10.21 How will you bring about the following conversions? (i) Ethanol to but-1-yne (ii) Ethane to bromoethene (iii) Propene to 1-nitropropane (iv) Toluene to benzyl alcohol (v) Propene to propyne (vi) Ethanol to ethyl fluoride (vii) Bromomethane to propanone (viii) But-1-ene to but-2-ene (ix) 1- Chlorobutane to n-octane (x) Benzene to biphenyl.(Advanced)

(i) Since the conversion of ethanol to but-1-yne involves the addition the two extra carbons that is why the conversion is carried out in 3 steps.

1. In the first step ethanol is treated with thionyl chloride (SOCl₂) in the presence of pyridine to give chloroethane

• In the second step the acetylene is treated with sodamide(NaNH₂) in the presence of liquid ammonia to give sodium acetylide

• The last step involves the reaction between chloroethane and sodium acetylide to give the final product as the But-1-yne and NaCl as the by-product.

• The bromination of ethane (Br₂ in the presence of light at 520-670K) gives bromoethane which on further treatme

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(i) Since the conversion of ethanol to but-1-yne involves the addition the two extra carbons that is why the conversion is carried out in 3 steps.

1. In the first step ethanol is treated with thionyl chloride (SOCl₂) in the presence of pyridine to give chloroethane

• In the second step the acetylene is treated with sodamide(NaNH₂) in the presence of liquid ammonia to give sodium acetylide

• The last step involves the reaction between chloroethane and sodium acetylide to give the final product as the But-1-yne and NaCl as the by-product.

• The bromination of ethane (Br₂ in the presence of light at 520-670K) gives bromoethane which on further treatment with alcoholic KOH results in the alkene called ethane which again on bromination with Br₂/CCl₄ gives dibromide(vicinal bromide) called 1,2-dibromoethane which on treatment with alcoholic KOH gives bromoethene as the final product.

• Propene on treatment with HBr in the presence of peroxide (anti-markovnikoff’s rule which states the negative part e. Br^- goes to the carbon which has more number of hydrogens and positive part i.e. H⁺ goes to the carbon which has lesser number of hydrogens) gives 1-bromopropane which on treatment with silver nitrite in the presence of alcohol or water gives 1-nitropropane as the final product.

• Chlorination of toluene (Cl₂ at 773K) gives benzyl chloride with the removal of HCl. Benzyl Chloride on further treatment with dilute KOH in the presence of heat gives benzyl alcohol as the final (dilute KOH removes Cl from the benzyl chloride and replaces it by OH)

• Propene is treated with Br₂/CCl₄e. bromination of alkene takes place to give dibromides, in this case 1,2-dibromopropane which on further treatment with alcoholic KOH gives propyne.(two times removal of KBr)

• Ethanol in treatment with thionyl chloride(SOCl₂) in the presence of pyridine gives ethyl chloride with the evolution of SO₂ The ethyl chloride on treatment with mercury fluoride gives ethyl fluoride (the Cl of ethyl chloride is being replaced by F from Hg₂F₂).

• Bromoethane on treatment with alcoholic KCN forms Acetonitrile with the removal of KBr. CN is added in the case where there is a need to increase the number of Further the acetonitrile is treated with CH₃MgBr(Grignard reagent) in the presence of ether, the intermediate so formed is hydrolysed, and the product formation takes place i.e. Propanone and NH₃ is obtained as the by- product.

• But-1-ene reacts with HBr to form 2-bromobutane(acc. To markovnikoff’s rule) and further 2- bromobutane is treated with alcoholic KOH in the presence of heat to form But-2-ene with the removal of HBr.(alcoholic KOH removes H from the carbon which has less number of hydrogens just next to the carbon to which halide is attached and gives the major product e. Saytzeff rule)

• The conversion of 1-chlorobutane to n-octane in the presence of Na metal and dry ether is called Wurtz Two equivalent Chlorobutane reacts to give n-octane as a final product and NaCl as the by-product.

 

The conversion of benzene to biphenyl using Na and dry ether is called FITTIG reaction.

Firstly, the benzene is treated with Br₂/FeBr₃ results in the formation of bromobenzene. It is an electrophilic substitution. Further the bromobenzene is treated with Na metal in presence of dry ether to form biphenyl as the final product and NaBr as the by-product.

 

If instead of Na metal, bromobenzene is treated with Cu metal then the reaction is called Ullmann’s reaction. The final product obtained in this reaction will also be biphenyl.

