Error in Cliffs?

[PharmLMD]

"For the molecule shown in the above figure, what will the predominant intermolecular forces be?"

The molecule shown was formaldehyde.

Intermolecular forces are forces between many different molecules.

Answer Choices:

A) dipole-dipole
B) Coordinate Covalent Bonding
C) Hydrogen Bonding
D) London Forces

I chose hydrogen bonding since the H's of each molecular will H bond to the carbonyl oxygen. However, the book says dipole-dipole since, it says "Carbon is directly bonded to oxygen, creating a permanent dipole force"

However, I believe this answer would only be true for INTRAmolecular forces not INTERmolecular forces.

 

[think]

"For the molecule shown in the above figure, what will the predominant intermolecular forces be?"

The molecule shown was formaldehyde.

Intermolecular forces are forces between many different molecules.

Answer Choices:

A) dipole-dipole
B) Coordinate Covalent Bonding
C) Hydrogen Bonding
D) London Forces

I chose hydrogen bonding since the H's of each molecular will H bond to the carbonyl oxygen. However, the book says dipole-dipole since, it says "Carbon is directly bonded to oxygen, creating a permanent dipole force"

However, I believe this answer would only be true for INTRAmolecular forces not INTERmolecular forces.

thats exactly wat i said to this problem when i was doing it..and i choose hydrogen bonding too..cliff has mistakes so maybe its one of them....but they usually dont make mistakes in explaining the problem soo..i dont know

 

[PharmLMD]

Yeah I found multiple mistakes in the same chemistry test too! There was another test talking about 1-fluoropropanoic acid. There is no such thing. You start counting from the carboxyl carbon, so you can't have a fluoro there unless you have a "benzoyl" and not a "benzoic" system.

Another error they mad was talking about the cis and trans. They blatently meant trans but wrote cis in the answer key and on the regular test. Then on another part talking about aldol formation they don't label what "R" is so you can't name the compound. It is mistakes like this that really make me look down on Cliffs.

 

[TheRxQueen]

This comes straight from Barron's Organic Chemistry the Easy Way:
(Regarding physical properties of aldehydes and ketones) "Because aldehydes and ketones have an oxygen, they can accept hydrogen bonds from water. Therefore, they are soluble in water, approximately as soluble as alcohols. Because aldehydes and ketones do not have any significantly partially positive hydrogens, they cannot be hydrogen-bond donors, and have lower B.P.'s that alcohols. However, because the C=O bond is polar, there are dipole-dipole attractions between two aldehydes or two ketones, so their B.P.'s are higher than alkanes."
This helps explain the dipole-dipole vs. hydrogen bonding answer given by Cliff's. Carbonyl compounds are polar and have substantial dipole moments.

 

[fenixtnlfan]

Dipole-dipole is an intermolecular force. I'm thinking dipole-dipole would be stronger than any hydrogen bonding because oxygen is electronegative. Hydrogen bonding is a type of dipole-dipole anyways. I hope that's right anyways.