Question

5. Stronger bonds generally absorb at higher frequencies, because of their greater stiffness.  

a) Place the C‐C, C=C, and C≡C in order of increasing vibrational frequency without looking at the expected wavenumbers.   

b) Place the nitrile bonds C‐N, C=N, and C≡N in order of increasing energy.

c) The O‐H bonds of alcohols and the N‐H bonds of amines are both strong and stiff.  Do you expect the vibrational frequencies to be lower or higher compared to C‐H bonds?  Explain.

d) Which peak will be more intense—a C=C peak or a C=O peak?

Please show and explain all steps thoroughly!

Answer 1

Bond	Frequency dependent bond energies	Stretching frequency
C-C	83(350)	1200
C=C	146(611)	1660
C=C	200(840)	2200
C-N	73(305)	1200
C=N	147(615)	1650
C=N	213(891)	2200

ThE frequency of the extending vibration relies on upon two variables:

(1) The mass of the particles

(2) The solidness of the bond

Heavier particles vibrate more gradually than lighter ones, so a C-D security will vibrate at a lower recurrence than a C-H security. More grounded bonds are stiffer than weaker bonds, and along these lines require more constrain to extend or pack them.

Along these lines, more grounded securities by and large vibrate quicker than weaker securities.

So O-H BOND which are more stronger than C-H bonds vibrate at higher frequencies.