The liquids 1-butanol and butanal have similar molar masses. W...

Question

The liquids 1-butanol and butanal have similar molar masses. Which is expected to have the higher boiling point? Explain your choices.

Accepted Answer

Hi, everyone. Welcome back. Here's our next problem. The compounds Pinel and one Pinol have comparable molecular mass masses and are both liquids at standard temperatures, identify the molecule with a higher boiling point and justify your answer. A one Pinol has a higher boiling point because it exhibits hydrogen bonding BP and now has a higher boiling point because it exhibits hydrogen bonding. D one Pinol has a higher boiling point because it exhibits dile dile forces or D Pinal has a higher boiling point because it exhibits dile dippo forces. So let's think about what factors affect our boiling point and then we can look at our molecules and see which are relevant to them. So as we recall, when we think about boiling point, the main factor that will go into that when comparing molecules is the strength of the intermolecular forces, the stronger the inter forces, we recall the higher the boiling point. Since the more each molecule is attracted to the other, the heart, more energy you'll have to put in to make the molecules spread apart in the gas form. So let's think about those various forms of IMF and which are the strongest of course, our strongest are ion dipole interactions. So if we have an ionic compound, that would be the strongest of all the second would be hydrogen bonds or H bonds, then we have dipole dipole interactions those so those interactions in a polar molecule with the partial negative and partial positive charges and finally, dispersion forces. So those very, very temporary areas of slight negative or slight positive charge just cause to the distribution and movement of electron, the electron cloud. And of course, dispersion forces are the only forces in nonpolar molecules. So with that in mind, let's look at the structures of our two compounds from their name, we say they're both five carbon molecules which makes sense since they have comparable molar masses pen and now that a L ending means it's an aldehyde. So five carbon aldehyde. So we'll draw that 12345, the line structure, five carbons, the final carbon has a double bond to an oxygen and a single bond to a hydrogen to make it an aldehyde. So this is our pal and our fentaNYL also five carbons with that pent prefix, 12345. And the last carbon having a single bond to a hydroxy group making it an alcohol one pol. So of course, both have the same hydrocarbon chain, but they have different functional groups. When we look at our aldehyde, we have this double bond between a carbon and an oxygen. And this does have a dipole moment. The electrons are more attracted to that oxygen and this is not canceled out by any other dipole moment on the molecule. So, fentaNYL is a polar molecule and will there have dipole di therefore have dipole dipole interactions. However, it doesn't exhibit hydrogen bonding. This hydrogen is not bound to an electron atom but to carbon. Whereas when we look at one pinol, we have this oh group which has the hydrogen bound to that electron oxygen. So just like water, although not quite as strongly, it will exhibit hydrogen bonding as a result. So since our Pantanal has hydrogen bonding, while our Pinel just has dile dial interaction, the one pinol will have the higher bing boiling point as a result. So our answer here will be choice. A one pinol has a higher boiling point because it exhibits hydrogen bonding. We look at our other answer. Choices choice BP and now does not have hydrogen bonding. So we eliminate choice B to C says one P and all has the higher boiling point, which is correct, but it says because it exhibits dipole dipole forces. Well, it does have dipole dipole forces since it's a polar molecule. But the hydrogen bonding is what gives it the higher boiling point since both molecules have dipole dipole forces. So that's why choice C is incorrect. And finally, choice D fentaNYL has a higher boiling point because it exhibits dile dile forces. Again, it's correct. That it does have those forces but they are weaker than the hydrogen body that occurs in one Piny. So it will not exhibit the higher boiling point but the lower boiling point. So that's why Trustee is incorrect. So once again, the molecule with a higher boiling point and the reason for that is choice a one Piny has a higher boiling point because it exhibits hydrogen bonding. See you in the next video.

The liquids 1-butanol and butanal have similar molar masses. Which is expected to have the higher boiling point? Explain your choices.

Key Concepts

Intermolecular Forces

Boiling Point

Molecular Structure

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