After studying this Unit, you will be able to. • name alcohols, phenols and ethers according to the IUPAC system of nomenclature;. • discuss the reactions. Free PDF download of Class 12 Chemistry revision notes & short key-notes for Chapter 11 - Alcohols, Phenols and Ethers to score high marks in exams, prepared by expert Chemistry teachers from latest edition of CBSE(NCERT) books. Previous Year Question Papers CBSE Class Chemistry Notes for class 12 Chapter Alcohols, Phenols and Ethers. Alcohols and Phenols. Alcohols and phenols are formed when a hydrogen atom in.
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Learn to recognize the alcohol, phenol, and ether functional groups. • Learn the IUPAC system for naming alcohols, phenols, and ethers. • Learn the important. The structures for alcohols, phenols, thiols, ethers and thioethers are shown below. Alkyl-OH. Alkyl-SH. Ph-OH. R-O-R R-S-R alcohol phenol ether thioether thiol. Class XII Chapter 11 – Alcohols Phenols and Ethers Chemistry Question Write IUPAC names of the following compounds: (i) (ii) (iii) (iv) (v) (vi) (vii) (viii).
Thus, the relative order of reactivity of the alcohols is justified. Acidic catalyst converts hydroxyl group into a good leaving group. Since, the rate determining step is the formation of carbocation, the ease of dehydration is Mechanism Step I Formation of protonated alcohol Step II Formation of carbocation Step III Formation of ethene by elimination of a proton In dehydration reaction, highly substituted alkene is the major product and if the major product is capable of showing cis-trans isomerism, trans-product is the major product.
A common reagent that selectively oxidises a primary alcohol to an aldehyde and no further is pyridinium chlorochromate pCC. Reactions of Phenols i Electrophilic substitution reactions The -OH group attached to the benzene ring activates it towards electrophilic substitution at ortho and para positions. This is because o-nitrophenol is steam volatile due to intramolecular hydrogen bonding while p nitrophenol is less volatile due to intermolecular hydrogen bonding which causes the association of molecules.
It is prepared as follows. It is obtained by destructive distillation of wood. Drinking of methanol causes blindness. It is used In the preparation of various beverages containing different percentages. Dihydric Alcohols These are generally called glycols because of their sweet taste.
Methods of Preparation Physical Properties 1. It is a colourless, syrupy liquid with sweet taste. Because of its tendency of formation of H-bonds, it is miscible with H2O and ethanol but not with ether. Chemical Properties It gives all the general reactions of -OH group.
The per-iodic acid cleavage of 1,2-g1ycols is sometimes called Malaprade reaction. Method of Preparation It is obtained as a by product in saponification reaction. Physical Properties 1.
It is a colourless, odourless, viscous and hygroscopic liquid. It is sweet in taste and steam volatile. It is soluble in water but insoluble in ether. Due to excessive H-bonding, it is highly viscous and has high boiling point.
Some of its specific reactions are : Glyceryl trinitrate or tri nitroglycerine, when adsorbed on Kieselguhr is known as dynamite. For example: Write the mechanism of acid-catalysed dehydration of ethanol to yield ethene. Class XII Chapter 11 — Alcohols Phenols and Ethers Chemistry Williamson ether synthesis is a laboratory method to prepare symmetrical and unsymmetrical ethers by allowing alkyl halides to react with sodium alkoxides.
Better results are obtained in case of primary alkyl halides. After the formation of ethene. Page 16 of Answer i If propene is allowed to react with water in the presence of an acid as a catalyst. How are the following conversions carried out? The acid consumed in step 1 is released in Step 3.
Name the reagents used in the following reactions: Extra energy is required to break these hydrogen bonds. Give reason for the higher boiling point of ethanol in comparison to methoxymethane. H3PO4 to give 1-propoxypropane.
Propanol undergoes dehydration in the presence of protic acids such as H2SO4. Answer The reaction of Williamson synthesis involves SN2 attack of an alkoxide ion on a primary alkyl halide.
Illustrate with examples the limitations of Williamson synthesis for the preparation of certain types of ethers. The mechanism of this reaction involves the following three steps: Page 20 of But if secondary or tertiary alkyl halides are taken in place of primary alkyl halides.
Answer 1-propoxypropane can be synthesized from propanol by dehydration.
This is because alkoxides are nucleophiles as well as strong bases. How is 1-propoxypropane synthesised from propanol? Write mechanism of this reaction. Preparation of ethers by acid dehydration of secondary or tertiary alcohols is not a suitable method. In case of secondary or tertiary alcohols. Answer The formation of ethers by dehydration of alcohol is a bimolecular reaction SN2 involving the attack of an alcohol molecule on a protonated alcohol molecule. Write the equation of the reaction of hydrogen iodide with: In the method.
Protonation Step 2: Nucleophilic attack Step 3: Deprotonation Question Answer i In aryl alkyl ethers. Page 22 of Explain the fact that in aryl alkyl ethers i The alkoxy group activates the benzene ring towards electrophilic substitution and ii It directs the incoming substituents to ortho and para positions in benzene ring.
Answer i Page 23 of Write the mechanism of the reaction of HI with methoxymethane. Answer The mechanism of the reaction of HI with methoxymethane involves the following steps: Protonation of methoxymethane: When HI is in excess and the reaction is carried out at a high temperature. Write equations of the following reactions: Show how would you synthesise the following alcohols from appropriate alkenes?
When 3-methylbutanol is treated with HBr. Give a mechanism for this reaction. Answer The mechanism of the given reaction involves the following steps: Protonation Page 26 of The secondary carbocation formed in step II rearranges to a more stable tertiary carbocation by a hydride ion shift from 3rd carbon atom.
Re-arrangement by the hydride-ion shift Step 4: Nucleophilic attack Page 27 of Classify the following as primary. Identify allylic alcohols in the above examples.
Answer The alcohols given in ii and vi are allylic alcohols. Show how are the following alcohols prepared by the reaction of a suitable Grignard reagent on methanal? Write structures of the products of the following reactions: Answer Page 33 of Ortho and para nitrophenols are more acidic than phenol.
Draw the resonance structures of the corresponding phenoxide ions. Predict the major product of acid catalysed dehydration of i 1-methylcyclohexanol and ii butanol Answer i.
Class XII Chapter 11 — Alcohols Phenols and Ethers Chemistry Resonance structure of the phenoxide ion Resonance structures of p-nitrophenoxide ion Resonance structures of m-nitrophenoxide ion It can be observed that the presence of nitro groups increases the stability of phenoxide ion. Write the equations involved in the following reactions: Write the reactions of Williamson synthesis of 2-ethoxymethylpentane starting from ethanol and 3-methylpentanol.
Answer In Williamson synthesis. Reimer-Tiemann reaction ii. Page 35 of In the reaction. In set i. Which of the following is an appropriate set of reactants for the preparation of 1- methoxynitrobenzene and why?
Predict the products of the following reactions: Flag for inappropriate content. Related titles. Jump to Page. Search inside document. Answer i ii iii iv v vi Page 3 of 37 3: Documents Similar To chemistry-alcohols-phenols-and-ethers.
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