# When using IR spectroscopy, why does a stronger bond have a higher wavenumber?

The wavenumber

#\mathbf(tildenu = 1/(2pic)sqrt(k/mu))# where:

#c# is the speed of light,#2.998xx10^(10)# #"cm/s"# .#k# is the force constant in#"kg/s"^2# of the bond between the two atoms in theharmonic oscillatormodel, which can alternatively be labeled theball-and-springmodel. The force constant value is generally in the hundreds.#mu# is the reduced mass;#mu = (m_1m_2)/(m_1 + m_2)# , where#m_i# is the molar mass of atom#i# .

Since for the same molecule,

A *higher* force constant *stiffer* "spring" (i.e. stronger bond).

Therefore, a *stronger* bond has a *higher* IR frequency when comparing the *same* type of vibrational motion (e.g. symmetric stretch with symmetric stretch, asymmetric bend with asymmetric bend, etc).

*CHALLENGE: Can you show me why the wavenumber frequency for* *for the symmetric stretch is* *whereas that of* *is* *? What does that tell you about the bond strength of* *?*

*Sign up to view the whole answer*

*By signing up, you agree to our Terms of Service and Privacy Policy*

*Sign up with email*

*Answer 2Sign up to view the whole answerSign up with email*

In IR spectroscopy, a stronger bond has a higher wavenumber because stronger bonds vibrate at higher frequencies, resulting in higher energy transitions and thus higher wavenumbers in the infrared spectrum.

By signing up, you agree to our Terms of Service and Privacy Policy

*Answer from HIX Tutor*

*Trending questions*

*How does mass spectrometry differ from other forms of spectroscopy?**What is the frequency range in #"cm"^(-1)# of #-OH# in water using infrared spectrometry?**How is IR spectroscopy used?**What are the differences between stretching vibration and bending vibrations?**Whats the difference between FTIR and Raman Spectroscopy?*

*Not the question you need?*

*HIX TutorSolve ANY homework problem with a smart AI*

- 98% accuracy study help
- Covers math, physics, chemistry, biology, and more
- Step-by-step, in-depth guides
- Readily available 24/7