Converting Carboxylic Acid to Alkane in one step via Hydrogen Iodide - is it possible?

[j***@mix.wvu.edu]

I've been doing some research and it looks like, in general, the way to turn the RCOOH into RCH3 is by a halogenation followed by reduction say with lithium aluminum hydride. However, would the following reaction not work?

RCOOH + 6HI -> RCH3 + 2H2O + 3I2
Carboxylic Acid + Hydrogen Iodide Alkane Water Iodine

Say, starting with Acetic Acid:

CH3COOH + 6HI -> CH3CH3 + 2H2O + 3I2
Acetic Acid + Hydrogen Iodide Ethane Water Iodine

Although I think this would require heat and possibly pressure. I cannot find any information on this reaction. Has anyone tried it or know if it would work? What would the yield be?

I'm not a chemist, I'm a physicist and computer programmer so I'm really uncertain about it. Would this be some kind of equilibrium reaction? I suppose this would a type of halogenation reaction but it seems like the end product of a reduction step (after halogenation). Perhaps its both? Any insight would be greatly appreciated.

Thanks,
***@confidesk.com (or doesn't know rather)

[Bodo Mysliwietz]

Post by j***@mix.wvu.edu
I've been doing some research and it looks like, in general, the way to turn the RCOOH into RCH3 is by a halogenation followed by reduction say with lithium aluminum hydride. However, would the following reaction not work?
RCOOH + 6HI -> RCH3 + 2H2O + 3I2
Carboxylic Acid + Hydrogen Iodide Alkane Water Iodine
CH3COOH + 6HI -> CH3CH3 + 2H2O + 3I2
Acetic Acid + Hydrogen Iodide Ethane Water Iodine

My first thought "It won't work".

Post by j***@mix.wvu.edu
Although I think this would require heat and possibly pressure.

Mostlikely, because Hydrogen iodine is not stable at elevated
temperature and decompose to Hydrogen and Iodine whereas it is an
equilibrium reaction.
2HI <---> H2 + I2

High temps. shift the equilibrium to the right, highP. to the left.

Post by j***@mix.wvu.edu
I cannot find any information on this reaction. Has anyone tried
it or know if it would work? What would the yield be?

Even i thought that it would not be possible i did a search and found
some hints in a German written book for organic synthesis via google books:
Houben-Weyl, Methods of Organic Chemistry Vol. V/1a, 4th Edition:
Alkanes, Cycloalkanes, ISBN-13: 9783131799241

--> English titel but German print, crazy! Hope you can find an english
translation.

The book briefly describes an old synthesis way (50 to ~ 130 years!) for
pure alkanes by reduction of carbocylic acids using HI*aq and red Phosphor.
--> A few grams of lauric acids, HI-solution (d=1.7 kg/l) and red P will
be put in a glass tube which is flame sealed later on. The capsule will
be heated up to arround 210 °C to 240 °C wheresas noticeable amounts of
iodine shouldn't be formed.

Another reaction is descirbed synthesis of pentacosane using
corresponding acid, HI-solution (d = 1.96kg/l), red P and arround 125 °C
for about 8hrs.

The recipes are traced back to:
A) F. Krafft, B, 1687, 1882
B) P.A. Levene u. C.J. West, J. Biol. Chem. 14, 257 (1913)

Post by j***@mix.wvu.edu
I'm not a chemist, I'm a physicist and computer programmer

... thus it would be better using a real Newclient for writting Usenet
conform artciles ;-)

Post by j***@mix.wvu.edu
so I'm really
uncertain about it. Would this be some kind of equilibrium reaction?

Finally not. The intermediate step seems to be forming R-J wich is a
slow reaction, whereas RJ --> HJ is a fast reaction (equil. is on the
right) but i couldn't find usefull information about other products.

Post by j***@mix.wvu.edu
I suppose this would a type of halogenation reaction but it seems like
the end product of a reduction step (after halogenation). Perhaps its

both?

Post by j***@mix.wvu.edu
Any insight would be greatly appreciated.

I hope you have got a start point now.

BR from Germany