Chem223 Sp2018 Lab 1 IR Spectroscopy Name 30 pts Q.1 What does IR spectroscopy m

Question

Chem223 Sp2018 Lab 1 IR Spectroscopy Name 30 pts Q.1 What does IR spectroscopy measure and what does it determine? Q,2 Frequency decreases with an increase in Q.3 What does the x-axis in the spectrum represent what does it measure? Q.4 The and increases with an increase in region in a spectrum gives information about the functional groups in a molecule. Q.5 The two most important bond vibrations in IR are ekht and bd Q.6 The stretch at -2800 cm is in most spectra and it correspond to a sp3 Q.7 The most important absorption for an alkene carbon double bond carbon occurs at Q.8 An OH stretch absorption is observed at- Q.9 A primary amine has two absorption bands at cm1 and an N-H bend at Q10 A secondary amine shows how many absorption bands Q.11 The sharpest absorption band is a carbonyl at cm What is the difference (absorption bands observed) between an alcohol and a carboxylic acid? Q.12 What is the difference (absorption bands observed) between an amine and and an amide? Q.13 Q.14 Where are the absorption peaks for a benzene ring found?

Explanation / Answer

1) IR spectroscopy measures vibrations of an atom caused by absorption of infrared radiation. It determines the functional group present in the compound.

2) Frequency decreases with increase of wavelength and increase with increase of energy.

3) x- axis represents wave number and measures percentage transmittance.

4) 2.5 to 15 micrometer , i.e., 4000-667 cm-1

6) C-H stretching frequency

7)  1680-1620 cm-1

8) i ) for alcohols and phenols(dilute solution) : 3650-3580 cm-1

ii ) for alcohols and phenols ( H - bonded) : 3550-3200 cm-1

iii ) for carboxylic acids : 2700-2500 cm-1

9) primary amine have 2 bands at 3500 cm-1 and N-H bends at 1600 cm-1

10) secondary amine shows 1 band

11) 1820 - 1670 cm-1

12) i ) For alcohol : a sharp O-H stretching frequency band is observed at 3650-3580 cm-1

ii) For carboxylic acid : a broad O-H stertching frequency is observed at 2700-2500 cm-1

and a sharp C=O stretching frequency is observed at 1725 - 1700 cm-1

13) 2 stretching frequency bands of N-H are observed at 3500 for both Amine and amide. But for amide one Sharp band of C=O observed at 1680-1630 cm-1

14) for benzene we see strong band at 3150-3020 of C-H stretching frequency and a weak or medium band 1600- 1450 for C-C bond

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