IR Spectroscopy

Question 1

3 techniques to provide evidence of the organic molecue you have made

Answer 1

IR, MS, and NMR

Question 2

IR

Answer 2

tells you what functional groups are present

Question 3

MS

Answer 3

tells you molecular weight, components of a mxture, isotopic distributions, and select functional groups

Question 4

NMR

Answer 4

tells you skeletal structure and select functional groups

Question 5

IR uses this type of radiation

Answer 5

electromagnetic (light)

Question 6

changes in vibrational motions of a molecule are caused by?

Answer 6

absorption of IR light

Question 7

bonds can ?

Answer 7

stretch or vibrate

Question 8

types of stretching (motion)

Answer 8

symetric and asymetric

Question 9

types of vibration

Answer 9

scissor, rock, twist, and wag

Question 10

bond strength and atom mass affect?

Answer 10

bond absorption

Question 11

Transmittance

Answer 11

when wavelength goes through and finds a bond to absorb, it will be low or high depending on the strength

Question 12

low transmittance

Answer 12

high absorption, strong peak

Question 13

high transmittance

Answer 13

low absorption, weak peak

Question 14

Sharp Peaks (represent?)

Answer 14

specific bond vibration (pure sample) (ex: carbonyls, nitriles, alkynes) (shown by?)

Question 15

broad peaks (represent?)

Answer 15

H-bonds or mixtures of secondary structures due to distribution of bond strength

Question 16

Group frequencies or Diagnostic region

Answer 16

(1500/cm<) include H-C/O/N, x triple bound to x, x=x=, and x=x (x= c/n/o),

Question 17

Fingerprint region

Answer 17

(1500/cm>) include C-X (X=C/N/O)

Question 18

Strong peaks

Answer 18

low, close to 0%

Question 19

Weak peaks

Answer 19

high, close to 100%

Question 20

saturated

Answer 20

only single bonds (no pi bonds), absorbs higher wave numbers, higher frequencies

Question 21

conjugated

Answer 21

alternating, long chain of bonds (x2, x1, x2, x1), absorbs lower wave numbers, lower frequencies (due to resonance)

Question 22

Functional groups of interest

Answer 22

OH, COOH, carbonyls, CC and CN x3 bonds, C-H bonds and their hybridization

Question 23

wording for IR report

Answer 23

disappearance/appearance of [strength] peaks at [wavenumber range] of [functional group]

Question 24

wavenumber is proportional to

Answer 24

frequency

Question 25

wavenumber is inversly proportional

Answer 25

wavelength

Question 26

if frequency of IR light = frequency of vibrational mode then...

Answer 26

IR light is absorbed and amplitude of bond stretch or bend increases

Question 27

main difference between OH in alcohol vs carboxylic acid

Answer 27

OH in COOH is momre jagged

Question 28

Energy is proportional to frequency

Answer 28

E=hv

Question 29

Energy is inversly proportional to wavelength

Answer 29

E= hc/⁁ cm(^-1)

Question 30

Energy is proportional wavenumber

Answer 30

E= (wavenumber) (cm^-1)

Question 31

more s character (sp)

Answer 31

high wavenumber, strong/short bond, more energy, more stretching frequency, harder to excite

Question 32

less s character (sp3)

Answer 32

low wavenumber, weak/long bond, less energy, less stretching frequency, easier to excite

Question 33

heavier atoms

Answer 33

low wavenumbers and frequency, easier to excite

Question 34

lighter atoms

Answer 34

high wavenumbers and frquency, harder to excite

Question 35

polarity affects stretching absorption band

Answer 35

more polar = more intense/stronger

Question 36

more C-H bonds

Answer 36

more peaks in fingerprint regions

Question 37

bend

Answer 37

in plane or out of plane