2<\/sub>. \n \nPhenols react with aq. NaOH to form sodium phenoxides. \n <\/p>\n(ii) Acidity of Alcohols: \nIt is due to the polar nature of O-H bond. Electron releasing groups increase electron density on O tending to decrease the polarity of O-H bond. The acid strength of alcohols decreases in the order: 1\u00b0> 2\u00b0 > 3\u00b0 alcohols.<\/p>\n
(iii) Acidity of Phenols: \nThe reaction of phenol with aqueous NaOH indicates that phenols are stronger acids than alcohols and water. Acidity of phenols can be explained by resonance. \n \nThe delocalisation of negative charge makes phenoxide ion more stable and favours the ionisation of phenol. \n <\/p>\n
The acidity of phenols increases if an electron-withdrawing group is present at 0- and p- position. Electron releasing groups decrease the acidity.<\/p>\n
(2) Esterification: \nAlcohols and phenols react with carboxylic acids, acid chlorides and acid anhydrides to form esters. \n <\/p>\n
Acefy\/afron: \nIntroduction of acetyl (CH3<\/sub>CO-) group in alcohols or phenols. Acetylation of salicylic acid produces aspirin. \n <\/p>\n(b) Reaction Involving Cleavage of C-0 Bond in Alcohols 1) Reaction with Hydrogen Halides: \nR – OH + HX \u2192 R – X + H2<\/sub>O \n(1) Lucas Test: \nAlcohols are distinguished by Lucas reagent (cone. HCI and ZnCl2<\/sub>). On treating with Lucas reagent, 3\u00b0 alcohol gives immediate turbidity, 2\u00b0 alcohol gives turbidity after few minutes, 10 alcohol do not produce turbidity at room temperature.<\/p>\n(2) Reaction with Phosphorus Trihalide (PCl3<\/sub>): \n3 R – OH + PCl3<\/sub> \u2192 3 R – Cl + H3<\/sub>PO3<\/sub>.<\/p>\n(3) Dehydration: \nAlcohols undergo dehydration to form alkenes on treating cone. H2<\/sub>SO4<\/sub> or H3<\/sub>PO4<\/sub>. \n \ne.g. ethanol undergoes dehydration by heating it with cone. H2<\/sub>SO4<\/sub> at 443 K. \n \nThe relative ease of dehydration of alcohols in the follows the order 3\u00b0 > 2\u00b0 > 1\u00b0<\/p>\n(4) Oxidation: \nIt i nvolves the formation of a \n \n <\/p>\n
1\u00b0 alcohols are oxidised to aldehydes. \n \nStrong oxidising agents such as acidified KMnO4<\/sub> or K2<\/sub>Cr2<\/sub>O7<\/sub> are used forgetting carboxylic acids from alcohols directly. A better reagent for oxidation of 1\u00b0 alcohol to aldehydes is pyridinium chlorochromate (PCC). \n \n2\u00b0 alcohols are oxidised to ketones by CrO3<\/sub>. \n \n3\u00b0 alcohols do not undergo oxidation.<\/p>\nDehydrogenation: \nWhen the vapours of a alcohols are passed over heated Cu at 573 K, \n1\u00b0 alcohols give addehyde. \n \n2\u00b0 alcohols give ketones. \n \n3\u00b0 alcohols undergo dehydration to give alkene. \n <\/p>\n
(c) Reactions of Phenols: \n(1) Electrophilic Aromatic Substitution: \nThe -OH group attached to the benzene ring activates it towards electrophilic substitution. It is 0- and p- directing. \n(i) Nitration: \n \no-Nitrophenol is steam volatile due to intramolecular H – bonding and p-Nitrophenol is less volatile due to intermolecular H -bonding. Hence the mixture can be seperated by steam distillation. \n <\/p>\n
(ii) Halogenation: \n <\/p>\n
(2) Kolbe\u2019s Reaction: \nPhenol, when treated with NaOH, forms sodium phenoxide which undergoes electrophilic substitution with CO2<\/sub> to give 2- Hydroxybenzoic acid (Salicylic acid). \n <\/p>\n(3) Reimer – Tiemann Reaction: \nOn treating phenol with CHCI3 in presence of aq. NaOH, 2 – Hydroxy benzaldehyde (Salicylaldehyde) is formed. \n <\/p>\n
(4) Reaction with Zn Dust: \n <\/p>\n
(5) Oxidation: \n <\/p>\n
