Chemical Forums
Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: eglaud on March 06, 2016, 03:50:09 PM
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1-decanol has an O-H bond, which in my book says is what decides if something can form a hydrogen bond. But I've read that 1-decanol does not form a hydrogen bond with water- why is this?
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Theoretically, an electronegative atom like nitrogen or oxygen does hydrogen bond with water. In practice, how do you know decanol is or isn't contributing to hydrogen bonding?
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I'm not sure, in this lab we found that it is non-polar, does that have anything to do with it? Like I said I thought it would form these bonds, I'm not sure why it wouldn't
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I too expect 1-decanol to enable a hydrogen bond with water. But would this imply that they mix?
1-decanol has a permittivity of 8.1, compared with 2.0 for decane. "Polar" may be a matter of definition, then: how much polar, and enough for your definition or not.
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1-decanol has an O-H bond, which in my book says is what decides if something can form a hydrogen bond. But I've read that 1-decanol does not form a hydrogen bond with water- why is this?
Alcohols have polar(O-H) bond and non -polar hydrocarbon ...compare the amount of non polar part with polar part ...
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I'm not sure, in this lab we found that it is non-polar, does that have anything to do with it? Like I said I thought it would form these bonds, I'm not sure why it wouldn't
This explanation of yours, in some ways is desperately missing a point, as the others have pointed out.
I know 1-decanol isn't water soluble.
And you say somehow that means it doesn't hydrogen bond.
Lookup the definition of hydrogen bonding. What does it mean for a molecule. You won't find water solubility as a property.
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I'm sorry I really don't understand the points you're making. All I've done is ask questions and yet you say that I've been making these claims that insoluble in water = doesn't hydrogen bond, but all I've said is that this is non-polar (in regard to what we've been taught is non-polar).
But regardless, clearly my knowledge on this subject is lacking, so could you explain why my book says that it will form a hydrogen bond when it doesn't? I just don't understand this subject.
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Ok let me help you ...if you check the solubility of alcohol family in water....lower members are highly soluble like CH3OH or C2H5OH ...however as you increase the hydrocarbon part which is non polar or hydrophobic solubility decreases for example C7H15OH or C10H21OH(decanol) though they can form hydrogen bonds with water due to OH part in the molecule but C10H15 --- is very big non polar part so it makes it insoluble in water.
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But regardless, clearly my knowledge on this subject is lacking, so could you explain why my book says that it will form a hydrogen bond when it doesn't? I just don't understand this subject.
Because it does form hydrogen bonds. With itself, and likely with water too. That's what "forms hydrogen bonds" means. I don't know why you said it at the beginning of the thread, and why you keep saying it when we correct you.
Look at the properties of water, which hydrogen bonds,compared to other elements which don't.And compare the boiling point of 1-decanol, and decane,and longer hydrocarbons.
[EDIT]
Like you've said, decanol is non-polar. But what does that have to do with hydrogen bonding, by any definition?
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I'm sorry I really don't understand the points you're making. All I've done is ask questions and yet you say that I've been making these claims that insoluble in water = doesn't hydrogen bond, but all I've said is that this is non-polar (in regard to what we've been taught is non-polar).
But regardless, clearly my knowledge on this subject is lacking, so could you explain why my book says that it will form a hydrogen bond when it doesn't? I just don't understand this subject.
1. Be aware that a molecule can form hydrogen bond with water without being able to dissolve in water.
2. From wikipedia:
A hydrogen bond is the electrostatic attraction between polar groups that occurs when a hydrogen (H) atom bound to a highly electronegative atom such as nitrogen (N), oxygen (O) or fluorine (F) experiences attraction to some other nearby highly electronegative atom.
That should give you some more clues.
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[...] solubility of alcohol family in water... lower members are highly soluble like CH3OH or C2H5OH [...]
Soluble or miscible?
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This thread illustrates some of the problems one encounters in teaching about polarity.
@OP, Water and diethyl ether are immiscible. However, water is more soluble in diethyl ether than it is in hexane. Why?
