Question

An alcohol (x) gives blue colour in Victormeyer’s test and 3.7 g of X when treated with metallic sodium liberates 560 mL of hydrogen at 273 K and 1 atm pressure what will be the possible structure of X?

Options

• CH₃CH(OH)CH₂CH₃

• CH₃ – CH(OH) – CH₃

• CH₃ – C(OH) (CH₃)₂

• CH₃ – CH₂ – CH(OH) – CH₂ – CH₃

Answer 1

CH₃CH(OH)CH₂CH₃

Explanation:

$$2\mathrm{R}-\mathrm{OH}+2\mathrm{Na}⟶2\mathrm{RONa}+\mathrm{H}{\phantom{A}}_2\uparrow$$ 2 moles of alcohol gives 1 mole of H₂ which occupies 22.4 L at 273 K and 1 atm

∴ number of moles of alcohol = ${\displaystyle \frac{2 \text{moles of R}-\text{OH}}{22.4 {\text{L of H}}_2}\times 560 \text{mL}}$

= 0.05 moles

∴ no. of moles = ${\displaystyle \frac{\text{mass}}{\text{molar mass}}}$

molar mass = ${\displaystyle \frac{3.7}{0.05}}$ = 74 g mol⁻¹

General formula for R – OH C_n H_2n+1 – OH

∴ n(12) + (2n+1) (1) + 16 + 1 = 74

14n = 74 – 18

14n = 56

∴ n = ${\displaystyle \frac{56}{14}}$ = 4

The 2° alcohol which contains 4 carbon is CH₃CH(OH)CH₂CH₃