joonkimdds

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Is it ionic, covalent, or something else?
O is group 7, H is group 1 so it seems like ionic bonding
but H can't lose electron, it can only gain to become H+
so then it can't be ionic bond.

Is it covalent? and if so, I wonder how CH3OH can become CH3O- and attack carbonyl carbon.
 
Jul 13, 2009
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Its a covalent bond. In CH3OH, the the OH group loses the H+ portion but leaves the electrons with Oxygen since oxygen is so electronegative. Essentially the bond of electrons that was shared between oxygen and hydrogen have stayed with oxygen and formed an electron pair and the H+ has left. The electron pair on CH3O: is what makes it nucleophillic.
 
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Its a covalent bond. In CH3OH, the the OH group loses the H+ portion but leaves the electrons with Oxygen since oxygen is so electronegative. Essentially the bond of electrons that was shared between oxygen and hydrogen have stayed with oxygen and formed an electron pair and the H+ has left. The electron pair on CH3O: is what makes it nucleophillic.
you mean polar covalent right?
 

license2kill

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Generally speaking, a bond between H and F, O, or N (very electronegative elements) constitutes a hydrogen bond according to Kaplan.

As for the methanol example, it is able to attack a carbonyl group on another entity b/c the carbonyl carbon has a electropositive characteristic due to the oxygen having the lion's share of electron density. Some textbooks show the mechanism in which methanol intact with the H attacking the carbonyl carbon and in turn possessing a positive charge on the oxygen of methanol. In turn, a water molecule somes to pick off the hydrogen from methanol, expunging the negative charge on oxygen. Correct me if I am wrong, but in these rxns involving carbonyl groups, an acid is introduced as a catalyst to facilitate this process.
(its been a while since I took orgo)^^

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Kneecoal

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yeah the general rule is supposed to be that H attached to F,O,N (FON!) is a hydrogen bond. hydrogen bonds are weaker than covalent bonds
 
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When you guys are describing it as "hydrogen bonding".. isn't h-bonding a intermolecular phenomenon? as in.. between two different molecules?

I know that H-boning can occur between two molecules that have a H's attached to electronegative atom (F, O, N).

Since the original question was about the type of bond between O-H .. if it is an intramolecular bond (within one molecule) then it has to be (polar)covalent in this case, no?
 
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fldnstrm

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When you guys are describing it as "hydrogen bonding".. isn't h-bonding a intermolecular phenomenon? as in.. between two different molecules?

I know that H-boning can occur between two molecules that have a H's attached to electronegative atom (F, O, N).

Since the original question was about the type of bond between O-H .. if it is an intramolecular bond (within one molecule) then it has to be (polar)covalent in this case, no?
I am going to have to aggree with arginine1 here. When looking at the actual bond between Oxygen and Hydrogen it would be polar covalent. Look at water for example, each water molecule has polar covalent bonds between the oxygen and hydrogens. It does however exhibit hydrogen bonding inrcreasing intermolecular forces thus causing boiling point to go up.

Also for OP to answer the last question on CH3OH being nucleophilic. Oxygen has two lone pairs thus making it nucleophilic, you don't even have to pull off the hydrogen first if you have a good leaving group like I-. You would have to pull off the hydrogen eventually so it would not just leave. I don't know if that makes sense, but to me it does.
 
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hydrogen bond
H-bond is an intermolecular bond (between molecules). I believe the OP is asking about the nature of O-H bond as an intramolecular bond (within the molecule).
It's a polar covalent bond!
 
Jul 13, 2009
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you mean polar covalent right?
I actually forgot about the polar part, but i suppose it is necessary to distinguish since it is heavily polar vs. say a covalent bond between C-H. Someone mentioned it supposed to be acid catalyze but I dont see how that would help. If anything I think it would need to be base catalyzed to remove the proton (H+) from the OH group of CH3OH.

For the others stating hydrogen bonding, it is correct that is INTERmolecular and occurs when hydrogen is bonded to extremely electronegative elements. Its a specific case of an extremely polar covalent bond. The only reason its weaker than covalent bond is because its not the actual sharing of an electron pair but rather a very strong dipolar attraction.
 

ongoingdat

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generally speaking, a bond between h and f, o, or n (very electronegative elements) constitutes a hydrogen bond according to kaplan.


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saDDS

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Is it ionic, covalent, or something else?
O is group 7, H is group 1 so it seems like ionic bonding
but H can't lose electron, it can only gain to become H+
so then it can't be ionic bond.

Is it covalent? and if so, I wonder how CH3OH can become CH3O- and attack carbonyl carbon.
what about reduction with LiAlH4, NaBH4, DIBAL, ect. this is a source of H- (hydride)