Some Commercially Important Alcohols<\/span> \n(1) Methanol (CH3<\/sub> – OH): \nIt is also known as wood spirit. Industrial preparation – Catalytic hydrogenation of carbon monoxide at high pressure and temperature and in the presence of ZnO-Cr2<\/sub>O3<\/sub> catalyst. \n \nMethanol is a colourless liquid, poisonous in nature, cause blindness and in large quantities causes even death. It is used as solvent in paints and varnishes.<\/p>\n(2) Ethanol (C3<\/sub> – CH2<\/sub> – OH): \nObtained commercially by fermentation of sugars. The enzyme invertase present in the yeast converts sugar into glucose and fructose, which undergo fermentation in presence of zymase, another enzyme found in yeast. \n <\/p>\nIt is a colourless liquid, used in paint industry as a solvent. \nRectified spirit – 95.6% ethanol. \nAbsolute alcohol – Pure anhydrous alcohol (100% alcohol) \nPower alcohol – Alcohol mixed with gasoline (1:4 ratio). \nDenatured spirit- The commercial alcohol is made unfit for drinking by mixing in it some CuSO4<\/sub>, pyridine or methanol. It is known as denaturation of alcohol.<\/p>\nEthers<\/span> \n1. Preparation of Ethers: \n(1) By Dehydration of Alcohols: \nAlcohols undergo dehydration in presence of protic acids. (H2<\/sub>SO4<\/sub>, H3<\/sub>PO4<\/sub>) \n <\/p>\n(2) Williamson Synthesis: \nAlkyl halides react with sodium alkoxide to form ether. \nR – X + R\u2019ONa \u2192 R – O – R\u2019 + NaX \nBetter results are obtained if alkyl halide is primary. \n \nIn case of secondary and tertiary akyl halides, elimination competes substitution. \n \nPhenols are also converted to ethers by this method. \n <\/p>\n
2. Physical Properties: \nEthers have much lower boiling points than alcohols. It is due to the presence of H-bonding in alcohols. Lower members of ethers are soluble\/miscible in water as they form hydrogen bonds with a water molecules. \n <\/p>\n
3. Chemical Reactions: \n(1) Cleavage ofC-0 Bond in Ethers: \nIt takes place under drastic conditions with excess of HX. \nR – O – R + HX \u2192 R – X + R – OH \nR – OH + HX \u2192 R – X + H2<\/sub>O \nAlkyl aryl ethers react with HX to give phenol and alkyl halide. \n <\/p>\nOrder of reactivity of hydrogen halides is Hl > HBr > HCI. In the reaction of ether with HI, if the ether contains primary or secondary alkyl groups, it is the lower alkyl group that forms alkyl iodide.<\/p>\n
e.g. CH3<\/sub> – O – CH2<\/sub>CH3<\/sub>l + H – l \u2192 CH3<\/sub>l + CH3<\/sub>CH2<\/sub>OH. When one of the alkyl group is a tertiary group, the halide formed is a tertiary halide. \n <\/p>\n(2) Electrophilic Substitution: \nIt occurs at o- and p- position as the -OR group is o- and p- directing. \n(i) Hologenation: \n <\/p>\n
(ii) Nitration: \nAnisole reacts with cone. HN03 as follows: \n <\/p>\n
(iii) Friedel-Crafts reaction: \n(a) Alkylation: \n \n(b) Acetylation: \n <\/p>\n
We hope the Plus Two Chemistry Notes Chapter 11 Alcohols, Phenols and Ethers help you. If you have any query regarding Plus Two Chemistry Notes Chapter 11 Alcohols, Phenols and Ethers, drop a comment below and we will get back to you at the earliest.<\/p>\n","protected":false},"excerpt":{"rendered":"
Plus Two Chemistry Notes Chapter 11 Alcohols, Phenols and Ethers is part of Plus Two Chemistry Notes. Here we have given Plus Two Chemistry Notes Chapter 11 Alcohols, Phenols and Ethers. Board SCERT, Kerala Text Book NCERT Based Class Plus Two Subject Chemistry Notes Chapter Chapter 11 Chapter Name Alcohols, Phenols and Ethers Category Plus […]<\/p>\n","protected":false},"author":7,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_genesis_hide_title":false,"_genesis_hide_breadcrumbs":false,"_genesis_hide_singular_image":false,"_genesis_hide_footer_widgets":false,"_genesis_custom_body_class":"","_genesis_custom_post_class":"","_genesis_layout":"","footnotes":""},"categories":[42728],"tags":[],"yoast_head":"\n
Plus Two Chemistry Notes Chapter 11 Alcohols, Phenols and Ethers - A Plus Topper<\/title>\n \n \n \n \n \n \n \n \n \n \n \n \n \n \n\t \n\t \n\t \n