KABOOOM(pyrojustforfun)
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Kolbe reaction
it's a way of preparing saturated/unsaturated hydrocarbons via electrolysis of aliphatic carboxilic acid alkali metal salts.<br>eg
:<br>2CH<sub>3</sub>COO<sup>-</sup> <s> ></s>
H<sub>3</sub>C-CH<sub>3</sub>
+2CO<sub>2</sub><br><br><sup>-</sup>OOC-CH<sub>2</sub>CH<sub>2</sub>-COO<sup>-</s
up> <s> ></s> H<sub>2</sub>C=CH<sub>2</sub> +
2CO<sub>2</sub><br>succinic acid<br><br>the above definition and examples come from The penguin dictionary of chemistry
(translated it back to its original language)<br>now just think about the endless possible reactions ...<br>trichloroacetic acid to
hexachloroethane, nitroacetic acid to dinitroethane, trinitroacetic acid to hexanitroethane, glycine to ethylene diamine, serine to
1,2-di(hydroxymethyl)ethylene diamine,<br>glyoxylic acid to glyoxal,<br>glyceric acid to erythritol, gluconic acid to
1,2,3,4,5,6,7,8-octahydroxyoctane, lactic acid to 2,3-dihydroxybutane,<br>acrylic acid to butadiene, methacrylic acid to 2,3-dimethylbutadiene,
maleic acid to acetylene or acetaldehyde,<br>oxime of mesoxalic acid to fulminic acid, pyruvic acid to imethylglyoxal, .......
Edit: corrected a typo (changed dimethylglyoxime to dimethylglyoxal)
[Edited on 20-11-2003 by KABOOOM(pyrojustforfun)]
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Theoretic
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Hmmm... Sounds nice! Under what conditions does this work?
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KABOOOM(pyrojustforfun)
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US 2,760,926 describes hydrocarbon aliphatic ethers prepared by electrolysis of salts of aliphatic carboxylic acids under anhydrous or substantially
anhydrous conditions
from <i>US 5,423,454 US5423454 Method of propellant gas generation</i> (electrochemically) :
<blockquote>quote:<hr>In a variation of the Kolbe reaction, a mixture of propionic acid and potassium propionate ,may be electrolytically
reacted to form 63 mole percent carbon dioxide, 15 mole percent butane, 14 mole percent ethane and 6 mole percent ethylene for almost 98% gaseous
product yield. Since the major product is still carbon dioxide, the flammability of the other gaseous products is suppressed by its presence, with all
of the gaseous products functioning as propellant.
In another variation of the Kolbe reaction, the use of dicarboxylic acids, dicarboxylic acid salts, hydroxy acids and hydroxy acid salts with suitable
ancillary agents, as subsequently described, can yield 2 or 3 molecules of carbon dioxide per electron transfer. Such systems are desirable when rapid
gas regeneration is required.
Conducting the Kolbe type reaction in a mixture of methanol and water improves efficiency over water alone. The efficiency of the reaction may be
further improved through the presence of foreign anions such as bicarbonate, dihydrogen phosphate, fluoride and sometimes sulfate. These anions may be
furnished as alkali or alkaline earth metal salts of sodium, potassium, calcium and barium. Such cations have not been found to have a significant
deleterious effect. The system should, however, be essentially free of cations of cobalt, copper, iron, lead and manganese since even low
concentrations of these metals have a deleterious effect.
Aromatic acids and aromatic acid salts, such as benzoic acid and benzyl acetate may be utilized in Kolbe type reactions. In general, however, it is
desirable to avoid such aromatics in reaction mechanisms where aromatics such as benzene are generated.
For aerosol applications using the Kolbe reaction, it is desirable that the minimum electrical potential for activation, i.e., the lowest voltage at
which the desired reactions begin, be between 2.1 and 3.0 volts. The current density is usually from 0.15 to 3 amperes per cm.sup.2 and preferably the
current density is in the area of 0.25 ampere per cm<sup>2</sup> <hr></blockquote>
<blockquote>quote:<hr>... If chemistry based upon the Kolbe reaction is used, an 8-ounce container will require an electron transfer of
about 2,470 coulombs or 0.69 ampere-hours at a minimum of 3 volts, to effect total dispensing of the product ...<hr></blockquote>
<blockquote>quote:<hr>EXAMPLE I
An electrolytic cell is made using an electrolyte comprising 60 ml of 5N aqueous acetic acid containing 5 grams of potassium acetate gelled with
methyl cellulose...
