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Kobold vor NH4
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[*] posted on 19-4-2020 at 01:36
Use For Menthol?


Hello everyone, I have about a half kilo or so of menthol, so I was wondering if there is
anything interesting I can do with it.
I know it functions like a secondary alcohol, but are any of its compounds interesting?




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[*] posted on 19-4-2020 at 01:53


I sometimes wondered if it could be used like camphor in Rast's method for measuring molar masses.


[Edited on 19-4-20 by unionised]
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[*] posted on 19-4-2020 at 02:20


Make some sodium. https://youtu.be/BsNoiFj3wlw
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Kobold vor NH4
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[*] posted on 19-4-2020 at 02:36


Yeah, I saw that awhile back. I found a post here that is just distilling a mixture of NaOH and Al, if that didn't work I was going to do it NurdRage's way.


EDIT: Found it http://www.sciencemadness.org/talk/viewthread.php?tid=82406

[Edited on 19-4-2020 by Kobold vor NH4]




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[*] posted on 19-4-2020 at 07:17


If sodium metal isn't interesting enough menthol valerate is a tranquilizer of some sort
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[*] posted on 19-4-2020 at 11:04


Quote: Originally posted by Kobold vor NH4  
Yeah, I saw that awhile back. I found a post here that is just distilling a mixture of NaOH and Al, if that didn't work I was going to do it NurdRage's way.


EDIT: Found it http://www.sciencemadness.org/talk/viewthread.php?tid=82406

[Edited on 19-4-2020 by Kobold vor NH4]


That's a pretty smart setup for home distillation of sodium. I was thinking about how I could purify sodium in a home setting, other than the stirring in dioxane method.

edit: Just thinking out loud, I wonder how well one of those Chinese induction heaters from eBay would work to heat up a CO2 canister containing sodium?

[Edited on 4-19-2020 by monolithic]
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[*] posted on 19-4-2020 at 11:08


draculic acid69 thx for interesting idea, it seems to be menthyl isovalerate, I will certainly try the synthesis in the future



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[*] posted on 19-4-2020 at 11:16


You can eliminate the alcohol with dilute H2SO4 to 3-menthene. There is probably a way to convert this to the tertiary hydroperoxide, which would function as a (sort of) chiral oxidant and is an OTC analog of tBuOOH.

[Edited on 19-4-2020 by clearly_not_atara]




[Edited on 04-20-1969 by clearly_not_atara]
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[*] posted on 19-4-2020 at 18:34


draculic acid69 its not that metallic sodium isn't interesting, I just prefer the other method.

Clearly_not_atara, if the 3-menthene is an alkene, it could be (eventually) turned into a Carboxylic acid, which could could then be esterified with menthol, right? Could be interesting. Anyone know if these would be possible/stable?

Alcohol->Alkene->Haloalkane->Nitrile->Carboxylic acid->Ester

[Edited on 20-4-2020 by Kobold vor NH4]




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[*] posted on 19-4-2020 at 18:52


Quote: Originally posted by Kobold vor NH4  
draculic acid69 its not that metallic sodium isn't interesting, I just prefer the other method.

Clearly_not_atara, if the 3-menthene is an alkene, it could be (eventually) turned into a Carboxylic acid, which could could then be esterified with menthol, right? Could be interesting. Anyone know if these would be possible/stable?

Alcohol->Alkene->Haloalkene->Nitrile->Carboxylic acid->Ester


That should read Alkene -> Haloalkane, but yes, that should be possible.

You could also (theoretically) take the haloalkane, react it with magnesium to get the Grignard, add carbon dioxide to get the carboxylate. Beats mucking with cyanide.

Making esters of menthol won't be very easy, as it's a secondary alcohol.




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[*] posted on 19-4-2020 at 20:09


Quote: Originally posted by Kobold vor NH4  
draculic acid69 its not that metallic sodium isn't interesting, I just prefer the other method.

Clearly_not_atara, if the 3-menthene is an alkene, it could be (eventually) turned into a Carboxylic acid, which could could then be esterified with menthol, right? Could be interesting. Anyone know if these would be possible/stable?

Alcohol->Alkene->Haloalkane->Nitrile->Carboxylic acid->Ester

[Edited on 20-4-2020 by Kobold vor NH4]


That would make an interesting ester
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[*] posted on 19-4-2020 at 21:13


Quote: Originally posted by DraconicAcid  
Quote: Originally posted by Kobold vor NH4  
draculic acid69 its not that metallic sodium isn't interesting, I just prefer the other method.

