Solution: (b) Conversion of alkyl halides into alcohols involves substitution reaction. (b) LiAlH4 Solution: (b) In o-nitrophenol, nitro group is present at ortho position. Reason (R): Addition of water in acidic medium proceeds through the formation of primary carbocation. Solution: (a, c, d) CrO3 in anhydrous medium, PCC and heating in presence of Cu (dehydrogenation) will oxidize primary alcohols to aldehydes. What happens when benzene diazonium chloride is heated with water? Solution: (d) Bond angle in ethers is slightly more than the tetrahedral angle due to repulsion between two bulky alkyl group. Due to the presence of the negative charge, the oxygen atom of the phenoxide ion donates electrons to the benzene ring to a large extent. Here we have given NCERT Exemplar Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers. Question 52. Solution: The alcohol combine with HCl to form protonated alcohol. If the molecules have a permanent dipole moment ~ 0, the total dipole moment in and external eld is: ~= ~ 0 + ~I (14) Orientation polarization P is only observed when the molecules have a permanent Question 55. Therefore, the reactivity of benzyl alcohols increases in the order: (II) < (III)<(I). It is volatile in nature and its vapour are explosive in nature. Solution: (d) IUPAC name of the compound is 2-propoxypropane. Question 62. Solution: (a) Only one alcohol contains chiral carbon atom. Propan-l-ol < butan-2-ol < butan-l-ol < pentan-l-ol. Solution: Alcohols are soluble in water because of hydrogen bonding with water molecules. Note: In aqueous solution, phenol ionizes to give phenoxide ion. Solution: In phenol, oxygen atom is attached to sp2-hybridised carbon atom while in alcohol, it is attached to sp3-hybridised carbon atom. The process of converting alkyl halides into alcohols involves . Q:-Describe a method for the identification of primary, secondary and tertiary amines. (iv) Hydroquinone is also known as quinol. Solution: (i —» d), (ii -» a), (iii -> f), (iv -> e), (v -> c), (vi -> b) . Consequently, the ring is activated slightly and, therefore, only monosubstitution occurs. Alcohols react with sodium metal to form alkoxides and hydrogen is liberated: This intermediate 3° carbocation is more stable than 2° carbocation as well as 1° carbocation. Solution: Biocatalysts are complex organic compounds which act as catalysts in reaction taking place in living organism. Hence former is more volatile than latter. (c) Pyridinium chlorochromate Solution: (a, c) Phenol reacts with bromine water to give a colourless tribromo derivative and gives a violet coloured complex with FeCl3. © copyright 2003-2020 Study.com. Question 21. Consequently, o-nitrophenol has a lower boiling point (214°C) than the others (m-nitrophenol 290°C; p-nitrophenol 279°C). Ether have a bent structure with a C-O-C bond angle of -112 degree Dipole moment is due to charge separation in polar molecules. Therefore, greater is the number, of alkyl groups present, smaller will be reactivity of alcohol. Assertion (A): Ethanol is a weaker acid than phenol. This contains about 50% sugar. Therefore, -NO2 group stabilizes the phenoxide ion. (a) Name the starting material used in the industrial preparation of phenol. Therefore the dipole moment of methanol is higher than phenol. Question 31. Hence the order of formation of alkyl halide in the above reaction is pri. (a) C6H5OH (b) C6H5CH2OH (C) (CH3)3COH (d) C2H5OH Nitration which is an electrophilic substitution reaction takes place more readily where the electron density is more. Explain a process in which a biocatalyst is used in industrial preparation of a compound known to you. Alcohols are very weak acids. Q.45. This is because the phenoxide ion obtained after the removal of H+ is resonance stabilised, while the ethoxide ion obtained after the removal of H+ is destabilised by +1 effect of ethyl group. Thus, o-nitrophenol does not form H-bond with H2O but m-nitrophenol and p-nitrophenol form H-bonds with H2O. Solution: In case of alkyl aryl ethers, the products are always phenol and an alkyl halide because due to resonance C6H5 – O bond has partial double bond character. Explain why alcohols and ethers of comparable molecular mass have different boiling points. (ii) In (CH3)2CH – O – CH3 unsymmetrical ether, one alkyl group is primary while another is secondary. Solution: 2-Chloroethanol is more acidic, due to -I effect of chlorine atom. As phenol is also known as, carbolic acid cannot be considered as aromatic alcohol. Explain. Solution: In phendl, C – O bond is less polar due to electron withdrawing effect of benzene ring, whereas in methanol C – O bond is more polar due to electron releasing effect of—CH3 group. answer! Solution: Assertion (A): Bond angle in ethers is slightly less than the tetrahedral angle. g. (i) Alcohol (ii) Phenols exhibit an (iii) Phenols has a smaller (iv) 2,3-dimethylbutanol has o ls exhibit an acidic character. Question 19. Question 18. Reason (R): Bromine polarizes in carbon disulphide. Thus, the halide ion attacks the smaller alkyl group and the products are BITSAT 2012: The vapour pressure of due to (A) Dipole moment (B) Dipole- dipole interaction (C) H- bonding (D) Lattice structure. (c) treatment with pyridinium chlorochromate Since -NO2 group is stronger electron withdrawing than -Cl group, therefore, stability of carbocation increases in the order: 0 1995 by John Wiley & Sons, Inc. Introduction T Which of the following reaction will yield phenol? The action of enzyme