...The current density through the electrolyte using platinum electrodes of 0.4 amperes per cm.sup.2 which yields 2.5 mole percent methane, 6.4 mole
percent ethane and 91 mole percent carbon dioxide. The reaction produces almost 100% gas. Current efficiency is found to be 82 percent when graphite
electrodes are used.<hr></blockquote>
<a
href="http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&p=1&u=/netahtml/search-bool.html&r=18&f=G&l=50&am
p;co1=AND&d=ptxt&s1='kolbe+reaction'&OS="kolbe+reaction"&RS="kolbe+reaction""><i>US
5,811,627 Alkylation reactions</i></a>:
<blockquote>quote:<hr>The Kolbe Reaction is a well known electrochemical reaction that involves an oxidation at an anode of the
carboxylate ion of an organic acid to produce either a free radical or a carbonium ion depending upon the electrode used and the voltage applied.
These reactions are as follows:
<img src="http://www.angelfire.com/rnb/pjff/Pat.gif">
where R is either a hydrogen or a saturated or unsaturated hydrocarbyl material, that can include, esters, amines, amides, ketones, etc. When a carbon
electrode is used instead of platinum, there is a tendency to remove two electrons at the anode, thereby generating a carbonium ion shown in equation
9. When precious metal anodes such as platinum, tin, gold, silver, or palladium, are used, the more usual course of the reaction is to generate the
free radical shown in equation 8. This radical can and often does couple with itself in a bi-radical coupling reaction in accordance with equation 10.
<hr></blockquote>
<blockquote>quote:<hr>In Topics in Current Chemistry, vol. 152, pages 92-151, the addition of Kolbe Radicals to double bonds was
discussed. Reference was made to the work of Louis Schmerling and James P. West reported in the Journal of the American Chemical Society, vol. 71,
2015-2019 (1949). The conclusions reached are provided on page 142 of volume 71. Among these conclusions were: (a) due to the high concentration of
radicals in the reaction layer in front of the electrode, termination and not propagation predominates even in the presence of alkenes; (b) in the
presence of high current, dimers are favored; (c) elevated pressures favor Kolbe Coupling; (c) high temperatures favor disproportionation; (d) high
current favored formation of additive monomers and low current favored additive dimers; (e) in the presence of reactive olefins such as butadiene,
isoprene, or styrene good yields of adduct were observed; (f) foreign cations ranging from most to least effective in producing lower yields are
Fe<sup>+2</sup> < Co<sup>+2</sup> < Ca<sup>+2</sup> < Mn<sup>+2</sup> <
Pb<sup>+2</sup> and alkali metals, alkaline rare earth metals, alkylammonium ions, zinc, or nickel ions do not seem to affect or influence
Kolbe Reactions.<hr></blockquote>
reference:<blockquote>quote:<hr>Details as to the best procedure for carrying out a Kolbe-like reaction are disclosed in Advances in
Organic Chemistry: Methods and Results, Published by lnterscience Publishers, Vol. 1, beginning on page 5 (QD 251.A36).<hr></blockquote>
<a
href="http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&p=1&u=/netahtml/search-bool.html&r=17&f=G&l=50&am
p;co1=AND&d=ptxt&s1='kolbe+reaction'&OS="kolbe+reaction"&RS="kolbe+reaction""><i>US
5,841,002 Process for the commercial production of polyhydroxy alcohols and glycols</i></a> :
<blockquote>quote:<hr>The Kolbe reaction was first carried out in 1849 and has been used since in organic synthesis. Among the simplest