Clearly_not_atara, if the 3-menthene is an alkene, it could be (eventually) turned into a Carboxylic acid, which could could then be esterified with menthol, right? Could be interesting. Anyone know if these would be possible/stable?

Alcohol->Alkene->Haloalkene->Nitrile->Carboxylic acid->Ester


That should read Alkene -> Haloalkane, but yes, that should be possible.

You could also (theoretically) take the haloalkane, react it with magnesium to get the Grignard, add carbon dioxide to get the carboxylate. Beats mucking with cyanide.

Making esters of menthol won't be very easy, as it's a secondary alcohol.


Secondary alcohols can form esters fine, through Fischer esterification. But reaction is slow because of steric hindrance. Making isopropyl acetate requires 18 hour reflux.

Theres no need to go from alcohol to alkene to haloalkane. Secondary Alcohols can be directly converted to alkyl bromides without rearrangement with phosphorus tribromide, but hazmat shipping is expensive. I have never done hydrohalogenation of an alkene, dunno how easy it is.

this would be a fun project




Edit: the fischer esterification step would be done in toluene, with TsOH generated in situation when sulfuric acid is added

[Edited on 20-4-2020 by Cou]
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[*] posted on 21-4-2020 at 04:04


Cou, that's a nice diagram, however it seems to me that PBr3 is out of my ability to handle safely, regardless of of its availability or cost or usefulness. Phosphorus(and Phosphine) is one of those things that I refuse to work with, as working with it seems what I would call "Hard-Core". Maybe sometime in the future.

Here's a diagram that I made, which is probably what I will do when my order of Magnesium arrives, sometime next month. Let me know if there's anything that I missed/got wrong. Ill do an update on it when I attempt the synthesis.

MentholEsterification.bmp - 881kB




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[*] posted on 21-4-2020 at 07:28


You don't need to go through the steps of dehydration alcohol to alkene, then hydrohalogenation. secondary alcohols can be directly converted to a racemic alkyl bromide by adding to azeotropic hydrobromic acid. the procedure would be similar to nurdrage's synthesis of 1-bromohexane: https://www.youtube.com/watch?v=Ydn1D4FSqkc . Alkyl bromides are easier to turn into grignard reagents than alkyl chlorides, and also easier to form b/c bromide ions are better nucleophiles, whereas making alkyl chlorides requires zinc chloride catalyst.



One difference between using PBr3 vs HBr to make alkyl bromides from alcohols is that PBr2 only reacts SN2 so that stereochemistry is inverted (the carbon atom containing the alcohol in menthol is chiral), whereas HBr reacts SN1 so a racemic mixture is made.

I thought dehydration of alcohols to alkenes is done in concentrated sulfuric acid, not dilute.

Vogel's practical organic chemistry doesn't have any procedures for hydrohalogenation of alkenes x(

also, wouldn't the hydrochlorination be markovnikov addition, so the chlorine is added to the tertiary carbon?




here is a revised diagram

5zICwIC.png - 100kB

[Edited on 21-4-2020 by Cou]

[Edited on 21-4-2020 by Cou]
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[*] posted on 21-4-2020 at 07:51


Could you de-hydrogenate the central cyclohexane ring to a benzene ring to give you thymol or oxidize it directly to thymoquinone?
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[*] posted on 21-4-2020 at 08:11


You could do it if you know how to build a fixed bed reactor. http://translationportal.epo.org/emtp/translate/?ACTION=desc...



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[*] posted on 21-4-2020 at 13:38


Quote: Originally posted by Cou  
I thought dehydration of alcohols to alkenes is done in concentrated sulfuric acid, not dilute.
It depends on the alcohol. According to Wikipedia, “ Menthol is easily dehydrated to give mainly 3-menthene, by the action of 2% sulfuric acid.” So it sounds like menthol dehydrates very readily.

Quote: Originally posted by Cou  
Vogel's practical organic chemistry doesn't have any procedures for hydrohalogenation of alkenes x(
It shouldn’t be too complicated. Dissolving the alkene in an aprotic solvent and bubbling in HCl or HBr has from a simple salt/sulfuric acid setup with drying trap should do the job perfectly.

Quote: Originally posted by Cou  
also, wouldn't the hydrochlorination be markovnikov addition, so the chlorine is added to the tertiary carbon
Yes, you’re correct. If he wanted the anti-markovnikov addition, he would need to use HBr with a catalytic amount of peroxide to set off a free-radical chain reaction. Overall, skipping the dehydration and going directly to the halide is much more practical.

