July 15, 2024, 07:12:09 AM
Forum Rules: Read This Before Posting


Topic: Rocket fuels beyond RG-1  (Read 24435 times)

0 Members and 1 Guest are viewing this topic.

Offline Enthalpy

  • Chemist
  • Sr. Member
  • *
  • Posts: 4038
  • Mole Snacks: +304/-59
Re: Rocket fuels beyond RG-1
« Reply #15 on: September 18, 2023, 02:16:13 AM »
Could the Kharasch addition make intermediates to cyclopropanes, azetidines, dihydroazetes? It puts halogens at proper distance.

Kharasch to 1,3-dihalopropane can have some merit. Then, cyclopropane and azetidine (picture) follow usual paths. R≠H improves the yield and can be removed later. R=cPr makes an efficient but volatile fuel.

Kharasch to (methyl)allyl chloride is less direct than usual routes. I see no merit for cyclopropene nor methylcyclopropene synthesis. No picture.

The scheme to dihydroazete (picture) obtains a halogen next to the amine. HX elimination is easier here than with a chloramine which might also create nasty compounds. I drew NH3, but a primary amine raises the yied from poor to excellent with dihalopropane, so some rest should be present and removed. The 2-haloazetidine may have more uses.

==========

When some compounds can run away thermally, the reactor must try to prevent it by design. Here ethylene may polymerize for instance.

I hope the thermal inertia of a material in close contact with said compound stabilizes it over a time scale range. A sturdy construction would resemble the catalyst I described there
  scienceforums
using a honeycomb winding of wire(s) sintered together and the flow outwards. The wires can have varied diameters and carry an inhibitor for the unwanted reaction. They can also carry a catalyst for the desired reaction. Or both, spread over the thickness or as a sandwich, for instance inhibitor - catalyst - inhibitor.

If the reactor needs pressure (apparently Kharasch doesn't usually), the unwanted reaction possibly happens already at the compressor. A Tesla compressor, which stacks many fine smooth spinning disks, would group both functions at one place for added safety. Expansion could happen in a Tesla turbine
  wikipedia

Marc Schaefer, aka Enthalpy

Offline Enthalpy

  • Chemist
  • Sr. Member
  • *
  • Posts: 4038
  • Mole Snacks: +304/-59
Re: Rocket fuels beyond RG-1
« Reply #16 on: September 18, 2023, 02:35:40 AM »
A hypothetic path to cPr-terminated ladderanes, looking much cheaper than here on August 23, 2023.

Andrist et al rearranged cyclopentadiene with light to bicyclopentene (housene), verified by Orgsyn
  orgsyn.org

The yield is very low, but the feed and light are cheap. An industrial process would harvest the bicyclopentene continuously before light isomerizes it, and would reinject the isomers. How? Err... GC at Orgsyn.

Maybe bicyclopentene is so much more reactive that an excess of acetylene pre-empts it. Or a wavelength excites selectively bicyclopentene which then reacts with the acetylene excess.

Marc Schaefer, aka Enthalpy

Offline Enthalpy

  • Chemist
  • Sr. Member
  • *
  • Posts: 4038
  • Mole Snacks: +304/-59
Re: Rocket fuels beyond RG-1
« Reply #17 on: September 30, 2023, 07:01:14 PM »
I suggested rotanes as rocket fuels on 12 Sep 2023. Those in the first table there, the three-membered rotanes, may have a production path for tons.

Fitjer at al reacted a cyclobutylcarbene on bicyclobutylidene to obtain the C12H18, center reaction of the illustration here.

Usual syntheses for bicyclobutylidene look complicated and expensive, but Imamoglu and Bencze did it by metathesis, top reaction here. For my untrained eye, better.

Can a similar path provide bicyclopropylidene and cyclobutylcyclopropylidene? Then the cyclobutylcarbene would produce the C10H14 and C11H16, bottom reaction.

Or if it does make a carbene, dibromocyclopropane has a natural production method and can react (not displayed) with cyclobutylcyclopropylidene and bicyclobutylidene to produce the coveted C10H14 and C11H16. I'd avoid the flammable C9H12.

Marc Schaefer, aka Enthalpy

Offline Enthalpy

  • Chemist
  • Sr. Member
  • *
  • Posts: 4038
  • Mole Snacks: +304/-59
Re: Rocket fuels beyond RG-1
« Reply #18 on: October 03, 2023, 07:26:57 PM »
In the first table on 12 Sep 2023, the four-membered rotanes too might have a production path for tons, see illustration.

De Meijere et al heated bicyclopropylidene and obtained much C12H16 rotane, just slowly.
  • Would a catalyst accelerate? Some exist for propadiene, butadiene and more.
  • The doxa demands light for this reaction, so let there be light.
  • I proposed a source of scalable 1mol/s cheap photons there
      chemicalforums
    One molecule produced per photon would equal 40t in a week of 5 days × 14 hours.

I haven't seen yet a convincing production of bicyclopropylidene.
  • Methylenecyclopropane seems elusive. Or would a longer compound undergo metathesis?
  • 1,1-bromocyclopropylcyclopropane can be dehalohydrogenated.
  • nBuLi dimerizes 1,1-dibromocyclopropanes obtained naturally, but (temporary) substitutions seem necessary.
  • Halogens recycling adds its complexity.
So can kg become tons?

From bicyclobutylidene, cyclobutylcyclopropylidene and hopefully bicyclopropylidene, cycloaddition would create three unsymmetrical pseudo-rotanes (bottom of illustration) and two symmetrical ones that can be kept for instance if their dissolution lowers the melting point. The wavelength influences the products mix.

Marc Schaefer, aka Enthalpy

Offline Enthalpy

  • Chemist
  • Sr. Member
  • *
  • Posts: 4038
  • Mole Snacks: +304/-59
Re: Rocket fuels beyond RG-1
« Reply #19 on: October 08, 2023, 05:19:26 PM »
Bypassing the unreported cPr=Me, would a convenient rearranged scheme provide cPr=cPr? The first speculative illustrated idea establishes the double bond before cyclizing. But do the compounds rearrange?

A second idea on the illustration proposes independently to obtain cBu=cPr by metathesis of cBu=cBu and cPr=cPr, reducing the effort. An adjusted mix of the three cyclodimerizes, preferably by light, the rest is reinjected as feed.

But if the reaction works, and with a good path to cBu=cPr, feeding the metathesis with cBu=cPr only to obtain also cBu=cBu and cPr=cPr would reduce the effort further. The metathesis conditions may adjust without separation the cBu=cBu plus cPr=cPr proportion. cBu=cPr would also center the dimer mix on C14 and the unsymmetrical compounds. Not illustrated.

Marc Schaefer, aka Enthalpy

Offline Enthalpy

  • Chemist
  • Sr. Member
  • *
  • Posts: 4038
  • Mole Snacks: +304/-59
Re: Rocket fuels beyond RG-1
« Reply #20 on: October 09, 2023, 06:56:13 PM »
Wikipedia mentions the dimerization.
Isomerization shall gain yield as the sought C6H12 has the least energy among alkenes.

Sponsored Links