October 24, 2021, 01:59:07 AM
Forum Rules: Read This Before Posting


Topic: aspirin and polarity  (Read 25403 times)

0 Members and 1 Guest are viewing this topic.

Offline ultrasound

  • New Member
  • **
  • Posts: 3
  • Mole Snacks: +0/-0
aspirin and polarity
« on: April 19, 2012, 03:04:42 PM »
I am trying to decide whether aspirin is a polar or non polar molecule.
I had thought that because it has both an ester group and a carboxylic acid group, it would be polar - the oxygens on those groups are all available for hydrogen bonding aren't they?
And if that is the case, is it because the oxygens have small electronegative charges?
If that is true, then surely aspirin is polar and will dissolve in water... but I have read on this forum that aspirin actually doesn't dissolve in water.
Where am I going wrong? ???

Offline sjb

  • Global Moderator
  • Sr. Member
  • ***
  • Posts: 3586
  • Mole Snacks: +219/-42
  • Gender: Male
Re: aspirin and polarity
« Reply #1 on: April 19, 2012, 03:20:16 PM »
I am trying to decide whether aspirin is a polar or non polar molecule.
I had thought that because it has both an ester group and a carboxylic acid group, it would be polar - the oxygens on those groups are all available for hydrogen bonding aren't they?
And if that is the case, is it because the oxygens have small electronegative charges?
If that is true, then surely aspirin is polar and will dissolve in water... but I have read on this forum that aspirin actually doesn't dissolve in water.
Where am I going wrong? ???

Aspirin is polar, but this is not a black and white property of molecules, just as ionic and covalent are merely extrema of bond descriptions. There are derivatives of aspirin, like salts, which are even more polar and water soluble

Offline ultrasound

  • New Member
  • **
  • Posts: 3
  • Mole Snacks: +0/-0
Re: aspirin and polarity
« Reply #2 on: April 19, 2012, 03:24:47 PM »
If aspirin is polar then why will it not dissolve in water?

Offline fledarmus

  • Chemist
  • Sr. Member
  • *
  • Posts: 1676
  • Mole Snacks: +203/-28
Re: aspirin and polarity
« Reply #3 on: April 19, 2012, 03:36:05 PM »
It is soluble in water - to the extent of 3 mg/mL. So, not particularly soluble.

A phenyl group is a large and very hydrophobic group - it takes a lot of polarity to solubilize something with a phenyl group on it.

Offline ultrasound

  • New Member
  • **
  • Posts: 3
  • Mole Snacks: +0/-0
Re: aspirin and polarity
« Reply #4 on: April 19, 2012, 04:09:25 PM »
I am being asked whether I think aspirin can cross the blood brain barrier and whether I think aspirin is addictive, and they want me explain my answer based on the polarity of the molecule. Nonpolar molecules can pass through the blood brain barrier into the brain which is lipid rich.  Polar molecules dont dissolve easily in the brain and nonpolar molecules do.
But I just can't seem to get a straight answer about the properties of aspirin!

Offline Babcock_Hall

  • Chemist
  • Sr. Member
  • *
  • Posts: 4930
  • Mole Snacks: +288/-22
Re: aspirin and polarity
« Reply #5 on: April 19, 2012, 06:22:00 PM »
At physiological pH, what is the ionization state of the carboxylic acid in asprin?

Sponsored Links