Esterfication (1 Viewer)

[Linda N]

Help... im confused

Is esterfication exothermic or endothermic?

 

[kimmeh]

endothermic because the reaction requires heat to take places. stuff evaporates and there is a dehydrating agent used.

 

[Linda N]

Thanx...

 

[t-i-m-m-y]

yes,
thats why we use reflux

 

[xiao1985]

well, raising temperature may not necessarily cuz tis endorthermic tho... cuz higher temp = higher rate of successful collision, = faster reaction rate...

cf habor process... (gee, nearly forgot the name ~phew) reaction is exothermic but heat is introduced to increase teh rate...

 

[CM_Tutor]

However, HSC esterifications (carboxylic acid + alcohol) are almost always endothermic, and so heating has the dual benefits of increasing reaction rate and increasing yield (Le Chatelier's Principle).

Uni Students Note: Many Uni esterifications are exothermic.

 

[kimmeh]

eep ! dont confuse us just yet *covers her ears to the sound of estrification being exothermic* noooooooooooooooooooo!

 

[CM_Tutor]

Originally posted by kimmeh
eep ! dont confuse us just yet *covers her ears to the sound of estrification being exothermic* noooooooooooooooooooo!

Sorry, I'm not trying to be difficult , but there is a valid point to bear in mind here.

There are many general reactions in the HSC that are classified as endothermic or exothermic, where these classifications follow logically from the properties of the reaction.

For example, a vapourisation reaction, like:

H₂O_(l) ---> H₂O_(g) deltaH = +43 kJmol^-1

is endothermic, as are all vapourisations, as they involve overcoming intermolecular interactions (or other bonds / forces), and thus must absorb energy and be endothermic.

Similarly, combustion reactions are necessarily exothermic.

Esterification reactions - that is, reactions that result in the formation of an ester - need not be endothermic. Done by the HSC method, they usually are, but they don't have to be. There is a first year experiment at USyd involving formation of an ester, where two reactants at room temperature are mixed, and the mixture spontaneously increases in temperature to about 80 C - clearly an exothermic process.

My point is: don't think of esterification as necessarily endothermic in the way that vapourisation is necessarily endothermic. By all means, remember the generalisation, but don't think of it as anything other than a convenient generalisation.

 

[cko]

ummm.... i think for the hsc syllubus it is safe to say that the esterification reaction is endothermic then..... right.... ??

 

[Linda N]

Im pretty sure that esterification is endothermic. Most of us says so and i've ask my teacher too.

 

[CM_Tutor]

Originally posted by cko
ummm.... i think for the hsc syllubus it is safe to say that the esterification reaction is endothermic then..... right.... ??

Yes, that is a safe thing to say for the HSC syllabus.

 

[Ragerunner]

Don't forget to remember how to draw the diagram to prepare as ester, and make sure you label the top of the refluxing equipment as OPEN. Otherwise your gonna blow up everything.

On another note...alkanoic acids and alkanols smell HORRIBLE. The smell was stuck on me for like 1 week. It was AWFUL

 

[kimmeh]

Originally posted by cko
ummm.... i think for the hsc syllubus it is safe to say that the esterification reaction is endothermic then..... right.... ??

that isnt needed under any dot point anyway isnt it?

Originally posted by Ragerunner
On another note...alkanoic acids and alkanols smell HORRIBLE. The smell was stuck on me for like 1 week. It was AWFUL

Butanoic acid .. YUCK omg, we had physics and we had to sit through a weeks smell of butanoic acid from the previuos chem class. so sickening-wouldnt that make it a health hazard?

 

[Xayma]

Originally posted by kimmeh
omg, we had physics and we had to sit through a weeks smell of butanoic acid from the previuos chem class. so sickening-wouldnt that make it a health hazard?

But wasnt that your chem class? And the stuff that got spilt on you.

 

[kimmeh]

Originally posted by Xayma
But wasnt that your chem class? And the stuff that got spilt on you.

yeah i got the suff spilt on me but for physics, the class that had chem before we came in like stunk their room worse than ours

 

[Xayma]

Originally posted by kimmeh
yeah i got the suff spilt on me but for physics, the class that had chem before we came in like stunk their room worse than ours

Still, you would have stunk out the other room and an innocent yr 10 class or something probably had to sit through it (although yr 10ers are never innocent)