[LancerIV]

Hi everybody, I am a student and I have a question related to reflux reaction to produce butyl acetate.
30ml of 1-butanol and 30ml of acetic acid were a added into a round bottom flask,after that, 1.5ml of concentrated sulfuric acid were added followed by 4 boiling chips.
During the reflux reaction, black small substances were formed inside the flask and then the solution eventually turned black after 30 minutes of heating. The volume of the solution become less after heating and the solution is totally black. Can anybody explain why this will occur? Sorry for bothering everyone.

[Guitarmaniac86]

The concentrated sulphuric acid is probably dehydrating the compound leaving a mess of black carbon behind. Try using less sulphuric acid or use a different acid like pTSA as the acid is catalytic and you dont need much.

[LancerIV]

The concentrated sulphuric acid is probably dehydrating the compound leaving a mess of black carbon behind. Try using less sulphuric acid or use a different acid like pTSA as the acid is catalytic and you dont need much.

Thank you for replying.All my other classmates were using the exactly same amount of concentrated sulphuric acid but they still can get the result. Is there any other possibilities??

[Guitarmaniac86]

How did they add the concentrated acid? Did they add it dropwise or did they put it all in at once? If you were the only one who had this trouble, did you do something different? Did everyone do the reaction for the same length of time and did anyone else get a black solution? I only ask these questions because there will be variation in how your classmates done this reaction versus how you done it.

You may still have some compound in the mixture but separating it out might be difficult if I am right and the acid did dehydrate the starting materials and product.

[stanleyykk]

I am guessing that you are using a sand bath... and you probably ignored it when it does it things.. You probably putted it too deep into the sand and it is way too hot and burn the solution. I am a student too. During my lab another student totally ignored the solution, didn't read the temperature, and as a result his solution turned into dark brown solution during a reflux for esterification. So I am guessing you just burnt your solution too.  In the end, that guy didn't finish the lab in time.