[lukas.stib]

Hello chemists,

I synthesized pentan-2-one from ethyl acetoacetate and sodium hydroxide. I did everything according to the instructions, where they used 10 g NaOH, 100 ml H2O and 15 g ethyl acetoacetate. For more product, I used three times everything, so 30 g NaOH, 300 ml H2O and 45 g ethyl acetoacetate. I refluxed for 2 hours. It is written in the instructions that 2 layers are to be formed after 2 hours refluxing, the oily layer is pentan-2-one. Unfortunately, nothing was created; I cooled the flask in cold water, and now, after 45 minutes, nothing still formed. Can you advise me what to do?

Thank you, Lukáš S.

[sjb]

How did you know that the reaction was complete after 2 hrs? Aside from the scaling issue, you don't have the same source of chemicals or set-up as the original paper. I would tend to use the times in papers as a guide rather than the absolute truth.

[lukas.stib]

I always perform syntheses as they say in the instructions. So you think I should have refluxed longer?

[Babcock_Hall]

Can you monitor the reaction by TLC?

[lukas.stib]

What´s TLC?

[Babcock_Hall]

Thin-layer chromatography.  You will need at least one solvent system and a means of detection.

[rolnor]

The boilingpoint of the startingmaterial is 180°C so TLC is not optimal, the product is volatile also.
Maybe run the reaction in the same scale as in the reference to start with?

[Babcock_Hall]

Particularly the product (on the basis of its volatility) would be difficult to detect, now that you mention it.

[lukas.stib]

Thank you very much.

[lukas.stib]

Hello chemists,

I'm re-synthesizing pentan-2-one, which I started yesterday. Now I did not use 3 times the raw materials, but I used the amount in the instructions, so 10 g NaOH, 100 ml H2O and 15 g ethyl acetoacetate. Now I perform reflux for more than 2 hours, as they write in the instructions. Reflux is more than 3 hours, and still 2 layers have not formed. I let the flask cool to normal temperature, and there are still no 2 layers.

I don't know what I did wrong; on your recommendation, I left the reflux for more than 2 hours, and it still doesn't bleed the product. Do you know what I'm doing wrong?

Thank you, Lukáš S.

[rolnor]

Its a bit of a mystery but now you know where to look for problem, is your startingmateriel OK? Does the product somehow evaporate?

[lukas.stib]

So, I cooled it down, but still no 2 layers. So I started distilling. Due to the fact that pentan-2-one has a high boiling point, distillation has already started around 60°C, and I do not know what it was. The smell was like acetone, so I guess it was pentan-2-one, but it had a different scent. I distilled to 98°C, then stopped. I think I can also smell ethyl alcohol, but I'm not sure. But the main smell of the distillate resembles acetone. I poured CaCl2 to dry, I'll let it dry until the next time.

And also my thermometer, which is from China, is probably not accurate, so the exact temperature of the start of distillation may have been different.

[AWK]

Did you used ethyl ester of 2-ethylacetoacetate?

[lukas.stib]

I used ethyl acetoacetate or ethyl-3-oxobutanoate (IUPAC).

[AWK]