materials to undergo the Kolbe reaction when electrolysed are carboxyllc acids. An acid of general formula RCOOH where R is a hydrogen atom, an alkyl
group or an aryl group will reversibly dissociate to yield hydrogen ions and ions of formula RCOO<sup>-</sup> . Generally the Kolbe
reaction is carried out in the presence of sodium or potassium carboxylate salts because many carboxylic acids are only weakly ionised and are
therefore poor conductors of electricity. These anions will, on electrolysis under suitable conditions, lose an electron to form free radicals of
formula RCOO<sup>.</sup> . These radicals are unstable and undergo decarboxylation to form R<sup>.</sup> and
CO<sub>2</sub>, thereby liberating carbon dioxide at the anode. Two R<sup>.</sup> radicals can unite to yield a compound of
formula R--R. Other compounds may also be synthesised under the Kolbe reaction conditions. For example, in aqueous solution OH<sup>-</sup>
ions will be present and on discharge will form HO<sup>.</sup> radicals which can combine with R<sup>.</sup> radicals to
produce alcohols of formula R--OH. The hydroxyl radicals can also participate in the oxidation of the organic compounds via hydrogen abstraction
reactions, addition to double bonds, and combination with organic radicals. Reactions of this type are believed to be responsible for the removal of
heavy but non-ionisable materials in the anode region. The reaction
2HO<sup>.</sup> <s> ></s> H<sub>2</sub>O<sub>2</sub>
<s> ></s> H<sub>2</sub>O + 1/2O<sub>2</sub>( 20)
is believed to be at least partially responsible for the formation of oxygen in the anode region.
Esters formed by the joining of R<sup>.</sup> and RCOO.sup.., i.e. RCOOR, hydrocarbons of formula RH, and olefins of formula containing
one less hydrogen atom than R<sup>.</sup> are also products under the Kolbe reaction conditions. Peroxy compounds of the formula HOOH,
ROOH or ROOR may also be formed by free radical combination under certain conditions.
In an electrolytic cell with anode and cathode regions the free carboxylic acid can be formed by the transfer of alkali metal ions through a membrane
dividing the regions. ##STR14##
The application of the Kolbe reaction and of other reactions which can occur under the Kolbe reaction conditions in organic synthesis has been
extensively reported and reviewed, for example in:
1) Svadkovskaya, G. E. and Voitkevich, S. A., "Electrolytic Condensation of Carboxylic Acids" in Russian Chemical Reviews, 29(3), 1960,
pages 161 to 167;
2) Koehl, W. J., "Anodic Oxidation of Aliphatic Acids at Carbon Anodes" in Journal of the American Chemical Society, 1964, pages 4686 to
4690; and
3) Eberson, Lennart, "The Chemistry of Carboxylic Acids", Interscience, 1969, pages 54 to 99.
According to the afore-mentioned article by Svadkovskaya, G. E. and Voitkevich, S. A., the anode material has an effect on the course of the reaction
in the electrolysis cell. Thus it was reported that in the electrolysis of acetates the highest yields of ethane were obtained using a smooth platinum
or iridium anode, while gold, nickel and platinised platinum anodes gave negative results. On the other hand graphite anodes gave moderate yields of
ethane.
In the process of the invention it is accordingly preferred to use an anode made of a material that promotes the Kolbe reaction. Thus it is preferred
to use smooth platinum or iridium anodes. Conveniently the cathodes are also smooth platinum electrodes.
