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Transcript
CAEP – 1 ALCOHOLS, ETHERS AND PHENOLS Alcohols : C1A Physical Properties : The lower alcohols are completely soluble in water but as the number of carbon atoms increases, solubility decreases. This solubility in water is due to intermolecular H-bonding between water and alcohols molecules due to their polar character. Increase in C-chain increases organic part hence solubility in water decreases. Isomeric 10, 20, 30 alcohols have solubility in order : 10 > 20 > 30. C1B Method of preparation of Alcohols : (i) Hydration of Alkenes : dil H SO 2 4 Intermediate is carbonium ion that can change to more stable carbanion ion by hydride shift, alkyl or phenyl shift. (ii) Hydrolysis of Alkyl Halides : R – X + aq. NaOH (or H2O) R – OH + NaX (or HX) Reaction can be S N1 or S N 2 . (iii) Reduction of Carbonyl Compounds (including acid derivative) : RCHO 4 4 RCH 2 OH 10 (b) 4 4 (c) (iv) LiAlH or NaBH (a) LiAlH or NaBH Acid, acid halide, ester and anhydride are reduced to 10 alcohol. Hydroboration and oxidation : H O , OH BH in THF 2 CH 3 CH CH 2 3 (CH 3 CH 2 CH 2 ) 3 B 2 CH 3 CH 2 CH 2 OH B(OH ) 3 The hydroboronation-oxidation (HBO) process gives product corresponding to anti-Markownikoff addition of H2O to the carbon-carbon double bond. (v) Oxymercuration-Demercuration : Hg ( OAc ) 2 H 2O NaBH 4 The alcohol obtained corresponds to Markownikov’s addition of water to an Alkene. (vi) (a) Through Grignard Reagent : Addition of Grignard Reagent on carbonyl compounds followed by hydrolysis yields alcohols nature of which depends upon types of carbonyl compounds used. Einstein Classes, Unit No. 102, 103, Vardhman Ring Road Plaza, Vikas Puri Extn., Outer Ring Road New Delhi – 110 018, Ph. : 9312629035, 8527112111 CAEP – 2 H O 3 + H2O R1, R2 can be H, alkyl or aryl but R3 is not H. Grignard reagent with epoxide and after hydrolysis gives 10 alcohol for e.g., (b) H O 2 Practice Problems : 1. 2. 3. Propene, CH3 – CH = CH2 can be converted into 1-propanol, Which of the reagent among the following is ideal to affect the conversion : (a) alkaline KMnO4 (b) B2H6 and alkaline H2O2 (c) O3/Zn (d) OsO4/CH2Cl2 Glycol may be obtained : (a) by the oxidation of ethylene with cold, dilute, alkaline permanganate solution (b) by the hydrolysis of ethylene bromide under reflux with aqueous sodium carbonate solution (c) by the hydrolysis of ethylene chlorohydrin on boiling with aqueous sodium bicarbonate (d) by any of the above methods Which of the following are the starting materials for the Grignard’s synthesis of tert. butyl alcohol (a) CH3MgI + CH3COCH3 (b) CH3MgI + CH3CHOHCH3 (c) CH3CH2MgBr + CH3COCH3 (d) CH3CH2MgBr + CH3CHO [Answers : (1) b (2) d (3) a] C2 Chemical Properties : (i) Dehydration of Alcohol : conc . H SO 2 4 Alcohols leading to conjugated alkenes are more easily dehydrated then those of alcohols leading to non-conjugated alkenes. Dehydration of alcohol is in the order 30 > 20 > 10 as intermediate is carbocation. (ii) Reaction with Halogen Acids : R – OH + HX RX + H2O Intermediate is carbonium ion. The order of reactivity of HX : HI > HBr > HCl for a given alcohol. (iii) Reaction with Phosphorous Halides and Thionyl Chloride : 3R – OH + PX3 3RX + H3PO3 (X = Br, I) R – OH + SOCl2 RCl + SO2 + HCl (iv) Acidic Character of Alcohol : RO – H + Na RO–Na+ + ½ H2 alkoxide Einstein Classes, Unit No. 102, 103, Vardhman Ring Road Plaza, Vikas Puri Extn., Outer Ring Road New Delhi – 110 018, Ph. : 9312629035, 8527112111 CAEP – 3 The order of acidic character of alcohol with metal is : CH3OH > 10 > 20 > 30. The relative acidities is as follows : RCOOH > C6H5OH > H2O > ROH > CH CH > NH3 > RH (v) Ester Formation (alcohol can act as a nucleophile also). Thus reactivity of alcohols for given acid is in order : CH3OH > 10 > 20 > 30 and those of acids for given alcohol is in order : HCOOH > CH3COOH > RCH2COOH > R2CHCOOH > R3CCOOH (vi) Oxidation of Alcohol : 1. Using Cu Cu (a) CH 3 CH 2 OH CH 3CHO H 2 0 300 C 0 1 Aldehyde Cu 0 (b) 300 C Cu 0 (c) 300 C 2. Oxidation using KMnO4/K2Cr2O7 (a) ( i ) KMnO RCH 2OH 4 RCOOH ( ii ) H (b) KMnO , CrO in glacial acetic , acid or K Cr O (c) 3. C3 4 3 2 2 7 Other reagents used for oxidation : (a) PCC (pyridinium chlorochromate) to oxidise 10 alcohols to aldehydes. (b) MnO2 selectively oxidises the OH group of allylic and benylic 10 and 20 alcohols to give aldehydes and ketones respectively. Test to distinguish 10, 20 and 30 Acohols : (a) Lucas Reagent (anhydrous ZnCl2/conc. HCl) (b) Oxidation (c) Victor Meyer Test Einstein Classes, Unit No. 102, 103, Vardhman Ring Road Plaza, Vikas Puri Extn., Outer Ring Road New Delhi – 110 018, Ph. : 9312629035, 8527112111 CAEP – 4 Practice Problems : 1. Identify (Z) in the following reactions series : PBr Alc . KOH H