[Seanlet]

So often, tests state the heat of combustion of a particular compound as if the values are common knowledge. I recently read that the LARGEST collection was about 9000 compounds! - an iota of a fraction of a % for even compounds with 10 carbons.

I also read of a ChemOffice plugin that estimated the heat of combustion with the acronym CHETAH but, as is human nature, it's known as Cheetah. This software is apparently no longer available.

Is there a ChemOffice plugin or indeed stand-alone software for estimating these values?

[Borek]

Unless you need a very accurate values, you can get a reasonably correct estimate from bond energies.

My bet is that if you need accurate values, no software will be able to produce it, when estimates are enough, you can calculate them manually.

[curiouscat]

Unless you need a very accurate values, you can get a reasonably correct estimate from bond energies.

My bet is that if you need accurate values, no software will be able to produce it, when estimates are enough, you can calculate them manually.

Lot depends on what class of compound. Some are so well studied that correlations are decently good now.

[Seanlet]

Have others looked into this CHETAH (cheetah) software? You dumped a SMILES string into it and it gave a (supposedly quite accurate) value. Bond-energy - what about ring-strain? When I used ChemBio3D to calculate the properties of styrene oxide, I get this:

------------ Property Broker ------------
Model: Untitled-1

ChemPropPro: Gibbs Free Energy = 103.52 kJ/mol
ChemPropPro: Heat Of Formation = -31.12 kJ/mol
ChemPropPro: LogP = 1.725
ChemPropPro: Vapor Pressure = 40.79 Pascal
error: GAMESS Interface: Gibbs Free Energy: Calculation failed - type not supported, failed on this molecule or possible licence error!
GAMESS Interface: Total Energy = -238579.4664 Kcal/Mol
-----------------------------------------


------------MMFF94 Minimization------------
  Iteration  155: Minimization terminated normally because the gradient norm is less than the minimum gradient norm
Final Energy: 21.6327 kcal/mol
Calculation completed
------------------------------------

----------- Property Broker ------------
Model: Untitled-1

ChemPropPro: Gibbs Free Energy = 103.52 kJ/mol
ChemPropPro: Heat Of Formation = -31.12 kJ/mol
ChemPropPro: LogP = 1.725
ChemPropPro: Vapor Pressure = 40.79 Pascal
error: GAMESS Interface: Gibbs Free Energy: Calculation failed - type not supported, failed on this molecule or possible licence error!
GAMESS Interface: Total Energy = -238579.4664 Kcal/Mol
-----------------------------------------
------------MMFF94 Minimization------------
  Iteration  155: Minimization terminated normally because the gradient norm is less than the minimum gradient norm
Final Energy: 21.6327 kcal/mol
Calculation completed
------------------------------------

------------MM2 Minimization------------
Pi System:    4   3   2   1   5   6
Warning: Some parameters are guessed (Quality = 1).
  Iteration  396: Minimization terminated normally because the gradient norm is less than the minimum gradient norm
  Stretch:                9.0215
  Bend:                  73.4238
  Stretch-Bend:          -1.9585
  Torsion:                2.2260
  Non-1,4 VDW:           -0.8164
  1,4 VDW:                7.7873
  Dipole/Dipole:          0.2924
Total Energy:            89.9759 kcal/mol
Calculation completed
------------------------------------

So the final energy is 21.6327 is it? The textbooks say that the oxirane-ring alone has strain-energy of 25Kcal/Mol...

I would suggest to all writers of tests that questions should be worded to include 'compound X, which was found to have Heat of Combustion of Y using a bomb-calorimeter'. Or more honestly 'Calculated Heat of Combustion' rather than being dropping in the value like Moses bringing down the tablets from the mountain'. Sorry - pet peeve.

I see that there is a plugin called Schrödinger's Jaguar - anyone know if that produces USABLE results?

Thanks for the replies so far but while I have a love of learning, I rarely like to be taught. Right now, postgrad school is heavy on the former & light on the latter which suits me.

I thank you
Seanlet

[curiouscat]

So the final energy is 21.6327 is it? The textbooks say that the oxirane-ring alone has strain-energy of 25Kcal/Mol...

Those values have no relation. The absolute Final Energy of a DFT calculation has no significance. Only differences matter.

[Seanlet]

Yes, thank you, I realize that. I'm just pointing out that if the oxirane ring has strain-energy of 25Kj/mol and heat of formation is -31.12, then the software is going to be WAY out.

Try it yourself, comparing styrene with styrene oxide.

That is why I asked if CHETAH (cheetah 2.0) or something similar were available as plug-ins.

www.dsto.defence.gov.au/publications/2393/DSTO-TR-1199.pdf

or if anyone knew of an on-line version.

 If you were about to go to your tutor and suggest a solvent-free reaction between styrene oxide & something (and depending what, specifically a polymer or specifically a monomer) using a catalyst so it works at RT, you want to KNOW energy-wise, where you are. At the moment I'm JUST using the ring-strain but if it DID go norks north,  what COULD happen.