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But regardless, clearly my knowledge on this subject is lacking, so could you explain why my book says that it will form a hydrogen bond when it doesn't? I just don't understand this subject.
Because it does form hydrogen bonds. With itself, and likely with water too. That's what "forms hydrogen bonds" means. I don't know why you said it at the beginning of the thread, and why you keep saying it when we correct you.
Look at the properties of water, which hydrogen bonds,compared to other elements which don't.And compare the boiling point of 1-decanol, and decane,and longer hydrocarbons.
[EDIT]
Like you've said, decanol is non-polar. But what does that have to do with hydrogen bonding, by any definition?
I am not saying being polar has anything to do with hydrogen bonds, I asked if it did but now I know that it does not. I wondered if it did because our current knowledge about this molecule is that it is nonpolar, so I wondered if there was a connection that's all. I keep saying it because other online sources disagree with that statement, that it does not form with hydrogen bonds with water. I still am confused about all this, so if two substances form hydrogen bonds then they can form one between each other?
If it changes anything, in our lab we found if these things were soluble w/ water and hexane, and conductive. The question asks "which of the following are able to hydrogen bond with water: ...1-decanol... Identify the structural feature which allows for its ability to hydrogen bond. Explain how H-bonding influences the solubility of each in water and hexane."
I'm not looking for an answer to copy, I want to understand why. So is the statement I said originally correct, that hydrogen bonding will occur between molecules that contain an O-H, N-H, or F-H bond? Because if that is true then I guess i'll ignore the other places online who say 1-decanol doesn't form a hydrogen bond with water and say I understand this
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So is the statement I said originally correct, that hydrogen bonding will occur between molecules that contain an O-H, N-H, or F-H bond? Because if that is true then I guess i'll ignore the other places online who say 1-decanol doesn't form a hydrogen bond with water and say I understand this
Well, yes, but I'd like to see the reference to the online sources that say decanol doesn't hydrogen bond. Maybe they're simply wrong, but maybe they're explaining something important we all need to understand better.
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I am not saying being polar has anything to do with hydrogen bonds, I asked if it did but now I know that it does not. I wondered if it did because our current knowledge about this molecule is that it is nonpolar, so I wondered if there was a connection that's all. I keep saying it because other online sources disagree with that statement, that it does not form with hydrogen bonds with water. I still am confused about all this, so if two substances form hydrogen bonds then they can form one between each other?
Polarity is a complex idea, and being able to form H-bonds does make a compound more polar, all else held equal. 1-decanol is both a hydrogen bond acceptor and a hydrogen bond donor. However in the case of 1-decanol, the large size of the nonpolar portion of the molecule has to be factored into the molecule's overall polarity.
Why is water more soluble in diethyl ether than it is in hexane?
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So is the statement I said originally correct, that hydrogen bonding will occur between molecules that contain an O-H, N-H, or F-H bond? Because if that is true then I guess i'll ignore the other places online who say 1-decanol doesn't form a hydrogen bond with water and say I understand this
Well, yes, but I'd like to see the reference to the online sources that say decanol doesn't hydrogen bond. Maybe they're simply wrong, but maybe they're explaining something important we all need to understand better.
The first source is from some answers to the lab, they don't list 1-decanol in their answer only in the question. The second source is just yahoo answers
https://quizlet.com/73672416/5-solubility-polarity-electrolytes-and-nonelectrolytes-flash-cards/
https://answers.yahoo.com/question/index?qid=20101011125715AA7B6Q5
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On top of this, how does the H-bonds affect solubility? Again, online I see people saying if it can make an H bond it will be soluble in water. My guess is since OH and NH are very polar, it would more or less mean that the molecule will be polar, the exception being the decanol because of all of the carbon atoms. Is this a simple explanation?
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Also I find another link saying that the non-polarity will offset the potential hydrogen bonding with 1-decanol.
http://www.answers.com/Q/Can_ethanol_glycerol_sucrose_urea_and_1-decanol_hydrogen_bond_with_water
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Those are students writing whatever they feel like, without a source. I would stick to your textbook's definition, unless you don't understand it for some reason.
