Waffles SS
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M-Cresol
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Cresols are organic compounds which are methylphenols. They are a widely occurring natural and manufactured group of aromatic organic compounds which
are categorized as phenols (sometimes called phenolics). Depending on the temperature, cresols can be solid or liquid because they have melting points
not far from room temperature. Like other types of phenols, they are slowly oxidized by long exposure to air and the impurities often give cresols a
yellowish to brownish red tint. Cresols have an odor characteristic to that of other simple phenols, reminiscent to some of a "coal tar" smell.
In its chemical structure, a cresol molecule has a methyl group substituted onto the benzene ring of a phenol molecule. There are three forms of
cresols that are only slightly different in their chemical structure and physical properties: ortho-cresol (o-cresol), meta-cresol (m-cresol), and
para-cresol (p-cresol). These forms occur separately or as a mixture. The word tricresol can be used as a synonym for cresol where it means a mixture
of o-, m- and p-cresols.
http://en.wikipedia.org/wiki/Cresol
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I want to find easy method for making M-cresole and i think diazotization of M-toluidine is easier way.
In this way we should make m-toluidine first but it seems making m-toluidine is more difficult than m-cresol.
M-toluidine prepare by m-nitrotoluene but unfortunately m-nitro toulene is minor isomer is nitration of toluene and this is really so difficult to
separate it.but it seems this route is easier way for making m-cresol.
First i want to try toluene nitration and separatimg m-isomer.does freezing method can separating m from p and o isomer?(i just know it can be
effective way for separating p from o isomer)
Is there better way?
[Edited on 9-1-2013 by Waffles SS]
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Nicodem
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Thread Moved
9-1-2013 at 10:15 |
sankalpmittal
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Mood: Confused....
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M-Cresol..
I don't think there is an easier method....
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kristofvagyok
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Quote: Originally posted by Waffles SS  |
First i want to try toluene nitration and separatimg m-isomer.does freezing method can separating m from p and o isomer? |
When nitrating toluene 2-nitrotoluene and 4-nitrotoluene will be produced and only traces of 3-nitrotoluene will form.
Usually 40-60% 4-nitrotoluene is produced, 30-40% 2-nitrotoluene and just only 1-3% 3-nitrotoluene.
So this would be a really non-efficient method for producing 3-nitrotoluene and m-cresol from it.
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Waffles SS
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Thanks kristofvagyok but i think this is easier method.What about separating meta Cresol from m/p Cresol(50%meta-50% para isomer mixture)?
Does freezing method is effective here?
M-cresol meting point:11.8 °C
P-cresol melting point:35.5 °C
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Cresol
Since 1965, when the recovery of cresols from coal tar and spent refinery caustics had become insufficient to meet the rising demand, these compounds
have been increasingly produced by synthesis. The processes now in use are
– Alkali fusion of toluenesulfonates
– Alkaline chlorotoluene hydrolysis
– Splitting of cymene hydroperoxide
– Methylation of phenol in the vapor phase
Alkali Fusion of Toluenesulfonates
Technical-grade m-cresol can also be produced by toluene sulfonation according to a process developed by the Honshu Chemical Industry Co. Steam at 165
◦C is introduced into
an toluenesulfonic acid mixture rich in m isomer obtained under thermodynamically controlled conditions as described above (isomerization for several
hours at 190 – 200 ◦C), whereupon
o- and p-toluenesulfonic acid are hydrolyzed back to sulfuric acid and toluene. The toluene is distilled with the steam; m-toluenesulfonic acid with a
purity above 90% remains, together with sulfuric acid. Side reactions during the isomerization and hydrolysis can be suppressed by adding sodium
sulfate (5 – 10 mol%, calculated on the basis of sulfuric acid) to the sulfonation batch. In this way, removal of the sulfuric acid that is formed
in the hydrolysis as a lower phase at ca. 140 – 150 ◦C is also possible. It is also possible to neutralize the hydrolysis mixture with
concentrated sodium hydroxide solution,filter off the resulting sodium sulfate at 80 ◦C, introduce the solution of sodium m-toluenesulfonate
into a sodium hydroxide melt, containing 10 – 15% potassium hydroxide to facilitate stirring,at an initial temperature of 330 ◦C, and tofuse
it at 340 ◦C.The distillation of the crude cresol phase obtained after acidification gives m-cresol with a purity of up to 98% in a yield of ca.
65%, calculated on the basis of reacted toluene .