The Kolbe reaction is not limited to carboxylic acids. Alkali metal carboxylates will also undergo electrolytic decomposition according to the
mechanism outlined briefly above and reported fully in the literature. Generally the Kolbe reaction is carried out in aqueous solution containing free
carboxylic acid and the corresponding alkali metal salt of the acid. <hr></blockquote>
I found more but I'm in a hurry.. maybe tomorrow
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KABOOOM(pyrojustforfun)
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from <a target=blank
href="http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&p=2&u=/netahtml/search-bool.html&r=51&f=G&l=50&am
p;co1=AND&d=ptxt&s1='kolbe+reaction'&OS="kolbe+reaction"&RS="kolbe+reaction"">US 4,097,344
Electrochemical coupling of perfluoroalkyl iodides</a>:<blockquote>quote:<hr>Electrolysis is conveniently carried out at a specified
constant current density, achieved by application of an anode potential above the cricical potential at which the Kolbe reaction starts, generally in
the range of 2.1-2.8 volts (normal hydrogen electrode)<hr></blockquote>
from <a
href="http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&p=2&u=/netahtml/search-bool.html&r=57&f=G&l=50&am
p;co1=AND&d=ptxt&s1='kolbe+reaction'&OS="kolbe+reaction"&RS="kolbe+reaction"">US 3,992,435
Process for electrolytic synthesis of polyalkylbiphenylpolycarboxylic acid compounds</a>:<blockquote>quote:<hr>...It is equally well
known that aromatic carboxylic acids in which the carboxyl group is directly attached to a benzene ring fail to undergo the Kolbe reaction to any
extent, as is reported by B. C. L. Weedon ("Anodic Syntheses With Carboxylic Acids" Quarterly Reviews Vol. 6, No. 4, 1952 p. 387-388).
Benzoic acid on electrolysis in methanol yields benzene rather than undergoing a coupling reaction<hr></blockquote>
I linked to patents just to show where I extracted them from. it's not necessary to read them all. the quotes give some info on condition in
which the kolbe reaction takes place.
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nightshade
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what about amino acids?
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MagicJigPipe
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| Quote: |
In general, however, it is desirable to avoid such aromatics in reaction mechanisms where aromatics such as benzene are generated.
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Why? It seems to me that benzene would be desirable. Perhaps this could be a possible new route to benzene production?
Now that they said that, I am very fascinated with this. I mean, most of us should have no use for actually preparing a mixture of methane and ethane
since this is basically natural gas but, products such as ethylene, propylene and benzene are VERY interesting!
I'm going to do some research on this reaction. I'll be back.
[Edited on 5-27-2008 by MagicJigPipe]
"There must be no barriers to freedom of inquiry ... There is no place for dogma in science. The scientist is free, and must be free to ask any
question, to doubt any assertion, to seek for any evidence, to correct any errors. ... We know that the only way to avoid error is to detect it and
that the only way to detect it is to be free to inquire. And we know that as long as men are free to ask what they must, free to say what they think,
free to think what they will, freedom can never be lost, and science can never regress." -J. Robert Oppenheimer
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indigofuzzy
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| Quote: |
I mean, most of us should have no use for actually preparing a mixture of methane and ethane since this is basically natural gas
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unless you're obsessed with green fuel...... make natural gas from vinegar, and skip the fossil fuels.
Hypothetically: could this reaction (with proper reagents) produce a soup of hydrocarbons similar to gasoline?
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12AX7
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By the sound of it, you'll get gasoline if you process pentanoic and hexanoic acids (yielding C8-10 straight chains).
Tim
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MagicJigPipe
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I'm still interested in the benzene that apparently is "undesirable". I still don't understand why the hell one would want to avoid making benzene.
Weird.
| Quote: |
Benzoic acid on electrolysis in methanol yields benzene rather than undergoing a coupling reaction
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Hell yes! I wonder what the yeilds would be? This seems like it might be a cheap and easy way to benzene even if the yields were 20%.
I am so going to try this once I receive my platinum electrode.
EDIT
I always thought gasoline was C5-C-12 with significant amounts of toluene, benzene, MTBE, trimethylbenzene and a small amount of naphthalene (and now
up to 10% EtOH). I wonder if a "straight" mix of C5-C12 aliphatic hydrocarbons would cause problems in a standard gasoline engine because of the
fairly large amounts of aromatic compounds in normal gasoline which they are designed to use.
[Edited on 6-7-2008 by MagicJigPipe]
"There must be no barriers to freedom of inquiry ... There is no place for dogma in science. The scientist is free, and must be free to ask any
question, to doubt any assertion, to seek for any evidence, to correct any errors. ... We know that the only way to avoid error is to detect it and
that the only way to detect it is to be free to inquire. And we know that as long as men are free to ask what they must, free to say what they think,
free to think what they will, freedom can never be lost, and science can never regress." -J. Robert Oppenheimer
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12AX7
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100 octane is measured as 100% octane. I don't remember if that's straight chain or one of the particularly branched versions (tertiary hydrocarbons
have higher octane as I recall).
