[nikitabhatt]

So we have to write a lab report on any topic of our choice . I chose my research question to be :
"investigating how the position of the double bond in a decene molecule(in 5 of its straight chain isomers) , effects the standard enthalpy change of combustion ?

I couldn't find much data online for 2-decene , 3-decene , 4-decene , 5 decene . so i don't really know if the standard enthalpy change of combustion actually increases decreases or remains the same with the change in position of the double bond ?

Help ?

[thetada]

The table here shows slight variation of enthalpy of combustion between but-1-ene and cis and trans but-2-ene, which at least shows that double bond position affects the enthalpy change.

http://www2.ucdsb.on.ca/tiss/stretton/database/organic_thermo.htm

Isn't the idea of a lab report to actually do some kind of investigation in the lab?

[Enthalpy]

Everything affects the heat of combustion - more or less. The position of the double bond not much except at 1, the cis/trans isomerism about as much beginning at position 3.

The CRC hdbk of Chem & Phys has tables for the standard enthalpy of formation, which are usually derived from the heat of combustion, and tell the same difference in the case of isomers. I've found only 1-decene there, but it does show the 1-, c-2-, t-2, c-3, t-3 isomers of hexene and heptene for instance, giving you an idea of the effect at hexene.

Congrats, you've just observed that Mankind badly lacks experimental data about heats of formation or combustion, and melting points even more so. Some were measured in the 1960s, but since estimation software is available, few measures are made and published - despite estimates are too bad to be useable. No data for 2-, 3-, 4-, 5-decene (not even in compilations like the Crc's) may perfectly mean that none has been published.

So my suggestions would be to

• Distinguish cis- and trans- isomers: as important as the position.
• Measure blends of them only if some proportion is standard in Nature.
• Carefully check the standard state (liquid 298K), in articles as well.
• Ignore software predictions, but compare with similar compounds to get a notion.
• Measure as well a few known compounds to double-check your practice.
• If the known compounds give you confidence, publish your results. Here or on arXiv for instance.

[Corribus]

The CRC is a good reference. However my first go-to place to look for data like this is the NIST chemistry webbook.

http://webbook.nist.gov/chemistry/

I checked and they do have heat of formation data for 1-decene there. I did not check on the others.

If you can't find the data, I'd suggest choosing simpler molecules... possibly octenes or heptenes. The larger the molecule the harder it is to make and purify, which means data is more scarce.

[Corribus]

PS, some more information for you.

You can find thermochemical information for several of the linear octenes in this open access journal (see table 3).

http://www.mdpi.com/1422-0067/8/5/407/htm

They appear to take many of their experimental values from a DIPPR database. I do not have access to this database, however:

http://dippr.byu.edu/#

The notekeeping of the above article isn't excellent. It looks like their formation values are in the liquid phase. I base this by comparing the value for 1-octene from the DIPPR database to that at the NIST database (reports gas phase).

You might also take a look at this article - although it doesn't include the compounds you want, it might have some relevant information for you:

Rockenfeller, J.D.; Rossini, F.D., Heats of combustion, isomerization, and formation of selected C7, C8, and C10 monoolefin hydrocarbons, J. Phys. Chem., 1961, 65, 267-272.

Finally, note that cis and trans alkenes will have different heats of formation, and this should be a part of your presentation and discussion. I'd look on SciFinder or another good database for references that report the decene values, but chances are if these compounds aren't reported in the NIST Webbook, their formation enethalpies may never have been reported in the peer-reviewed literature because the NIST database seems pretty comprehensive. Therefore I suggest going to the octenes, which should give you the same types of comparisons. You may also consider comparing thermochemical data for alkenes of different chain lengths and branching topologides.

Good luck, sounds like a great topic!