Ullmann's Enc. of Industrial Chemistry2007
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That is only high yield industrial method for making M-cresol, but i think it is more difficult than diazotization of M-toluidine method
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Prometheus23
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Instead of nitrating toluene and trying to isolate the small percentage of 3-nitrotoluene produced in the reaction I would suggest nitrating
benzaldehyde instead. Benzaldehyde when nitrated gives primarily 3-nitrobenzaldehyde. Here is a procedure for the nitration of benzaldehyde.
http://www.orgsyn.org/orgsyn/prep.asp?prep=cv3p0644
You can then reduce the aldehyde and nitro groups to methyl and amino groups respectively, with whatever means you wish, to give you m-toluidine. This
procedure outlines the use of SnCl2/HCl to reduce 3-nitrobenzaldehyde to 3-aminobenzaldehyde as well as the diazotization to form
3-hydroxybenzaldehyde.
http://www.orgsyn.org/orgsyn/prep.asp?prep=cv3p0453
Of course you may decide to go about the reductions in a different manner, this is at least a place to start.
Hope this was helpful, and if you do end up trying this synthesis out please share your results!
[Edited on 1/14/2013 by Prometheus23]
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Waffles SS
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Interesting,
I think nitration of benzoic acid is cheaper and also the major product is M-nitro benzoic acid
http://www.orgsyn.org/orgsyn/prep.asp?rxntypeid=181&prep...
But i dont : this is possible to reduce carboxylic group to methyl group by Sn/HCl or not!(sure catalyst hydrogenation is best method for this step)
[Edited on 15-1-2013 by Waffles SS]
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Prometheus23
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No, carboxylic acids like benzoic acid will not be reduced directly to the alkane by Sn/HCl or any other reducing system I know of that is available
to the amateur experimenter. Hence why I suggested benzaldehyde as the starting material. It is more expensive than benzoic acid, but the aldehyde can
be reduced with the clemmensen reduction to a methyl group.
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Waffles SS
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Carboxylic acids reduce to alcohol by LiAlH(or catalyst hydrogenation) and then alcohol to alkane (hydrogenation is cheaper and more economical
method)
4 RCO2H + 3 LiAlH4 =4 H2 + 4 RCH2OM + metal oxides= 4 RCH2OH + metal hydroxides
http://www2.chemistry.msu.edu/faculty/reusch/virttxtjml/crba...
also benzaldehyde is more expensive than benzoic acid
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kristofvagyok
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Wouldn't that be this method a littlebit expensive compared to the price of m-cresol?
Also the reduction can go to methyl group with LiAlH4 in ether, in up to 50% yield if an activated benzoic acid is hydrogenated, e.g: anthranilic acid
or in your case 3-amino-benzoic acid. -J. Am. Chem. Soc. 81, 610 (1959)
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Waffles SS
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@kristof sure LiAlH4 is expensive method , i want to say there is other reducing system (like LiAlH4 in ether or catalyst hydrogenation ) for reducing
carboxylic acid to alcohol and then alkane.I didnt say LiAlH4 is economical method,just this is possible way
[Edited on 16-1-2013 by Waffles SS]
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Prometheus23
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Waffle SS you cut my quote short of its full meaning as well as not understanding it. What I said was:
"carboxylic acids like benzoic acid will not be reduced directly to the alkane by Sn/HCl or any other reducing system I know of that is available to
the amateur experimenter"
Carboxylic acids will not be reduced DIRECTLY from the acid to the alkane by Sn/HCl. They will also not be reduced DIRECTLY to the alkane by any
reducing systems that are available to the amateur. Or at least I assumed you would not have access to anything of this nature (LiAlH4 in ether) since
you wish to make m-cresol and are apparently concerned with the cost of such a synthesis. I apologize if this is in fact within your abilities, but as
you were asking about this synthesis in the first place as well as asking if Sn/HCl would reduce a carboxylic acid, I assumed it was not.
Besides the slightly more expensive benzaldehyde would more than pay for itself by avoiding the need for such things as LiAlH4 and anhydrous ether.
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Waffles SS
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Thanks Prometheus23 (I found out this is not possible to reduce carboxylic group to methyl group by Sn/HCl)
I want to use Catalytic Hydrogenation but i cant find more information about this way(how much pressure?what catalyst is better for each step?)
I think Catalytic Hydrogenation will reduce Carboxylic acid to alkane in two step but in one pot,First Carboxylic acid reduce to alcohol in
hydrogenation reactor at certain pressure and Temp( 10 bar pressure and PtO2 catalyst at RT should be sufficient) and then alcohol to alkane in
certain pressure even without opening reactor and Quickly after first hydrogenation step.
Also there is no need for SN/HCl method if we Catalytic Hydrogenation (m-toluidine prepare directly from 3-nitro benzoic acid in one pot)
A. T. Nielsen (1962). "The Isomeric Dinitrocyclohexanes. II. Stereochemistry". J. Org. Chem. 27 (6): 1998–2001.
doi:10.1021/jo01053a019
[Edited on 17-1-2013 by Waffles SS]
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