April 17, 2021, 09:47:22 PM
Forum Rules: Read This Before Posting


Topic: I'm weak with IR and need to identify important peaks in this spectrum.  (Read 290 times)

0 Members and 1 Guest are viewing this topic.

Offline PandHero

  • New Member
  • **
  • Posts: 5
  • Mole Snacks: +0/-0
This is from a lab to separate an unknown binary mixture. This compound after performing a solubility test, I determined to be a carboxylic acid. I need help in identifying the peaks and determining what they are.

https://imgur.com/a/RXiROtN

Offline Borek

  • Mr. pH
  • Administrator
  • Deity Member
  • *
  • Posts: 26420
  • Mole Snacks: +1719/-402
  • Gender: Male
  • I am known to be occasionally wrong.
    • Chembuddy
Please read the forum rules.

You have to show your attempts at answering the question, this is a forum policy.
ChemBuddy chemical calculators - stoichiometry, pH, concentration, buffer preparation, titrations.info, pH-meter.info

Offline PandHero

  • New Member
  • **
  • Posts: 5
  • Mole Snacks: +0/-0
Sorry I had a lecture here is my attempt, I'm not sure if all these peaks are relevant to the identity of the compound or if I am labelling them correctly.

https://imgur.com/a/M97PdhT

Offline Babcock_Hall

  • Chemist
  • Sr. Member
  • *
  • Posts: 4616
  • Mole Snacks: +279/-20
Do you know anything about the relationship between the frequencies of C-H stretches and the hybridization of the carbon atom?

Offline PandHero

  • New Member
  • **
  • Posts: 5
  • Mole Snacks: +0/-0
I know about it in theory but I don't know how to identify it.

Offline Babcock_Hall

  • Chemist
  • Sr. Member
  • *
  • Posts: 4616
  • Mole Snacks: +279/-20
What would you predict on the basis of the length and strength of various C-H bonds?  You can check your predictions here:

https://www.cpp.edu/~psbeauchamp/pdf/spec_ir_nmr_spectra_tables.pdf


Offline PandHero

  • New Member
  • **
  • Posts: 5
  • Mole Snacks: +0/-0
I'm not sure if the sp2 C-H is correct or is that should be NH2. Also are the smaller peaks irrelevant, and at what point should I disregard the fingerprint region, my professor has been mixed on this.

One thing that is throwing me off is the fact that I know this is a carboxylic acid but I don't clearly see the O-H stretch of it.

https://imgur.com/ddwcKlq

Offline Babcock_Hall

  • Chemist
  • Sr. Member
  • *
  • Posts: 4616
  • Mole Snacks: +279/-20
2960 cm-1 is too low to be sp2CH.  The carboxylic acid signals that I have seen do not look like your spectrum; therefore, I am also puzzled by this.

Offline PandHero

  • New Member
  • **
  • Posts: 5
  • Mole Snacks: +0/-0
https://imgur.com/a/0gw2DQd

I do have this IR for the liquid portion of my unknown, however I determined this to be some type of neutral compound after the solubility test since it was insoluble in all the solvents up to H2SO4. I TA confirmed that these were the correct traits of my compounds.

I've also attached an image of my solid unknown. For the IR I dissolved it in a minimum amount of DCM. It had a bit of a yellowish tint. My liquid was clear, and the solid was dissolved in it and turned it yellow pre-separation.

Sponsored Links