Answer to Question #107428 in Organic Chemistry for Katy Wildman

Question

Methyl salicylate, C8H8O3, is the chemical responsible for wintergreen flavouring. It can be produced by heating salicylic acid, C7H6O3, with methanol, CH3OH.

This image shows C sub 7 H sub 6 O sub 3 + CH sub 3 OH, reaction arrow, C sub 8 H sub 8 O sub 3 + H sub 2 O.

An organic chemist reacts 6.70 g of salicylic acid with excess ethanol to produce 5.80 g of methyl salicylate.

What is the theoretical yield?

Answer 1

methyl salicylate = C₈H₈O₃

m(C₇H₆O₃) = 6.70 g.

m(experimental)(C₈H₈O₃) = 5.80 g.

M(C₈H₈O₃) = 8*Ar(C) + 8*Ar(H) + 3*Ar(O) = 8*12 + 8*1 + 3*16 = 152 (g/mol);

M(C₇H₆O₃) = 7*Ar(C) + 6*Ar(H) + 3*Ar(O) = 7*12 + 6*1 + 3*16 = 138 (g/mol).

Solution:

salicylic acid + methanol --(t^oC)--> methyl salicylate + water.

The equation of a chemical reaction:

C₇H₆O₃ + CH₃OH --(H⁺ / t^oC)--> C₈H₈O₃ + H₂O.

According to the chemical equation: n(C₇H₆O₃) = n(C₈H₈O₃).

n(C₇H₆O₃) = m(C₇H₆O₃) / (C₇H₆O₃) = (6.70 g) / (138 g/mol) = 0.04855 mol.

n(C₇H₆O₃) = n(C₈H₈O₃) = 0.04855 mol

n(C₈H₈O₃) = m(C₈H₈O₃) / M(C₈H₈O₃);

m(calculated)(C₈H₈O₃)=n(C₈H₈O₃) * M(C₈H₈O₃) = (0.04855 mol)*(152 g/mol) = 7.3796 g = 7.38 g.

The theoretical yield = m(experimental)(C₈H₈O₃) / m(calculated)(C₈H₈O₃) = 5.80 g / 7.38 g = 0.7859

The theoretical yield = 0.7859 or 78.59%.

Answer: 78.59 % is the theoretical yield.