Tim
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MagicJigPipe
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According to Wikipedia 100 octane would be pure iso-octane.
| Quote: |
Octane number is the number which gives the percentage, by volume, of iso-octane in a mixture of iso-octane and normal heptane, that would have the
same anti-knocking capacity as the fuel which is under consideration. For example, gasoline with the same knocking characteristics as a mixture of 90%
iso-octane and 10% heptane would have an octane rating of 90. [1]...
...References
1. ^ Page 992. Brown, Theodore, and LeMay, Eugene, et al. Chemistry: The Central Science. Ninth edition. Pearson Education Inc. Upper Saddle River,
NJ. 2003. ISBN 0-13-066997-0.
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[Edited on 6-7-2008 by MagicJigPipe]
"There must be no barriers to freedom of inquiry ... There is no place for dogma in science. The scientist is free, and must be free to ask any
question, to doubt any assertion, to seek for any evidence, to correct any errors. ... We know that the only way to avoid error is to detect it and
that the only way to detect it is to be free to inquire. And we know that as long as men are free to ask what they must, free to say what they think,
free to think what they will, freedom can never be lost, and science can never regress." -J. Robert Oppenheimer
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not_important
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yup - straight chain alkanes are rather bad fuel for Otto cycle engines, having a low octane rating, but good fuel for Diesel engines as they have
decent to good cetane numbers. Aromatics in general have very good octane ratings, but the US and some other countries have limits on total aromatic
content and tight limits on benzene levels. The alkanes are C4-C12, the exact range being determined by climate.
So to make decent gasoline you need to reform straight chain to branched chain. Conditions similar to those used in reforming will thermally
decarboxylate fatty acids. The Kolbe reaction just isn't that energy efficient, I suspect the thermal-catalytic routes to that range of hydrocarbons
are much more effective.
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nightshade
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so how could one make the kolbe work for amino acids and sodium acetate.
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not_important
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| Quote: | Originally posted by nightshade
so how could one make the kolbe work for amino acids and sodium acetate. |
You mean a mixed Kolbe? Doesn't work well when there is a amino, hydroxy, or alkoxy group alpha to the carboxylate carbon.
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woelen
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I have done quite some experimenting with the Kolbe reaction (and made a web page about it and a thread over here at sciencemadness) and it only seems
to work well with unsubstituted acids. E.g. acetate gives ethane, propionate gives n-butane, etc. I did tests with chloroacetic acid, and that gives
CO and CO2.
The reaction with succinic acid seems interesting though and that is something which I will try. This could be a nice route to ethene, a gas which
otherwise is not easily prepared without some decent glassware and heating apparatus.
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nightshade
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Well I read somewhere it said that alpha acids can't bond little or no product is made.i down loaded chem guys notes,and even they say a alpha acid
won't work.in another book i got it only even number carbon acids can be used.Amino acids are alpha amino acids are they not .
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MagicJigPipe
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So, has anyone tried benzoic acid? I'm surprised I am the only one that is anxious to see if this works considering the virtual unavailability of
benzene in the US and the large setup cost of the sodium benzoate decarboxylation.
