Question about CaH2

[dwarfer]

<sup>Will calcium hydride produce solvated electrons in ammonia??

Let me display my ignorance further,as I am without ego:

firstly, WTF is H+ doing latching onto Ca++ for gods fucking sake?  Totally rude.

Second of all, since it is a reducing agent in it's own rights,

could it be contraindicated in a Birch type reaction
 for some strange reason that obviates the apparent benefit
 of providing a surfeit of "hydrogen doning" constituents..  

well, at LEAST i didn't go to the "advanced chemistry" section. 
I try to keep my humiliation more local..</sup>


     

[Rhodium]

As it is a hydride, it is not H⁺ added to Ca²⁺, it's rather two hydrides (H^-) which is bonded to Ca²⁺.

[stratosphere]

calcium itself will produce solvated electrons, and is cheaper/more available then CaH2.

if one found themselves stuck with a boxcar of CaH2 and really wanted solvated electrons, i suppose one could thermally decompose it to calcium metal+H2.

does the (unbalanced) reaction CaH2 + AlCl3 --> CaCl2 +Ca(AlH4)2 occur? or does that only work for LiH

[dwarfer]

Like an old dog delighted with discovery of a long-
forgotten bone ( no freudian jokes please), I'm filled
with curiosity as to how molecular hydrogen is convinced
to attract a couple of electrons into that smallest of orbitals, split, and become married, temporarily, to a nice bone constituant such as Calcium.

I've looked on the web for info on how it is made, with no good luck so far.

However, I do not expect my basic chemistry ignorance to be alleyed here, and thank you for the response.

"XXXXXXXXXXXXXXXXXXXX can with almost 2 pounds of calcium hydride. Apparently these were used to inflate weather balloons."

FYI, somebody else I never heard of paid $20 for it.

further, "As a chemical reagent this stuff is very useful as a potent drying agent for various organic solvents eg xylene, benzene, hexane acetonitrile, either, dimethylformamide, dimethylsulfoxide to name a few I could find on the net, also it can be used as a reducing agent similar in action to lithium aluminum hydride but somewhat slower and a fraction of the cost and MUCH MUCH SAFER, hint you can blow torch a chunk of this stuff to red hot without it even burning up (the dust is somewhat flammable though) more than a glow like charcoal that goes out upon cooling, with LiAlH4 it goes Chernobyl in a big fire-ball immediately."

All in all, interesting enough to acquire, even given the ignorance of the new owner, maybe..?? (we'll see..)

===============

SOANYWAY:

follow my simple thoughts..

Upon disassociation, you have immediatly available not only a couple of lonesome electrons BUT (oivey)

Seems promising, anyway.  Can anyone predict what would happen if some CaH2 was introduced into ammonia?

[stratosphere]

apparently i have been misinformed about the price of CaH2, but following the logic that elemental Ca must be produced as a precursor to CaH2, it would therefore follow that in a freemarket economy Ca would be cheaper then CaH2 per mole, however bees do not operate in a freemarket economy because we are largely preoccupied with evasive tactics.

if you blow torched a chunk of CaH2 im almost certain it would decompose to Ca(s) and H2(g).

how does H2 and Ca combine despite size difference?
  you have to look at ground state energies.
a protons juicy unfilled chasm of a ground state is about 13.6eV deep, which means that a hydrogen radical can add a second electron to its spatial ground state, forming a hydride ion, the energy of adding the second electron would also be very close to -13eV (although it will be slightly less due to e on e repulsion).
 the highest occupied orbital of calcium is not as deep, so you can see what ensues, basically the calcium "surface" electrons jump onto the hydrogen forming a hydride.
really not too different from how  calciums valence electrons would jump onto a Cl radical.

[hypo]

> I'm filled with curiosity as to how molecular hydrogen is convinced
> to attract a couple of electrons into that smallest of orbitals, split,
> and become married, temporarily, to a nice bone constituant such as Calcium.

actually metal hydrides can be made exactly that way: metal + molecular H2
(usually at high temperature). interestingly CaH2 is an exothermic compound meaning
that 1 mol CaH2 is energetically more favorable than 1 mol Ca and 1 mol H2.

what do we learn from this? Ca's wish to get rid of 2 electrons is bigger
than H2's desire not to take 2 electrons and become 2H-. (well ofcource
that's simplicistic - there's other energetic reasons why compounds form).
(the splitting of H2 part is greatly enhanced by a high temperature ->
but that's the kinetic aspect)

not so surprising, when you consider that H- has exactly the same electron
structure as He, a noble gas. and noble gas configuration is the holy grail
of atoms, isn't it? (well, simplicistically speaking again..   ).

there's other methods to make hydrides, one beeing cross-hydrogenation (if
that is even a word). i.e. moving H- from one metal to another.

then some compounds have hydrogens that can act as hydrides (hydridoids?   ):
take for example the formiate in the leuckart reaction: HCOO-. CO2 pisses off
and H- stays behind.

am i reasonably comprehensible?  