SO , room temp . Ethanol 3 ( X ) ( Y ) 2 4 ( Z ) H 2 O , heat (a) 2. (b) CH3CH2OH (c) CH3CH2OSO3H (d) C2H5OC2H5 An organic compound gives hydrogen on reacting with sodium metal. It also gives iodoform test and forms an aldehyde of molecular formula C2H4O on oxidation with acidified dichromate. The compound is : (a) 3. CH2 = CH2 CH3OH (b) CH3COOH (c) CH3CHO (d) C2H5OH The order of reactivity of the following alcohols, towards conc. HCl is (a) I > II > III > IV (b) I > III > II > IV (c) IV > III > II > I (d) IV > III > I > II [Answers : (1) b (2) d (3) c] C4 Ethers Nomenclature of Ethers : Cyclic ethers can be named in severay ways : In another system, a cyclic three membered ether is named as oxirane and a four membered ether is called oxetane. C5 Methods of Preparation of Ether : (a) Williamson Synthesis : Example : (i) Einstein Classes, Unit No. 102, 103, Vardhman Ring Road Plaza, Vikas Puri Extn., Outer Ring Road New Delhi – 110 018, Ph. : 9312629035, 8527112111 CAEP – 5 (ii) Discussion : Phenol in Williomson’s synthesis : Because phenols are stronger acids than alcohols they can react with NaOH to change into sodium phenoxide ion. But alcohols can be converted into sodium alkoxide ion by reaction with sodium metal only. [Alkyl halide used here can not be aryl halide as it does not undergo nucleophilic substitution easily] R – X can be X = –Cl, –Br, I, (b) – OSO3CH3 etc. Ethers by Intermolecular Dehydration of Alcohols : Alcohols can dehydrate to form alkenes. 10 Alcohols can also dehydrate to form ethers. The formation of ether takes places by S N 2 mechanism mainly, with one molecule acting as the nucleophile and with another protonated molecules of the alcohol acting as the substrate. Finally this method is not useful for the preparation of ether with 30 alcohol because they form alkene too easily. This method is not useful for the praparation of unsymmetrical ethers from primary alcohols because the reaction leads to a mixture of products. (c) Ethers may be prepared by the addition of alcohols to alkenes in the presence of acid e.g. Practice Problems : 1. Which route provides a better synthesis of ether : (a) I (b) II (c) equal (d) none [Answers : (1) b] C6 Reactions of Ethers : (a) Ethers are comparitavely unreactive compounds. The ether linkage are quite stable towards bases, oxidizing agent, reducing agents. Ether can undergo just one kind of reaction, cleavage by acids : HX R O R HX RX R OH RX R X Reactivity of HX : HI > HBr > HCl Einstein Classes, Unit No. 102, 103, Vardhman Ring Road Plaza, Vikas Puri Extn., Outer Ring Road New Delhi – 110 018, Ph. : 9312629035, 8527112111 CAEP – 6 Cleavage takes place only under quite vigourous conditions : concentrated acids (usually HI or HBr) and high temperature. Oxygen of the ether is basic, like the oxygen of alcohol. The initial reaction between an ether and an acid is undoubtedly formation of the protonated ether. Cleavage then involves the nucleophilic attack by halide ion on this protonated ether, with displacement of the weakly basic alcohol molecule. As we might expect primary alkyl group tend to undergo S N 2 and 30 tend to undergo S N1 . (b) Acid Hydrolysis : C 2 H 5 O C 2 H 5 H 3O 2C 2 H 5OH . (c) Acid Hydrolysis of Epoxide : (d) Formation of Halohydrin : H O 3 HX Practice Problems : 1. Ethoxy ethane does not react with (a) 2. HI (b) conc. H2SO4 (c) PCl5 (d) Na An ether, (A) having molecular formula, C6H14O, when treated with excess of HI produced two alkyl iodides which on hydrolysis yield compounds (B) and (C). Oxidation of (B) gives an acid (D), whereas oxidation of (C) results in the formation of a mixed ketone, (E). Thus structures of (A) is (a) (b) (c) (d) CH3CH2CH2CH2OCH2CH3 [Answers : (1) d (2) c] Einstein Classes, Unit No. 102, 103, Vardhman Ring Road Plaza, Vikas Puri Extn., Outer Ring Road New Delhi – 110 018, Ph. : 9312629035, 8527112111 CAEP – 7 PHENOLS C7A Structure and Nomenclature of Phenols : Compounds that have a hydroxyl group directly attached to benzene ring are called phenols. Thus phenol is specific name of hydroxy benzene Compounds that have a hydroxyl group attached to a polycyclic benenoid ring are chemically similar to phenols, but they are called napthols and phenanthrols, e.g. C7B Physical Properties of Phenols : The presence of hydroxy groups in the molecules of phenols means that phenols are like alcohols in being able to form strong intermolecular hydrogen bonds. This hydrogen bonding causes phenols to be associated and therefore to have higher boiling points than hydrocarbons of the same molecular weight. C8A Synthesis of Phenols : Laboratory Synthesis : The most important laboratory synthesis of phenols is by hydrolysis of arenediazonium salts. This method is highly versatile and the conditions required for the diazotisation step and the hydrolysis step are mild. 1. General Reaction : Specific Example : Industrial Synthesis : 2. Hydrolysis of Cholorobenzene (Dow Process) : Einstein Classes, Unit No. 102, 103, Vardhman Ring Road Plaza, Vikas Puri Extn., Outer Ring Road New Delhi – 110 018, Ph. : 9312629035, 8527112111 CAEP – 8 (The mechanism for the reaction probably involves benzyne intermediate) 3. Alkali Fusion of Sodium benzene sulfonate : Sodium benzene sulfonate is melted (fused) with sodium hydroxide at 3500C to produce sodium phenoxide acidification then yields phenol. 