[discodermolide]

I think nox is pointing out that that BenFrank1 has so far managed to resurrect a dead 7 month old thread and post mostly nonsense in this one with a rather heavy dose of misplaced arrogance. Not the most auspicious start to chemicalforums life...

Hey azmanam, do you have any of that popcorn left?

Thank you for the explanation. I wasn't aware this had already been posted.

[nox]

Dan is correct, except I should point out the thread in question was 7 years (not months) old

Sort of makes you wonder what his motivation for joining chemicalforums was

[yufgyfyu]

No reason, just boredom.

[azmanam]

Now let's discuss how NaH can oxidize alcohols to aldehydes

RCOH + NaH --> RCHO

http://totallysynthetic.com/blog/?p=1903

/troll

[Honclbrif]

@azmanam

What? If I recall it was a critical step in the synthesis of hexacyclinol...

[discodermolide]

@azmanam

What? If I recall it was a critical step in the synthesis of hexacyclinol...

I think you are right! If I recall the NMR's were run by the "Blues Brothers" from Berlin!
So it must be correct.

[nox]

@azmanam

What? If I recall it was a critical step in the synthesis of hexacyclinol...

I think you are right! If I recall the NMR's were run by the "Blues Brothers" from Berlin!
So it must be correct.

BIONIC BROTHERS YOU FOOL!!

And don't forget he used 100% CDCl₃ so the technician had to manually insert the chloroform peak.

[azmanam]

The Blues Brothers?  They still owe you money, fool!




(I'll have four fried chickens and a coke.)
(And some dry, white toast.)

[discodermolide]

@azmanam

What? If I recall it was a critical step in the synthesis of hexacyclinol...

I think you are right! If I recall the NMR's were run by the "Blues Brothers" from Berlin!
So it must be correct.

I knew it was B.. Something brothers
But we forgot the 5 technicians that were acknowledged!
Got the paper in my collection it's a mouseterpiece or is it masterpiece?

BIONIC BROTHERS YOU FOOL!!

And don't forget he used 100% CDCl₃ so the technician had to manually insert the chloroform peak.

[orgopete]

I resisted posting on this question as I wasn't seeking another way to increase my negative snacks. However, with all being said, I didn't think as stated, it was such a bad question. "Would this work?" or perhaps better "Could this work?"

I have no disagreement with what has been posted so far. One could choose stoichiometry such that one ends up with the calcium salt of the acid. However, what happens next?

If you wanted to make a methyl ketone, you could react a carboxylic acid with sodium hydride to make the sodium salt. Then react it with methyllithium to make the ketone (after work-up). NaH can act as a reducing agent, but I cannot think of an example. Could CaH2 also act as a reducing agent?

     (CH₃COO^-)₂Ca⁺² + CaH₂  + heat(?) ??

Obviously, I am looking at this differently. I don't know what will or will not happen. I am not defending the poster. I don't know this was what he or she may have been thinking. I am simply looking at it as a chemistry question. Could CaH₂ add to a C=O group and under what conditions? Think about it, AlH_n (yes), CaH₂ (?), NaH (sometimes). (It would have been better to be MgH₂ or BeH₂, but it isn't my question.) When can electrons add to a carbonyl group? It is almost paradoxical paralleling substitution reactions. The best nucleophiles are not the most basic electrons. I expect from the properties of calcium for it to more strongly coordinate with electrons which may make it a better nucleophile than NaH (or KH). 

[karbon]

Treating a carboxylic acid with calcium hydride would yield this product (CH3COO^-)2Ca⁺

However, to reduce it you would afterwards need to make the hydride from calcium hydride attack the C=O bond, which most likely would never happen. Calcium hydride is a base. Not a reducing agent.

If you really want to reduce a carboxylic acid with a hydride reducing agent, esterify the acid with an alcohol and reduce afterwards with LiAlH₄ at -78C for about 2 hours.

[Honclbrif]

From what I understand, H^- is a rather hard nucleophile (second only to F^- Carey and Sundberg, 5th Ed. Part A, Pg 15). The reason why Al hydride derivatives are such good reducing agents compared to other hydrides is that coordination with Al hardens up the carbonyl, making it more receptive to a harder nucleophile. Ca is a fairly hard acid too, but I don't know if it has the strength to make this reaction feasible.

[karbon]

Calcium hydride is still a much much harder nucleophile than AlH₄^-. So hard you you can't call it a nucleophile...

[orgopete]

That's it. If you heated the heck out of calcium acetate and calcium hydride, you are saying acetaldehyde and calcium oxide couldn't result because hydride is too hard? Can someone just try it?

A point I wish to make is that donation of a pair of electrons is complicated. If calcium hydride can donate electrons to water, why can it not donate electrons to carbon? I understand how one might like to argue hard and soft theory, but I don't necessarily agree. For example, because the crystal strength of calcium hydride may be much greater than any forces to solubilize it. Calcium hydride may not react not because it lacks reactivity, but it may not react because it is insoluble or another reaction takes place in preference, such as elimination reactions.

If you search for calcium hydride reductions, you can find examples though not the reaction in question. It can reduce sulfur or something like that. Would that match hard-soft arguments?
http://onlinelibrary.wiley.com/doi/10.1002/ejic.200701255/full (I don't know what is in this as I don't have access.)

[karbon]

That paper describes a calcium hydride complex, not calcium hydride.