[quadsofdgods]

(sorry since the questions are from different areas i couldnt figure out a good general subject without writing a long title)

Ethers

1) Does Williamson`s Synthesis produce unsymmetrical ethers or can it also produce symmetrical?
My guess is both depending on the Na alkoxide and the Haloalkane

2) Incomplete dehydration of an alcohol always produces a symmetrical ether?
My guess: Yes

3) In the preparation of ethoxyethane where i extract the impure ether by distillation,
the flask which will be attached to the distillation system will contain the conc H2SO4 and ethanol.
My notes state you must add one to the other slowly, stop, cool to prevent loss of ethanol, continue adding the rest and repeat the stop and cool thing. I`m guessing you are adding the acid to the alcohol (correct?)
Wouldnt this stop and cooling thing be redundant considering we are going to distill it?
Couldn`t you just dump them all together and quickly hook it up to the distilling tower?

4) Ethers are unreactive yet are still polar. My basic knowledge tells me that something which isnt polar like an alkane would be less reactive and therefore better to store chemicals (ex. Lithium Aluminum hydride) in? OR does the slight polar nature of ether make it good for storing both polar and non-polar molecules?

Esters
( R-OH + R*COOH   RC(=O)OR* + H2O )

Na2CO3 is used to purify esters by removing the unreacted acids (according to what i have in front of me)

Na2CO3 + H2SO4    Na2SO4 + CO2 + H2O
the CO2 will evolve into the air and H2O 'join' the H2O that formed from the main reaction  
How is the Na2SO4 removed?

RCOOH + Na2CO3   RCOONa + CO2 + H2O
how will the Na carboxylic acid salt be removed?
will it dissolve into the unreacted alcohol which in turn is mixed with the water and they can be separated from the ester by a seperating funnel?

If h2so4 is present will it eliminate the need to separate the ester from everything due to it removing the water?  

[Honclbrif]

1. Yes to the second part.

2. Depends on which dehydration pathway you're talking about. What else can happen when you acidify an alcohol? (think about primary, secondary, tertiary sites)

3. If your EtOH boils off before the reaction goes to completion your yield will suffer. This is the exact situation that reflux condensers were invented for. Furthermore, if combining reagents results in an exotherm, "just dumping them together" is rarely the recommend method. It tends to result in reaction volcanoes painting the interior of your hood, or worse.

4. Many ethers are prone to peroxidation over time, so if you can avoid storing something in it you should. However, there are a few things for which nothing else will really do.

As for the esters, usually an aqueous workup with a base wash will remove the excess acid. As you said, the carboxylate (and sulfate) gets carried away in the aqueous phase. Many alcohols are insoluble in water so they would stay in your organic phase and must be removed by other means.

[quadsofdgods]

1. Yes to the second part.

2. Depends on which dehydration pathway you're talking about. What else can happen when you acidify an alcohol? (think about primary, secondary, tertiary sites)

hmm nothing comes to mind nor can i find anything in my notes about this.

I know dehydration at 180*C (degrees Celsius) with h2so4 makes alkenes [complete dehydration]
dehydration at 140*C + h2so4 makes ethers (incomplete dehydration)
alcohol + h2so4 at room temp results in alkyl hydrogensulphate

my guess is the formation of alkyl hydrogensulphates?



3. If your EtOH boils off before the reaction goes to completion your yield will suffer. This is the exact situation that reflux condensers were invented for. Furthermore, if combining reagents results in an exotherm, "just dumping them together" is rarely the recommend method. It tends to result in reaction volcanoes painting the interior of your hood, or worse.

ahh silly me, didnt even think of that, so one should add the acid to the alcohol not vice versa? (similar to adding acid to water and not vice versa)

4. Many ethers are prone to peroxidation over time, so if you can avoid storing something in it you should. However, there are a few things for which nothing else will really do.

As for the esters, usually an aqueous workup with a base wash will remove the excess acid. As you said, the carboxylate (and sulfate) gets carried away in the aqueous phase. Many alcohols are insoluble in water so they would stay in your organic phase and must be removed by other means.


at my level they are most likely not going to give me any insoluble alcohols, so can i assume that just pouring in water whilst keeping the hole mixture in a separating funnel then i remove the lower aqueous layer (of water and alcohol) will suffice to remove the alcohol?

Thanks for the replies, much appreciated!