INTERMOLECULAR?

Intermolecular forces?

• Stuck on these 3 questions, any help really appreciated =) Background to the questions: The people who devise new perfumes think of the mixture as a sequence of 'notes'. You first smell the 'top notes' but the main effect depends on the 'middle notes', while the more lasting elements of the perfume are the end notes. The overall balance of the 3 is critical. This means that the volatility of perfume chemicals is of great importance to the perfumer. In this example: 2 top notes: 2 aldehydes, boiling temp: 168 and 117 2 middle notes: 2 alcohols: boiling temp: 146 and 224 2 end notes: 2 musks: melting temp: 53 and 55 1) Using knowledge of intermolecular forces why are aldehyde's useful as top notes whilst alcohols more commonly used for middle notes 2)Using knowledge of intermolecular forces why do the musks used as end notes also help 'fix' or retain the more volatile components of a perfume? 3) Using knowledge of intermolecular forces why are the alcohols more soluble in water than the aldehydes? Thank you so much!

• Answer:

  1: Aldehydes have the 2nd most powerful intermolecular force called dipole-dipole forces because of the the electronegative Oxygen, which makes it slightly polar. It has the lowest boiling point because of this and its molecular size. 2: It's probably because musk is a very stable looking compound--- it's practically non-polar (it uses vanderwal force). U can look at a molecule at any website, and it looks like it has no direction where it retains a pole. And... it's molecules are huge, meaning it would be very difficult to evaporate. 3. Alcohol has the most powerful intermolecular force called Hydrogen bonding (dipole-dipole on steroids). It's more polar than aldehydes, and in order to mix well with water, a molecule has to be polar.