Side note: it’s nice to see you being productive and helpful, Cou. Your new signature is very large though.




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[*] posted on 21-4-2020 at 20:06


I just remembered that HBr substitution on secondary carbons can cause rearrangement, so the bromine may end up on the tertiary carbon. That is why I originally suggested PBr3

This means you need to either use PBr3 (Stereochemistry inversion), or dehydrate to the alkene and do anti-markovnikov addition of HBr to the alkene (racemic)



[Edited on 22-4-2020 by Cou]

Screenshot_8.png - 17kB

correction on that diagram: the bond connecting the cyclohexane ring to the isopropyl group should be a straight line for the 2nd two molecules, not pointing into the page

[Edited on 22-4-2020 by Cou]




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[*] posted on 22-4-2020 at 02:16


Here's a file that I found the other night for the dehydration http://jan.ucc.nau.edu/~jkn/235L5-Dehydration.htm . Ill revise my diagram on my previous post either tonight or tomorrow.
I haven't got any Bromides or HBr, so Ill have to order some.

[Edited on 22-4-2020 by Kobold vor NH4]




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[*] posted on 22-4-2020 at 05:50


Quote: Originally posted by Kobold vor NH4  
Clearly_not_atara, if the 3-menthene is an alkene, it could be (eventually) turned into a Carboxylic acid, which could could then be esterified with menthol, right? Could be interesting. Anyone know if these would be possible/stable?

Alcohol->Alkene->Haloalkane->Nitrile->Carboxylic acid->Ester

You don't need to go through the alcohol to make the bromide and you definitely don't want to mess with cyanide or Grignards at the level you're at right now.

If you want to make a carboxylic acid a better way would be to cleave the alkene with KMnO4. That's only two steps.




[Edited on 04-20-1969 by clearly_not_atara]
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[*] posted on 22-4-2020 at 06:46


But where would the carbon that's in the carboxylic group come from? Without cutting it open, I do not see how a carboxylic could be formed.

I've mainly studied and worked with inorganic compounds, I have experience working with hazardous compounds, I have the safety mindset, there's just some things that I don't like.

EDIT:
I haven't worked with cyanides for the aforementioned reasons. I haven't worked with Grignards, Organics or Organometallics because my focus has mainly been on mineral-bearing rocks.

[Edited on 23-4-2020 by Kobold vor NH4]




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[*] posted on 22-4-2020 at 07:10


KMnO4 will indeed “cut open” the alkene under acidic conditions at high temperature. What you end up with is a carboxylic acid on the formerly secondary carbon of the alkene, and a ketone on the formerly tertiary carbon.



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[*] posted on 22-4-2020 at 07:34


Quote: Originally posted by Kobold vor NH4  
I've mainly studied and worked with inorganic compounds, I have experience working with hazardous compounds, I have the safety mindset

Could you provide some examples? So far you haven't heard of many reactions that I usually think of as elementary. Cyanide tends to dissuade even relatively experienced members of this forum. Grignards usually require air-free techniques that are not common in inorganic chemistry.

[Edited on 22-4-2020 by clearly_not_atara]




[Edited on 04-20-1969 by clearly_not_atara]
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[*] posted on 22-4-2020 at 07:54


Quote: Originally posted by Texium (zts16)  
KMnO4 will indeed “cut open” the alkene under acidic conditions at high temperature. What you end up with is a carboxylic acid on the formerly secondary carbon of the alkene, and a ketone on the formerly tertiary carbon.






Screenshot_1.png - 18kB

correction version of the diagram i posted above, the stereochemistry was wrong


[Edited on 22-4-2020 by Cou]

Untitled.png - 17kB

[Edited on 22-4-2020 by Cou]




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[*] posted on 22-4-2020 at 08:37


Quote: Originally posted by Cou  
Quote: Originally posted by Texium (zts16)  
KMnO4 will indeed “cut open” the alkene under acidic conditions at high temperature. What you end up with is a carboxylic acid on the formerly secondary carbon of the alkene, and a ketone on the formerly tertiary carbon.








correction version of the diagram i posted above, the stereochemistry was wrong


[Edited on 22-4-2020 by Cou]



[Edited on 22-4-2020 by Cou]


You should have a straight line on the carbonyl, not a dashed wedge.




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