1)In contrast to alkenes, the oxidative cleavage of alkynes with either KMnO4 or

Question

1)In contrast to alkenes, the oxidative cleavage of alkynes with either KMnO4 or O3, yield the same products. Write the equatioen for the oxidation of 1-pentyne and 2-pentyne showing the products obtained.

2)Terminal alkynes show acids characteristics because they reacts with strong bases such asNaNh2,sodiumamide. the resulting product is an acetylide anion. when this strong anion is reacted with an alkyl halide, the carbon chain increases in lenght by the same number of carbons as that in the alkyl halide, provided the alkyl halide is primary. propose a synthesis for the preparation of ch3ch2c=_cch2ch3. show the equation and conditions for synthetic scheme.

Explanation / Answer

1) Oxidation of Alkynes

Ethyne is oxidised by a dilute aqueous solution of potassium permanganate to form oxalic acid. Thus, if ethyne is bubbled through a solution of potassium permanganate the solution is decolourised. This is Baeyer's test for unsaturated organic compounds.

That is the generalized formula. So 1-pentyne is CH3CH2CH2CCH3 and it oxidizes to CH3CH2CH2COOH (Butanoic acid). 2-pentyne is CH3CH2CCCH3 and it oxidizes to CH3CH2CH(COOH)CH3 (2-methyl butanoic acid).

2) For terminal alkynes the addition of water follows the Markovnikov rule, as in the example below, and the final product ia a methyl ketone.

RCCH + H2O + HgSO4 + H2SO4

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