SM2 - 14-9-2012 at 05:34
Or, there are some reactions (especially catalytic), which require the activation energy to be reached (endo-thermic), and once that threshold has
been met, they are exothermic until the very end.
With this in mind, I'm wondering if a little pinch of P2S5 and a few drops of CH3OH in a nice smooth mortar, will bubble away at room temp, and leave
the most disgusting fart in it's wake. Is it straight endo or exo? Thanks.
AndersHoveland - 14-9-2012 at 12:23
I would think this would be a likely possibility:
A more likely possibility:
(8)CH3OH + P2S5 --> (2)H3PO4 + (3)(CH3)2S + (2)CH3SH
From "Science Madness": "An alcohol plus phosphorous pentasulphide will make a thiol"
(an example of a thiol is CH3CH2SH )
I also found this: "The mercaptans may be prepared... by heating the alcohols with phosphorus pentasulfide."
("Introduction to Sulfur Functional Groups" by James Richard Fromm) Thiols are often referred to as mercaptans.
"...state that O,O,S-trimethyl phosphorodithioate was obtained from the reaction of methanol with phosphorus pentasulfide." Alfred E. Lippman, 1966
This has a formula (CH3O)2P(=S)(SCH3).
However, apparently alcohols can still be used as solvents for reactions involving P2S5,
Babak Kaboudin and Dawood Elhamifar in Iran "...found that reaction of benzonitrile with phosphorus pentasulfide in ethanol under reflux gave
thiobenzamide in 82% yield after a much shorter reaction" with high yields.
Basically C6H5CN reacted to produce C6H5C(=S)NH2.
"Preparation of phosphorothioate esters from benzyl alcohol and phosphorus pentasulfide"
(United States Patent 3102130)
These esters have the formula (C6H5CH2O)3P=S.
In a different paper, ("Preparation of fluoroolefins by reaction of polyfluorochlorocarbinols with phosphorus pentasulfide" R. A. Bekker, G. V.
Asratyan, É. P. Lur'e and B. L. Dyatkin),
CH3C(CF2Cl)2OH with at least a five-fold excess of P2S5 was refluxed for 2 hours, producing CH2=C(CF2Cl)2 in 58% yield.
“The present invention relates to a process, wherein an alcohol and/or phenol is reacted with phosphorus pentasulfide in the presence of a catalyst
<,such as an ammonium salt,> with the resultant formation of O,O-dialkyl-, O,O-diaryl- or O-alkyl-O-aryldithiophosphoric acids.” (United
States Patent 4397791)
These would have a general formula of (PhO)2PS2H. Here is a diagram of a similar acid ester: http://www.lookchem.com/UserFilesUpload/5%2820%29.png
The reaction between P2S5 and phenol tends to be more complex (read about "Lawesson's Reagent").
SM2 - 15-9-2012 at 09:00
AndersHoveland,
Thanks for the advice. Really, all I wanted ti know is weather P2S5 will render methyl mercaptan upon addition of methanol. But what is the easiest,
most practical way to make P2S5? Since Nicoderm saw it fit to move the topic to fundamentals/beginnings, perhaps he could grace us with his unlimited
knowledge, as I certainly can't find an easy method using flowers of and red.
Rogeryermaw - 15-9-2012 at 10:20
you're not likely to find an easy way. there are so many possible compounds between phosphorus and sulfur some of which begin from reacting sulfur
with phosphorus dissolved in carbon disulfide. this may be of interest to you: http://en.wikipedia.org/wiki/Diphosphorus_trisulfide#Prepara...
SM2 - 15-9-2012 at 10:49
Thanks man,
I'd be happy with any method which yielded the mercaptan on addition of two ingredients. And I figured with sulfur so available, and RedP even more
available, this might be a route to explore. But no, the inorganics involved in making P4H10 and their interactions, are as complex as many many orgo
rxns i've seen. ugh! Thanks!