 As we said before, the strength of dipole-dipole attractions is greater than that of van der Waals forces, but less than that of hydrogen bonds. This means that the boiling points of aldehydes and ketones, which are held together largely by dipole-dipole attractions, are higher than those of alkanes, which are non-polar, and therefore only have van der Waals forces. However, as you see in this table, they are not as high as those of alcohols, which are held together by hydrogen bonds. You can also see that when you compare aldehydes and ketones with the same number of carbons, their boiling points are roughly comparable. Now, why have I compared them by the number of carbons? Why not compare the smallest aldehyde with the smallest ketone? Remember that van der Waals forces, although weak, do have an effect on the boiling point. You see this in the fact that boiling point increases as the carbon chain gets longer. For everything, alcohols, aldehydes, ketones, alkanes, as you know. It's therefore inconsistent to compare methanol with propanone, because the larger propanone molecules will have significantly greater van der Waals forces holding them together. Now, solubility, because aldehydes and ketones can form hydrogen bonds with water, the smaller molecules in these groups are miscible in water, like alcohols. As with alcohols though, as the carbon chain lengthens, it becomes less and less favorable for these molecules to be dissolved in water, and so their solubility drops again much like alcohols.