CHAPTER PRACTICE PROBLEMS CHEMISTRY

Transcription

1 APTER PRACTICE PRBLEMS EMISTRY Electrophilic Aromatic Substitution Name : Batch : Date : rientation influence of groups 1. Predict the characteristics of -NH + as a substituent. activating, o/p directing activating, m-directing deactivating, o/p directing deactivating, m-directing 2. Predict the characteristics of -CN as a substituent. activating, o/p directing activating, m-directing deactivating, o/p directing deactivating, m-directing. Predict the characteristics of -2 as a substituent. activating, o/p directing activating, m-directing deactivating, o/p directing deactivating, m-directing 4. Which of the following substituted benzene derivatives would furnish three isomers when one more substituent is introduced? (a) (b) (c) (d) all ut of A and B, two structures, A exists mainly in enol form, where as B exists mainly in Keto form. Explain in brief. Friedel Crafts reactions 1. (Multiple Choice) All of the following are limitations to the Friedel-Crafts alkylation reaction except highly deactivated aromatic rings are unreactive under Friedel-Crafts conditions. over-alkylation of the ring is a distinct possibility. aniline derivatives are so reactive that over-alkylation is a possibility. carbocation rearrangement can occur during the reaction. (E) Friedel-Crafts reactions do not occur if an amine derivative is atttached to the ring. 2. The major product from the Friedel-Crafts reaction of 1-bromobutane with Al and benzene is likely to be bromobenzene butylbenzene sec-butylbenzene tert-butylbenzene. Explain the following observations C6H5 and C6D6 undergo nitration practically at the same rate under comparable. Friedel Crafts alkylation of toluene with benzyl bromide (using Ga as the Lewis acid catalyst) gives initially ~ 40% each of ortho and para-products and only about 20% meta-product. But after a short time interval, the meta-isomer dominates (~50%) over the ortho (~20%) and (~0%). Why? Explain. Electrophilic aromatic substitution reactions 4. Each of the given molecules contains two rings. Which of the two rings undergoes electrophilic aromatic substitution reaction more readily?give structure of the major product formed on nitration. CNH

2 APTER PRACTICE PRBLEMS EMISTRY N2 N2 2 phenyl benzoate 5. Predict the major product formed when benzene reacts with the following reagents : t-butyl bromide / Al 1-chlorobutane / Al Isobutyl alcohol /BF 2/Fe (E) Isobutene / HF (F) 1, 2-Dichloroethane /Al (G) Benzoyl chloride / Al (H) C / H /Al/Cu (I) 1-Chloro-2, 2-dimethyl propane / Al

3 APTER PRACTICE PRBLEMS EMISTRY 6. Convert C 6H 6 C 6H 5NH 2 C 6H 5( 2) Ph PhI PhH PhF PhPh PhH PhCN p-nitro nitrobenzene Benzene. (E) (F) Benzene Naphthalene Pyrrole C 6H 5C Phenol. phthalic acid. 2-amino pyrrole. Al? 7. Electrophilic aromatic substitution amounts to replacement of E+ for H+ on an aromatic ring. D = heavy hydrogen (deuterium) If a benzene ring included both H and D, the reaction (compared to normal benzene) would be expected to be: faster, replacing D more than H faster, replacing H more than D slower, replacing H more than D same rate, replacing H and D equally 8. To prepare m-chloronitrobenzene from benzene, one should first nitrate, then chlorinate first chlorinate, then nitrate 9. The preferred position for nitration of 4-hydroxybenzoic acid is How many different isomers are there for trichlorobenzene? How many different isomers are there for bromochlorophenol? A mixture of (a) triethylamine, (b) benzoic acid, and (c) butylbenzene is dissolved in diethyl ether. The ether solution is shaken with aqueous H, then separated, and the aqueous solution is saved in flask

4 APTER PRACTICE PRBLEMS EMISTRY 1. The ether solution is next shaken with aqueous NaH, then separated, and that aqueous solution is saved in flask 2. The ether solution is saved in flask.the original three compounds are now located in flasks 1, 2, and. Who's where? 1 (a), 2 (b), (c) 1 (a), 2 (c), (b) 1 (b), 2 (a), (c) 1 (b), 2 (c), (a) Give step/steps for the conversion of given compounds 1. C /Fe? 2/hv 4. C 6H N 2 Cu/dryether/ conc.nh NaN2/ H Sn/conc.H (E) CuCN/HCN H2/ H / C6H5H/ H (F) (G) 6. 2/Fe 50 0 C H2S C 7. Na/NH(l)

