BP of aldehydes vs alcohols

[inaccensa]

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Why are the BP's of aldehydes lower than that of alcohols. Aldehyde is capable of hydrogen bonding. Alcohol can form 2 H bonds, so can aldehydes. Can anyone please explain.

Thanks!!

 

[minutemen11]

aldehydes CANNOT form hydrogen bonds... this is why their BP's are lower.... and the alcohol can only form 1 more intermolecular H bond. Carboxy acids have a higher BP because not only do they have H-bonding but also the formation of an enolate can result in 2 H bonds.

amines will therefore have around the same BP as alcohols due to H-bonding i think..

 

[ezsanche]

Why are the BP's of aldehydes lower than that of alcohols. Aldehyde is capable of hydrogen bonding. Alcohol can form 2 H bonds, so can aldehydes. Can anyone please explain.

Thanks!!

When we are talking about boiling we are talking about intermolecular forces.

In order for H-bonding to occur you need an hydrogen atom that is DIRECTLY attached to a F,O, or N (hydgrogen likes to have FON). Is there an hydrogen atom that is DIRECTLY attached to any one of these elements in an Aldehyde molecule? How about in an alcohol?

 

[inaccensa]

When we are talking about boiling we are talking about intermolecular forces.

In order for H-bonding to occur you need an hydrogen atom that is DIRECTLY attached to a F,O, or N (hydgrogen likes to have FON). Is there an hydrogen atom that is DIRECTLY attached to any one of these elements in an Aldehyde molecule? How about in an alcohol?

I kept thinking that as long as aldehydes have O and H, they can form H bonds with each other. If you look at water, 2 water molecules can form H bonds with each other. Is this simply because, the H in aldehydes does not carry a partial positive charge?

 

[ezsanche]

I kept thinking that as long as aldehydes have O and H, they can form H bonds with each other. If you look at water, 2 water molecules can form H bonds with each other. Is this simply because, the H in aldehydes does not carry a partial positive charge?

Yeah you are right the hydrogen of the aldehyde do not carry a partial positive charge hence it can not H-bond with itself. Water can form hydrogen bond with each other becuase the hydrogen has parital positive charge because it is attached to a electronegative atom (oxygen)