nachra
Harmless
Posts: 8
Registered: 6-1-2013
Member Is Offline
Mood: No Mood
|
|
allyl bromide from propyleneglycol??
Im not sure but i think ive heard of substances like PBr3 being used to replace an OH goup. Could using a 1:1/2 molar ratio cause only one OH group
per molecule to be replaced or would some molecules have both OH groups replaced leaving some molecules completely unaffected? Then if this works
could the new product be dehydrogenated leaving allyl bromide, i think ive read that potassiumhydrogensulfiide or something like that would work but
im no chemist.
Also i was considering this with the 1,3-propylenediol isomer but the other isomer seems more common place so would it work with this as well. More
importantly *chemical supplier A* sells 500gs of propylenediol for 100$ but sells 3kgs dipropyleneglycol for th same price, the problem being its
mixed isomers and they do not offer it as the single isomer with both OH groups located on the end of the carbon chain so itd be important to make
sure the process works with both isomers. If so then would it be possible to acid hydrolize the ester group in dipropyleneglycol? If so i assume one
propane chain would take the OH and the other would be left with a double bond? Again i am no chemist so please correct my ignorance. Thanks in
advance.
[Edited on 6-1-2013 by nachra]
|
|
|
killer_lapin
Harmless
Posts: 47
Registered: 23-7-2010
Location: Qc, CAN
Member Is Offline
Mood: No Mood
|
|
What are you willing to do with allyl bromide after? allylation of an aromatic compound? not such a good idea you might want to look somewhere else
for that.
otherwise, this is not an efficient reaction anyway, there is to many by product. and if you intend to do this i suggest the utilisation of a fume
hood otherwise you might destroy your sight.
|
|
|
nachra
Harmless
Posts: 8
Registered: 6-1-2013
Member Is Offline
Mood: No Mood
|
|
I appreciate the insight but could you elaborste on the potential of side products?
|
|
|
killer_lapin
Harmless
Posts: 47
Registered: 23-7-2010
Location: Qc, CAN
Member Is Offline
Mood: No Mood
|
|
If you do a bromination with PBr3 for exemple with 1,3-propanediol you'll have a mixture of 1,3-dibromopropane, 3-bromopropan-1-ol and starting
material, even if you have an exces of the alcohol.
But if you use 1,2-propylenediol you'll still have a mixture but the 2-bromopropan-1-ol might be favorised because it's a secondary alcohol.
Considering de next step (elimination) with the first product (3-bromopropan-1-ol) you would produce allylalcohol and maybe some polymerisation.
With the second approche (2-bromopropan-1-ol) you can have 2 products:allylalcohol and 1-propenol, and again maybe polymerisation. but the second
methode, i Think would favorise the 1-propenol because of the resonnance.
And all of this is considering that you produce allylalcohol to brominate it after, if you intend to brominate all the hydroxyl- group and do a
selective elimination afterward, i'll tell you that you would get even more by product since this reaction is not relly selective.
And simple question what is it for? lacrymator gas?
|
|
|
nachra
Harmless
Posts: 8
Registered: 6-1-2013
Member Is Offline
Mood: No Mood
|
|
Simply using theoretical synthesis to further my understanding of chemistry. I really do appreciate the response btw. I have recently read that allyl
alcohol can be formed from reacting glycerol and formic acid. Do you know the mechanism of how this reaction would proceed? If you dont feel like
going into detail if you give me the name if the type of reaction i could research the rest. Also you said 3-bromopropan-1-ol would be formed as a bi
product, would that not be the case since there would only be one OH? Of would the double bond be suceptible to attack?
|
|
|
killer_lapin
Harmless
Posts: 47
Registered: 23-7-2010
Location: Qc, CAN
Member Is Offline
Mood: No Mood
|
|
The 3-bromopropan-1-ol is from the 1,3-propanediol wich is an isomer of propylenediol that you've mention yourself. So there is two OH group. For the
glycerol formic acid reaction i don't know the mechanism but it might be similar as the Eschweiler–Clarke reaction where the formic acid act as a
reducing agent. But I know that the intermediate is a glycerolformate on the position 1. So if it's really important i guess i could come with an
hypothetical mechanism for this reaction wich is a better approach for an amateur chemist that the use of PBr3.
|
|
|
Nicodem
|
Thread Moved
7-1-2013 at 07:40 |
![[*]](images/xpblue/default_icon.gif){kind=icon}