In many ways, those groups are similar to our group here, but we do have a dialog of people addressing each other, that Yahoo Answers lacks.
Can you see from the chart I posted what hydrogen bonding is meant to mean? Its also visible in the way decanol interacts with itself, giving it a higher boiling point than even longer carbon chains that don't have an OH to hydrogen bond with itself.
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On top of this, how does the H-bonds affect solubility? Again, online I see people saying if it can make an H bond it will be soluble in water. My guess is since OH and NH are very polar, it would more or less mean that the molecule will be polar, the exception being the decanol because of all of the carbon atoms. Is this a simple explanation?
The solubility of 1-hexanol in water is 0.6 g hexanol per 100 grams of water.
http://chemed.chem.purdue.edu/genchem/topicreview/bp/2organic/alcohols.html
According to one source, the solubility of hexane in water is 9.5 mg/L at 25 deg C
McAuliffe C; J Phys Chem 70: 1267-75 (1966)
https://pubchem.ncbi.nlm.nih.gov/compound/hexane#section=Melting-Point
What does this suggest about the hydrogen bonding in 1-hexanol?
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Those are students writing whatever they feel like, without a source. I would stick to your textbook's definition, unless you don't understand it for some reason.
In many ways, those groups are similar to our group here, but we do have a dialog of people addressing each other, that Yahoo Answers lacks.
Can you see from the chart I posted what hydrogen bonding is meant to mean? Its also visible in the way decanol interacts with itself, giving it a higher boiling point than even longer carbon chains that don't have an OH to hydrogen bond with itself.
No I don't really see the connection between the chart and hydrogen bonding, sorry.
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The solubility of 1-hexanol in water is 0.6 g hexanol per 100 grams of water.
http://chemed.chem.purdue.edu/genchem/topicreview/bp/2organic/alcohols.html
According to one source, the solubility of hexane in water is 9.5 mg/L at 25 deg C
McAuliffe C; J Phys Chem 70: 1267-75 (1966)
https://pubchem.ncbi.nlm.nih.gov/compound/hexane#section=Melting-Point
What does this suggest about the hydrogen bonding in 1-hexanol?
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I see that a hydrogen bond encourages solubility here, right?
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Yes.
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Okay that makes sense, because it'll bond to the hydrogen, essentially dissolving it. What about hexane? I know hexane can't form h-bonds, but it wouldn't discourage it right? Or because they form h-bonds they'll bond to each other and not dissolve as well? Thanks
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OK. We're getting closer to some of your points of confusion.
Okay that makes sense, because it'll bond to the hydrogen, essentially dissolving it.
Depends on "it"
What about hexane? I know hexane can't form h-bonds, but it wouldn't discourage it right?
Oh. Most definitely not. Hydrogen bonding occurs between a hydrogen, bonded to to an oxygen, nitrogen, etc and also to another oxygen, nitrogen, etc. There is no hydrogen bonding involved with hydrogens bonded to carbon.
Or because they form h-bonds they'll bond to each other and not dissolve as well? Thanks
Nope. Hexane doesn't hydrogen bond with itself.
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It's important to realize that all molecular substances that can be liquid or solid have some forces that bond the molecules together. The hydogen bond is just one of them.
So when water mixes with an other liquid or dissolves a solid, some intermolecular bonds must be broken - some preexist in water, others in the other compound. Sometimes the new bonds are extremely favourable (ammonia, hydrogen chloride...) and the result is clear. Sometimes the change is neutral or slightly unfavourable, but it still happens to a variable amount because heat shuffles the molecules. Sometimes it's so unfavourable that nothing perceivable happens.
So "is there some hydrogen bond" doesn't suffice to answer "do they mix". Mixing water and alcohols of varied carbon backbone length needs to break some existing bonds. Do you see what bonds preexist and how the carbon backbone length influences this?
In a next step, you can imagine heterogeneous "mixes", or better colloids, where only one molecule end "mixes" with water, for instance soaps.