Picric-A - 12-8-2008 at 12:32
I have recently taken an interest in Organic Chemistry.
One of the biggest things holding me back is the seemingly endless amount of simple reaents needed to perform experiments.
Some poeple have the luxury of being able to buy chemicals to suit their need. some people know what exact type of paint thinner to look for when
buying methylbenzene, for example.
I have to admit i am pretty useless when it comes to looking for certain types of paint thinners to get methyl benzene ect...
I have recently been thinking, what is extremly easy to buy, with no suspicious dealers involved and no questions asked... Petrol is what i decided
upon. Through furthur research on what petrol contains exactly i decided this was the best source:
http://en.wikipedia.org/wiki/Gasoline
In the source it states these ingredients commonly found in petrol (i have added boiling points) :
Hydrocarbons- carbon chains from 5--> 12 (varies)
Benzene (up to 5%) (80.1 °C)
Toluene (up to 35%) (110.6 °C)
Napthalene ( up to 1%) (218 °C)
Trimethylbenzene ( up to 7%) (170 °C)
Methyl tert-butyl ether (up to 18%) (55.2 °C)
Unfortunatly my computer fails to open a msds of unleadded petrol so i can not see the other 10 ingredients but form the list i thoguht distillation
seems easy.
what i would do is heat the petrol to around 69 degrees tp start with, letting the hydrocarbons chain 5-6 boil off. tthen at 80degrees start
collecting benzene and so on.
Has anybody tried obtaining things like benzene form petrolor has anyone had any experiencec they would like to share?
Many thanks,
Picric-A
matei - 12-8-2008 at 13:02
At 80 degrees you will collect a mixture of benzene and aliphatic hydrocarbons. Aromatic hydrocarbons can be extracted from petrol using adequate
solvents (I think it was a thread a while ago on that subject). You just can't separate pure substances from such a mixture by distillation, even with
an extremely performant fractionating column. Anyway, you have to keep in mind that using simple distillation you can separate well substances which
have a b.p. difference of at least 50 deg. C or so.
Picric-A - 12-8-2008 at 13:43
well i was going to use a fractionating colum but i agree it will be hard to seperate the benzene from the other compounds with similar boiling
points, i havnt thought about solvent extraction...
Klute - 12-8-2008 at 17:12
Oh, even with a nice column, you would need one hell of a reflux ratio etc to isolate benzene or toluene... There is a reason why they make 100m high
rectification towers in rafineries 
I would suggest not to abandon on the quest for solvents, but look elsewhere than jsut the conventional hardware shops. Certain small stores selling
cleaning products, industrials washing, etc can get you technical solvents dirt cheap.
Better use the gasoline to look around with your car than to distill it IMHO
not_important - 12-8-2008 at 22:06
What makes up your petrol is going to vary from country to country. Gasoline in the USA will yield very little benzene, I believe under 5% total
substituted benzenes such as toluene and xylene, and MTBE is being phased out.
Len did some tests to try to measure the aromatics in Australian petrol, and found it was fairly high.
You'll need a good fractionating column to get decent separations, as already said. On the other hand, for just general purpose hydrocarbon
solvent, low grade fractionation will yield low boiling petroleum ether - best when 'winter' gasoline is used. The cuts with aromatics in them can be
used for some reactions, a mild permanganate will remove alkenes, after that HNO3, H2SO4, or Cl2/Br2 with iron catalyst will yield the corresponding
substituted aromatics which will be much easier to separate from the non-reactive alkanes.
Sauron - 13-8-2008 at 04:01
Distillation is very energy intensive. Even if you could succeed, which you really can't, you would have the world's most expensive solvents. Toluene
is cheap and often can be found OTC just as an example.
This is really a blind alley.
ScienceSquirrel - 13-8-2008 at 04:17
Ronsonol, a light petroleum spirit sold for use in petrol lighters and for stain removal, can be used as a petroleum ether substitute at a pinch.
It works out quite expensive but if you just need a few ml it is bearable.
Picric-A - 13-8-2008 at 13:56
yes sciencesquirrel thats what i use,
i dont agree that its expencive though, i buy myn around £5 a litre! cheaper than propanone
Klute - 13-8-2008 at 15:06
5 quid a liter IS expensive