therefore, the weaker the alkalinity of leaving group is, the more stable the anion formed is and it will be more easier for the leaving group to Teave the central carbon atom; that isto say. the reactant is more easier to be substituted. The alkalinity order of halogen ion is! < Br < Cl Br>cr> -. Therefore, in four halides with the same alkyl and different halogens, the order of substitution reaction rate isRI>RBr> RCI> RF. In addition, ifthe leaving group is very easy to Teave, many carbocation intermediates are generated in the reaction and the reaction is based ‘on Sy! mechanism. If the leaving group is not easy to leave, the reaction is based on S,,? mechanism. Influences of solvent polarity: In S,1 reaction, the polarity of the system increases from the reactant to the transition state, because polar solvent has a greater sabilizing effecton the transition state than the reactant, thereby reduce activation energy and accelerate the reaction. In $2 reaction, the polarity of the system generally does not change from the reactant to the transition state and only charge dispersion occurs. At this time, polar solvent has a great stabilizing effect ‘on Nu than the transition state, thereby inereasing activation energy and slow down the reaction rate. In a word, the level of solvent polarity has influence on both Sy and $.2 reactions, but with different results. Generally speaking, weak polar solvent is favourable for S,.? reaction, while strong polar solvent js favorable for Sy! reaction, because only under the action of polar solvent can halogenated hydrocarbon dissociate into carbocation and halogen ion and solvents with a strong polarity is favourable for solvation of carbocation, mcreasing its stability. Generally speaking, the substitution reaction of tertiary haloalkane is based on Sy] mechanism in solvents with a strong polarity (for example, ethanol containing water). Answer the following questions: (a) WhyisSy1 mechanism favoured in polar solvent? (6) Why does 1-iodo-2,2-dimethyl propane react faster than 1-fluoro-2,2-dimethyl propane? ‘Why S,? mechanism is favoured by non-polar solvents? Give example. Or ‘Why water has higher dielectric constant (79) than Chloroform: (4.72)1 Is chloroform soluble in water? Give reason. © ©