U2 Topic-7 (Intermolecular forces

The more branching in the molecule = less points of contact between adjacent molecules
therefore overall London force is lower

since A has no branches it has strongest London force and so highest B.P

Hydrogen bonding is the strongest intermolecular force.
State with reason whether the following has Hydrogen bond:
HF

HI

Carboxylic acids like CH3COOH

HF = has H-bonding, due to F being very electronegative

HI = no H-bonding as Iodine is not very electronegative

Carboxylic acids like CH3COOH = has H-bonding, due to presence of OH group

Explain whether each of these molecules have hydrogen bonding:

CH3CH2NH2 (ethylamine)

CH4

CH3OH (methanol)

CH4

CH3CH2NH2 (ethylamine) = has H-bonding, presence of N-H bond


CH4 = no H-bonding, as no N, O, F bonded to it

(CH4, CCl4, H2S and PH3 also have no H-bonding)


CH3OH (methanol) = has H-bonding due to OH group

Amides (CH3CONH2) = has H-bonding because of N–H and lone pairs on O
(allows strong hydrogen bonding)

Define hydrogen bonding (2marks)

This is an intermolecular interaction between a hydrogen atom of a molecule (or molecular fragment) bonded to an atom which is more electronegative than hydrogen and another atom in the same or a different molecule

the 3 electronegative atoms are: F, N or O
hydrogen atom must become slightly positive

• Q. says between molecules so intermolecular forces and covalent is NOT INTERmolecular but INTRAmolecular

• also HI has no hydrogen bonding (as I is not electronegative enough)

• no ions so ionic bond not possible
  
  therefore answer is London forces
  
  

More hydrogen bonding increases a liquid's viscosity because it creates strong intermolecular forces that resist flow

trimethylamine (CH3)3N –→ No hydrogen bonding.
Although it contains nitrogen, all the hydrogen atoms are bonded to carbon atoms, not to the nitrogen atom.