Question

The IR spectrum of compound E (C8H6) is shown in the figure below. What is the structure of E?

2. The IR spectrum of compound E (C&He) is shown in the figure below. Compound E reacts with bromine in carbon tetrachloride and has an IR absorption band at about 3300 cm What is the structure of E? Wavelength (um) 2.5 7 8 9 10 12 15 20 30 40 005 0.10 020 0.30 0 40 0.50 0.60 0.80 2.0 4000 3500 3000 2500 2000 1800 1600 1400 1200 1000 800 600 400 200 Wavenumber (cm")

Answer 1

Molecular Formula = C₈H₆

DBE = [(8×2)+2]-6/2 = 6

Therefore it contains one aromatic ring it indicates fragment -C₆H₅

and another figment is –C₂H

and a molecule is phenylacetylene

1) A sharp intense band at nearly 3300 indicates C_sp3-H stretching vibration

2) The weak absorption at 2120 Cm^-1 is due to C?C stretching vibration

3) A broad and medium intensity band at nearly 1240 Cm^-1 is probably the first overtone of ?C-H out-of-plane bending

4) The broad and weak absorption at 630 Cm^-1 corresponds to the acetylenic C-H out-of-plane bending vibration

5) Aromatic C-H absorption nearly 3100 Cm^-1 observed

6) Aromatic C-H overtone and combination of C-H out-of-plane bending vibration is observed at 2000 and 1667 Cm^-1

Br Br Br2/CCl A sharp intense band at nearly 3300 indicates Csp2-H stretching vibration