Molar mass of the hydrocarbon (X) which on ozonolysis consumes one mole of $\mathrm{O}_{3}$ per mole of (X) and gives one mole each of ethanal and propanone is ______ $\mathrm{g\ mol}^{-1}$ (Molar mass of C: $12\ \mathrm{g\ mol}^{-1}$, H: $1\ \mathrm{g\ mol}^{-1}$)

JEE Main · 2023 · 08 Apr 2023 · Shift 1 · Hydrocarbons

Molar mass of the hydrocarbon (X) which on ozonolysis consumes one mole of

O_{3}

per mole of (X) and gives one mole each of ethanal and propanone is ______

g mol^{- 1}

(Molar mass of C:

12 g mol^{- 1}

, H:

1 g mol^{- 1}

)

Answer: 70

Solution

Ozonolysis cleaves a carbon–carbon double bond, and each double bond consumes one mole of

O_{3}

; since (X) uses exactly one mole it contains a single C=C bond. The two carbonyl fragments reveal the carbon skeleton on either side of that bond. Ethanal,

C H_{3} CHO

, has two carbons and comes from a

C H_{3} CH =

end, while propanone,

(C H_{3})_{2} CO

, has three carbons and comes from a

(C H_{3})_{2} C =

end, because joining the two carbonyl carbons through a double bond must regenerate the original alkene. That reunion gives

(C H_{3})_{2} C = CHC H_{3}

, which is 2-methylbut-2-ene with molecular formula

C_{5} H_{10}

. Its molar mass is

5 (12) + 10 (1) = 70 g mo l^{- 1}

JEE Main · 2023 · 08 Apr 2023 · Shift 1 · Integer answer

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JEE Main · 2023 · 08 Apr 2023 · Shift 1 · Hydrocarbons

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