4. From Cumene Hydroperoxide : I II This cumene is oxidized to cumene hydrolperoxide Finally, when treated with 10% sulfuric acid, cumene hydroperoxide undergoes a hydrolytic rearrangement that yields phenol and acetone. C8B Chemical Properties of Phenol : 1. Reaction of Phenol as Acid : Strength of phenols as acids : Although phenols are structurally similar to alcohols, they are much stronger acids. The pKa values of most alcohols are of the order of 18. However the pKa values of phenols are smaller than 11. Let us compare two superficially similar compounds cyclohexanol ane phenol. Although phenol is weak acid when compared with carboxylic acid such as acetic acid (pKa = 4.75) phenol is much stronger than cyclohexanol by a factor of 8. Einstein Classes, Unit No. 102, 103, Vardhman Ring Road Plaza, Vikas Puri Extn., Outer Ring Road New Delhi – 110 018, Ph. : 9312629035, 8527112111 CAEP – 9 Phenols are more acidic than cyclohexanol because of following reasons : Phenoxide ion is more resonance stabilized than phenol. Resonance structures of phenoxid ion do not involve charge separation. No resonance structure can be written for cyclohexanol and its anion of course. The benzene ring of phenol acts as if it were as electron withdrawing group when we compare it with cyclohexanol. That causes –OH oxygen to be more positive. Reason : Carbon atom that bears hydroxyl group in phenol is sp2 hybridized, whereas in cyclohexanol sp3 bybridised. Greater the S– characted more electronegative the carbon. Thus carbon of benzene is more electronegative than cyclohexanol. Because phenols are more acidic than water, the following reaction goes almost completion. The reaction between cyclohexanol and NaOH does not occur to significant extent as H2O is stronger acid than 1-wexanol. Acidity order of Phenols : (a) (b) (c) (d) (e) Distinguishing and separating phenols from alcohols and carboxylic acids : 1. Phenols dissolve in aqueous sodium hyroxide whereas most alcohols with six carbon atoms or more do not. Thus we can distinguish them. 2. Alcohols with five carbon atoms are more or less soluble in NaOH but do not form appreciable amount of sodium alkoxide. 3. Most phenols are not solible in aqueous sodium bicarbonate, but carboxylic acids are soluble. Einstein Classes, Unit No. 102, 103, Vardhman Ring Road Plaza, Vikas Puri Extn., Outer Ring Road New Delhi – 110 018, Ph. : 9312629035, 8527112111 CAEP – 10 C9 Other reactions of the O – H Group of Phenols : 1. Phenols react with carboxylic acid anhydrides and acid chlorides to form esters. Thest reactions are similar to alcoholic as we have already discussed in alcohols. 2. Phenols in the Williamson Synthesis : Because phenols are more acidic than alcohols they can be converted to sodium phenoxide through the use of sodium hydroxide (rather than use of sodium metal, the reagent that convert alcohols to alkoxide ion). (a) X General Reaction : ArOH NaOH ArO N a R ArOR NaX [ X Cl , Br , I ] (b) Cleavage of Alkyl-Aryl Ether : conc . HX HX C6 H 5 O R C6 H 5 OH no rxn. RX heat 3. Reactions of the Benzene ring of Phenol : (a) Bromination : The hydroxyl group is a powerful activating group and an ortho-para director in electrophilic substitution. Phenol itself react with Br2 in aqueous solution to yield 2, 4, 6-tribromophenol. Note that a Lewis acid is not required for the bromination of this highly activated ring. (b) Monobromination of phenol can be achieved by carrying out the reaction in carbon disulfide (CS2) at low temperature. Conditions that reduce the electrophilic activity of bromine. The major product is the para isomer. Einstein Classes, Unit No. 102, 103, Vardhman Ring Road Plaza, Vikas Puri Extn., Outer Ring Road New Delhi – 110 018, Ph. : 9312629035, 8527112111 CAEP – 11 4. (a) Nitration : Phenol react with dilute nitric acid to yield a mixture o- and p-nitrophenol Although the yield is relatively low (because of oxidation of ring). The ortho and para isomers can be separated by steam distillation. o-Nitrophenol is more volatile isomer because its intramolecular hydrogen bonding. p-Nitrophenol is less volatile because intermolecular H-bonding causing association among molecules. Thus o-nitrophenol passes over