is inhibited when the concentration of alcohol exceeds 14%. NCERT Exemplar ProblemsMathsPhysicsChemistryBiology. The enzyme zymase (found in yeast) converts glucose and fructose to ethanol. HNO3. (a) Propan-1 -ol, butan-2-ol, butan-1 -ol, pentan-l-ol Do ethers have dipole moments? During fermentation CO2 is released. (d) Reaction with RMgX followed by hydrolysis (c) Explain why Lewis acid is not required in bromination of pheflol? Thus phenol is a stronger acid than ethanol. Thus, R – O – R is polar. (iii) In this case, one of the alkyl group is tertiary and the other is primary. What is the correct order of reactivity of alcohols in the following reaction? (c) dehydrohalogenation reaction (d) rearrangement reaction Question 58. Solution: Nitro group is electron is electron withdrawing while -CH3 group is electron releasing. Question 65. ANS (1) -OH group increases the electron density more at ortho and para positions through its electron releasing resonance effect. < sec. Question 43. Question 64. Which of the following is most acidic? (iii) Phenol is converted into picric acid (2, 4, 6-trinitro-phenol) by the reaction of phenol with cone. (v) Neutral ferric chloride give purple/red colour when treated with phenols. So, it is used in perfumes. (ii) Ethanol is a good solvent for fatty and waxy substances. Solution: The mechanism of acid catalysed addition of water (hydration) to alkenes involves the following three steps: Which one of the following compounds will not be soluble in sodium bicarbonate ? . 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Question 46. (c) Phenol (d) m-Chlorophenol Question 12. That's … How many alcohols with molecular formula C4H10O are chiral in nature? 4. As grapes ripen, the quantity of sugar increases and the yeast grows on the skin of the grapes. Nitration of phenol gives ortho- and para- products only. We hope the NCERT Exemplar Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers help you. HNO3 and with cone. Question 13. Why para-nitrophenol is more acidic than ortho-nitrophenol in hindi: Acidity of nitrophenol - Duration: ... Dipole Moment, Molecular Polarity & Percent Ionic Character - Duration: 16:01. Solution: (b, c) In benzylic alcohols, the -OH group is attached to a sp3 hybridised carbon atom next to an aromatic ring. Write the mechanism of the reaction of HI with methoxybenzene. On the other hand, in o-methylphenol and in o-methoxyphenol and in o-methoxyphenol, electron releasing group (-CH3-OCH3) . Question 59. Reason (R): Lewis acid polarizes the bromine molecule. So, the order of reactivity of alcohols in the given reaction is 3° > 2° > 1°. C6H5OH + NaOH -> C6H5ONa + H2O. The subsequent acidification of sodium salicylate gives. IUPAC name of the compound Explain why nucleophilic substitution reactions are not very common in phenols. Similarly methoxy group is an electron releasing group which decreases the acidity of phenol and the effect is more pronounced at ortho and para positions. Mark the correct order of decreasing acid strength of the following Reason (R): Nitro group helps in the stabilization of the phenoxide ion by dispersal of negative charge due to resonance. In compounds (a) and (d), the -OH group is attached to a sp3 hybridised carbon atom but this carbon is not attached to the benzene ring. Ortho nitrophenol is much more volatile in steam due to chelation. Solution: (i —> d), (ii —» e), (iii —> b), (iv —» a) First unstable intermediate is formed which undergoes a proton shift to form sodium salicylate. Phenol is less acidic than . show Force display type and show dipole moments in molecules. ... Ortho-nitrophenol has intramolecular H-bonding and paranitrophenol has intermolecular H-bonding. Solution: This can be explained as under: (b) Propan-1 -ol, butan-1 -ol, butan-2-ol, pentan-1 -ol Write steps to carry out the conversion of phenol to aspirin. Question 5. (a) CrO3 in anhydrous medium Question 44. The dipole moment has magnitude and direction. This helps in the attachment of Co2 which is a weak electrophile to the benzene ring finally giving salicylic acid. A small percentage of it is used in antifreeze formulations. It forms intra-molecular H bonds while the para- and meta isomers cannot do so. Solution: Question 24. (i) Cresols are organic compounds which are methyl phenols. So a separation of charges occurs. the presence of the intramolecular hydrogen bonding in ortho-nitrophenol have been studied. 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Reactions of fatty acid with NaOH through the formation of intermediate carbocation chloride shows nucleophilic reaction! Are: Question 35 2-chloroethanol is more stable than 2° carbocation as well as carbocation... Colorless to pale yellow liquid used to treat acne, seborrheic dermatitis and other skin.., R – O bond leading to its dipole moment of ortho nitrophenol in molecular weight )!: Propan-l-ol < butan-2-ol < butan-l-ol < pentan-l-ol out by adding hydrogen in presence of,! Pyridine and HC1 ( Pyridinium chlorochromate ) C3H5 N HCr03Cl form H-bonds H2O. Converts glucose and fructose carbocation as well as 1° carbocation p-xylene, the dipole moment of ortho nitrophenol of bromine occurs even the! There are three forms of cresol: o-cresol, p-cresol and w-cresol dichlorobenzene is a colorless pale! Substitution and its rate depends upon the group already present in the mechanism... While the para- and meta isomers can not do so ring the bond. 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