[vahid (OP)]

Hello guys
I am a senior petroleum engineering student
In the case of chemical solvents and hydrocarbon washings, I have a question that I couldn't find any answer.
What happens when a chemical solvent such as toluene, dichloromethane, methanol or ethanol inject or pour into a stone that is contaminated with hydrocarbons (paraffin/aromatics)?
how a non-polar solvent dissolve a non-polar solute and vice-a-versa?
how does this mechanism work?
does an exchange of ions take place?
Is there a chemical reaction?
Can you please show it in a picture?
(sorry for bad English)

[chris]

This is an @Bored chemist question!

[vahid (OP)]

I saw @boredchemist 's answers about solvents
But the responses were general and what I am looking for is an exact explanation of the mechanism of the Dissolving paraffin and aromatics in polar and non - polar solvents

[Bored chemist]

The driving force behind dissolving, for example, paraffin wax in diesel is entropy.
Does that help?

[Kryptid]

It's been a while since I've thought about this. If I recall correctly, it has something to do with how strongly molecules are attracted to each other. In the case of oil and water, water molecules are polar. This polarity makes the water molecules act somewhat like tiny magnets (or more appropriately, "electrets"), making their strength of attraction to each other stronger. For nonpolar molecules like oil, they are more weakly attracted to each other because they either do not have this feature or it is much weaker than in water. So molar mass for molar mass, oil molecules are weakly attracted to each other and water molecules are strongly attracted to each other.

However, the polarity of the water molecule can induce a temporary dipole moment more strongly in an oil molecule than another oil molecule could. This increases the attraction that the oil molecule can have towards the water molecule. So the oil molecule is actually more strongly attracted to the water than it is to other oil molecules. Why then, doesn't oil dissolve in water? The reason is because water molecules are more strongly attracted to each other than they are to the oil molecules. Therefore, water molecules will preferentially surround themselves with other water molecules, excluding most of the oil molecules in the process.

So based on my (possibly naive) reasoning, substances dissolve each other best when their molecules attract each other by similar amounts. So a weakly-bound, non-polar liquid (like petroleum) can dissolve a weakly-bound, non-polar solid (like paraffin), where as a strongly-bound, polar liquid (like water) can dissolve strongly-bound, polar or ionic solids (like salt). It's interesting to note that when molecules are too large, neither polar nor non-polar liquids will dissolve them effectively (like cellulose).

[vahid (OP)]

That's right @Kryptid I've found the same answer on the internet.
For example, Hexane (C6H14), and Pentane (C5H12) are both non-polar held together by London Dispersion forces and dissolution occurs between them.
-Non-polar substances do not dissolve in water since:
1. Water molecules are polar
2. Water molecules are held together by hydrogen bonds
Why not dissolve?
Not enough energy is present to break the hydrogen bonds since hydrogen bonds are stronger than dispersion forces, and there is no compensating force between a non-polar molecule and a water molecule.

[evan_au]

Solid paraffin consists of long hydrocarbon chains that get easily tangled around each other, so the weak intermolecular bonds are enough to make it go solid at quite a high temperature.

In contrast, a small-molecule organic liquid consists of many small molecules that are too small to get easily tangled with each other, so they are liquid at room temperature. In fact, ethane and methane are gases at room temperature, so adding some hydrogen bonding (eg ethanol) or a big chlorine molecule (eg dichloromethane) keeps them liquid at room temperature, and easier to handle. More importantly, there is a much greater density of molecules in a liquid., and this makes it easier to overcome the molecular attraction between the paraffin molecules.

The small organic molecules will have a similar affinity to the long-chain molecules as the paraffin molecules have to each other, so they will become more mobile. When a long-chain hydrocarbon is completely surrounded by short-chain hydrocarbons, it can no longer get tangled with others, and it will be a liquid at temperatures where the pure paraffin would be solid.

[Bored chemist]

The principle reason that, for example, oil doesn't dissolve in water is that, to do so it would have to get in between water molecules. But those water molecules attract eachother  quite strongly, so the oil is effectively "squeezed out".

[palak]

The simplest answer is that like dissolves like. A non polar solute will be dissolved by a non polar solvent because the two are attracted to one another and the bonds binding the molecules of the non polar solute are broken. A polar solute, on the other hand is not attracted by the non polar solvent and so the bonds are not broken. Equally, a polar solvent won't dissolve a non polar material.

[puppypower]

Hello guys
I am a senior petroleum engineering student
In the case of chemical solvents and hydrocarbon washings, I have a question that I couldn't find any answer.
What happens when a chemical solvent such as toluene, dichloromethane, methanol or ethanol inject or pour into a stone that is contaminated with hydrocarbons (paraffin/aromatics)?
how a non-polar solvent dissolve a non-polar solute and vice-a-versa?
how does this mechanism work?
does an exchange of ions take place?
Is there a chemical reaction?
Can you please show it in a picture?
(sorry for bad English)

Have you ever heard of a process called steam distillation. This is where you inject steam into mixture of organic solvents and oil. The steam will allow the organics to distill, below their boiling point. For example, oils that boil at 250C can be distilled at 100C using steam distillation. 

Steam distillation shows that water is actually is good solvent for organics. However, water is much better for polar solvents, due to the larger free energy advantage within the polar solvents.

In the case of steam, the boiling point has broken all the hydrogen bonds, so renewed water-water binding does not offer much free energy advantage, compared to organic bonding. Now water can opt to dissolve organics. The term hydrophobic is a misnomer since organics are not afraid of water. Water can bind to organics. However, water prefers to hydrogen bond to other water, due to the free energy advantage. Water can also go the other way, if the first option is not available.

An analogy is you might really like love prime rib, but like hamburger. If the two are being served, you will always pick prime rib. But if prime rib is not an option, burgers can be very good.

With steam distillation, the steam dissolves organics in the vapor phase. This is where the hydrogen bonds are the least competitive, with respect to the water-organic binding.

In hydrothermal water, which is water above its critical point, all the hydrogen bonds are broken, like as in steam, but the water exists as a dense fluid. This phase of water is a very aggressive solvent for  organics, due the much higher surface contact density between water and organics. It can also dissolve minerals like quartz.