steam and p-Nitrophenol remain in the distillation flask. (b) 5. Sulfonation : Phenol reacts with concentrated sulfuric acid to yield mainly o-sulphonated product if the reaction is carried out at 250C and mainly the para substituted product if the reaction is at 1000C. 6. Kolbe’s Reaction : The phenoxide ion is even more suceptible to electrophilic aromatic substitution, then phenol itself. High reactivity of phenoxide ion is used in a reaction called as kolbe reaction. In kolbe reaction carbon dioxide act as the electrophile. Reaction of salicylic acid with acetic anyhydride yields widely used pain reliver aspirin. Einstein Classes, Unit No. 102, 103, Vardhman Ring Road Plaza, Vikas Puri Extn., Outer Ring Road New Delhi – 110 018, Ph. : 9312629035, 8527112111 CAEP – 12 7. The Clasien rearrangement : Clasien rearrangement can also take place when allyl vinyl ether are present 8. Diel Alder reaction is also pericyclic reaction : 9. Quinones : Oxidation of hydroquinone gives quinone 10. Reimer-Tiemann Reaction : 11. Fries rearrangement : Rearrangement involves RCO+, which then attacks the ring. Einstein Classes, Unit No. 102, 103, Vardhman Ring Road Plaza, Vikas Puri Extn., Outer Ring Road New Delhi – 110 018, Ph. : 9312629035, 8527112111 CAEP – 13 Practice Problems : 1. 2. 3. When phenol is distilled with zinc dust, the main product is (a) biphenyl (b) benzene (c) benzaldehyde (d) phenolphtalein When sodium benzene sulphonate is fused with sodium hydroxide (solid), the product formed is (a) benzene (b) phenol (c) benzene triphenol (d) none of these (c) C6H5COOH Which of the following acids is strongest (a) 4. C6H5SO3H (b) CH3COOH (d) (COOH)2 Phenol is less acidic then (a) p-nitrophenol (b) ethanol (c) cresol (d) benzyl alcohol ( i ) O2 5. Cumene (X) and (Y) (ii ) H 2O, H (X) and (Y) respectively are 6. (a) toluene, propene (b) toluene, propylchloride (c) phenol, acetone (d) phenol, acetaldehyde In the following compounds the order of acidity is 7. (a) III > IV > I > II (b) I > IV > III > II (c) II > I > III > IV (d) IV > III > I > II When phenol reacts with benzene diazonium chloride, the product obtained as (a) phenyl hydrazine (b) p-amino azobenzene (c) phenol hydroxylamine (d) p-hydroxy azobenzene Zinc 8. Conc . HNO 3 Zn Phenol distillati ( A ) Conc ( B )) NaOH (C) . In the above reaction, compounds (A), on . H SO at 60 0 2 4 (B) and (C) are (a) benzene, nitrobenzene and aniline (b) benzene, dinitrobenzene and m-nitroaniline (c) toluene, nitrobenzene and m-toluidine (d) benzene, nitrobenzene and hydrazobenzene [Answers : (1) b (2) b (3) a (4) a (5) c (6) d (7) d (8) d] Einstein Classes, Unit No. 102, 103, Vardhman Ring Road Plaza, Vikas Puri Extn., Outer Ring Road New Delhi – 110 018, Ph. : 9312629035, 8527112111 CAEP – 14 SINGLE CORRECT CHOICE TYPE 1. Identify (Z) in the reaction series, HBr Hydrolysis CH 2 CH 2 ( X ) ( Y ) 6. NaBH LiAlH 4 A B 4 CH 3 OH NaOH A and B I( excess ) ( Z ) 2 2. 3. (a) C2H 5I (b) C2H5OH (c) CHI3 (d) CH3CHO are : A compound (X) of the formula C3H8O yields a compound C3H6O on oxidation. To which of the following class of compounds could (X) belong (a) (a) aldehyde (b) secondard alcohol (c) alkene (d) tert. alcohol Identify (Z) in the series, in both cases (b) Conc . H 2 SO 4 in both cases Br 2 C 3 H 7 OH 0 ( X ) ( Y ) 170 C Excess of ( Z ) Alc . KOH (a) (c) (b) (d) (c) CH3 – C CH 7. (d) 4. 5. How many isomers of C5H11OH will be primary alcohols : (a) 5 (b) 4 (c) 3 (d) 2 An alcohol on oxidation is found to give CH3COOH and CH3CH2COOH. The structure of the alcohol is (a) CH3CH2CH2OH (b) CH3CH2CH(OH)CH3 (c) CH3CH(OH)CH2CH2CH3 (d) (CH3)2C(OH)CH2CH3 formation of A and B is not possible Out of butane, butanol-1, butanal and butanone, the decreasing order of their boiling point is (a) butane > butanol > butanal > butanone (b) butanol > butane > butanal > butanone (c) butanone > butanal > butanol > butane (d) butanol > butanal > butanone > butane 8. + CO2 390 K HCl X ; P product X in the reaction is (a) Einstein Classes, Unit No. 102, 103, Vardhman Ring Road Plaza, Vikas Puri Extn., Outer Ring Road New Delhi – 110 018, Ph. : 9312629035, 8527112111 The CAEP – 15 13. (b) (c) 14. Phenols do not react with (a) sodium bicarbonate (b) sodium hydroxide (c) potassium hydroxide (d) ferric chloride ClOCCH C 6 H 5 OH 3 C 6 H 5 OOCCH NaOH ( aq .) 3 The above reaction is an example of (d) 9. In the reaction PI KCN Hydrolysis C 2 H 5 OH 3 ( A ) ( B ) (C ) 15. The product (C) is (a) acetic acid (b) formic acid (c) oxalic acid (d) propionic acid 16. (a) acetylation (b) benzoylation (c) Schotten-Baumann reaction (d) Reimer-Tiemann reaction Phenol on standing in air develops a red colour due to formation of (a) cyclohexane (b) resorcinol (c) phenoquinone (d) quinol ( i ) CHCl / NaOH Salicyladehyde Phenol 3 ( ii ) H 10. The ether — O — CH 2 — This reaction is known as when treated with conc. HI produces : 17. (a) (b) —CH2OH (a) Gattermann aldehyde synthesis (b) Duff reaction (c) Perkin reaction (d) Reimer-Tiemann reaction Phenol on treatment with dil HNO3 gives (a) picric acid (b) o- and p-nitro phenols (c) o- and m-nitro phenols (d) p- and m- nitro phenols NaBD4 18. (c) —I CH3CH = CH2 product X H 2O2 / OH X is : (a) (d) 11. 