5 APTER PRACTICE PRBLEMS EMISTRY 8. + N 2 Cu/dryether/ conc.nh NaN2/ H Sn/conc.H (E) CuCN/HCN H2/ H / C6H5H/ H (F) (G) 1. Which among the following compounds can give elimination reaction? N All of these 2. Which among the given compound will give thermal elimination? 2 2 H 2 All of these. Dehydrohalogenating agent for alcohol is alc. KH/ NaH/ RNa/ All of these 4. Dehydrating agent for alcohol is P25 Conc. H2S4 Anhy. Zn2 All of these 5. Which alkyl halide will give E2 reaction? C AC C C6H5 2 2 F 2 I 6H5 C C2H5 6. Which alcohol will give E1 reaction: C 2H 2 2H All of these H 7. Which compound will D1cb reaction is: CF C6H5 2 2 F N 2 C H All of these 6 5 C 8. Reaction intermediate of E1 reaction is: carbocation carbanion carbene free radical 9. Reaction intermediate of E1cb reaction is: carbocation carbanion benzyne free radical 10. In the given reaction:

6 APTER PRACTICE PRBLEMS EMISTRY [X] will be C N 2 alc.kh/ X 2 C 2 C 2 = Which of the following pairs is correctly matched? Saytzeff rule, least substituted alkene E1cb reaction, Hoffmann elimination Hoffmann rule, most substituted alkene E1 raction, Hoffmann elimination 12. Consider the following statements: (i) In E2 reaction of acyclic compounds both leaving groups should be antiperiplanar (ii) In E2 reaction of cyclohexane derivative both leaving groups should be present on axial position (iii) In E1 reaction product formation takes place by Hoffmann rule. (iv) In E1cb reaction product formation takes place by saytzeff rule. f these statements: i, ii and iii are correct i, ii and iv are correct iii and iv are correct I and ii are correct 1. Consider the following statements: (i) Pyrrolytic elimination is always syn elimination (ii) In pyrrolytic elimination product formation takes place by most stable eclipsed conformation (iii) In pyrrolytic elimination product formation takes place by Hoffmann rule. (iv) In pyrrolytic elimination product formation takes place by Saytzeff rule i, ii and iv are correct i and ii are correct i, ii and iii are correct ii and iii are correct 14. Chloroform on treatment with alc. KH/ gives: Methane Methyl alcohol Formic acid Dichlorocarbene 15. Dichloromethane on treatment with alc. KH/ gives: Carbene dichlorocarbene singlet chlorocarbene Triplet chlorocarbene 16. In which reaction product formation takes place by Saytzeff rule: Na/ 2 4 (i) (ii) C (iii) 2 alc.kh/ C X H (iv) CF Con. H S / alc.kh/ Select the correct answer from the codes given below: i, ii and iii ii and iii i, ii and iv ii, iii and iv 17. In the given reaction: [X] will be C 2 alc.kh/ X 2

7 APTER PRACTICE PRBLEMS EMISTRY 2 C =2 18. In the given reaction: H Conc. H S / 2 4 Number of alkenes formed will be: one two three four 1. 2 Major Product (P), P is 2 / Al 2. A A is Mixture of and. Mg A D 2 B Identify B in the reaction. D D

8 APTER PRACTICE PRBLEMS EMISTRY 19. Which one of the following is correctly matched: 2 2 N, E2 reaction C, E2 reaction H 2 2H, E1 reaction C, E1cb reaction 20. Which of the following is correctly matched? H C, E1 reaction 2 H, E1cb reaction H C, thermal elimination 2 2 N 1. Ethylbenzene can be prepared from acetophenone with Zn(Hg) and H LiAlH acetophenone with 4 C2H5 benzene reacts with in presence of toluene reacts with in presence of Al Al H, E1cb reaction 2. Which of the following is an electrophilic substitution reaction? H S + H 2 S 4 + S conc. + HN conc. 2 N + H conc. H 2 S 4 + H 2 H P 4 + H C 2 h H C HC + H 2

9 APTER PRACTICE PRBLEMS EMISTRY Assignment 5 Concepts of Acids and Bases ANSWER SHEET Questions Answers Questions Answers Questions Answers 1 D 21 C 1 B 2 D 22 D 2 D D 2 C A 4 D 24 C 4 B 5 A 25 D 5 D 6 A 26 B 6 D 7 D 27 B 7 D 8 D 28 C 8 D 9 B 29 B 9 A 10 C 0 A 40 B