Propanol is very soluble in water, but ethanethiol and chloroe...

Question

Propanol is very soluble in water, but ethanethiol and chloroethane are only slightly soluble. Explain.

Accepted Answer

Hi, everybody. Our next problem says state the main reason why 12 ethane diol is very soluble in water. But one butane dial is only slightly soluble and tetra fluoro methane is insoluble. And all of our answer choices begin, 12 ethane dial is very soluble in water because so I'm going to assume it's starting that way. And then I'll read the end part. So for choice A, it's very soluble in water because it has the most similar size to water. B because it has the least number of carbons C because it has the most electron element or d because it has the most similar IMF to water. Well, let's first draw our structures. So we have kind of a picture of the structure and nature of these molecules. 12 ethane diol ethane means there's only two carbons and then there's an alcohol group on each of these carbons. So it kind of makes a zigzag, the two middle corners here are carbons and then we have an oh group on either end, then we have one butane vial, which would be a four carbon chain with an sh group on the first carbon So I'll write HS and then four carbons, 1234 and then tetra fluoro methane is of course, a carbon with four fluoride group surrounding it in that tetrahedral geometry you'd expect. So we'll draw those just so we can envision the geometry there. That's important because when we look at tetra chloro methane, the ch the carbon fluorine bond is normally very polar fluorine is very electron and would draw the electrons towards itself and have a strong delta negative. However, because we have four fluorine in this tetrahedral geometry, their dipole moments will cancel each other out. Meaning that this is a completely nonpolar molecule. So now let's think about our other two molecules here, Ethane dial, we have an equal ratio 1 to 1 of carbon and oxygen. We know we have that electronegativity difference between oxygen and carbon, which is quite large and just like water, you have hydrogen bonding present those oh groups can participate in hydrogen bonding with water molecules. When we look at our one butane thol, we have twice as many carbons. So a larger nonpolar part, the sh group does result in a polar bond between the sulfur and the carbon sulfur is more electron than carbon. But sulfur being the row below oxygen is not as electron as oxygen. So it's bond participation in those dipole dipole interactions with water will not be quite as strong due to the lesser difference in or the smaller dipole moment. I should say as well as having a larger non polar uh region. So when we think about solubility in water, we think about the fact that like dissolves like so water being a polar molecule with hydrogen bonding capability, the greatest solubility will be that ethane thiol as we know due to its ability to hydrogen bond. And so we see choice D which says it's very soluble because it has a most similar IMF to water would be our main reason that ability to participate in hydrogen bonds, whatever we have something like main reason, it means some of our answer choices, other answer, choices may be correct but just not the best answer. Or in this case, the main reason. So we should take a look at them and make sure nothing else is going to come in. That turns out to be more important than our reason and choice D. So choice A says it has the most similar size to water. Well, this does, does have somewhat of an effect because the small size of the ethane diol means there's a smaller nonpolar region. But again, this isn't the most important reason that participation in hydrogen bonding sort of trumps everything else and certainly the size of the molecule. So choice A, we eliminate choice B because it has the least number of carbons. Again, as we discussed, that does have a factor because it has a smaller nonpolar area of its, of its molecule as opposed to our butane thiol with four carbons. But again, the hydrogen bonding will be a much greater factor. So that's why choice B isn't our answer and choice C that it has the most electron element. Well, this just isn't true. Tetra fluoro methane has fluoride, which is an even more electron element. And the difference in electronegativity between fluorine and carbon is even greater than that between oxygen and carbon. But as we discussed, those dipole moments cancel each other out resulting in overall and nonpolar molecule. So choice C just isn't, isn't correct. So definitely not our main reason. So once again, that main reason why 12 ethane dial is very soluble in water is choice D because it has the most similar IMF to water. See you in the next video.

Propanol is very soluble in water, but ethanethiol and chloroethane are only slightly soluble. Explain.

Key Concepts

Polarity

Hydrogen Bonding

Molecular Structure

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