12. —OH Artificial oil of bitter almonds or oil of Mirabane is the name given to (a) chlorobenzene (b) benzaldehyde (c) aniline (d) nitrobenzene (b) (c) Which does not have a carboxyl group (a) picric acid (b) ethanoic acid (c) aspirin (d) benzoic acid Einstein Classes, (d) none is correct Unit No. 102, 103, Vardhman Ring Road Plaza, Vikas Puri Extn., Outer Ring Road New Delhi – 110 018, Ph. : 9312629035, 8527112111 CAEP – 16 19. Which route provides a better synthesis of ether : 21. Hydrolysis of the following gave : 3O H CH3CHO + X X is : 20. (a) I (b) II (c) equal (d) none (a) Consider reduction of 2-butanone NaBD 4 B 2 butanone NaBD 4 A D 2O H 2O (b) (c) A, B and C are : (a) in all cases (d) 22. (b) , none is correct Compound (A), C4H10O, is found to be soluble in sulphuric acid. (A) does not react with sodium or potassium permanganate. When (A) is heated with excess of HI, it is converted into a single alkyl halide. The (A) is (a) CH3OCH2CH2CH3 (b) CH3CH2OCH2CH3 , (c) (d) (c) , 23. The product (D) in the following sequence of reaction is : ( aq ) Na C 2 H 4 HBr (A) NaOH (B) ( 3I (C) CH (D) , (d) Einstein Classes, (a) butane (b) ethane (c) propane (d) ethyl methyl ether in all cases Unit No. 102, 103, Vardhman Ring Road Plaza, Vikas Puri Extn., Outer Ring Road New Delhi – 110 018, Ph. : 9312629035, 8527112111 CAEP – 17 24. The major product obtained when 3-phenyl-1, 2-propane-diol is heated with H2SO4 is (a) C6H5 – CH2 – CO – CH3 (b) C6H5 – CH2 – CH2 – CHO (c) C6H5 – CH2 – CH = CH2 (d) 25. When phenol is reacted with CHCl3 and NaOH followed by acidification, salicylaldehyde is obtained. Which of the followed species are involved in the above mentioned reaction as intermediates : (a) 26. The reaction of CH3CH = CH — —OH with HBr gives : (a) CH3CHBrCH2 — —OH (b) CH3CH2CHBr— —OH (c) CH3CHBrCH2— —Br (d) CH3CH2CHBr— —Br (b) (c) ANSWERS (SINGLE CORRECT CHOICE TYPE) (d) Einstein Classes, 1. 2. 3. c b c 4. 5. 6. 7. 8. 9. 10. b c c d d d d 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. d a a a c d b b b b 21. 22. 23. 24. 25. 26. c b d d a b Unit No. 102, 103, Vardhman Ring Road Plaza, Vikas Puri Extn., Outer Ring Road New Delhi – 110 018, Ph. : 9312629035, 8527112111 CAEP – 18 EXCERCISE BASED ON NEW PATTERN 1. COMPREHENSION TYPE Which of the following product(s) is/are obtained ? Comprehension-1 (a) P only Oxiranes are synthesized by treating an alkene with an organic peroxy acid. This process is known as epoxidation. The highly strained three-membered ring in epoxide makes it much more reactive towards nucleophilic substitution than other ethers. (b) Q only (c) Equal mixture of P and Q (d) Unequal mixture of P and Q The most commonly used peroxy acid is Oxiranes are synthesized by treating an alkene with an organic peroxy acid. This process is known as epoxidation. The highly strained three-membered ring in epoxide makes it much more reactive towards nucleophilic substitution than other ethers. Comprehension-2 (a) 4. In the reaction (b) P or/and Q (c) where P is (cis-2,3-dimethyoxirane) and Q is . The (d) 2. The base-catalyzed ring opening of the epoxide is represented as follows CH 2 OH + CH3CH2O– CH 3 P or/ product(s) obtained is/are and Q where P is and Q is 5. (a) P only (b) Q only (c) Equal mixture of P and Q (d) Unequal mixture of P and Q The reaction of C6H5MgBr with the oxirane may be represented as which of the following product(s) is/are obtained ? 3. (a) P only (b) Q only (c) Equal mixture of P and Q (d) Unequal mixture of P and Q The acid-catalyzed ring opening of the expoxide is represented as follows + CH3OH P or/and Q where P is Einstein Classes, and Q is EtOH C6H5MgBr + P or/and Q where P is and Q is H Which of the following product(s) is/are obtained ? (a) P only (b) Q only (c) Equal mixture of P and Q (d) Unequal mixture of P and Q Unit No. 102, 103, Vardhman Ring Road Plaza, Vikas Puri Extn., Outer Ring Road New Delhi – 110 018, Ph. : 9312629035, 8527112111 CAEP – 19 6. The acid-catalyzed hydrolysis of an epoxide gives (a) an alcohol (b) a glycol (c) an aldehyde (d) a ketone 10. Comprehension-3 Given are the two reactions P 11. 7. 