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Topic: How to remove 1-pentanol from 1-bromopentane?  (Read 944 times)

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Offline lukas.stib

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Re: How to remove 1-pentanol from 1-bromopentane?
« Reply #15 on: November 15, 2020, 02:39:59 AM »
Hello chemists,

I distilled bromopentane with water. The first drops dripped at 65°C, and so it dripped to 115°C. Odor I can't tell what it is, something between bromopentane, pentanol etc. The product dripped at about 115 - 123°C. I think it is pure.

Offline AWK

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Re: How to remove 1-pentanol from 1-bromopentane?
« Reply #16 on: November 15, 2020, 04:14:37 AM »
At the beginning of the distillation, did you observe the pentanol drops floating on the surface of the distillate around 100C? No smell but floating drops of pentanol would indicate its presence in the sample. The boiling point of 1-bromopentane is about 129°C (12-bromopentane is about 118°C). What were you distilling?

locant corrected
« Last Edit: November 15, 2020, 05:14:49 AM by AWK »
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Offline lukas.stib

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Re: How to remove 1-pentanol from 1-bromopentane?
« Reply #17 on: November 15, 2020, 04:21:56 AM »
No, no drops floated on the surface, everything seemed like one mixture.

Based on the fact that from 115°C and higher, everything was dripping quickly and to the end, so I think it is already a pure product. It smells different from pentanol, strangely, sweeter.

Offline AWK

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Re: How to remove 1-pentanol from 1-bromopentane?
« Reply #18 on: November 15, 2020, 04:27:45 AM »
Check the boiling point of your pentanol.
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Offline lukas.stib

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Re: How to remove 1-pentanol from 1-bromopentane?
« Reply #19 on: November 15, 2020, 04:40:19 AM »
They write 136 - 139°C on the bottle cover.

Offline AWK

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Re: How to remove 1-pentanol from 1-bromopentane?
« Reply #20 on: November 15, 2020, 04:47:51 AM »
Still, check it experimentally.
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Offline lukas.stib

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Re: How to remove 1-pentanol from 1-bromopentane?
« Reply #21 on: November 15, 2020, 04:54:15 AM »
OK, thank you.

Offline rolnor

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Re: How to remove 1-pentanol from 1-bromopentane?
« Reply #22 on: November 15, 2020, 05:15:57 AM »
I think you should avoid sniffing on the mixture, this is a alkylating agent, not healthy for you.

Offline lukas.stib

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Re: How to remove 1-pentanol from 1-bromopentane?
« Reply #23 on: November 15, 2020, 05:27:13 AM »
Yes, I know.

Offline lukas.stib

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Re: How to remove 1-pentanol from 1-bromopentane?
« Reply #24 on: November 17, 2020, 02:32:00 AM »
I tried distilling pentanol. Slowly it started dripping at 132°C, then a lot of dripping from 135°C to 137°C. All it smell as pentanol.

Offline AWK

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Re: How to remove 1-pentanol from 1-bromopentane?
« Reply #25 on: November 17, 2020, 03:08:01 AM »
When using simple distillation without a rectifying column, a sharp boiling point is rarely achieved.
The result obtained by you does not allow for unambiguous interpretation.
You can also try to carefully wrap the fragment of the distillation set shown in the drawing with aluminum foil and repeat the distillation.
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Offline lukas.stib

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Re: How to remove 1-pentanol from 1-bromopentane?
« Reply #26 on: November 17, 2020, 04:06:13 AM »
But I had the distillation set whole wrapped in aluminum foil; this is how I perform each distillation with a boiling point higher than water to "get" the fumes to the condenser.

Interestingly, when the water boiled, it showed 100°C.


Offline AWK

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Re: How to remove 1-pentanol from 1-bromopentane?
« Reply #27 on: November 17, 2020, 04:19:24 AM »
For now, you only have a good chance that you have received the correct chemical, but there is no absolute certainty. One could still check the thermometer by distilling some known compound with a boiling point in the range of 130-150°C.
The NMR science lab would give a definite answer very quickly.
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Offline lukas.stib

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Re: How to remove 1-pentanol from 1-bromopentane?
« Reply #28 on: November 17, 2020, 05:07:14 AM »
OK, thank you very much. I appreciate it very much.

Offline lukas.stib

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Re: How to remove 1-pentanol from 1-bromopentane?
« Reply #29 on: November 28, 2020, 06:53:54 AM »
Hello chemists,

I distill again bromopentane, to which I added water, about 20 ml. Now the drops drip at 88 - 90°C. Drip style: in this temperature range, nothing drips for a while and suddenly a large amount of liquid flows, and for a while the drops drip in quick succession. According to the refractive index, however, it looks like bromopentane (high refractive index of the liquid), I don't understand it when the boiling point is much higher (possible azeotrope with water?). . Everything takes place between 88 - 90°C. After about 2-3 hours, the temperature stagnated. Slowly I started to increase the performance, and started to drip the substance at 124°C, here I started to collect, and it looks like bromopentane. At the beginning it was cloudy with water, + drops of water from the cooler, I dry it with CaCl2.
Now the problem: it's about half as much as I had before, I don't understand. It seems that a lot of bromopentane dripped at 88 - 90°C because: the first distillate with two layers I separated, and the upper one is actually water with pentanol (according to the smell), but the lower, larger layer looks like bromopentane: it is a mobile, shiny liquid . Can you please explain to me why such an amount (about 50 ml) dripped from the beginning at a much lower temperature?

Can I try to mix my pure distilled bromopentane with this and try to distill without added of water?

I will add that I do not have a stirrer, so I do not mix the mixture; I have pieces of porcelain inserted there like cooking stones.

One more thing. I dried the first heavier layer from the first distillation with CaCl2, and an interesting thing: while I dried the distilled product well, bromopentane is already transparent, so 50 ml of liquid is not: CaCl2 is still at the bottom and the solution is white, see photo. Could it be that even though there is bromopentane, there may be a lot of pentanol in it, which is probably soluble in it, and CaCl2 has formed this white turbidity with it?


Thank you very much. Lukáš S.
« Last Edit: November 28, 2020, 07:25:52 AM by lukas.stib »

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