Boiling point of bonds

[joonkimdds]

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According to my class note
H-bond>cation anion> covalent > ion-dipole> dipole dipole

According to DAT destroyer #80 genchem
H bond is weaker than a covalent bond.


My question
1. isn't H bond dipole-dipole? so then why is my class note saying that one has the highest and the other one has the lowest BP? I think they should be the same.

2. Stronger bond requires more heat to break thus has higher BP. If I apply this to my class note, H bond is stronger bond than covalent bond. This is different from what Destroyer says though.


I am confused 😕

 

[yuppers]

According to my class note
H-bond>cation anion> covalent > ion-dipole> dipole dipole

According to DAT destroyer #80 genchem
H bond is weaker than a covalent bond.


My question
1. isn't H bond dipole-dipole? so then why is my class note saying that one has the highest and the other one has the lowest BP? I think they should be the same.

2. Stronger bond requires more heat to break thus has higher BP. If I apply this to my class note, H bond is stronger bond than covalent bond. This is different from what Destroyer says though.


I am confused 😕

Covalent bond is the strongest bond; it is a intramolecular bond. The rest are intermolecular bonds. Covalent > ionic > H-bond > DD > VDW
1. H-bond is specialized DD. It occurs between H and F's, O's, and N's. H-bonds are stronger therefore should have higher boiling point.
2. BP does not break covalent bonds that would be cracking of hydrocarbons for example. BP breaking intermolecular forces NOT intramolecular forces. The molecules with covalent bonds in your class notes probably just have VDW forces or even DD.

 

[joonkimdds]

Covalent bond is the strongest bond; it is a intramolecular bond. The rest are intermolecular bonds. Covalent > ionic > H-bond > DD > VDW
1. H-bond is specialized DD. It occurs between H and F's, O's, and N's. H-bonds are stronger therefore should have higher boiling point.
2. BP does not break covalent bonds that would be cracking of hydrocarbons. BP breaking intermolecular forces NOT intramolecular forces. The molecules with covalent bonds in your class notes probably just have VDW forces or even DD.

Since H bond is a specialized DD, I guess I can just memorize like that and say it has higher BP than just any other DD.

But I am still confused about the 2nd answer.

Here is a question asked from my note

Q. which has higher BP
A. CH3CH2CH2OH
B. CH3CH2CH2CH2CH3

Since A has H bond, and B has covalent bond, the answer was A.

 

[yuppers]

Since H bond is a specialized DD, I guess I can just memorize like that and say it has higher BP than just any other DD.

But I am still confused about the 2nd answer.

Here is a question asked from my note

Q. which has higher BP
A. CH3CH2CH2OH
B. CH3CH2CH2CH2CH3

Since A has H bond, and B has covalent bond, the answer was A.

BP is relationship between two molecules. 2 A's = H-bond together. 2 B's = VDW forces. So A has a higher boiling point.

 

[joonkimdds]

BP is relationship between two molecules. 2 A's = H-bond together. 2 B's = VDW forces. So A has a higher boiling point.

Ohh....I get it now 😀
Thank you 😍
By the way, is ionic (cation-anion) stronger than H bond? I guess my note had an error.

 

[yuppers]

Ohh....I get it now 😀
Thank you 😍

Yeah, ionic is stronger. I would check to make sure in a text book.
👍 figured I would sit here and refresh till you did since I hate waiting a day for a response to something I want to know in a hurry.... speaking of my other thread....

 

[NyCzPeter]

Ionic is definitely stronger than a H-bond but keep in mind that Covalent bonds are the strongest bonds of all. However, INTRAmolecular bonds such as covalent and ionic bonds have no effect on boiling and melting pts. Only INTERmolecular bonds such as vander walls aka induced dipole, H-bonds etc

 

[whateveryoulike]

According to my class note
H-bond>cation anion> covalent > ion-dipole> dipole dipole

According to DAT destroyer #80 genchem
H bond is weaker than a covalent bond.


My question
1. isn't H bond dipole-dipole? so then why is my class note saying that one has the highest and the other one has the lowest BP? I think they should be the same.

2. Stronger bond requires more heat to break thus has higher BP. If I apply this to my class note, H bond is stronger bond than covalent bond. This is different from what Destroyer says though.


I am confused 😕

i think youre getting things a bit confused. there is no such thing as a boiling point for a bond. boiling points are related to molecules and what kind of attraction they have for eachother. your logic is getting messed up because youre trying to mix 2 entirely different characteristics into one.

the strength of molecular attraction is based on charges and distances. covalent bonds have the largest charge separation (and often times the shortest distance) hence having boiling points considerably higher than the other options. hydrogen bonding (between water molecules) is a type of dipole-dipole attraction and is the only one of the intermolecular forces with the misleading title of "bond". i say this a lot around here but i feel it needs to be said, go back and reread your original textbook, youll be much better off in the end.

 

[Contach]

Ionic is definitely stronger than a H-bond but keep in mind that Covalent bonds are the strongest bonds of all. However, INTRAmolecular bonds such as covalent and ionic bonds have no effect on boiling and melting pts. Only INTERmolecular bonds such as vander walls aka induced dipole, H-bonds etc

isn't an ionic bond a unique example? Say for instance you have Na+ Cl- , and you want to boil a pure molten NaCl (l), then you are going to have to overcome the INTERmolecular bonds to create Cl(g) or Cl2(g). and whatever Na boils into.....

But now we are just complicating matters..