8. conc. HCl (CH3)3C – CH2OH Q The reactions (I) and (II), respectively, proceed via (a) (a) S N1 and S N1 mechanisms (b) S N1 and S N 2 mechanisms (c) S N 2 and S N1 mechanisms (d) S N 2 and S N 2 mechanisms conc . HCl (I) (II) The reactions I and II, respectively, proceed via S N1 and S N1 mechanisms (b) S N1 and S N 2 mechanisms (c) S N 2 and S N1 mechanisms (d) S N 2 and S N 2 mechanisms The reactions I and II, respectively, follow (a) first-order and first-order rate laws (b) first-order and second-order rate laws (c) second-order and first-order rate laws (d) second-order and second-order rate laws MATRIX-MATCH TYPE Matching-1 Column - A (A) Column - B H CH 2 CH CH 3 H 2O The products P and Q, respectively, are (a) (p) CH 3 C HCH 3 | and (B) (CH3)3C – CH2 – Cl (b) OH ( i ) C H MgI 2 5 CH 2O (q) ( ii ) H 2O and (C) ( i ) CH MgI CH 3CHO 3 CH3CH2CH2OH (r) ( ii ) H 2 O HOCH2CHOHCH3 (CH3)3C – CH2 – Cl (c) and (D) dil . OH / KMnO CH 2 CHCH 3 4 (s) CH3COOH Matching-2 (d) Column - A and Column - B CH3 | (A) | CH 3 9. 1. Mg , Et O 2 CH 3 C Br 2. CO 2 3. H The reactions I and II, respectively, follow (p) (a) first-order and first-order kinetics (CH3)3CCH2OH (b) first-order and second-order kinetics (c) second-order and first-order kinetics (d) second-order and second-order kinetics Comprehsnion-4 Given are the two reactions (I) n-C4H9OH + HBr C4H9Br + H2O (II) (CH3)3COH + HBr (CH3)2Br + H2O Einstein Classes, CH 3 | (B) 1. CN CH 3 C Br | CH 3 (q) 2. OH , H 2 O 3. H 3 O (CH3)3CCOOH Unit No. 102, 103, Vardhman Ring Road Plaza, Vikas Puri Extn., Outer Ring Road New Delhi – 110 018, Ph. : 9312629035, 8527112111 CAEP – 20 6. CH 3 | (C) 1. KMnO , OH (a) CH 3 C CH 2 OH 4 | Which of the following reactions are wrong . ZnCl CH2OHCH2OH anhyd 2 2. H CH3 (r) (CH3)3CCH2COOH (b) CH3CHO CH2OHCH2OH 773 k (c) 2 4 HOCH2CH2OH (d) 3 4 HOCH2CH2OH CH3 | (D) 1. KMnO , OH CH 3 C CHO 4 | 2. H Conc. H SO distil . CH3 (s) O || (CH 3 ) 3 C C CH 3 Conc. H PO distil . MULTIPLE CORRECT CHOICE TYPE 1. 2. 3. 4. 5. Ethyl bromide can be converted into ethyl alcohol by (a) heating with moist silver oxide (b) heating with dry silver oxide (c) heating with alc KOH (d) heating with aqous KOH 7. Which of the following yield carboxylic acid as the product an oxidation with acidified K2Cr2O7 ? (a) 1-Butanol (b) 1-Propanol (c) 2-Propanol (d) 2-Butanol 8. Which gives turbidity with HBr (a) (b) (c) (d) Select correct statements Which of the following reagents/conditions can convert 2-propanol to acetone ? (a) like, alcohols, phenols also easily protonated (a) LiAlH4 (b) Cu/573 K (b) (c) K2Cr2O7/H+ (d) H2/Pd phenol has smaller dipole moment than methanol (c) Bioling point of ethylene glycol is more than glycerol (d) Glycerol reacts with oxalic acid at 503k to give allyl alcohol Select wrong statements (a) phenol reacts with Na2CO3 and liberates CO2 gas (b) phenols turn blue litmus to red (c) reactivity of methanol with sodium metal is more than that of isopropyl alcohol (d) methanol gives iodoform test 9. Ethanol and ethylene glycol can be distinguished by which of the following tests ? (a) Lucas test (b) Iodoform test Select correct statements (c) Periodic test (a) sodium ethoxide is prepared by reaction of ethanol with aqous sodium hydroxide (d) Victor-Meyer test (b) Picric acid dissolves in NaHCO3 solution (c) Phenol is a weaker acid than carbonic acid (d) Dynamite contains T.N.T. Einstein Classes, 10. Alcohols may act as (a) Oxidising agent (b) Reducing agent (c) Lewis base (d) Bronsted acid Unit No. 102, 103, Vardhman Ring Road Plaza, Vikas Puri Extn., Outer Ring Road New Delhi – 110 018, Ph. : 9312629035, 8527112111 CAEP – 21 Assertion-Reason Type 5. Each question contains STATEMENT-1 (Assertion) and STATEMENT-2 (Reason). Each question has 4 choices (A), (B), (C) and (D) out of which ONLY ONE is correct. 1. (A) Statement-1 is True, Statement-2 is True; Statement-2 is a correct explanation for Statement-1 (B) Statement-1 is True, Statement-2 is True; Statement-2 is NOT a correct explanation for Statement-1 (C) Statement-1 is True, Statement-2 is False (D) Statement-1 is False, Statement-2 is True STATEMENT-2 : Esterification is a reversible reaction. 6. 2. STATEMENT-1 : Alkenes can be change into alcohols by oxymercuration-demercuration reaction. STATEMENT-2 : In this reaction addition occurs according to Markovnikov’s rule. 7. STATEMENT-1 : Acidic strength p-Niprophenol is more than O-Nitrophenol. of STATEMENT-2 : The effect of negative I-effect weakens steadily with increasing distance from the substitument. STATEMENT-1 : We can not dry ethanol by anhydrous CaCl2 STATEMENT-2 : Ethanol form calcium salt (C2H5O)2Ca. STATEMENT-1 : During acid catalysed esterification oxygen atom of alcohol is present in ester molecule. 8. STATEMENT-1 : m-Methoxyphenol is more acidic than phenol. STATEMENT-2 : There is a negative I-effect of –OCH3 group. STATEMENT-1 : Acid catalysed dehydration of t-butanol is faster than n-butanol. STATEMENT-2 : The order of stability of carbocation is 30 > 20 > 10. 