Quiz 3 (IR)

Question 1

define spectroscopy

Answer 1

the study of interaction of electromagnetic radiation (light) with molecules

Question 2

light travels in ___

Answer 2

waves

Question 3

energy of a photon = __ = __ = ___. h=____

Answer 3

Ɛ, hv, hc/λ.

h= planck’s constant.

Question 4

λ=

Answer 4

wavelength (cm-1)

Question 5

v=

Answer 5

frequency (Hz)

Question 6

λv=c=____

Answer 6

3.00x10^8 ms-1

Question 7

low energy = ___ frequency = ___wavelength

Answer 7

low energy = low frequency = long wavelength

Question 8

high energy = ___ frequency = ___wavelength

Answer 8

high energy = high frequency = short wavelength

Question 9

what is spectrum

Answer 9

plot of the amount of light absorbed or transmitted vs the energy of the light (λ or v)

Question 10

are you going to ace this quiz?

Answer 10

YES

Question 11

Energy absorbed by molecules in excited states can include: (3)

Answer 11

Electronic excitation (UV/Visible).
Vibration/rotation excitation (Infrared/MW).
Nuclear spring excitation (NMR).

Question 12

Infrared transitions require a ______ to occur

Answer 12

bond dipole

Question 13

the more polar the IR bond dipole, the ____ intense the absorption

Answer 13

more

Question 14

Intensity of an absorption band depends on

Answer 14

the number of bonds responsible for the absorption

Question 15

1-butene

Answer 15

infrared active.

Asymmetrical about C=C bond, has dipole moment

Question 16

2,3-dimethyl-2-butene

Answer 16

infrared inactive.

Asymmetrical about C=C bond, no dipole moment

Question 17

2,3-dimethyl-2-heptene

Answer 17

infrared active, but very weak absorption band

Question 18

hv excited vibrational energy levels in IR spectroscopy, which takes

Answer 18

~1-10 Kcal/mol of changes

Question 19

Generalizations of IR (4)

Answer 19

Stronger bonds absorb at higher wavenumbers (larger k).
Stretches absorb at higher wavenumber than bends (larger k).
Bonds to H absorb at higher wavenumber (small mass).
Polar bonds have more intense absorptions (smaller %T).

Question 20

v=4000cm-1 (hydrogen region) would mean

Answer 20

light atom

Question 21

v=2300-2000cm-1 (triple-bond region) would mean

Answer 21

strongest multiple bonds

Question 22

v=1900-1500cm-1 (double-bond region) would mean

Answer 22

mix of single and double bonds

Question 23

v=500cm-1 (single-bond region, bend, fingerprint region) would mean

Answer 23

lots of bands: single bonds, angle bending, and torsions, in/out of plane combinations

Question 24

Hydrogen Region decreasing bond strength

Answer 24

OH > NH > CspH > Csp2H > Csp3H > O=CH

Question 25

Triple bond region decreasing bond strength

Answer 25

C=-N > C=-C

Question 26

Double bond region decreasing bond strength

Answer 26

O=C, N=C, C=C

Question 27

Fingerprint region

Answer 27

C-O > aromatic ring