Hi, I need some help with IR spectroscopy . For a methylene (-CH2-) unit, where de carbon atom has an sp3 hibridation, What are the vibrational modes, (stretching or else) present?
I'm currently studying the subject, I find it hard to 'see' how the bonds vibrate in this molecule, which is why I don't know the answer.

Question

Hi, I need some help with IR spectroscopy . For a methylene (-CH2-) unit, where de carbon atom has an sp3 hibridation, What are the vibrational modes, (stretching or else) present? 
I'm currently studying the subject,  I find it hard to 'see' how the bonds vibrate in this molecule,  which is why I don't know the answer.

aaronandyson · Answer

What do you know abut this question?

tatianagomezb · Answer

I know molecules vibrate, and at certain frequency you can measure it in a spectrum. How does this molecules vibrate is what I'm asking. Especifically in this case, is there symmetrical stretching, if so why? I also know that there's a difference in charge density in de CH bond. I'm currently doing an organic chemistry course and what we see of IR is pretty basic

aaronq · Answer

Look at example 3 for some examples of the vibrational modes of the methylene group http://chemwiki.ucdavis.edu/Core/Physical_Chemistry/Spectroscopy/Vibrational_Spectroscopy/Vibrational_Modes