3. STATEMENT-1 : Phenol is more reactive then benzene towards electrophillic substitution reactions. STATEMENT-2 : In case of phenol the intermediate carbocation is more resonance stabalised. 4. STATEMENT-1 : Methanol is stronger acid than water. STATEMENT-2 : Among mono-hydric aliphatic alcohols methanol is strongest acid. (Answers) EXCERCISE BASED ON NEW PATTERN COMPREHENSION TYPE 1. d 2. a 3. b 4. a 5. a 7. a 8. c 9. a 10. c 11. c 6. b 2. [A-q; B-q; C-r; D-q] 5. b, c 6. a, b 5. B 6. B MATRIX-MATCH TYPE 1. [A-p; B-q; C-p; D-r] MULTIPLE CORRECT CHOICE TYPE 1. a, d 2. a, b 3. b, c 4. a, d 7. a, b, c 8. b, d 9. b, c 10. c, d 3. A 4. D ASSERTION-REASON TYPE 1. C 2. B 7. B 8. A Einstein Classes, Unit No. 102, 103, Vardhman Ring Road Plaza, Vikas Puri Extn., Outer Ring Road New Delhi – 110 018, Ph. : 9312629035, 8527112111 CAEP – 22 INITIAL STEP EXERCISE (SUBJECTIVE) 1. Convert ethanol into (i) n-propanol; (ii) n-butanol. 2. Arrange EtOH, CF3CH2OH, and CCl3CH2OH in order of increasing strength as acids and give your reasons. 3. Convert propene into (i) n-PrOH; (ii) iso PrOH. 4. Complete the following equation : HNO 3 C 6 H10O 4 (C)(A) heat (C) (iv) C 6 H 6 CH 2 CHCH 2Cl AlCl 3 (A ) HF i ) BH 3 / THF ( (B) heat C9 H10 (C) ( ii ) H 2 O 2 ,OH 5. (v) Convert (i) n – C4H9OH into MeC CMe; (ii) n-PrOH into cis-hex-2-ene. 6. A concentrated aqueous solution of HBr reacts with EtOH to give EtBr, but a concentrated aqueous solution of NaBr does not. Explain. 7. Complete the following equations : (i) 10. ? n-C4H9OH n-C3H7CO2H H ? ? (ii) Me2CO + EtMgI (iii) 2 ? ? EtCOEt + MeMgI 11. 12. 9. 3, 3-Dimethyl-butan-2-ol loses a molecule of water in the presence of conc. H2SO4 to give tetramethyl ethylene as a major product. Suggest a suitable mechanism. n-Butyl alcohol from acetylene. (b) Allyl alcohol from propene. (c) Glycerol from acetone or isopropyl alcohol or propene. 13. (i) ( Alc .) CH 3CH 2 CH 2 OH PBr 5 ( A ) KOH ( B) HBr (C) NH 3 ( D) / I2 Mg CH 3CH 2 OH P ( A ) ( B) How will you obtain : (a) Propanol-1 from propanol-2 (three steps.) (b) Ethanol from methanol (three steps) (c) Vinyl acetate from ethyl alcohol. (d) Ethanol from acetylene. Arrange the following in order of their increasing basicity : H2O, OH—, CH3OH, CH3O— Complete the following equations : (ii) (a) H O (iv) 8. Outline a synthesis of each alcohol from the indicated starting materials : Give reasons for the following : (i) Acid catalysed dehydration of t-butanol is faster than that of n-butanol. (ii) When t-butanol and n-butanol are separately treated with a few drops of dilute KMnO4, in one case only, the purple colour disappears and a brown precipitate is formed. Which of the two alcohols gives the above reaction and what is the brown precipitate ? 14. Write out the structures of all the possible isomeric diols derived from the butanes, and indicate which can be oxidised with periodic acid. 15. Arrange the following in order of increasing b.p., and give your reasons. (CH2OH) 2, (CH 2OMe) 2, HOCH2CH2OMe. ( i ) HCHO ( (C) ii ) H O / H 2 (iii) 2SO 4 C 6 H12 O(A) H C 6 H10 (B) HNO 3 heat Einstein Classes, heat Unit No. 102, 103, Vardhman Ring Road Plaza, Vikas Puri Extn., Outer Ring Road New Delhi – 110 018, Ph. : 9312629035, 8527112111 CAEP – 23 16. Convert : 24. Outline the reaction sequence for the conversion of methanol to ethanol (the number of steps should not be more than three). 25. Convert : (i) n-C4H9OH into MeC CMe; (ii) n-PrOH into cis-hex-2-ene. 26. 17. 18. A compound (X) containing C, H and O is unreactive towards sodium. It does not add up bromine. It does also not react with Schiff’s reagent. On refluxing with excess of HI, (X) gives only (Y). (Y) on hydrolysis gives (Z) which can be converted to (Y) by the action of P and I2. Compound (Z) on oxidation gives an acid of equivalent mass 60. What are (X), (Y) and (Z) ? (ii) 20. 21. 22. An optically active alcohol A (C6H10O) absorbs two moles of hydrogen per mole of A upon catalytic hydrogenation and gives a product B. The compound B is resistant to oxidation by CrO3 and does not show any optical activity. Deduce the structures of A and B. 28. When t-butanol and n-butanol are separately treated with a few drops of dilute KMnO4, in one case only, the purple colour disappears and brown ppt. is formed. Which of the two alcohols gives the above reaction and what is the brown ppt ? 29. Why does ethylene oxide react readily with nucleophiles such as ammonia, whereas THF is inert to nucleophilic attack by ammonia ? 30. Show the steps by which the following alkyne can be converted into seven membered ring. Account for the following : (i) 19. 