> Seems promising, anyway.  Can anyone predict what would happen if some CaH2
> was introduced into ammonia

i don't think it will give solvated electrons, if that is what you're after...

[dwarfer]

Thank you for your time.  I have resonating memories of "lyman balmer paschun bracket pfund"
 archaically rattling around
as related topics
in my old Physics "mental library" subsection,
 under energy levels of hydrogen spectra,
quantum levels of..  
=

Oh well:  if you add it to water you get a buncha hydrogen
and CaO.  To ammonia you get what??  no reaction?
===============

The price is low because it's military surplus cans used to inflate weather balloons..

Even if not applicable to what I have in mind, the possibilities are interesting..  

============

The part about

it can be used as a reducing agent similar in action to lithium aluminum hydride but somewhat slower

Is that true??

[hypo]

> if you add it to water you get a buncha hydrogen
> and CaO.  To ammonia you get what??  no reaction?

well... water, being somewhat acidic constantly produces
H+, which has an electron deficiency. combined with H-,
a very electron-rich fragment this gives quite a violent
reaction.

NH3 doesn't split off H+, it can only take a H+. it's an
electron-rich compound, so i think it won't react with
H-. maybe it will give a complex with the Ca++.
but honestly: i'm only guesstimating....  

> Is that true??

it should definitely be a reducing agent. the question is:
is it good enough? again, i don't know.

[dwarfer]

go to that place and enter "calcium hydride" and see a
"buy it now" for $65, and two others..

i cant say the place, but it's opposite could be a west mountain??Item number: 3269937177  
 ==============

oh jesus, you can get 20 cans for $65, that's 40 lbs....

Now if i JUST knew  that I would USE that much... 

what to do with ALL that hydrogen??

[dwarfer]

Now I feel better about the $20 I forked over for one can.

I'm going to see what the shipping charges are on 20 cans...

===========

Particularly if you can get easy calcium with it..  as reffed above.

Also, one guy says in water it makes CaO: another says CaOH..??  I would think the latter??

=

Hey Determined: what do you use it for??

[Rhodium]

CaH₂ + H₂O -> CaO
CaO + H₂O -> Ca(OH)₂

[stratosphere]

[dwarfer]

It depends on how much water you add 
Posted by:  Rhodium (Chief Bee)

Uh yeah  
========================
BIG whoop..

(modified)congratulations  you lucky fuck you
now own one case of calcium hydride 20 cans about 40 lbs
shipping 30.00 for a total of 92.00

That oughta hold ole Marve fer a while..

============

Guess what:  I don't believe I'm going to be using
as much de-hydrated epsom's salt in the future..
===============

Also:  a few grams into my 20,000 PSI burst strength
stainless steel "bomb" with a few grams of water, and
some norephedrine, ephedrine, norpseudoephedrine, and pseudoephedrine, abit of HCl and a drop or two of H2SO4, and some 10% Pd on Carbon..??

Wait: the CaO is gonna be aprob.... never mind, more thought needed.

[dwarfer]

you blow torched a chunk of CaH2 im almost certain it would decompose to Ca(s) and H2(g).

At about what temperature would the departure of the
2 H's  be likely?

I'm not thinking of using a blowtorch, though...  ??

[stratosphere]

At about what temperature would the departure of the
2 H's  be likely?

according to the jtbaker msds, the decomp occurs at 1250F, actually much higher then i would have anticipated.
as for instance NaH decomposes at 280C

[dwarfer]

Having both my interest piqued and an excess of
army green cans each individually filled with
pounds of the stuff, I've (naturally) begun noticing
it in documents I read.

Wiz referred to it's use in the reduction of chloro
methamphetamine.

Post 480374 (missing)

(Rhodium: "Racemization of Optically Active Ephedrines", Stimulants) refers to racemization  (example 4) using
a hydride.


and another person reported on it's use in reduction
with Pd..

nifty stuff..  ":<)

[ning]

Ca will displace Na from its salts. This means that CaH2 should produce NaH from dry salt. What a person could do with a massive quantity of metallic sodium or potassium is up to their imagination  

Mix up a proper mixture of KCl and NaCl, add your NaH and heat to 300 C to drive off the hydrogen--produce a room-temperature liquid metal! Then just pour it off the formed CaCl2 and have fun! Throw blobs in the neighbor's pool, see what a droplet would do to your skin (ouch), use it to derust, well, anything.

Wish those cans were in my back room...