"There must be no barriers to freedom of inquiry ... There is no place for dogma in science. The scientist is free, and must be free to ask any
question, to doubt any assertion, to seek for any evidence, to correct any errors. ... We know that the only way to avoid error is to detect it and
that the only way to detect it is to be free to inquire. And we know that as long as men are free to ask what they must, free to say what they think,
free to think what they will, freedom can never be lost, and science can never regress." -J. Robert Oppenheimer
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Ritter
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| Quote: | Originally posted by KABOOOM(pyrojustforfun)
it's a way of preparing saturated/unsaturated hydrocarbons via electrolysis of aliphatic carboxilic acid alkali metal salts.<br>eg
:<br>2CH<sub>3</sub>COO<sup>-</sup> <s> ></s>
H<sub>3</sub>C-CH<sub>3</sub>
+2CO<sub>2</sub><br><br><sup>-</sup>OOC-CH<sub>2</sub>CH<sub>2</sub>-COO<sup>-</s
up> <s> ></s> H<sub>2</sub>C=CH<sub>2</sub> +
2CO<sub>2</sub><br>succinic acid<br><br>the above definition and examples come from The penguin dictionary of chemistry
(translated it back to its original language)<br>now just think about the endless possible reactions ...<br>trichloroacetic acid to
hexachloroethane, nitroacetic acid to dinitroethane, trinitroacetic acid to hexanitroethane, glycine to ethylene diamine, serine to
1,2-di(hydroxymethyl)ethylene diamine,<br>glyoxylic acid to glyoxal,<br>glyceric acid to erythritol, gluconic acid to
1,2,3,4,5,6,7,8-octahydroxyoctane, lactic acid to 2,3-dihydroxybutane,<br>acrylic acid to butadiene, methacrylic acid to 2,3-dimethylbutadiene,
maleic acid to acetylene or acetaldehyde,<br>oxime of mesoxalic acid to fulminic acid, pyruvic acid to imethylglyoxal, .......
Edit: corrected a typo (changed dimethylglyoxime to dimethylglyoxal)
[Edited on 20-11-2003 by KABOOOM(pyrojustforfun)] |
I have experience with the Kolbe elerctrolysis. One major limitation is decarboxylation of the acids. The other is the very corrosive effect on the Pt
electrodes. And if you are using two different acids A & B, you will also get the coupling products A-A, B-B as well as A-B.
Ritter
=============================
\"The production of too many useful things results in too many useless people.\"
Karl Marx
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Dr.3vil
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benzoic acid
From "electrochemistry oforganic compounds"
walther Lob
1906
Benzoic Acid.—Benzoic acid and its salts were examined
by several investigators, first by Matteuci,1 then by Brester,2
but most thoroughly by Bourgoin.3
The result of all these investigations is to show that here
no secondary reactions take place, as was observed in the case
of the fatty acids, but that the only effect of the current is to
produce a separation into hydrogen (or metal) and the acid
radical, the latter regenerating the acicl at the positive pole.
In an alkaline solution it is possible to so increase the oxida-
tion that the benzoic acid is destroyed. The decomposition prod-
ucts which then appear at the anode are carbon dioxide, carbon
monoxide, and sometimes acetylene. The odor of bitter
almonds is also frequently observed.
A thorough investigation was made by Lob,4 who employed
a current having a potential of 6-7 volts and a current density
of 15-20 amp. per sq. cm. and obtained a small quantity of
1 Bull. soc. chim. 10, 209 (1868).
2 Jahresb. f. Chem. (1866), 87.
3 Bull. soc. chim. 9, 431 (1867).
4 Ztschr. f. Elektrochemie, 2, 663; 3, 3 (1896).
a substance containing sodium, but the chemical nature of
which has not yet been determined. There is formed besides
this compound a small quantity of benzaldehyde; as well as
acetylene and carbon monoxide. Under no circumstances do
diphenyl or other hydrocarbons occur; nor do fatty acids
appear, which is otherwise generally the case in an extensive
oxidation of this character.
According to the investigations of Schall,1 diphenyl does,
however, occur if a solution of sodium benzoate in molten
benzoic acid is electrolyzed at 100 volts between silver elec-
trodes.
-EDIT-
since we are talking about electrons and uses for benzoic acid or its salt
how about benzoic acid to:
benzyl alcohol
benzaldehyde
see https://sciencemadness.org/talk/viewthread.php?tid=2223
Electrolytic Reduction of Aromatic Carboxylic Acids. I. Reduction of Benzoic Acid under Pressure
Shin-ichi Ono and Tsuneo Yamauchi
Bulletin of the Chemical Society of Japan , Vol. 25 (1952) No. 6 pp.404-407
[Edited on 30-7-2008 by Dr.3vil]
[Edited on 30-7-2008 by Dr.3vil]
DR.3vil
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