Suppose that water and an ester with a short hydrocarbon chain were mixed in solution. Given that the ester's hydrocarbon chain is short, then the Hydrogen bonds between water and water molecules would be broken, resulting in the formation of Hydrogen bonds between an oxygen from the ester functional group and the Hydrogen from the water molecule. Regarding this I have a few questions:
1. Would it matter whether the hydrogen bonds occured with the Oxygen that has a double bond with the carbon (i.e from the carboxylic acid) or if it were to occur between the single bonded oxygen atom from the alcohol?
2. Suppose a small ester was dissolved in water. The hydrogen bonds between water molecules and dispersion and dipole-dipole forces between ester molecules would break and new bonds would form between the ester and the water molecules. How would energy be released from breaking these bonds and would it necessarily have to be equal to the energy required to form new bonds between water and the ester.
Another question:
Would the ester be able to dissolve in an organic solvent? I had a quick search online but didn't find anything helpful. I believe that the ester would be unable to dissolve in non-polar solvents, but therefore, because it is polar, it can then be able to dissolve in polar substances. Correct?
And: Are there exceptions to the rule 'like dissolves like' and to what degree are we required to understand this for the purposes of VCE?
Thank you in advance.
1. You'll find that esters don't dissolve greatly in water. Methyl formate (chemical name methyl methanoate) is the smallest ester possible and does not fully dissolve in water (i.e. put too much of it in water and it won't dissolve. In contrast, ethanol is fully miscible with water, aka mixes in all proportions).
Anyway, the most polar region is the COO carbon. It has three bonds to oxygens, so it is quite positive. For more complicated reasons (resonance), the C=O oxygen is slightly more negative than the other oxygen, so any hydrogen bonding would preferentially occur with that oxygen.
2. Re energy bonding, dissolving does not have to release energy. Often, actually, dissolving costs energy. For instance, anything that dissolves more in hot water than in cold water requires energy to dissolve. Common table salt is an example. Now, I don't have the figures on the top of my head, but I would imagine that the ester costs energy to dissolve in water, because the dipole bonds are not stronger than water's hydrogen bonds.
You may wonder, if it costs energy, why does it dissolve? The answer is, there is an intrinsic benefit to mixing. If you inject some helium into a large room, after some time the helium will expand to fill the entire room. It does so because the helium is statistically much more likely to be in a larger volume than in a small one, and we call this statistical phenomenon entropy. The same is true for dissolving. The ester molecules would prefer to be able to be in the entire volume of water for their entropy to increase (aka spread over a larger region). However, there is an energy cost in the dissolving, so you have to weight up the entropy benefit of dissolving and any heat released.
3. Esters aren't as polar as you may think; as mentioned above, ethanol dissolves more readily than methyl formate in water, and they both have two carbons. You can heuristically think of this as because the COO group disperses the charge over a larger distance, so there isn't as much of an imbalance in the charge distribution. In contrast, in an alcohol, there is a pretty well-defined + and - end. Therefore, esters dissolve worse than alcohols of similar sizes. Now, octan-1-ol has a pretty poor solubility in water, so you can bet that any ester with a similar number of carbons would also not dissolve well in water.
Now, guess what? Fats are esters. And you know what fats dissolve very well in? Organic solvents. Fats consist of long chain fatty acids (think 18 carbons or so) that react with glycerol (think three carbons with an alcohol on each one; all three can form ester bonds) to form triglycerides.
4. Exceptions to 'like dissolves like'? Plenty. Look at all of the ionic compounds that don't dissolve in water. Ionic compounds are meant to be the 'pinnacle' of polarity, yet metal hydroxides, metal oxides, metal iodides, metal bromides, some metal chlorides and others like barium sulfate don't dissolve in water. You are expected to know what ionic compounds dissolve in water. The reason for the variation in dissolution behaviour is complicated and I won't go into it.
1. Doesn't matter both Oxygen atoms have 2 lone pairs (allowing them to form Hydrogen bonds with water molecules)
2. Good question but sorry, got no idea 
3. If it was an ester with a long carbon chain, then yes it would dissolve in an organic solvent (long carbon chain negates the effect of the polar ester group, therefore making it relatively non polar)
If it was an ester with a small carbon chain, then it would probably dissolve in polar solvents like water (as it is relatively polar)
Exceptions: in particular conditions (temperature and pressure), sometimes you can have non-polar stuff dissolving in polar substances or vice versa. E.g. benzene rings (non-polar) can dissolve in water at the right conditions. For VCE Chem, I don't think you'd be expected to know which substances are exceptions to the rule
Hope this helps
Benzene rings dissolving in water? Benzene's solubility in water at room temperature is something like 2 g/L, so its solubility is limited. For it to dissolve in water, you really need a polar group on it. Phenol's solubility in water jumps to 8 g/L, for instance, and it just has one alcohol on it. So, you wouldn't refer to it as the solubility of the benzene ring as such.
In fact, methyl ethanoate dissolves pretty poorly in water, but is miscible (dissolves in all proportions) with diethyl ether, a non-polar solvent. This suggests that esters can be treated as being non-polar.
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