Calcium chloride in esterification???? (1 Viewer)

[bEAbEA]

Why is calcium chloride added to the reaction when preparing an ester? WE added it at the very end, before distilling, but I don't understand why.
Help would be appreciated.

 

[mitochondria]

CaCl₂ is a dehydrating agent, meaning that it removes water formed during esterification:

recall that esterification involves an acid reacting with an alcohol, and a water molecule is evolved when each unit of alcohol reacts with each uni of acid, and CaCl₂ is used to remove the water in your mixture, you can think of it as a way for purifying your preparation

hope that helps ^______^ ooh, and lemons and lemonade are greeeat xD

 

[Dreamerish*~]

CaCl₂ is a dehydrating agent, meaning that it removes water formed during esterification:

recall that esterification involves an acid reacting with an alcohol, and a water molecule is evolved when each unit of alcohol reacts with each uni of acid, and CaCl₂ is used to remove the water in your mixture, you can think of it as a way to purifying your preparation

hope that helps ^______^ ooh, and lemons and lemonade are greeeat xD

hi mito
don't we usually use concentrated H₂SO₄ catalyst in esterification? and i thought that this was the dehydrating agent.

 

[jumb]

hi mito
don't we usually use concentrated H₂SO₄ catalyst in esterification? and i thought that this was the dehydrating agent.

They do the same job, but sulfuric acid is what the syllabus says (I think).

 

[MedNez]

Yep. I just checked some of my notes. They agree with H2SO4.

 

[jumb]

Actually, I was wrong, the syllabus only says "describe the purpose of using acid in esterification for catalysis"

hsc onlines summary of this point:

http://hsc.csu.edu.au/chemistry/core/acidic/chem935/chem935net.html#net4

 

[Dreamerish*~]

Actually, I was wrong, the syllabus only says "describe the purpose of using acid in esterification for catalysis"

hsc onlines summary of this point:

http://hsc.csu.edu.au/chemistry/core/acidic/chem935/chem935net.html#net4

so it's acid, not calcium chloride which is a salt.
well, better to know both i guess so you can show off your knowledge in exams =)

 

[jumb]

so it's acid, not calcium chloride which is a salt.
well, better to know both i guess so you can show off your knowledge in exams =)

I think you're better off saying sulfuric acid, as the dot point asks for an acid. If you instead say a salt, you won't be satisfying the dot point.

 

[xiao1985]

calcium carbonate, i think would work similar to other dehydrating salts, such as magnesium sulfate... would completely dehyrate any presence of water... i would think H2SO4 can only limitedly absorbe water from the reagent...

 

[rnitya_25]

CaCl₂ is a dehydrating agent, meaning that it removes water formed during esterification:

recall that esterification involves an acid reacting with an alcohol, and a water molecule is evolved when each unit of alcohol reacts with each uni of acid, and CaCl₂ is used to remove the water in your mixture, you can think of it as a way to purifying your preparation

hope that helps ^______^ ooh, and lemons and lemonade are greeeat xD

that was a prfect expnantion.....couldn;t have said it beter myself....juust one more thing, the thin about esterification, always remember, its where:
alkanol + alkanoic acid --> ester(alkyl alkanoate) + water, so when you have CaCl2, you can work it out from the generalised equation...just a thought

 

[nit]

OK, why you don't use calcium chloride in esterification reactions goes slightly beyond the scope of the syllabus. However, calcium chloride simply can't be used to catalyse the esterification reaction because a suitable catalyst for the reaction (ie sulfuric acid and any mineral acid in general) requires donatable protons to allow for the mechanism of the esterification reaction to proceed. This is the main reason why sulfuric acid is used. A two-in-one benefit of sulfuric acid is that it can dehydrate the solution and shifty the equilibrium position in accordance with Le Chatelier's Principle. However, without that proton, sulfuric acid is useless as a catalyst. The reason why we don't use sulfuric acid at the end to get rid of all the aqueous solution that will be caught by the final ester molecule is that, in general, sulfuric acid is a strong oxidising agent and rather nasty to organic compounds. A much better, milder dehydrating agent to use at the end is calcium chloride/ magnesium sulfate etc - really any mild, unreactive compound that is hygroscopic.