Comparing solubility of different length hydrocarbons in non polar solvent

[snlee3]

In a non polar solvent, which would a larger or smaller hydrocarbon chain be more soluble? How about branched or unbranched? I know larger and unbranched hydrocarbon chains would have more london dispersion forces, but since they are all nonpolar does the more polar character make them less soluble?

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[FeralisExtremum]

In a non polar solvent, which would a larger or smaller hydrocarbon chain be more soluble? How about branched or unbranched? I know larger and unbranched hydrocarbon chains would have more london dispersion forces, but since they are all nonpolar does the more polar character make them less soluble?

Not sure what you mean here - if it's just a hydrocarbon, and it's a non-polar solvent, there should be no polar character anywhere.

 

[DAT Destroyer]

In a non polar solvent, which would a larger or smaller hydrocarbon chain be more soluble? How about branched or unbranched? I know larger and unbranched hydrocarbon chains would have more london dispersion forces, but since they are all nonpolar does the more polar character make them less soluble?

This is a very sophisticated question. Normally, small polar molecules and branched polar molecules dissolve very well in polar solvents. However, your question was about nonpolar compounds in nonpolar solvents. It is hard to give you an EXACT answer because slight differences are not so easy to measure and solvents vary widely. I have searched a few books and even a Google search of the chemical literature and have not seen any direct studies. It appears if a hydrocarbon is dissolved in a nonpolar solvent, it it usually soluble to all extents whether small, medium or large, branched or unbranched. If the molecule has ANY polarity, this can reduce the ability to dissolve somewhat. Through the years I have never had a problem with nonpolar molecules in nonpolar solvents, however when polarity and dipoles are considered then sometimes trial and error is needed. If I find any literature data, I will post it.

One final point..... If a molecule is extremely large such as a polymer and we noted that it didnt dissolve as well as a smaller hydrocarbon, a possible reason would be that portions of the chain existed in a conformation such as a helix which could in theory interact differently with the solvent.

Dr. Jim Romano

 

[snlee3]

This is a very sophisticated question. Normally, small polar molecules and branched polar molecules dissolve very well in polar solvents. However, your question was about nonpolar compounds in nonpolar solvents. It is hard to give you an EXACT answer because slight differences are not so easy to measure and solvents vary widely. I have searched a few books and even a Google search of the chemical literature and have not seen any direct studies. It appears if a hydrocarbon is dissolved in a nonpolar solvent, it it usually soluble to all extents whether small, medium or large, branched or unbranched. If the molecule has ANY polarity, this can reduce the ability to dissolve somewhat. Through the years I have never had a problem with nonpolar molecules in nonpolar solvents, however when polarity and dipoles are considered then sometimes trial and error is needed. If I find any literature data, I will post it.

One final point..... If a molecule is extremely large such as a polymer and we noted that it didnt dissolve as well as a smaller hydrocarbon, a possible reason would be that portions of the chain existed in a conformation such as a helix which could in theory interact differently with the solvent.

Dr. Jim Romano

Thank you for taking the time to give such a long response. I think I get it, but I just want to clarify with a couple examples.

1. Say we have a H3CCH3 compared with a H3CCH2CH2CH2CH3 in a non polar solvent. H3CCH3 would be more soluble because it has the weakest IMFs and thus more nonpolar character

2. Say we have 2 H3CCH2CH2CH2CH3 in a non polar solvent, but one is more branched than the other. The more branched one would be more soluble because it has the weakest IMFs and thus more nonpolar character?

 

[DAT Destroyer]

No....as stated........nonpolar molecules dissolve equally well or if branched in a nonpolar solvent.......If it was POLAR solvents.........and polar medium then.....smaller and branched dissolves better.