27. Which of the following is the correct method for synthesising methyl tert-butyl ether and why. (a) (CH3)3C – Br + NaOMe (b) CH3Br + NaOBu 2, 2-Dimethyl oxirane can be cleaved by acid (H+). Write methanism. How would you bring the following conversions : (i) Ethyl iodide to diethyl ether. (ii) Methyl iodide to methyl ethyl ether. . Compound (A), C4H10O, is found to be soluble in sulphuric acid. (A) does not react with sodium or potassium permanganate. When (A) is heated with excess of HI, it is converted into a single alkyl halide. What is (A) ? Which of the two reactions would you use to prepare Me3COMe, and why ? (i) Me3CBr + MeO—K+ ; (ii) Me3CO—K+ + MeBr FINAL STEP EXERCISE (SUBJECTIVE) 1. A, on ozonolysis, gives nonane-2, 8-dione. What is A and how is it formed ? Complete the following equations : (i) HI MeOEt ? (ii) Na Et 2O ? 2. What are A to E in the following reactions ? 3. What reagent could you use for the following conversions ? (iii) 2SO 4 H 2 O Me 2 C CH 2 H ? Me 3COH ? pressure 23. pressure The reaction between HI and C2H4 in EtOH gives predominantly EtI, whereas the reaction with HCl under the same conditions gives predominantly Et2O. Explain. Einstein Classes, (i) MeCO(CH2)2CO2Et MeCHOH(CH2)2CO2Et Unit No. 102, 103, Vardhman Ring Road Plaza, Vikas Puri Extn., Outer Ring Road New Delhi – 110 018, Ph. : 9312629035, 8527112111 CAEP – 24 4. 5. 6. (ii) HO2C(CH2)4COCl HO2C(CH2)4CH2OH (iii) O2N(CH2)2CN O2N(CH2)2CH2NH2 (iv) O2N(CH2)2CH = CH2 H2N(CH2)2 CH = CH2 (v) O2N(CH2)2CH = CH2 O2N(CH2)3CH3 (vi) Me2CHCOCl Me2CHCHO (vii) O2N(CH2)3CHO O2N(CH2)3CH2OH An alcohol (A) when heated with concentrated H2SO4 gives an alkene (B). When (B) is bubbled through bromine water and the product obtained is dehydrohalogenated with excess of sodamide, a new compound (C) is obtained. The compound (C) gives (D) when treated with dilute H 2SO 4 in presence of HgSO4. (D) can also be obtained either by oxidising (A) with KMnO4 or from acetic acid through its calcium salt. Identify (A), (B), (C) and (D). Compound ‘X’ (molecular formula C5H8O) does not react appreciably with Lucas reagent at room temperature but gives a white precipitate with ammonical silver nitrate solution. With excess of MeMgBr, 0.42 g of ‘X’ gives 224 mL of CH4 at STP. Treatment of ‘X’ with H2 in presence of Pt catalyst followed by boiling with HI, gives n-pentane. Suggest structure for ‘X’ and write the equations involved. and (C). Oxidation of (B) gives an acid (D), whereas oxidation of (C) results in the formation of a mixed ketone, (E). Give structures of (A) to (E). 9. A neutral compound (A) having C, H and O, on refluxing with HI yields methyl iodide and an alkyl iodide (B), which contains 74.6 per cent iodine. (B) when treated with moist Ag2O produces a product which undergoes the haloform reaction. Characterize (A), what would have been produced if (B) were treated with dry Ag2O ? 10. An organic compound (A) C4H9Cl on reacting with aqueous KOH gives (B) and on reaction with alcoholic KOH gives (C) which is also formed on passing the vapours of (B) over heated copper. The compound (C) readily decolourises bromine water. Ozonolysis of (C) gives two compounds (D) and (E). Compound (D) reacts with NH2OH to give (F) and the compound (E) reacts with NaOH to give a alcohol (G) and sodium salt (H) of an acid. (D) can also be prepared from propyne on treatment with water in presence of Hg2+ and H2SO4. Identify (A) to (H) with proper reasoning. 11. Compound (A) gives Lucas test in 5 minutes. When 6 gm of (A) is treated with sodium metal, 1120 mL of hydrogen is evolved at STP. Assuming (A) to contain one atom of oxygen per molecule, write the structural formulae of (A). Compound (A) when treated with PBr3, gives compound (B) which when treated with benzene in presence of anhydrous aluminium chloride gives compound (C). Write down the structural formulae of (B) and (C) and also write the reactions involved. 12. How would you convert : Complete the following equations : (i) Toluene to p-nitro benzyl ethyl ether. 13. 0.037 g of an alcohol, ROH, was added to CH3MgI and the gas evolved measured 11.2 cm3 at S.T.P. What is the mol. wt. of ROH ? On dehydration, ROH gives an alkene which on ozonolysis gives acetone as one of the products. ROH on oxidation easily gives an acid containing the same number of carbon atoms. Give structures of ROH and the acid with proper reasoning. 14. Give products of each reaction. (ii) 7. Complete the following equations : (i) CrO 3 (a) (ii) i ) HCO 3 H ( ? ( ii ) H (b) aq . H 2SO 4 1) Hg ( OOCCF3 ) 2 / CH 3OH ( ( 2 ) NaBH 4 (iii) ( i ) B2 H 6 CH 2 CH(CH 2 ) 2 CH CH 2 ( ? ii ) H O ;OH 2 8. 2SO 4 H CH 3OH 2 An ether, (A) having molecular formula, C6H14O, when treated with excess of HI produced two alkyl iodides which on hydrolysis yield compounds (B) Einstein Classes, (c) (d) Unit No. 102, 103, Vardhman Ring Road Plaza, Vikas Puri Extn., Outer Ring Road New Delhi – 110 018, Ph. : 9312629035, 8527112111