8.3 IR spectroscopy

Question 1

how IR spectroscopy works

Answer 1

covalent bonds vibrate when IR radiation is absorbed

Question 2

describing absorption bands (5)

Answer 2

strong, medium, weak
broad, narrow

Question 3

hydroxyl groups are read…

Answer 3

near 3300 cm-1
VERY BROAD

Question 4

carbonyl groups are read…

Answer 4

near 1700 cm-1
NARROW

Question 5

primary amino groups are read…

Answer 5

near 3300 cm-1
TWO SHARP “FANGS”

Question 6

amide bands are […] than amine bands

Answer 6

BROADER

Question 7

hydroxyl group in carboxylic acids compared to alcohols

Answer 7

looks like broad hairy beards

Question 8

alcohols, compared to carboxylic acids,

Answer 8

don’t have a carbonyl band

Question 9

alkane vs alkene spectra

Answer 9

alkenes have a single peak above 3000 cm-1, corresponding to the one double bond

Question 10

ketone vs aldehyde wavenumber

Answer 10

ketone near 2900 cm-1

aldehyde has TWO medium peaks near 2900 and 2700 cm-1

Question 11

(IR) carbonyl group, no hydroxyl group means…

Answer 11

either aldehyde, ketone, or ester

eliminates carboxylic acid