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<p>(i) Since the conversion of ethanol to but-1-yne involves the addition the two extra carbons that is why the conversion is carried out in 3 steps.</p><ol><li>In the first step ethanol is treated with thionyl chloride (SOCl₂) in the presence of pyridine to give chloroethane</li></ol><div><div><picture><source srcset="https://images.shiksha.com/mediadata/images/articles/1690439506phpHIVMql_480x360.jpeg" media="(max-width: 500px)"><img src="https://images.shiksha.com/mediadata/images/articles/1690439506phpHIVMql.jpeg" alt="" width="369" height="114"></picture></div><div><ul><li>In the second step the acetylene is treated with sodamide(NaNH₂) in the presence of liquid ammonia to give sodium acetylide</li></ul><div><div><picture><source srcset="https://images.shiksha.com/mediadata/images/articles/1690439559phpeAP9IY_480x360.jpeg" media="(max-width: 500px)"><img src="https://images.shiksha.com/mediadata/images/articles/1690439559phpeAP9IY.jpeg" alt="" width="382" height="92"></picture></div><div><ul><li>The last step involves the reaction between chloroethane and sodium acetylide to give the final product as the But-1-yne and NaCl as the by-product.</li></ul><div><div><picture><source srcset="https://images.shiksha.com/mediadata/images/articles/1690439643php6cXvO6_480x360.jpeg" media="(max-width: 500px)"><img src="https://images.shiksha.com/mediadata/images/articles/1690439643php6cXvO6.jpeg" alt="" width="433" height="235"></picture></div><div><ul><li>The bromination of ethane (Br₂ in the presence of light at 520-670K) gives bromoethane which on further treatment with alcoholic KOH results in the alkene called ethane which again on bromination with Br₂/CCl₄ gives dibromide(vicinal bromide) called 1,2-dibromoethane which on treatment with alcoholic KOH gives bromoethene as the final product.</li></ul><div><div><picture><source srcset="https://images.shiksha.com/mediadata/images/articles/1690439797phpEb0k6B_480x360.jpeg" media="(max-width: 500px)"><img src="https://images.shiksha.com/mediadata/images/articles/1690439797phpEb0k6B.jpeg" alt="" width="399" height="159"></picture></div><div><ul><li>Propene on treatment with HBr in the presence of peroxide (anti-markovnikoff’s rule which states the negative part e. Br^- goes to the carbon which has more number of hydrogens and positive part i.e. H⁺ goes to the carbon which has lesser number of hydrogens) gives 1-bromopropane which on treatment with silver nitrite in the presence of alcohol or water gives 1-nitropropane as the final product.</li></ul><div><div><picture><source srcset="https://images.shiksha.com/mediadata/images/articles/1690439834phppIciWS_480x360.jpeg" media="(max-width: 500px)"><img src="https://images.shiksha.com/mediadata/images/articles/1690439834phppIciWS.jpeg" alt="" width="438" height="135"></picture></div></div><ul><li>Chlorination of toluene (Cl₂ at 773K) gives benzyl chloride with the removal of HCl. Benzyl Chloride on further treatment with dilute KOH in the presence of heat gives benzyl alcohol as the final (dilute KOH removes Cl from the benzyl chloride and replaces it by OH)</li></ul><div><div><picture><source srcset="https://images.shiksha.com/mediadata/images/articles/1690439860php4CWtWg_480x360.jpeg" media="(max-width: 500px)"><img src="https://images.shiksha.com/mediadata/images/articles/1690439860php4CWtWg.jpeg" alt="" width="503" height="164"></picture></div></div><ul><li>Propene is treated with Br₂/CCl₄e. bromination of alkene takes place to give dibromides, in this case 1,2-dibromopropane which on further treatment with alcoholic KOH gives propyne.(two times removal of KBr)</li></ul><div><div><picture><source srcset="https://images.shiksha.com/mediadata/images/articles/1690439893phpdgGTDF_480x360.jpeg" media="(max-width: 500px)"><img src="https://images.shiksha.com/mediadata/images/articles/1690439893phpdgGTDF.jpeg" alt="" width="591" height="99"></picture></div></div><ul><li>Ethanol in treatment with thionyl chloride(SOCl₂) in the presence of pyridine gives ethyl chloride with the evolution of SO₂ The ethyl chloride on treatment with mercury fluoride gives ethyl fluoride (the Cl of ethyl chloride is being replaced by F from Hg₂F₂).</li></ul><div><div><picture><source srcset="https://images.shiksha.com/mediadata/images/articles/1690439921phpn8w1vo_480x360.jpeg" media="(max-width: 500px)"><img src="https://images.shiksha.com/mediadata/images/articles/1690439921phpn8w1vo.jpeg" alt="" width="442" height="72"></picture></div></div><ul><li>Bromoethane on treatment with alcoholic KCN forms Acetonitrile with the removal of KBr. CN is added in the case where there is a need to increase the number of Further the acetonitrile is treated with CH₃MgBr(Grignard reagent) in the presence of ether, the intermediate so formed is hydrolysed, and the product formation takes place i.e. Propanone and NH₃ is obtained as the by- product.</li></ul><div><div><picture><source srcset="https://images.shiksha.com/mediadata/images/articles/1690439955phpWF6SuT_480x360.jpeg" media="(max-width: 500px)"><img src="https://images.shiksha.com/mediadata/images/articles/1690439955phpWF6SuT.jpeg" alt="" width="423" height="124"></picture></div></div><ul><li>But-1-ene reacts with HBr to form 2-bromobutane(acc. To markovnikoff’s rule) and further 2- bromobutane is treated with alcoholic KOH in the presence of heat to form But-2-ene with the removal of HBr.(alcoholic KOH removes H from the carbon which has less number of hydrogens just next to the carbon to which halide is attached and gives the major product e. Saytzeff rule)</li></ul><div><div><picture><source srcset="https://images.shiksha.com/mediadata/images/articles/1690439981phpDE3h1J_480x360.jpeg" media="(max-width: 500px)"><img src="https://images.shiksha.com/mediadata/images/articles/1690439981phpDE3h1J.jpeg" alt="" width="652" height="131"></picture></div></div><ul><li>The conversion of 1-chlorobutane to n-octane in the presence of Na metal and dry ether is called Wurtz Two equivalent Chlorobutane reacts to give n-octane as a final product and NaCl as the by-product.</li></ul><div>&nbsp;</div><p>The conversion of benzene to biphenyl using Na and dry ether is called FITTIG reaction.</p><p>Firstly, the benzene is treated with Br₂/FeBr₃ results in the formation of bromobenzene. It is an electrophilic substitution. Further the bromobenzene is treated with Na metal in presence of dry ether to form biphenyl as the final product and NaBr as the by-product.</p><div>&nbsp;</div><p>If instead of Na metal, bromobenzene is treated with Cu metal then the reaction is called Ullmann’s reaction. The final product obtained in this reaction will also be biphenyl.</p></div></div></div></div></div></div></div></div>

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