Lab: Like? Hate? and question

[mozart_fan]

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We are doing lab-I hate labs- in organic chem. It is called "synthesis of ethanol by fermentation of sucrose"

So i have the mixture made. It has been reacting for a week. Then were are going to filter it blah blah....and then purify
the ethanol by simple and then fractional distillation. I understand that in simple distillation...the two compounds must be soluable...
and they are...and two different boiling points...which they are...what i dont get is WHAT THE HECK am i separating ethanol from...
the lab is always like this...is it water...but it cant be cuz water has a higher bpt than ethanol! Sucrose?

as a side note...does anyone else here not like lab? I dont. Well...sometimes its fun...but overall I dont like them. I had an instructor in gen chem
that gave extermely long post lab assigments...it sucks when a 2 credit class turns into almost the lecture...

id rather be a bookworm than a lab rat...lecture rules

 

[dgroulx]

We are doing lab-I hate labs- in organic chem. It is called "synthesis of ethanol by fermentation of sucrose"

So i have the mixture made. It has been reacting for a week. Then were are going to filter it blah blah....and then purify
the ethanol by simple and then fractional distillation. I understand that in simple distillation...the two compounds must be soluable...
and they are...and two different boiling points...which they are...what i dont get is WHAT THE HECK am i separating ethanol from...
the lab is always like this...is it water...but it cant be cuz water has a higher bpt than ethanol! Sucrose?

as a side note...does anyone else here not like lab? I dont. Well...sometimes its fun...but overall I dont like them. I had an instructor in gen chem
that gave extermely long post lab assigments...it sucks when a 2 credit class turns into almost the lecture...

id rather be a bookworm than a lab rat...lecture rules

I loved o-chem lab. When you are distilling, the compound with the lowest boiling point turns to vapor first. The vapor goes down the condenser and turns back into liquid which you collect in your flask. Water boils at a higher temperature, so all the remaining liquid will still be water when you stop the distillation. Just keep an eye on your thermometer so you know when to stop it.

 

[All4MyDaughter]

I think I remember this lab. I think the point of it is to recognize that you won't get a very pure separation (of ethanol and water) with simple distillation because the ethanol-water azeotrope has a bp very similar to pure ethanol.

In fractional distillation you can separate the ethanol, the azeotrope and the water more carefully because you can be more precise about the temperature and you remove each fraction as it comes across the column.

What you distill fractionally should have a higher proof than what you distill via simple distillation.

 

[SomeGuy]

"synthesis of ethanol by fermentation of sucrose"

Sounds like the most useful lab I've ever heard of.

 

[ultracet]

Sounds like the most useful lab I've ever heard of.

any thing that i could get etoh out of would be extremely useful!

 

[All4MyDaughter]

Yup, brew your own, but watch out for the methanol by-products.

 

[SomeGuy]

Yup, brew your own, but watch out for the methanol by-products.

Well, the methanol is an alcohol from fermenting wood and wood-like substances (such as pectin), so as long as we're dealing with sugar, we're pretty much ok. Just to be safe though, since methanol has a lower bp than both water and ethanol, throw away whatever comes over first. And if you follow this step after each distillation (assuming you're doing it more than once), you shouldn't worry at all. Your body is actually quite capable of dealing with small amounts of methanol anyway.

Carbon filtering (via brita filter) can be used to get rid of other impurities, but there shouldn't be too many when we're dealing with straight sugar.

That's the nice thing about table sugar, its already refined for brewing goodness 🙂

And don't forget about what they use to treat methanol poisoning! Ethanol... for days! So don't stop drinking!

 

[ZpackSux]

Geesh.. only if you guys would study pharmacotherapy like the way you pay attention to fermentation and EtOH distillation..

 

[ultracet]

Geesh.. only if you guys would study pharmacotherapy like the way you pay attention to fermentation and EtOH distillation..

you're right....

if only i had, i wouldn't be concerned about my GPA now