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Distinguish between the pair of compounds by their infrared spectra: Compound A CH3CH2CH2N(CH3)2...

Question:

Distinguish between the pair of compounds by their infrared spectra:

Compound A CH3CH2CH2N(CH3)2 and Compound B CH3CH2CH2NH2

a. Compound A will show an NH absorption while Compound B will not.

b. Compound B will show an NH absorption while Compound A will not.

c. The infrared spectra will be the same for both compounds.

d. There is no way to differentiate between the two compounds using IR.

Infrared Spectroscopy

Infrared spectroscopy is a powerful tool used in organic chemistry to determine what functional groups are present in a compound. Bonds are constantly vibrating; stretching and bending. The frequency at which these vibrations occur are different for different bonds. The two factors that change the frequency at which a bond vibrates are the stiffness of the bond i.e. bond order, and the mass of the atoms within a bond.

The equation which relates the frequency of light that a molecule will absorb in order to vibrate, and also shows how the stiffness of a bond and mass can affect this frequency, is:

{eq}\nu\ =\ \frac{1}{2\pi}\ \sqrt\frac{k}{\mu} {/eq}

k is the force constant of a bond, measured in N/cm, which corresponds to the stiffness of a bond. {eq}\mu {/eq} is the reduced mass of the bond measured in kg, and {eq}\nu {/eq} is the frequency of vibration given in cm{eq}^-1 {/eq}

Answer and Explanation:

Compound A and B differ in that the nitrogen (N) atoms are bonded to different species. In compound A, the nitrogen is bonded to two CH{eq}_3 {/eq}...

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Vibrational Spectroscopy: Definition & Types

from Physical Science: Help and Review

Chapter 10 / Lesson 18
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