Synthesis of aspirin

[jake_f]

Actually, I just have some doubts with my experiment result.

 

The equation for the reaction,

 

C7H6O3 + C4H6O3 -> C9H8O4 +CH3COOH

 

I started off with 2.42g of salicylic acid (C7H6O3) which is about 0.175 mole of it. By right, based on the equation, one mole of salicylic acid should yield one mole of aspirin (C9H8O4). So 0.175 mole of Aspirin is expected at the end of the experiment.

 

And the expected mass of aspirin should be 3.15g. But at the end of the experiment, I only got 1.1g of aspirin. Which when calculated in percentage yield, is only 34.92%. So should I presume that I made some mistake during the course of the experiment?

 

When I asked my lecturer about it, he just give me a smile which make me even more suspicious about my results.

[John Cuthber]

Yeilds are seldom 100%.

To say where the rest of the stuff has gone we would need more details of the experiment.

[hermanntrude]

In the past i've had yields anywhere between 120%( water in my product making it seem heavier than it is) and 0.5% (actually not a bad yield for that particular reaction, which has literally hundreds of possible by-products. If you're sure about your calculations, that's what you got.

[Mr Skeptic]

Yeilds are seldom 100%.

 

Especially for organic reactions. If this was your first organic reaction, you're probably used to the much higher yields from inorganic reactions, where many reactions are extremely close to 100%

[Horza2002]

There are only a few reactions in organic chemistry that are even close to being 100%. Without knowing the exact procedure....i guess some was lost via work up and side reactions...generally 70-80% yields are considered excellent