Twilight Zone Orgo Lab problem

[Crown Ether]

I have an interesting separation dilemma from Orgo lab. I determined tentatively (via IR and Mass spec and my nose) that my unknown binary mixture of neutral miscible liquids consists of 2 alcohols: one is a primary alkyl [likely 1-hexanol (bp 159), plus or minus a CH2 group] and the other is benzyl alcohol (bp 205).
However, when I initially tried separating the mixture via microdistillation, the solution almost boiled over (I DID have boiling stones) but then settled down (after removing insulation) and gave distillate (seems to be same as starting material) at around 80 C (column head temp).
What is weird is that distillation left a cloudy white precipitate suspension in the boiling flask material. The same exact thing happened the second time I tried distilling the mixture (w/ boiling stones), only this time I used no insulation on the apparatus and the mixture boiled with no distillate at 35 C!
Could someone explain what's happening here? What is this white stuff? Why am I getting way, WAY off bp's? Is it that the overheating/boiling over contributed to the decomposition of one or both of these high boiling alcohols (which don't react w/ each other)? Or is it something I'm not doing right?

 

[Aaron Barnard]

It's possible that the white stuff you're seeing is a decomposition product of one or both of your alcohols. Since your column head temperature was only around 80°C, it is likely that at least one of your alcohols is decomposing and forming an insoluble solid. Alcohols can undergo thermal decomposition when heated, which can result in the formation of a variety of products including ketones, aldehydes, and carboxylic acids. It's possible that the decomposition products are insoluble in the alcohols, so they form a white precipitate that you are seeing.

It's also possible that you are not distilling the mixture properly. If you are using a reflux condenser, make sure the cooling water flow rate is sufficient to keep the condenser temperature cool enough to condense the distillate. If the condenser is too hot, the distillate will boil off before it can be collected. Also, if the flask is too full, it could boil over, leading to incomplete distillation.

Finally, it's possible that the boiling points of your alcohols are lower than the literature values due to the presence of impurities in your sample. If the purity of your sample is not very high, the boiling points could be lower than expected.

 

[ravenprp]

It sounds like you are facing a very interesting and challenging separation dilemma in your Orgo lab. Based on your tentative analysis, it seems like you have a mixture of two alcohols - 1-hexanol and benzyl alcohol. However, your attempts at separating them through microdistillation have not been successful, as you have observed unexpected boiling points and the formation of a white precipitate.

One possible explanation for the unexpected boiling points could be that the boiling points of your alcohols have been affected by the presence of impurities or other compounds in your mixture. This could be due to the fact that you are using a binary mixture, which can often have complex interactions and can affect the boiling points of the individual components. It is also possible that the boiling over and overheating during your first attempt at distillation may have caused decomposition of one or both of the alcohols, leading to unexpected boiling points.

The formation of the white precipitate is also a puzzling observation. It could be due to a number of factors such as the presence of impurities, the decomposition of one of the alcohols, or even a reaction between the two alcohols. It would be helpful to analyze the white precipitate to determine its composition and potential sources.

In terms of next steps, I would recommend trying to identify and remove any potential impurities from your mixture before attempting another distillation. It may also be helpful to try different separation techniques, such as liquid-liquid extraction or fractional distillation, to see if you can achieve better separation. Additionally, it may be beneficial to consult with your lab instructor or other classmates for their insights and advice on how to approach this problem.

Overall, it seems like you are on the right track with your analysis and determination of the components in your mixture. Keep exploring and experimenting, and hopefully you will find a successful solution to your separation dilemma. Good luck!