SPECTROSCOPY FINAL EXAM QUESTIONS AND ANSWERS -6

SPECTROSCOPY FINAL EXAM QUESTIONS AND ANSWERS #6

Absorption of what type of electromagnetic radiation results from the interaction
between the radiation and the change in the net dipole moment of the absorbing
functional group?
A. X-Rays
B. Radio waves
C. Microwaves
D. Ultraviolet light
E. Infrared - correct answer E. Infrared

Function group IR adsoption peak in 2100 to 2250, sometimes not present, which one?
A. Carbonyl
B. Alkyne
C. Alcohol
D. Nitrile
E. Carboxylic acid - correct answer B. Alkyne

What lowers energy stretching frequency? - correct answer Conjugation

In IR spectroscopy the C=O bond has a _______ stretching frequency than C=S bond
because ________. - correct answer higher;
O atom has less mass than S atom

Absorption of UV visible energy by a molecule results in:
A. Vibrational transitions
B. Electronic transitions
C. Rotational transitions
D. Nuclear transitions
E. None of the above - correct answer B. Electronic transitions

Longer wavelength of UV visible light? - correct answer increase conjugation

C=C -- +30
Alkyl off conjugation +5

Addition of alkyl or methyl group to conjugated diene will do what? - correct answer
increase wavelength by 5 nm

Mass spectrum - correct answer Br - M+2 as large as M+
Cl - M+2 a third as large as M+
I - I+ at 127; large gap
N - odd M+, some even fragments
S - M+2 larger than usual (4% of M+)

True or False