How does anisole react with methyl chloride?

The following chemical reaction will take place when anisole undergoes Friedel Craft's alkylation reaction in the presence of catalyst like aluminium halide AlCl 3 which acts as a Lewis acid and carbon sulphide to form 2 -Methoxy toluene and 4 -Methoxy toluene. The major product formed during the reaction is 4 -Methoxy toluene and 2 -Methoxy toluene exists as a minor product. Therefore, the alkyl group is introduced at ortho and para positions.

Explain the mechanism for acid catalysed dehydration of ethanol to ethene.

When alcohols are heated with a protonic acid such as conc. H 2 SO 4 or H 3 PO 4 at 170 ∘ C , they get dehydrated to form alkenes. The chemical reaction is- CH 3 CH 2 OH Ethanol → H 2 SO 4 , 170 ∘ C CH 2 = CH 2 Ethene + H 2 O Mechanism- The acid dehydration of ethanol to yield ethene occurs in three steps- 1. Ethanol combines with a proton from the acid to form a protonated alcohol. 2. The protonated alcohol loses the water molecule and forms a carbocation. 3. The carbocation then eliminates a proton and undergoes rearrangement of electrons to form the alkene.

Between phenol and alcohol which is more acidic? Why?

The acidic character of alcohols is due to the polar nature of O – H bond. An electron-releasing group increases electron density on oxygen tending to decrease the polarity of O - H bond. This decreases the acid strength of alcohols. Whereas, in phenol, the hydroxyl group, is directly attached to the sp 2 hybridised carbon of benzene ring which acts as an electron withdrawing group. Due to this, the charge distribution in the phenol molecule causes the oxygen of – OH group to be positive which increases the polarity of O – H bond and results in an increase in acidification of phenols than that of alcohols.

How anisole reacts with bromine in ethanoic acid? Write the chemical equation for the reaction.

Anisole undergoes bromination with bromine in ethanoic acid even in the absence of iron (III) bromide catalyst to form a mixture of ortho and para bromo anisole. It happens due to the activation of the benzene ring by the methoxy group. It is an example of an electrophilic substitution reaction. The hydrogen atom attached to the benzene ring is replaced with a bromine atom.

How do you prepare methoxy ethane by Williamson's ether synthesis?

Williamson's synthesis is an important laboratory methods for the preparation of symmetrical and unsymmetrical ethers. In this method, an alkyl halide is allowed to react with sodium alkoxide. Ethers containing substituted alkyl groups (secondary or tertiary) may be prepared by this method. This reaction involves S N 2 attack of an alkoxide ion on the primary alkyl halide. Better results are obtained if the alkyl halide is primary. Therefore, the following reaction will take place for the preparation of Methoxyethane from bromoethane and sodium ethoxide- CH 3 Br Bromoethane + CH 3 CH 2 ONa Sodium ethoxide → CH 3 OCH 2 CH 3 Methoxyethane + NaBr

Explain the Kolbe's reaction with equation.

Conversion of phenol to salicylic acid can be carried through Kolbe's reaction. The named reaction involves the generation of phenoxide ion by treating phenol with sodium hydroxide which is reactive than phenol towards electrophilic aromatic substitution. Hence, it undergoes electrophilic substitution with carbon dioxide, a weak electrophile. Ortho-hydroxybenzoic acid is formed as the main reaction product. The following chemical reaction will take place forming different products at different stages-

What is the reagent 'A' used in the following equation? R - COOH → A R - CH 2 OH

Carboxylic acids on reduction with lithium aluminium hydride or with hydrogen in the presence of copper chromite are reduced to alcohols. It can also be carried out with diborane in tetrahydrofuran(THF). The following chemical reaction will take place- R - COOH → or B 2 H 6 , THF LiAlH 4 , ether R - CH 2 OH

E M B I B E

EMBIBE CHAPTER WISE PREVIOUS YEAR PAPERS FOR CHEMISTRY>Chapter -1 - Alcohols, Phenols and Ethers>Karnataka Board-2019>Q 6

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12th Karnataka Board

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Explain the mechanism of acid catalysed dehydration of ethanol to ethene.

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