Rank the following according to boiling point, highest to lowest:
a. CH₃CH₂CH₂OH
b. CH₃CH₂(OH)CH₂OH
c. CH₃CH₂CH₃
d. CH₂(OH)CH(OH)CH₂OH

Question

Rank the following according to boiling point, highest to lowest:

a. CH₃CH₂CH₂OH

b. CH₃CH₂(OH)CH₂OH

c. CH₃CH₂CH₃

d. CH₂(OH)CH(OH)CH₂OH

Accepted Answer

Hi everybody. Let's look at our next problem. Arrange the following. In order of increasing boiling point, we have four different molecules. And then our choices A through D are these four molecules in different order. So let's look at each one of those after thinking about what affects boiling point. So boiling point is affected by how strong the intermolecular forces are between molecules. The stronger the IMF the higher the boiling point as it takes more energy put in to make the molecule spread apart in a gas. So what are the different IMF forces which are the strongest ones, the strongest, of course are ion dipole interactions? And then after that hydrogen bonds after that dipole dipole interactions and the lowest of all are dispersion forces. Shall let's look at each of these and we see that we have all of them have alcohol groups, different numbers of them and different length chains. So what are the factors in these structures that will affect boiling point? Well, length of carbon chain will affect that because the longer the chain, the greater the surface area. And so that means more chance or more of these dispersion forces since wherever that most molecules will interact. Well, you'll see these dispersion forces acting as temporary tiny little attractions. So a longer chain will have a higher boiling point, high BP. And then the number of O groups will affect boiling point because the oh groups are capable of hydrogen bonding. So the greater the number, the higher the boiling point now, which of these is a bigger factor. Well, that will be the alcohol groups. And that's because those um hydrogen bonds are stronger IMF s than the dispersion forces. So we'll put an asterisk by a number of oh groups since that's the more significant. So when we look at our molecules to try and order them, we see that we have a 12345 carbon chain with two hydroxy groups on the chain. And then a hydroxy group branched off. So that would be three hydroxy groups on a molecule with six carbons molecule. For molecule one or molecule two, we just have methanol. So one carbon. So one carbon 10 for number three, we have 123 carbons and 20 groups. And then for molecule number four, we have two carbons and 20 groups. So we know that our molecule number one, which has three hydroxy groups will have the highest boiling point, more hydroxy groups than anything else. So we would expect that to be last. So number one should be our last option since that will have the highest boiling point. Well, only choice C has number one as the last option. So we can eliminate, just by looking at that, we can eliminate A B and D. So A has number one listed. First. B has it listed second and D has it listed third. But we'd like to be a little more thorough going through everything. But again, just remember on a test, you wouldn't have to go any further. So that's our highest boiling point. Next, we would look at our two molecules that have two hydroxy groups. So that's three and four. So now we look at the length of the carbon chain. Well, molecule three has three carbons, while molecule four has two carbons, so the longer chain would have the higher boiling point. So molecule three will be the next highest. So it should be third in the list and then molecule four should be second. And we see that in choice C that is indeed the case. And then finally, molecule two with just one hydroxy group and one carbon would be our lowest boiling point. So this corresponds with what we see in choice C. So choice C will be our answer. In order of increasing boiling point, we have 243 and then one. So choice C is that correct answer? See you in the next video.

Rank the following according to boiling point, highest to lowest:
a. CH₃CH₂CH₂OH
b. CH₃CH₂(OH)CH₂OH
c. CH₃CH₂CH₃
d. CH₂(OH)CH(OH)CH₂OH

Verified video answer for a similar problem:

Key Concepts

Boiling Point and Intermolecular Forces

Hydroxyl Groups and Alcohols

Structural Isomerism

Rank the following according to boiling point, highest to lowest:a. CH3CH2CH2OHb. CH3CH2(OH)CH2OHc. CH3CH2CH3d. CH2(OH)CH(OH)CH2OH

Verified video answer for a similar problem:

Key Concepts

Boiling Point and Intermolecular Forces

Hydroxyl Groups and Alcohols

Structural Isomerism

Rank the following according to boiling point, highest to lowest:
a. CH₃CH₂CH₂OH
b. CH₃CH₂(OH)CH₂OH
c. CH₃CH₂CH₃
d. CH₂(OH)CH(OH)CH₂OH