Or has the world changed so much that 25 years ago researchers found the heat of combustion of every single reagent they planned to use? Yes, I KNOW I'm going overboard on this but aren't more people shocked that while EVERYTHING has as CAS, & ini string and 99 out 100 times all of the other physical data, energy of combustion isn't one of them....

[curiouscat]

Never heard of Chetah before. Why don't you try one of the mainstream DFT packages?

Gaussian? Wein2K? QuantumExpresso? VASP? CASTEP?

Some are free too.

[Seanlet]

Wow - ALL of those products look absolutely fascinating. Many thanks. It's going to be interesting to perform the same calculations on each, just to see how they match up.

IS it just me though, or should the heat of combustion be made a standard for MSDS?

I put a link to a discussion of CHETAH in my last post. It seems like it was designed specifically to estimate the heat of combustion for theoretical testing of explosives. Not an area that interests me; I leave that crazy stuff to Prof. Dr. Thomas M. Klapötke. I urge everyone to enjoy the videos, but not accept an offer to look around his lab. Same goes for Vil Mirzayanov - 'just say no' if he proffers a bottle for you to enjoy the bouquet.

Thanks all!

[curiouscat]

IS it just me though, or should the heat of combustion be made a standard for MSDS?

I don't know of any minimum set of parameters that has to be on an MSDS. Forget, heat of combustion, but is there even a well defined minimums list?

[Seanlet]

Good question. In the UK at least, yes. There is software for making up MSDS forms. 3E is the company behind the biggest US one.

I THINK the law is the same in all of the West and India. The Chinese have their own for internal use (of data, not form) and it isn't as slipshod as I imagined!

[DrCMS]

Good question. In the UK at least, yes. There is software for making up MSDS forms. 3E is the company behind the biggest US one.

I THINK the law is the same in all of the West and India. The Chinese have their own for internal use (of data, not form) and it isn't as slipshod as I imagined!

Well you think wrong, it it getting closer with the implementation of CLP/GHS. 

An MSDS is there to provide safety information not useful data for theoretical chemists.   The heat of combustion is a bit of an irrelevance because if you've got your material on fire you've got it very badly wrong.  Values like flash point and autoignition temp are useful to ensure you do not have a fire.

[Seanlet]

And I can assure you that to transport ANY chemical in the EU requires an MSDS - it's a criminal offence NOT to have one.

Maybe if the US wasn't so lax, we wouldn't be hearing of SUMMER SCHOOL undergraduates playing with t-BuLi resulting in said student dying.

And don't get me started on HF... Watch this:

http://news.linktv.org/videos/explosion-spreads-acid-cloud-southeast-of-seoul-linkasia

Can you kind of GRASP why a decent MSDS is important.



Obviously 'I think Wrong'. The whole point of the thread was so I REALLY had covered all of the bases, but chemists get lazy just like other people (just on a much higher wage) and complacency is evidently even more common than I thought... Please supply address, I have 2l of magic methyl in a coke bottle, let me know how it tastes ;-)

[DrCMS]

And I can assure you that to transport ANY chemical in the EU requires an MSDS - it's a criminal offence NOT to have one.

Absolute rubbish spouted as facts by a fool who thinks they know more than they actually know.

The transport of chemicals and supply of chemicals are two separate sets of laws. 

ONLY chemicals classified as hazardous for supply and given R and S phrases under the CHiP classification or H and P phrases under the new CLP classification need an MSDS to be supplied to the user in the EU. 

The US is different and expects an MSDS even for non-hazardous chemicals for labour law reasons.  That's a bit stupid because the MSDS is meant to be there to give info on hazards and if there are none you do not need an MSDS.

Those fewer materials that are classified as hazardous for transport and given a UN no. and PG need to be shipped in approved packaging for that class and PG, accompanied by hazardous paperwork (DGN and instructions in writing) and need hazchem trained drivers. An MSDS quite often goes with such a shipment but it is not a legal requirement for shipping because the MSDS is for the user not for the haulier.

Maybe if the US wasn't so lax, we wouldn't be hearing of SUMMER SCHOOL undergraduates playing with t-BuLi resulting in said student dying.

What happened to Sheri Sangji was a tragedy and indicatives of the poor standards of supervision and health and safety awareness of Universities in general and is NOT just a US issue you can act smug about.

Obviously 'I think Wrong'. The whole point of the thread was so I REALLY had covered all of the bases, but chemists get lazy just like other people (just on a much higher wage) and complacency is evidently even more common than I thought... Please supply address, I have 2l of magic methyl in a coke bottle, let me know how it tastes ;-)

You started this thread talking about Heat of Combustion calculation and after you suggested they should be included on an MSDS and I pointed out why that was not what the MSDS is for you started spouting false information dressed up as fact, made wild statements about a tragedy and then threats of poisoning me.  Grow up and go actually read the laws about transport (http://www.legislation.gov.uk/uksi/2009/1348/contents/made) and supply (http://www.echa.europa.eu/web/guest/regulations/clp/legislation) before you comment on them again.

[Seanlet]

-Don't argue with idiots, they will only drag you down to their level and beat you with experience

[curiouscat]

Absolute rubbish spouted as facts by a fool who thinks they know more than they actually know.

+1

You couldn't have put it better.